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Green Mountain, IA Natural Disasters and Weather Extremes

 
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The chance of earthquake damage in Green Mountain is about the same as Iowa average and is much lower than the national average. The risk of tornado damage in Green Mountain is higher than Iowa average and is much higher than the national average.

Topics:Earthquake IndexVolcano IndexTornado IndexOther Weather Extremes EventsVolcanos NearbyHistorical Earthquake EventsHistorical Tornado Events

Earthquake Index, #492

Green Mountain, IA
0.00
Iowa
0.00
U.S.
1.81

The earthquake index value is calculated based on historical earthquake events data using USA.com algorithms. It is an indicator of the earthquake level in a region. A higher earthquake index value means a higher chance of an earthquake.

Volcano Index, #1

Green Mountain, IA
0.0000
Iowa
0.0000
U.S.
0.0023

The volcano index value is calculated based on the currently known volcanoes using USA.com algorithms. It is an indicator of the possibility of a region being affected by a possible volcano eruption. A higher volcano index value means a higher chance of being affected.

Tornado Index, #75

Green Mountain, IA
291.74
Iowa
236.74
U.S.
136.45

The tornado index value is calculated based on historical tornado events data using USA.com algorithms. It is an indicator of the tornado level in a region. A higher tornado index value means a higher chance of tornado events.

Other Weather Extremes Events

A total of 4,000 other weather extremes events within 50 miles of Green Mountain, IA were recorded from 1950 to 2010. The following is a break down of these events:

TypeCountTypeCountTypeCountTypeCountTypeCount
Avalanche:0Blizzard:13Cold:12Dense Fog:0Drought:6
Dust Storm:0Flood:489Hail:1,399Heat:2Heavy Snow:39
High Surf:0Hurricane:0Ice Storm:24Landslide:0Strong Wind:41
Thunderstorm Winds:1,693Tropical Storm:0Wildfire:0Winter Storm:19Winter Weather:0
Other:263 

Volcanos Nearby

No volcano is found in or near Green Mountain, IA.

Historical Earthquake Events

No historical earthquake events that had recorded magnitudes of 3.5 or above found in or near Green Mountain, IA.

No historical earthquake events found in or near Green Mountain, IA.

Historical Tornado Events

A total of 104 historical tornado events that had recorded magnitude of 2 or above found in or near Green Mountain, IA.

Distance (miles)DateMagnitudeStart Lat/LogEnd Lat/LogLengthWidthFatalitiesInjuriesProperty DamageCrop DamageAffected County
3.81961-04-23342°02'N / 92°55'W42°04'N / 92°46'W7.40 Miles800 Yards062.5M0Marshall
5.51951-06-01342°04'N / 92°55'W1.50 Miles880 Yards070K0Marshall
6.81989-05-24442°12'N / 93°00'W42°11'N / 92°45'W13.50 Miles150 Yards0025.0M0Marshall
8.32001-05-10242°13'N / 92°45'W42°11'N / 92°42'W4.00 Miles750 Yards0035K0Tama
 Brief Description: Tornado moved out of Grundy County into Tama County. Track was through mostly rural areas with limited damage. A cold front frontal system located to the northwest of Iowa began to sink southeast into the state during the late afternoon of the 10th. This was in fact the same cold front that set off the thunderstorm activity the previous night. The atmosphere had become quite unstable by the late afternoon with temperatures in the 80s and dew point temperature in the low to mid 60s. CAPE values were in the 2000 to 3500 J/kg range. Thunderstorms erupted during the mid afternoon hours over the north central counties of the state. These storms produced hail of one to one and one half inches in diameter. The instability of the atmosphere, combined with a favorable sheer profile, contributed to the rather quick development of tornadic supercells. The first tornado touched down in Greene County. This tornado touched down briefly and did little damage. As the afternoon progressed, the hail became larger with several reports of hail up to golf ball size from central Iowa east into the east central counties. Some of the largest hail occurred southwest of State Center in Marshall County. Baseball size hail pelted the area, causing considerable damage. One supercell produced a family of at least four tornadoes in the Grundy County area. It is very fortunate that the tornadoes from this storm did not hit within a populated area. Two of the tornadoes were fairly large. At one point, the strongest tornado was about one half mile wide based on reports from a respectable storm chaser. This tornado tracked south through eastern Grundy County and crossed into Tama County. One barn was destroyed by the larger tornado, with a house damaged by the second strong tornado. Miraculously, though the first tornado totally destroyed the barn on a farm near Conrad, none of the animals inside were injured. In fact, it was reported that the livestock appeared to be enjoying their newfound freedom as they wandered the fields at the farm. There were reports of several small tornadoes touching down in central Iowa, however they were little more than brief touchdowns. As the event progressed into the early evening hours, the thunderstorms too on a more multi-cellular structure. The large cluster of storms lost their tornadic characteristic and returned to large hail producers. Hail from three quarter inch to one and three quarter inch was common for the next several hours as the entire area moved southeast slowly. By the mid evening hours the storms began to weaken. As they did, a few reports of winds of 60 to 70 MPH were received. In addition to the wind and hail, the storms produced locally heavy rainfall. Flash flooding was also a problem with this event. The cluster of storms that dropped the tornadoes in Grundy County during the late afternoon hours caused flash flooding in the south part of the county. Rainfall near Conrad was between 2.5 and 5 inches in under two hours time. This flooded roads with some of the state roads in the south part of the county under water. The water receded fairly quickly. A merger of cells took place over Monroe County during the mid evening hours. This resulted in very heavy rainfall in the area with reports of up to 4 inches received. Flash flooding resulted with numerous roads being closed by overflowing creeks by the mid to late evening hours.
9.31989-05-24442°11'N / 92°45'W42°12'N / 92°37'W8.00 Miles150 Yards0025.0M0Tama
10.72001-05-10242°15'N / 92°55'W42°14'N / 92°54'W1.70 Miles200 Yards00150K0Grundy
 Brief Description: Most in open country. One barn hit and destroyed. A cold front frontal system located to the northwest of Iowa began to sink southeast into the state during the late afternoon of the 10th. This was in fact the same cold front that set off the thunderstorm activity the previous night. The atmosphere had become quite unstable by the late afternoon with temperatures in the 80s and dew point temperature in the low to mid 60s. CAPE values were in the 2000 to 3500 J/kg range. Thunderstorms erupted during the mid afternoon hours over the north central counties of the state. These storms produced hail of one to one and one half inches in diameter. The instability of the atmosphere, combined with a favorable sheer profile, contributed to the rather quick development of tornadic supercells. The first tornado touched down in Greene County. This tornado touched down briefly and did little damage. As the afternoon progressed, the hail became larger with several reports of hail up to golf ball size from central Iowa east into the east central counties. Some of the largest hail occurred southwest of State Center in Marshall County. Baseball size hail pelted the area, causing considerable damage. One supercell produced a family of at least four tornadoes in the Grundy County area. It is very fortunate that the tornadoes from this storm did not hit within a populated area. Two of the tornadoes were fairly large. At one point, the strongest tornado was about one half mile wide based on reports from a respectable storm chaser. This tornado tracked south through eastern Grundy County and crossed into Tama County. One barn was destroyed by the larger tornado, with a house damaged by the second strong tornado. Miraculously, though the first tornado totally destroyed the barn on a farm near Conrad, none of the animals inside were injured. In fact, it was reported that the livestock appeared to be enjoying their newfound freedom as they wandered the fields at the farm. There were reports of several small tornadoes touching down in central Iowa, however they were little more than brief touchdowns. As the event progressed into the early evening hours, the thunderstorms too on a more multi-cellular structure. The large cluster of storms lost their tornadic characteristic and returned to large hail producers. Hail from three quarter inch to one and three quarter inch was common for the next several hours as the entire area moved southeast slowly. By the mid evening hours the storms began to weaken. As they did, a few reports of winds of 60 to 70 MPH were received. In addition to the wind and hail, the storms produced locally heavy rainfall. Flash flooding was also a problem with this event. The cluster of storms that dropped the tornadoes in Grundy County during the late afternoon hours caused flash flooding in the south part of the county. Rainfall near Conrad was between 2.5 and 5 inches in under two hours time. This flooded roads with some of the state roads in the south part of the county under water. The water receded fairly quickly. A merger of cells took place over Monroe County during the mid evening hours. This resulted in very heavy rainfall in the area with reports of up to 4 inches received. Flash flooding resulted with numerous roads being closed by overflowing creeks by the mid to late evening hours.
10.92001-05-10242°17'N / 92°49'W42°14'N / 92°46'W4.00 Miles875 Yards0035K0Grundy
 Brief Description: Tornado dropped down north of Beaman and progressed southeast. Crossed into Tama County from Grundy County. Most of the track was through open country. A cold front frontal system located to the northwest of Iowa began to sink southeast into the state during the late afternoon of the 10th. This was in fact the same cold front that set off the thunderstorm activity the previous night. The atmosphere had become quite unstable by the late afternoon with temperatures in the 80s and dew point temperature in the low to mid 60s. CAPE values were in the 2000 to 3500 J/kg range. Thunderstorms erupted during the mid afternoon hours over the north central counties of the state. These storms produced hail of one to one and one half inches in diameter. The instability of the atmosphere, combined with a favorable sheer profile, contributed to the rather quick development of tornadic supercells. The first tornado touched down in Greene County. This tornado touched down briefly and did little damage. As the afternoon progressed, the hail became larger with several reports of hail up to golf ball size from central Iowa east into the east central counties. Some of the largest hail occurred southwest of State Center in Marshall County. Baseball size hail pelted the area, causing considerable damage. One supercell produced a family of at least four tornadoes in the Grundy County area. It is very fortunate that the tornadoes from this storm did not hit within a populated area. Two of the tornadoes were fairly large. At one point, the strongest tornado was about one half mile wide based on reports from a respectable storm chaser. This tornado tracked south through eastern Grundy County and crossed into Tama County. One barn was destroyed by the larger tornado, with a house damaged by the second strong tornado. Miraculously, though the first tornado totally destroyed the barn on a farm near Conrad, none of the animals inside were injured. In fact, it was reported that the livestock appeared to be enjoying their newfound freedom as they wandered the fields at the farm. There were reports of several small tornadoes touching down in central Iowa, however they were little more than brief touchdowns. As the event progressed into the early evening hours, the thunderstorms too on a more multi-cellular structure. The large cluster of storms lost their tornadic characteristic and returned to large hail producers. Hail from three quarter inch to one and three quarter inch was common for the next several hours as the entire area moved southeast slowly. By the mid evening hours the storms began to weaken. As they did, a few reports of winds of 60 to 70 MPH were received. In addition to the wind and hail, the storms produced locally heavy rainfall. Flash flooding was also a problem with this event. The cluster of storms that dropped the tornadoes in Grundy County during the late afternoon hours caused flash flooding in the south part of the county. Rainfall near Conrad was between 2.5 and 5 inches in under two hours time. This flooded roads with some of the state roads in the south part of the county under water. The water receded fairly quickly. A merger of cells took place over Monroe County during the mid evening hours. This resulted in very heavy rainfall in the area with reports of up to 4 inches received. Flash flooding resulted with numerous roads being closed by overflowing creeks by the mid to late evening hours.
12.61965-06-27242°03'N / 92°35'W003K0Tama
13.01989-05-30442°14'N / 92°59'W42°16'N / 92°58'W2.00 Miles200 Yards002.5M0Grundy
14.41991-03-22242°16'N / 93°00'W42°16'N / 92°59'W1.00 Mile50 Yards00250K0Hardin
15.31953-03-21241°53'N / 92°37'W42°03'N / 92°33'W11.70 Miles100 Yards0025K0Tama
16.31962-05-28241°52'N / 92°47'W05250K0Marshall
16.31969-06-06241°52'N / 92°47'W0025K0Marshall
16.51989-05-24442°13'N / 93°13'W42°12'N / 93°00'W12.50 Miles150 Yards0025.0M0Hardin
17.01989-05-30442°17'N / 93°10'W42°14'N / 92°59'W9.00 Miles200 Yards032.5M0Hardin
17.71958-07-14242°12'N / 92°30'W0025K0Tama
17.81966-04-19341°51'N / 92°43'W41°52'N / 92°42'W00250K0Poweshiek
18.61969-06-11241°50'N / 92°47'W1.00 Mile100 Yards0025K0Marshall
18.91978-09-16341°58'N / 93°11'W41°52'N / 93°00'W11.30 Miles200 Yards000K0Marshall
19.11991-03-22242°16'N / 92°59'W42°29'N / 92°47'W19.00 Miles50 Yards00250K0Grundy
19.81966-04-19341°52'N / 92°42'W42°02'N / 92°17'W24.10 Miles400 Yards04250K0Tama
20.21981-04-10241°53'N / 93°10'W41°57'N / 93°05'W5.60 Miles500 Yards092.5M0Marshall
21.51959-05-09242°06'N / 92°24'W0025K0Tama
21.71960-04-16342°20'N / 92°35'W42°22'N / 92°32'W2.30 Miles800 Yards00250K0Grundy
22.21966-10-14242°23'N / 92°56'W42°26'N / 92°58'W2.70 Miles100 Yards003K0Grundy
22.21978-09-16341°52'N / 93°00'W41°42'N / 92°46'W16.40 Miles200 Yards22250K0Jasper
23.71969-06-29241°48'N / 92°36'W1.00 Mile250 Yards0025K0Poweshiek
24.21953-05-10241°53'N / 92°27'W0025K0Tama
25.11959-05-31242°03'N / 93°26'W42°13'N / 93°11'W17.00 Miles440 Yards00250K0Story
26.81990-03-13342°01'N / 93°23'W42°08'N / 93°18'W9.00 Miles100 Yards01250K0Story
26.91991-03-22342°14'N / 93°22'W42°24'N / 93°09'W16.00 Miles70 Yards002.5M0Hardin
27.21989-05-24442°11'N / 93°27'W42°13'N / 93°13'W13.00 Miles150 Yards0025.0M0Story
27.51965-08-26241°52'N / 93°15'W41°49'N / 93°12'W3.00 Miles100 Yards0025K0Jasper
27.61956-04-26242°00'N / 92°20'W42°00'N / 92°16'W2.30 Miles440 Yards003K0Tama
27.81965-08-26241°54'N / 93°18'W41°52'N / 93°15'W1.90 Miles100 Yards0225K0Story
27.91971-05-31242°24'N / 92°27'W1.00 Mile200 Yards0025K0Black Hawk
28.11966-04-19242°27'N / 92°36'W42°29'N / 92°33'W2.30 Miles200 Yards0025K0Grundy
28.31962-05-07241°54'N / 93°18'W00250K0Story
28.81953-05-20342°18'N / 93°18'W42°33'N / 93°03'W21.30 Miles400 Yards000K0Hardin
28.81973-06-04241°42'N / 93°03'W41°44'N / 93°01'W1.30 Miles250 Yards00250K0Jasper
28.91966-04-19342°02'N / 92°17'W42°05'N / 92°14'W3.00 Miles400 Yards00250K0Benton
29.21986-09-28441°46'N / 93°20'W41°46'N / 93°00'W14.00 Miles250 Yards002.5M0Jasper
29.81978-09-16341°42'N / 92°46'W41°39'N / 92°42'W4.10 Miles200 Yards4432.5M0Poweshiek
30.21971-05-31342°06'N / 92°18'W42°12'N / 92°10'W9.40 Miles600 Yards00250K0Tama
31.02008-05-25242°33'N / 92°52'W42°33'N / 92°51'W1.00 Mile75 Yards00300K2KGrundy
 Brief Description: EVENT NARRATIVE: This was the initial tornado touchdown point. The tornado continued on into Butler County. EPISODE NARRATIVE: A very intense upper low was located over the southwest U.S. and lifted northeast during the weekend of the 24th into the morning of the 26th. The seasons first strong push of deep moisture moved into Iowa on the 25th with surface temperatures warming into the mid 80s and dew points surging into the upper 60s to low 70s. Precipitable water values were near 1.5 inches. The dry slot pushed north across the area the previous night as the warm front lifted north. The primary surface low was located over northern Minnesota. A cold front extended south from the low into northwest Iowa. The airmass became very unstable by the mid afternoon hours. MUCAPE rose to between 4000 and 5000 J/kg. Lifted indices fell to -8 to -11 C. There was a considerable amount of both DCAPE at 1000-1500 J/kg and cape in the -10 to-30 C. layer of the atmoshpere, between 400 and 600 J/kg. The freezing level was around 13,200 feet. The environment was quite sheared with effective shear in the 40 to 50 kt range. LCL values were between 1000 and 1500 meters. The airmass was initially capped. During the late afternoon hours, a small cluster of thunderstorms formed over north central into northeast Iowa. The storms became severe very quickly. Initially, the storms dropped hail up to golf ball in size. One became a strong super cell and produced a major tornado. This cell, in addition to being tornadic, also produced hail of baseball to softball in size and winds in excess of 90 MPH. The tornado track was from approximately 2 miles south of Aplington to Parkersburg, then continued to New Hartford and across northern Black Hawk County. The average path width ranged from 0.6 to 0.7 miles near Parkersburg to just north of New Hartford. The path constricted to near one quarter mile wide east of New Hartford to north of Waterloo. The width then increased to near 1.2 miles wide north of Dunkerton before dissipating near the Black Hawk and Buchanan County line. The tornado was on the ground for approximately 43 miles. In addition to the main tornado, a satellite tornado was observed by storm chasers and one off duty NWS employee. It was located south of the main tornado and was on the ground for a little over a mile in Grundy County. Initial reports indicated 9 fatalities with 7 in Parkersburg (pop 1889) and 2 in New Hartford (pop 637). There were at least 50 injuries, with 4 of those in critical condition. Two of the fatalities occurred a few days after the tornado from injuries sustained in the tornado. The last fatality occurred on 7 Nov. A 61 year old female sustained injuries in the stairwell of her home when a 2 x 4 was thrown through her right side lung. She was hospitalized and died several months later of complications. Significant structural damage occurred across the southern end of Parkersburg and along a path to just north of New Hartford. Numerous structures completely destroyed from Parkersburg to near New Hartford. The tornado continued eastward to just north of the Waterloo and Cedar Falls area. Significant damage also occurred north of Dunkerton where the tornado increased to its greatest path width. This storm also produced substantial straight line wind damage along the southern periphery of the storm just south of the tornado track. News accounts indicated that a receipt from Parkersburg was found around 1915 CST 3 miles north of Prairie du Chien, WI, 109 miles to the northeast. Receipits were also found in Clayton County at Elkader, and full scrapbook pages and photos were found in far northeast Bremer County at Sumner. Preliminary estimates that straight line winds of 90 to 100 MPH occurred with this storm. At 1637 CST, the Waterloo Airport recorded a 93 MPH wind gust. Survey results suggest that straight line wind damage was the cause of the severe damage at the recreational vehicle dealership north of Cedar Falls. At least 627 homes were damaged, including 288 homes destroyed in Parkersburg, 88 in New Hartford, 15 in Hazelton and another 50 in Black Hawk County. In addition, 58 had major damage, 33 had moderate damage, 2 were inaccessible, and 93 damaged but able to be occupied. There were also 21 businesses destroyed. Governor Chet Culver declared both Butler and Black Hawk disaster areas with both given the State Declaration. A Federal Disaster Declaration occurred two days later for both Butler and Black Hawk Counties. The tornado was rated a low end EF5 by a Quick Response Team (QRT) in portions of Parkersburg and north of New Hartford with peak winds estimated at 205 MPH. For historical reference, the last F5 tornado to hit Iowa was on 13 June 1976 in Boone and Story Counties in the town of Jordan, with a 21 mile path length. The last F4 tornado to hit Iowa was in Union, Madison, and Dallas Counties with a 56 mile path length on 8 April 1999. There was one other smaller tornado during the evening. A tornado touched down in Clarke County and was on the ground for a short time southeast of Osceola. After the initial thunderstorm area developed over north central and northeast Iowa, a large complex developed over southeast Nebraska. The two areas of storms filled in to form a squall line by the mid evening hours. The complex over Nebraska then pushed east and northeast along the squall line. A considerable amount of severe weather was generated during the evening as this occurred. Along the squall line, high winds and hail were common with the dominant mode of severe weather being hail of up to golf ball in size. As the MCS out of Nebraska advanced east, a tail extending south from the centroid took on a bow echo configuration and raced east across Iowa at 65 MPH. Very high winds occurred with this feature with numerous locations reporting winds of 65 to 85 MPH. Some of the higher winds included an 85 MPH wind gust in the Winterset area and numerous reports of 75 to 85 MPH winds from Madison, Dallas, Warren and Polk Counties. Lightning struck a house in Ankeny. The house was set on fire by the strike.
31.21999-07-02242°34'N / 92°49'W42°32'N / 92°39'W8.50 Miles50 Yards0075K3KGrundy
 Brief Description: A very active weather pattern was in place over the central U.S. A strong west-northwest wind flow was in place over the state. Meanwhile a warm front was lifting north from the southern Plains. The warm front separated the cooler and dry air to the north from very humid air to the south. Dew point temperatures in the air to the south of the front were in the mid 70s to low 80s. Precipitable water values were near 2 inches as well. A meso scale convective system formed over north central Nebraska and south central South Dakota during the previous night. The remains of this system drifted into west central Iowa during the predawn hours. One cell became severe during the morning. This was to be the pattern for much of the rest of the day as the cells that formed became super cellular, with each supercell lasting about 2 hours. By the early afternoon hours, surface based CAPE values were approaching 6000 J/kg just to the south of the thunderstorm genesis region. Once the storms formed they became supercells quickly. Very strong sheer was in place with strong southeast surface winds veering to westerly winds in the mid levels. Even though freezing levels were in excess of 15,000 feet, the storms were prolific hail producers. WSR-88D VIL values with many of the supercells exceeded 90 kg/m/m. There was also some high winds with the storms at times as many of the cells were rotating as was seen with WSR-88D imagery. The first high winds occurred early in the severe event as 64 MPH winds blasted into the Dow City area of Crawford County. Winds of 66 MPH were recorded at the Denison Municipal Airport as the storm moved through. Damage was reported in many areas of the county. During the day there were also other spotty reports of wind damage, however most of the were were in the 40 to 50 MPH range. A few other cells did produce severe criteria winds as they moved into the central and northeast counties of the state with wind damage reported in Hardin, Hamilton, and Boone Counties. These storms developed during the period of time the weather system was changing from a supercell type system into more of a multi-cell system. The main severe weather event of the day was the hail. Hail reports of one inch up to golf ball size were too numerous to mention. Some of the hail was larger than tennis balls. Baseball size hail fell in Guthrie County, into Adair and Dallas Counties as one of the cells advanced east-southeast. The largest hail actually fell east of Casey in Guthrie County. Softball size hail fell there, smashing windshields on numerous cars. Needless to say, crop damage was widespread from west central into central Iowa along the paths of the two to three supercells that moved through the area. Scattered crop damage occurred with the multi-cellular storms over central into northeast Iowa as well. An example of the damage caused by the hail came by way of a report from Crawford County. Reports indicated hail damaged 80,000 to 100,000 acres of crops with widespread damage. Roads and ditches sustained between $150,000 and $200,000 in damage. Tree removal in the county was #30,000, with $100,000 damage to homes and businesses in the county. By the early evening, the weather system had made a transition from severe weather to heavy rain. Intense rainfall occurred over northeast Iowa. Flash flooding was widespread over northern Grundy, southern Butler, southern Bremer, and most of Black Hawk Counties. A large swath of 6 to 8 inch rainfall occurred over the Beaver Creek basin, causing flash flooding in the area and an eventual flood of near record proportions. County officials reported the flooding as very serious with countless roads and highways under water. Cars were stranded and thousands of basements were flooded by the onslaught of heavy rain. One report indicated several head of cattle lost as they were drown by the flood waters in Grundy County. No doubt, this was not the only case of livestock loss due to the flooding. Another report from the Dewar area, east of Waterloo, indicated about a block of railroad was washed out. Damage there was reported to 33 houses, a car repair shop, and a tavern. Rainfall was in excess of three inches per hour in many areas. The heaviest rainfall officially was around 9 inches. Some unofficial reports in the Cedar Falls area included up to 9 inches of rainfall in a 90 minute period. The observer at Parkersburg picked up 6.55 inches of rain in under 3 hours. A bucket survey in the area showed rainfall of 11 to 14 inches at a few locations in Butler County. The heavy rain occurred as a series of storms formed and trained over the same areas. The complex of thunderstorms that developed was a back developing complex. Late in the life of the system, one of the storms became severe. This storm displayed a meso circulation on the WSR-88D in Johnston, IA, though it was not all that well formed. The storm was the last in the series of storms and layed down a path of damage. The swath was about 13 miles long, extending across southern Butler and northern Grundy Counties. The damage path looked to be more downburst in nature, though there were reports of a tornado imbedded in the flow pattern. The situation was not all that different from the meso cyclone/tornado system that moved through Boone, Dallas, and Polk Counties about a year earlier on 29 June 1998. The tornado caused damage to several farmsteads along the road. The worst hit was on farmstead where all of the farm buildings were destroyed and only the superstructure of the farmhouse remained. Debris was wrapped up in trees for many miles along the path. One other tornado did occur earlier in the day. The tornado came from one of the supercells over western Iowa. A relatively small tornado touched down in Audubon County west of Hamlin. There was little damage reported with this tornado.
31.51999-07-02242°34'N / 92°53'W42°33'N / 92°47'W4.50 Miles35 Yards0025K1KButler
 Brief Description: A very active weather pattern was in place over the central U.S. A strong west-northwest wind flow was in place over the state. Meanwhile a warm front was lifting north from the southern Plains. The warm front separated the cooler and dry air to the north from very humid air to the south. Dew point temperatures in the air to the south of the front were in the mid 70s to low 80s. Precipitable water values were near 2 inches as well. A meso scale convective system formed over north central Nebraska and south central South Dakota during the previous night. The remains of this system drifted into west central Iowa during the predawn hours. One cell became severe during the morning. This was to be the pattern for much of the rest of the day as the cells that formed became super cellular, with each supercell lasting about 2 hours. By the early afternoon hours, surface based CAPE values were approaching 6000 J/kg just to the south of the thunderstorm genesis region. Once the storms formed they became supercells quickly. Very strong sheer was in place with strong southeast surface winds veering to westerly winds in the mid levels. Even though freezing levels were in excess of 15,000 feet, the storms were prolific hail producers. WSR-88D VIL values with many of the supercells exceeded 90 kg/m/m. There was also some high winds with the storms at times as many of the cells were rotating as was seen with WSR-88D imagery. The first high winds occurred early in the severe event as 64 MPH winds blasted into the Dow City area of Crawford County. Winds of 66 MPH were recorded at the Denison Municipal Airport as the storm moved through. Damage was reported in many areas of the county. During the day there were also other spotty reports of wind damage, however most of the were were in the 40 to 50 MPH range. A few other cells did produce severe criteria winds as they moved into the central and northeast counties of the state with wind damage reported in Hardin, Hamilton, and Boone Counties. These storms developed during the period of time the weather system was changing from a supercell type system into more of a multi-cell system. The main severe weather event of the day was the hail. Hail reports of one inch up to golf ball size were too numerous to mention. Some of the hail was larger than tennis balls. Baseball size hail fell in Guthrie County, into Adair and Dallas Counties as one of the cells advanced east-southeast. The largest hail actually fell east of Casey in Guthrie County. Softball size hail fell there, smashing windshields on numerous cars. Needless to say, crop damage was widespread from west central into central Iowa along the paths of the two to three supercells that moved through the area. Scattered crop damage occurred with the multi-cellular storms over central into northeast Iowa as well. An example of the damage caused by the hail came by way of a report from Crawford County. Reports indicated hail damaged 80,000 to 100,000 acres of crops with widespread damage. Roads and ditches sustained between $150,000 and $200,000 in damage. Tree removal in the county was #30,000, with $100,000 damage to homes and businesses in the county. By the early evening, the weather system had made a transition from severe weather to heavy rain. Intense rainfall occurred over northeast Iowa. Flash flooding was widespread over northern Grundy, southern Butler, southern Bremer, and most of Black Hawk Counties. A large swath of 6 to 8 inch rainfall occurred over the Beaver Creek basin, causing flash flooding in the area and an eventual flood of near record proportions. County officials reported the flooding as very serious with countless roads and highways under water. Cars were stranded and thousands of basements were flooded by the onslaught of heavy rain. One report indicated several head of cattle lost as they were drown by the flood waters in Grundy County. No doubt, this was not the only case of livestock loss due to the flooding. Another report from the Dewar area, east of Waterloo, indicated about a block of railroad was washed out. Damage there was reported to 33 houses, a car repair shop, and a tavern. Rainfall was in excess of three inches per hour in many areas. The heaviest rainfall officially was around 9 inches. Some unofficial reports in the Cedar Falls area included up to 9 inches of rainfall in a 90 minute period. The observer at Parkersburg picked up 6.55 inches of rain in under 3 hours. A bucket survey in the area showed rainfall of 11 to 14 inches at a few locations in Butler County. The heavy rain occurred as a series of storms formed and trained over the same areas. The complex of thunderstorms that developed was a back developing complex. Late in the life of the system, one of the storms became severe. This storm displayed a meso circulation on the WSR-88D in Johnston, IA, though it was not all that well formed. The storm was the last in the series of storms and layed down a path of damage. The swath was about 13 miles long, extending across southern Butler and northern Grundy Counties. The damage path looked to be more downburst in nature, though there were reports of a tornado imbedded in the flow pattern. The situation was not all that different from the meso cyclone/tornado system that moved through Boone, Dallas, and Polk Counties about a year earlier on 29 June 1998. The tornado caused damage to several farmsteads along the road. The worst hit was on farmstead where all of the farm buildings were destroyed and only the superstructure of the farmhouse remained. Debris was wrapped up in trees for many miles along the path. One other tornado did occur earlier in the day. The tornado came from one of the supercells over western Iowa. A relatively small tornado touched down in Audubon County west of Hamlin. There was little damage reported with this tornado.
32.12008-05-25542°33'N / 92°51'W42°34'N / 92°33'W16.00 Miles1235 Yards95075.0M75KButler
 Brief Description: EVENT NARRATIVE: First EF5 tornado in Iowa since 13 June 1976. Nine deaths and 50 injuries occurred in Butler County. Tornado moved out of Butler County and continued in Black Hawk County. EPISODE NARRATIVE: A very intense upper low was located over the southwest U.S. and lifted northeast during the weekend of the 24th into the morning of the 26th. The seasons first strong push of deep moisture moved into Iowa on the 25th with surface temperatures warming into the mid 80s and dew points surging into the upper 60s to low 70s. Precipitable water values were near 1.5 inches. The dry slot pushed north across the area the previous night as the warm front lifted north. The primary surface low was located over northern Minnesota. A cold front extended south from the low into northwest Iowa. The airmass became very unstable by the mid afternoon hours. MUCAPE rose to between 4000 and 5000 J/kg. Lifted indices fell to -8 to -11 C. There was a considerable amount of both DCAPE at 1000-1500 J/kg and cape in the -10 to-30 C. layer of the atmoshpere, between 400 and 600 J/kg. The freezing level was around 13,200 feet. The environment was quite sheared with effective shear in the 40 to 50 kt range. LCL values were between 1000 and 1500 meters. The airmass was initially capped. During the late afternoon hours, a small cluster of thunderstorms formed over north central into northeast Iowa. The storms became severe very quickly. Initially, the storms dropped hail up to golf ball in size. One became a strong super cell and produced a major tornado. This cell, in addition to being tornadic, also produced hail of baseball to softball in size and winds in excess of 90 MPH. The tornado track was from approximately 2 miles south of Aplington to Parkersburg, then continued to New Hartford and across northern Black Hawk County. The average path width ranged from 0.6 to 0.7 miles near Parkersburg to just north of New Hartford. The path constricted to near one quarter mile wide east of New Hartford to north of Waterloo. The width then increased to near 1.2 miles wide north of Dunkerton before dissipating near the Black Hawk and Buchanan County line. The tornado was on the ground for approximately 43 miles. In addition to the main tornado, a satellite tornado was observed by storm chasers and one off duty NWS employee. It was located south of the main tornado and was on the ground for a little over a mile in Grundy County. Initial reports indicated 9 fatalities with 7 in Parkersburg (pop 1889) and 2 in New Hartford (pop 637). There were at least 50 injuries, with 4 of those in critical condition. Two of the fatalities occurred a few days after the tornado from injuries sustained in the tornado. The last fatality occurred on 7 Nov. A 61 year old female sustained injuries in the stairwell of her home when a 2 x 4 was thrown through her right side lung. She was hospitalized and died several months later of complications. Significant structural damage occurred across the southern end of Parkersburg and along a path to just north of New Hartford. Numerous structures completely destroyed from Parkersburg to near New Hartford. The tornado continued eastward to just north of the Waterloo and Cedar Falls area. Significant damage also occurred north of Dunkerton where the tornado increased to its greatest path width. This storm also produced substantial straight line wind damage along the southern periphery of the storm just south of the tornado track. News accounts indicated that a receipt from Parkersburg was found around 1915 CST 3 miles north of Prairie du Chien, WI, 109 miles to the northeast. Receipits were also found in Clayton County at Elkader, and full scrapbook pages and photos were found in far northeast Bremer County at Sumner. Preliminary estimates that straight line winds of 90 to 100 MPH occurred with this storm. At 1637 CST, the Waterloo Airport recorded a 93 MPH wind gust. Survey results suggest that straight line wind damage was the cause of the severe damage at the recreational vehicle dealership north of Cedar Falls. At least 627 homes were damaged, including 288 homes destroyed in Parkersburg, 88 in New Hartford, 15 in Hazelton and another 50 in Black Hawk County. In addition, 58 had major damage, 33 had moderate damage, 2 were inaccessible, and 93 damaged but able to be occupied. There were also 21 businesses destroyed. Governor Chet Culver declared both Butler and Black Hawk disaster areas with both given the State Declaration. A Federal Disaster Declaration occurred two days later for both Butler and Black Hawk Counties. The tornado was rated a low end EF5 by a Quick Response Team (QRT) in portions of Parkersburg and north of New Hartford with peak winds estimated at 205 MPH. For historical reference, the last F5 tornado to hit Iowa was on 13 June 1976 in Boone and Story Counties in the town of Jordan, with a 21 mile path length. The last F4 tornado to hit Iowa was in Union, Madison, and Dallas Counties with a 56 mile path length on 8 April 1999. There was one other smaller tornado during the evening. A tornado touched down in Clarke County and was on the ground for a short time southeast of Osceola. After the initial thunderstorm area developed over north central and northeast Iowa, a large complex developed over southeast Nebraska. The two areas of storms filled in to form a squall line by the mid evening hours. The complex over Nebraska then pushed east and northeast along the squall line. A considerable amount of severe weather was generated during the evening as this occurred. Along the squall line, high winds and hail were common with the dominant mode of severe weather being hail of up to golf ball in size. As the MCS out of Nebraska advanced east, a tail extending south from the centroid took on a bow echo configuration and raced east across Iowa at 65 MPH. Very high winds occurred with this feature with numerous locations reporting winds of 65 to 85 MPH. Some of the higher winds included an 85 MPH wind gust in the Winterset area and numerous reports of 75 to 85 MPH winds from Madison, Dallas, Warren and Polk Counties. Lightning struck a house in Ankeny. The house was set on fire by the strike.
32.31990-06-28342°33'N / 93°03'W42°32'N / 93°01'W2.00 Miles90 Yards002.5M0Hardin
33.11970-07-14242°19'N / 93°26'W42°17'N / 93°23'W1.30 Miles250 Yards0025K0Hardin
33.22007-09-30241°34'N / 92°45'W41°42'N / 92°36'W12.00 Miles1250 Yards002.5M1.0MPoweshiek
 Brief Description: EVENT NARRATIVE: Tornado moved into Poweshiek County from Jasper County. It lifted west of Malcom. EPISODE NARRATIVE: A very dynamic weather system moved into Iowa during the afternoon of the 30th. The system was more reminiscent of what one would expect in April or May. A close upper level low pressure, negatively tilted, lifted northeast through the central U.S. The structure was very classic in appearance with a well defined comma cloudy, dry slot, and warm conveyor in place. By the early evening, the surface low became stacked with the upper low and was located over eastern Nebraska. A defined dry line extended south-southeast out of the low. Surface temperatures warmed into the mid 70s to mid 80s ahead of the low, with dew points in the mid to upper 60s. Dew points behind the dry line dropped into the upper 30s to mid 40s. The airmass became unstable by the late afternoon with CAPE values around 1000 J/kg and lifted indices in the -2 to -4 C. range. Strong dynamics were in place with a 90 kt mid level jet in place, a low level jet of 60 to 70 kts, and an effective shear of 45 to 55 kts. The freezing level was quite high ahead of the approaching low and was between 13,000 and 14,000 feet. The high freezing level, combined with the limited CAPE of 100 to 200 J/kg in the -10 to -30 C. layer of the atmosphere, limited hail production. The downdraft CAPE was in the 600 to 1000 J/kg range, with an LCL of about 1250 meters. Thunderstorms formed in two locations. The first was along the east edge of the dry slot across Kansas. These storms became severe and lifted northeast quite rapidly into southern and central Iowa. Spotty wind damage was reported and one of the storms dropped one inch diameter hail in Marion County. The storms became tornadic as the moved into central Iowa. During the evening of Sunday 30 September 2007 two tornadoes struck portions of Marion, Jasper, Mahaska, and Poweshiek Counties. The first tornado produced EF0 to EF2 damage along its track and was rated EF2 on the Enhanced Fujita Scale with maximum winds of 125 mph. The track was 22 miles in length from 4 miles northeast of Pella to 1 mile north of Interstate 80, 2 miles west of Malcom. Much of the track was three to five tenths of a mile wide, but as wide as seven tenths of a mile at times. The second, shorter and weaker tornado was 5 miles in length and rated EF1 on the Enhanced Fujita Scale. The track began just south of Highway 6, 2.75 miles northwest of Malcom with a maximum width of 150 yards narrowing to 25-50 yards. The storm hit a farmstead just east of 110th street producing EF1 damage with speeds just under 100 mph. The tornadoes caused extensive damage on a farmstead near Malcom with three barns totally destroyed. The barns were 20 by 30 feet, 20 by 40 feet, and 60 by 100 feet. In addition, numerous other damage reports came in from along the track. Fortunately, there were no deaths or injuries from the tornadoes. Thunderstorms also formed close to the upper low center on the nose of the dry punch. There were several reports funnel clouds, along with spotty reports of high winds and hail. A storm chaser confirmed a tornado touchdown 2 NNW of Lytton in Sac county and was on the ground until 4 W of Jolley in Calhoun county. The tornado was in open country and was a small EF0 tornado. One inch diameter hail fell in Sac County, with numerous reports of pea to marble size hail.
33.31967-06-08242°00'N / 93°36'W42°02'N / 93°19'W14.40 Miles100 Yards00250K0Story
33.81971-05-31242°33'N / 93°02'W42°36'N / 92°57'W4.50 Miles300 Yards00250K0Hardin
34.01960-04-16342°22'N / 92°32'W42°28'N / 92°05'W23.70 Miles800 Yards15250K0Black Hawk
34.51965-07-18242°18'N / 92°12'W0.50 Mile50 Yards000K0Black Hawk
34.91965-08-26442°18'N / 92°12'W42°18'N / 92°11'W002.5M0Black Hawk
34.91991-03-22341°54'N / 93°38'W42°14'N / 93°22'W27.00 Miles70 Yards002.5M0Story
35.01990-03-13241°56'N / 93°30'W41°53'N / 93°24'W3.00 Miles60 Yards002.5M0Story
35.81953-05-20342°09'N / 93°42'W42°18'N / 93°18'W22.70 Miles400 Yards100K0Story
36.61953-06-07241°42'N / 92°45'W41°52'N / 91°45'W52.70 Miles200 Yards000K0Poweshiek
36.71965-08-26442°18'N / 92°11'W42°15'N / 92°06'W4.70 Miles200 Yards1172.5M0Benton
36.91990-06-28342°38'N / 93°10'W42°33'N / 93°03'W7.00 Miles90 Yards002.5M0Franklin
37.01998-06-27242°35'N / 92°56'W42°41'N / 92°32'W20.50 Miles75 Yards0010K2KButler
 Brief Description: Iowa was located in the warm sector of a developing storm system to the west. The warm front had moved to the northern Iowa border during the afternoon of the 27th with dew point temperatures in the mid 70s to around 80 blanketing the state in the warm sector. Initially, the airmass was capped, preventing thunderstorms from forming during the afternoon. Slightly cooler air moved in during the evening hours. In addition to the slightly cooler air moving in aloft, a cold front was poised over eastern Nebraska ready to move east into the state. Thunderstorms erupted rapidly by early evening with hail and high winds reported over northern Iowa. There were numerous reports of hail of an inch or larger in diameter, with a few reports of golf ball size hail. High winds were also a problem with many of the storms producing 60 to 70 MPH wind gusts. Reports of tree and power line damage were widespread. There were a few tornadoes as well. One tracked across open country in Cerro Gordo County before damaging a house south of Clear Lake. Another tornado touched down near Swaledale in Cerro Gordo County and passed southeast of Mason City. Much of the track was over open country, however one house was destroyed near Swaledale by this tornado. The longest track tornado moved across Butler and Bremer Counties. It also passed through open country, causing damage to crops and out buildings. In addition to these, there were a few brief touchdowns reported. Iowa soil remained very saturated with numerous rivers at or near flood stage. Heavy rainfall of near 4 inches in a couple hours time caused flash flooding in Cerro Gordo County. A widespread area of north central into northeast Iowa received heavy rainfall. Many areas picked up two to four inches of rain in a few hour period. This resulted in urban and small stream flooding, and ultimately general river flooding in the days that followed. As the storms moved through Worth County, lightning struck an outbuilding west of Kensett. The building was set on fire and destroyed.
37.01968-04-03241°34'N / 93°05'W41°37'N / 93°00'W5.20 Miles150 Yards0025K0Jasper
37.01975-11-09342°12'N / 92°28'W42°41'N / 92°03'W39.40 Miles33 Yards002.5M0Tama
38.01956-08-12341°32'N / 92°45'W41°35'N / 92°40'W5.10 Miles200 Yards0825K0Poweshiek
38.01950-06-15341°59'N / 93°36'W41°58'N / 93°29'W5.60 Miles300 Yards050K0Story
38.71978-06-26241°35'N / 92°32'W0.70 Mile100 Yards012.5M0Poweshiek
38.91991-04-27241°42'N / 92°18'W41°44'N / 92°14'W4.50 Miles50 Yards00250K0Iowa
39.01964-05-07242°31'N / 92°20'W42°28'N / 92°12'W7.10 Miles200 Yards02725.0M0Black Hawk
39.32007-09-30241°30'N / 92°49'W41°34'N / 92°45'W6.00 Miles1250 Yards001.0M500KJasper
 Brief Description: EVENT NARRATIVE: Tornado moved into Jasper County from Mahaska County, then continued northeast into Poweshiek County. EPISODE NARRATIVE: A very dynamic weather system moved into Iowa during the afternoon of the 30th. The system was more reminiscent of what one would expect in April or May. A close upper level low pressure, negatively tilted, lifted northeast through the central U.S. The structure was very classic in appearance with a well defined comma cloudy, dry slot, and warm conveyor in place. By the early evening, the surface low became stacked with the upper low and was located over eastern Nebraska. A defined dry line extended south-southeast out of the low. Surface temperatures warmed into the mid 70s to mid 80s ahead of the low, with dew points in the mid to upper 60s. Dew points behind the dry line dropped into the upper 30s to mid 40s. The airmass became unstable by the late afternoon with CAPE values around 1000 J/kg and lifted indices in the -2 to -4 C. range. Strong dynamics were in place with a 90 kt mid level jet in place, a low level jet of 60 to 70 kts, and an effective shear of 45 to 55 kts. The freezing level was quite high ahead of the approaching low and was between 13,000 and 14,000 feet. The high freezing level, combined with the limited CAPE of 100 to 200 J/kg in the -10 to -30 C. layer of the atmosphere, limited hail production. The downdraft CAPE was in the 600 to 1000 J/kg range, with an LCL of about 1250 meters. Thunderstorms formed in two locations. The first was along the east edge of the dry slot across Kansas. These storms became severe and lifted northeast quite rapidly into southern and central Iowa. Spotty wind damage was reported and one of the storms dropped one inch diameter hail in Marion County. The storms became tornadic as the moved into central Iowa. During the evening of Sunday 30 September 2007 two tornadoes struck portions of Marion, Jasper, Mahaska, and Poweshiek Counties. The first tornado produced EF0 to EF2 damage along its track and was rated EF2 on the Enhanced Fujita Scale with maximum winds of 125 mph. The track was 22 miles in length from 4 miles northeast of Pella to 1 mile north of Interstate 80, 2 miles west of Malcom. Much of the track was three to five tenths of a mile wide, but as wide as seven tenths of a mile at times. The second, shorter and weaker tornado was 5 miles in length and rated EF1 on the Enhanced Fujita Scale. The track began just south of Highway 6, 2.75 miles northwest of Malcom with a maximum width of 150 yards narrowing to 25-50 yards. The storm hit a farmstead just east of 110th street producing EF1 damage with speeds just under 100 mph. The tornadoes caused extensive damage on a farmstead near Malcom with three barns totally destroyed. The barns were 20 by 30 feet, 20 by 40 feet, and 60 by 100 feet. In addition, numerous other damage reports came in from along the track. Fortunately, there were no deaths or injuries from the tornadoes. Thunderstorms also formed close to the upper low center on the nose of the dry punch. There were several reports funnel clouds, along with spotty reports of high winds and hail. A storm chaser confirmed a tornado touchdown 2 NNW of Lytton in Sac county and was on the ground until 4 W of Jolley in Calhoun county. The tornado was in open country and was a small EF0 tornado. One inch diameter hail fell in Sac County, with numerous reports of pea to marble size hail.
40.01965-09-16242°07'N / 93°36'W0.50 Mile100 Yards0025K0Story
40.71974-08-12441°45'N / 92°11'W2.00 Miles100 Yards02250K0Iowa
40.82005-11-12242°03'N / 93°38'W42°08'N / 93°36'W9.00 Miles100 Yards01250K0Story
 Brief Description: Tornado moved from Boone County into Story County. One minor injury occurred on the west side of Ames. A very intense weather system developed over the central U.S. during the day on the 12th. A strong upper level system moved through the area with mid and upper level winds in the 70 to 90 kt range. Low level winds of 35 to 50 kts transported moisture north into the system. High temperatures reached the mid 60s to low 70s, with dew point readings approaching 60 by late afternoon. A surface low developed over northern Kansas during the previous night and lifted northeast into eastern South Dakota during the afternoon of the 12th, then into central Minnesota as a 985 mb low by late evening. The atmosphere became quite unstable with CAPE values reaching 1000 J/kg by late afternoon. The Lifted Index values were in the -5 C. range. Being as it was in November, the freezing level was quite low during the event, in the 10,000 to 11,000 foot range. Though the soundings were quite unidirectional, there was plenty of shear with zero to 6 km shear values around 65 kts. Thunderstorms erupted during the afternoon in west central in to southwest Iowa. The storms became severe quite quickly. Initially the storms produce quarter to golf ball size hail, with 2 1/2 inch diameter hail falling in Dallas County. Hail up to baseball size fell in Greene County as well. The system transitioned into a tornadic system within an hour with several tornadoes touching down in the central sections of the state. At least 9 communities were hit by tornadoes and 65 homes damaged or destroyed. An 82 year old woman was killed in Stratford when the tornado demolished her home. In a 2 or 3 block area of downtown Woodward, at least 12 houses were totally destroyed. There was one minor injury in Ames, two serious injuries in the Woodward area, and three injuries in Stratford. Due to the extensive damage to property caused by the tornadoes, Iowa Governor Vilsack declared Boone, Story, Webster, Dallas and Hamilton Counties disaster areas. A long-lived tornado tracked through several counties across central Iowa during the late afternoon hours of Nov. 12, 2005. The tornado path is estimated at 27.5 miles long and between 100 and 150 yards wide along the damage path. Tornado (1) initially touched down just west of E Avenue (just south of Boxholm in northwest Boone county), one half mile south of Boone County Highway E18 at approximately 4:27 p.m as an F1 tornado. The tornado then tracked northeast across E Avenue, hitting a farm just north of E18, damaging the home and some out buildings. It also flipped over one pickup truck and killed two horses at this location. The tornado continued northeast, spreading debris across F Avenue just north of 125th Street as it maintained F1 intensity. Two additional homes were damaged with outbuildings destroyed as the tornado tracked northeast across G and H Avenues near 105th Avenue. It then intensified to an F2 tornado as it crossed the Boone/Webster county line. Another home was heavily damaged and a large outbuilding destroyed just north of the Boone/Webster county line. The tornado quickly moved northeast, crossing 390th Street and headed toward the Des Moines River, weakening to an F1 tornado. A continuous, but weak damage path was observed crossing the river as the tornado tracked across open farmland and land adjacent the Des Moines River. The tornado has been rated an F1 tornado during this time. After crossing County D64 in Webster county, the tornado struck another farm near 370th Street and Washington Avenue, damaging the residence and destroying a machine shed along with most of its contents. The tornado again intensified to an F2 at this location. The tornado then headed toward Stratford, crossing the Webster and Hamilton county line just west of County Road D54. The tornado entered Stratford at 4:46 p.m. on the west-central end of town, heavily damaging many homes. The tornado crossed the city park and then exited the city near the north-central portion of Stratford. Numerous homes were heavily damaged with one fatality. As the tornado left Stratford, it continued on a northeast track, lifting and dropping to the ground several times as an F0 and F1 tornado. It damaged three additional farms northeast of Stratford with the last damaged farm north of 320th Street and west of County Road R21 in Hamilton County. Tornado (2) touched down one mile west of Minburn in Dallas County according to the aerial survey. The tornado tracked northeast for about eight miles, producing F0-F1 damage before intensifying near Highway 141. The tornado produced F2 damage at a farm one mile southwest of Woodward, and continued to produce F2 damage through the south and east portions of Woodward. The tornado dissipated one mile northeast of Woodward. Severe houses slid off their foundations in Woodward, and a double-wide home was flipped upside down into the street. Total path length was 11 miles. Tornado (3) touched down in open fields one mile northwest of Madrid. It hit a home three miles north of Madrid on Highway 17, producing F1 damage. One other farm site sustained damage as the tornado moved northeast. The tornado dissipated after a six mile track. Tornado (4) started just west of Ames near the Highway 30 and Lincoln Way Split, according to the aerial survey. The tornado produced F1-F2 damage on the northwest fringe of Ames. It weakened as it moved northeast, before intensifying again and produced F2 damage to a farm site just south of Gilbert. F1 damage occurred as the tornado crossed highway 69. The tornado dissipated three miles south of Story City after a 10 mile track. Tornado (5) was a short-lived satellite tornado that was on the ground for 1.6 miles ending at the southwest edge of Story City. The aerial survey showed very minor damage. Tornado (6) developed one mile west of Roland and tracked across the extreme southeast corner of Hamilton county before entering Hardin county. The tornado produced damage up to F1 intensity to rural farm sites in far northern Story county and five miles south of Radcliffe in Hardin county. The KCCI-TV aerial survey indicated the track was nine miles in length. Tornado (7) was a brief touchdown just south of Williams in Hamilton County. No damage was found from this brief tornado and it is not shown here. Tornado (8) was briefly sighted near Blakesburg in Monroe County. The tornado produced minor damage to a farm building but was not surveyed. Tornado (9) touched down briefly north of Steamboat Rock in Hardin County. The tornado caused little damage. Tornado (10) was actually the first tornado of the day. It formed from the same supercell that eventually moved northeast into the Stratford area. The tornado caused little damage as it moved through fields south of the Scranton Area. Tornado (11) was a brief touchdown on the southwest edge of the Ames City limits. This tornado was from the same parent cell as the previous tornado that touched down in Ames, but was distinct. The tornado was weak and lifted lawn chairs and caused some shingle damage. This tornado was ANTICYCLONIC in nature.
41.01967-06-07242°03'N / 93°37'W1.00 Mile100 Yards0025K0Story
41.21986-09-28441°45'N / 93°36'W41°46'N / 93°21'W6.00 Miles250 Yards002.5M0Polk
41.31976-06-13242°07'N / 93°39'W42°08'N / 93°36'W1.30 Miles200 Yards0025K0Story
41.31971-05-18341°54'N / 92°05'W41°57'N / 92°01'W4.30 Miles300 Yards0025K0Benton
41.72000-05-11342°31'N / 92°27'W42°36'N / 92°07'W18.50 Miles400 Yards1251.8M10KBlack Hawk
 Brief Description: Multi-vortex, regerative tornado F72PH The seasons first tornado outbreak took place during the late afternoon and early evening hours of the 11th. During the day, very strong warm air advection took place. Temperatures warmed rapidly during the day with highs reaching the mid to upper 90s over about the southwest half of the state. Dew point temperatures were in the upper 60s to low 70s. This combination produced CAPE values in excess of 8000 J/kg. During the afternoon, a strong cap was in place with 700 mb temperatures around +16 C. This prevented convection from firing during the afternoon. Toward evening, thunderstorms broke through the cap over northeast Iowa. The storms went from initial echo to tornadic storms in less than 50 minutes. A supercell formed west of the Waterloo area. This cell became a splitting cell and produced a brief tornado in Grundy County as the right moving cell split off, and golf ball size hail in Bremer County from the left moving cell. The cell moved off quickly, however additional supercells back developed over the same area. the strongest tornado developed in the Cedar Falls area and tracked across the northern portions of Waterloo. This cell produced a strong tornado which was actually a multi-vortex tornado based on reports from storm chasers in the area. At one point, west of Dunkerton, three tornadoes each one quarter mile wide were on the ground with this storm. The tornado damaged several houses and a few farmsteads along the way. Reports indicated between 5 and 10 houses in Black Hawk County were totally destroyed, and another 15 to 20 sustained significant damage. A total of at least 41 structures sustained at least some damage. In addition to the tornado, damage also occurred south of the track as RFD winds estimated as high as 100 MPH were observed. Dunkerton was hard hit as the tornado moved through. Heavy damage was reported at a coop elevator in Dunkerton, with 10 of 16 grain elevators damaged. A roof was removed from a church as well, resulting in about $500,000 damage. The City Hall building was destroyed in Dunkerton. The City Hall was housed in a series of double wide trailers since ironically the former City Hall building was destroyed just last year in the floods of '99. As the tornado moved through the fairly densely populated area, numerous injuries were reported. Some of the injuries were severe with limbs being cut off by flying debris. One woman lost both one arm and one hand, and had her back broken. She passed away 17 days after her injuries occurred. Six of the injuries occurred at a nursing home that was hit by the tornado. They occurred as the 139 residents were being evacuated. Reports indicated the width of the tornado was up to three-quarters of a mile at its widest. The damage path from the storm was around one and one half miles wide. The tornado continued moving east and crossed into Buchanan County, about 4 miles northeast of Dunkerton. A short time later, another cell developed in the Dunkerton area and dropped a tornado. That tornado struck a farm northwest of town, destroying the farm house and seven outbuildings. In addition to the damage that occurred to the structures, the family dog and one of the five horses on the farm were killed. Reports indicate a letter from one of the farm houses destroyed was found 60 miles away from Dunkerton in the town of Monona in Clayton County. Polly Mill's rural Dunkerton farmhouse was shredded by the tornado. She lost some of her late husband's military medals, pages out of the family Bible, and part of her collection of letters and first-issue stamps. Sixty miles away, on a farm east of Monona, the letter was found in an envelope carrying a first-day issue, 5-cent stamp commemorating the Battle of New Orleans. There was yet a third round of tornadic storms in the Dunkerton area. The last tornado touched down near Dunkerton and developed southward. Two houses in the town of Dunkerton were destroyed by this tornado. In addition to the tornadoes, very heavy rain fell in a narrow area of Black Hawk County. Reports of 3 inches or more of rain was received from the area. Soil conditions were very dry at the time. The dry soil conditions helped preclude any significant flooding. By the afternoon of the 12th, Iowa Governor Vilsack had declared Black Hawk County a state disaster area.
42.21990-03-13241°44'N / 93°37'W41°56'N / 93°30'W12.00 Miles60 Yards0152.5M0Polk
42.31976-06-13242°25'N / 92°16'W42°36'N / 92°08'W14.00 Miles100 Yards0025K0Black Hawk
42.31989-05-24442°14'N / 93°49'W42°11'N / 93°27'W19.00 Miles150 Yards0025.0M0Hamilton
42.61961-04-23342°04'N / 92°46'W42°15'N / 91°13'W80.30 Miles800 Yards162.5M0Tama
42.61976-06-13542°06'N / 93°42'W42°11'N / 93°36'W7.30 Miles880 Yards000K0Story
42.72008-05-25242°34'N / 92°33'W42°37'N / 92°04'W24.00 Miles2100 Yards02025.0M155KBlack Hawk
 Brief Description: EVENT NARRATIVE: Tornado moved in from Butler County and became very broad as it headed toward Fairbank. Tornado lifted on the Buchanan County border. EPISODE NARRATIVE: A very intense upper low was located over the southwest U.S. and lifted northeast during the weekend of the 24th into the morning of the 26th. The seasons first strong push of deep moisture moved into Iowa on the 25th with surface temperatures warming into the mid 80s and dew points surging into the upper 60s to low 70s. Precipitable water values were near 1.5 inches. The dry slot pushed north across the area the previous night as the warm front lifted north. The primary surface low was located over northern Minnesota. A cold front extended south from the low into northwest Iowa. The airmass became very unstable by the mid afternoon hours. MUCAPE rose to between 4000 and 5000 J/kg. Lifted indices fell to -8 to -11 C. There was a considerable amount of both DCAPE at 1000-1500 J/kg and cape in the -10 to-30 C. layer of the atmoshpere, between 400 and 600 J/kg. The freezing level was around 13,200 feet. The environment was quite sheared with effective shear in the 40 to 50 kt range. LCL values were between 1000 and 1500 meters. The airmass was initially capped. During the late afternoon hours, a small cluster of thunderstorms formed over north central into northeast Iowa. The storms became severe very quickly. Initially, the storms dropped hail up to golf ball in size. One became a strong super cell and produced a major tornado. This cell, in addition to being tornadic, also produced hail of baseball to softball in size and winds in excess of 90 MPH. The tornado track was from approximately 2 miles south of Aplington to Parkersburg, then continued to New Hartford and across northern Black Hawk County. The average path width ranged from 0.6 to 0.7 miles near Parkersburg to just north of New Hartford. The path constricted to near one quarter mile wide east of New Hartford to north of Waterloo. The width then increased to near 1.2 miles wide north of Dunkerton before dissipating near the Black Hawk and Buchanan County line. The tornado was on the ground for approximately 43 miles. In addition to the main tornado, a satellite tornado was observed by storm chasers and one off duty NWS employee. It was located south of the main tornado and was on the ground for a little over a mile in Grundy County. Initial reports indicated 9 fatalities with 7 in Parkersburg (pop 1889) and 2 in New Hartford (pop 637). There were at least 50 injuries, with 4 of those in critical condition. Two of the fatalities occurred a few days after the tornado from injuries sustained in the tornado. The last fatality occurred on 7 Nov. A 61 year old female sustained injuries in the stairwell of her home when a 2 x 4 was thrown through her right side lung. She was hospitalized and died several months later of complications. Significant structural damage occurred across the southern end of Parkersburg and along a path to just north of New Hartford. Numerous structures completely destroyed from Parkersburg to near New Hartford. The tornado continued eastward to just north of the Waterloo and Cedar Falls area. Significant damage also occurred north of Dunkerton where the tornado increased to its greatest path width. This storm also produced substantial straight line wind damage along the southern periphery of the storm just south of the tornado track. News accounts indicated that a receipt from Parkersburg was found around 1915 CST 3 miles north of Prairie du Chien, WI, 109 miles to the northeast. Receipits were also found in Clayton County at Elkader, and full scrapbook pages and photos were found in far northeast Bremer County at Sumner. Preliminary estimates that straight line winds of 90 to 100 MPH occurred with this storm. At 1637 CST, the Waterloo Airport recorded a 93 MPH wind gust. Survey results suggest that straight line wind damage was the cause of the severe damage at the recreational vehicle dealership north of Cedar Falls. At least 627 homes were damaged, including 288 homes destroyed in Parkersburg, 88 in New Hartford, 15 in Hazelton and another 50 in Black Hawk County. In addition, 58 had major damage, 33 had moderate damage, 2 were inaccessible, and 93 damaged but able to be occupied. There were also 21 businesses destroyed. Governor Chet Culver declared both Butler and Black Hawk disaster areas with both given the State Declaration. A Federal Disaster Declaration occurred two days later for both Butler and Black Hawk Counties. The tornado was rated a low end EF5 by a Quick Response Team (QRT) in portions of Parkersburg and north of New Hartford with peak winds estimated at 205 MPH. For historical reference, the last F5 tornado to hit Iowa was on 13 June 1976 in Boone and Story Counties in the town of Jordan, with a 21 mile path length. The last F4 tornado to hit Iowa was in Union, Madison, and Dallas Counties with a 56 mile path length on 8 April 1999. There was one other smaller tornado during the evening. A tornado touched down in Clarke County and was on the ground for a short time southeast of Osceola. After the initial thunderstorm area developed over north central and northeast Iowa, a large complex developed over southeast Nebraska. The two areas of storms filled in to form a squall line by the mid evening hours. The complex over Nebraska then pushed east and northeast along the squall line. A considerable amount of severe weather was generated during the evening as this occurred. Along the squall line, high winds and hail were common with the dominant mode of severe weather being hail of up to golf ball in size. As the MCS out of Nebraska advanced east, a tail extending south from the centroid took on a bow echo configuration and raced east across Iowa at 65 MPH. Very high winds occurred with this feature with numerous locations reporting winds of 65 to 85 MPH. Some of the higher winds included an 85 MPH wind gust in the Winterset area and numerous reports of 75 to 85 MPH winds from Madison, Dallas, Warren and Polk Counties. Lightning struck a house in Ankeny. The house was set on fire by the strike.
42.72007-09-30241°28'N / 92°52'W41°30'N / 92°49'W3.00 Miles1250 Yards00500K250KMahaska
 Brief Description: EVENT NARRATIVE: Tornado moved into Mahaska County from Marion County, then continued northeast into Jasper County. EPISODE NARRATIVE: A very dynamic weather system moved into Iowa during the afternoon of the 30th. The system was more reminiscent of what one would expect in April or May. A close upper level low pressure, negatively tilted, lifted northeast through the central U.S. The structure was very classic in appearance with a well defined comma cloudy, dry slot, and warm conveyor in place. By the early evening, the surface low became stacked with the upper low and was located over eastern Nebraska. A defined dry line extended south-southeast out of the low. Surface temperatures warmed into the mid 70s to mid 80s ahead of the low, with dew points in the mid to upper 60s. Dew points behind the dry line dropped into the upper 30s to mid 40s. The airmass became unstable by the late afternoon with CAPE values around 1000 J/kg and lifted indices in the -2 to -4 C. range. Strong dynamics were in place with a 90 kt mid level jet in place, a low level jet of 60 to 70 kts, and an effective shear of 45 to 55 kts. The freezing level was quite high ahead of the approaching low and was between 13,000 and 14,000 feet. The high freezing level, combined with the limited CAPE of 100 to 200 J/kg in the -10 to -30 C. layer of the atmosphere, limited hail production. The downdraft CAPE was in the 600 to 1000 J/kg range, with an LCL of about 1250 meters. Thunderstorms formed in two locations. The first was along the east edge of the dry slot across Kansas. These storms became severe and lifted northeast quite rapidly into southern and central Iowa. Spotty wind damage was reported and one of the storms dropped one inch diameter hail in Marion County. The storms became tornadic as the moved into central Iowa. During the evening of Sunday 30 September 2007 two tornadoes struck portions of Marion, Jasper, Mahaska, and Poweshiek Counties. The first tornado produced EF0 to EF2 damage along its track and was rated EF2 on the Enhanced Fujita Scale with maximum winds of 125 mph. The track was 22 miles in length from 4 miles northeast of Pella to 1 mile north of Interstate 80, 2 miles west of Malcom. Much of the track was three to five tenths of a mile wide, but as wide as seven tenths of a mile at times. The second, shorter and weaker tornado was 5 miles in length and rated EF1 on the Enhanced Fujita Scale. The track began just south of Highway 6, 2.75 miles northwest of Malcom with a maximum width of 150 yards narrowing to 25-50 yards. The storm hit a farmstead just east of 110th street producing EF1 damage with speeds just under 100 mph. The tornadoes caused extensive damage on a farmstead near Malcom with three barns totally destroyed. The barns were 20 by 30 feet, 20 by 40 feet, and 60 by 100 feet. In addition, numerous other damage reports came in from along the track. Fortunately, there were no deaths or injuries from the tornadoes. Thunderstorms also formed close to the upper low center on the nose of the dry punch. There were several reports funnel clouds, along with spotty reports of high winds and hail. A storm chaser confirmed a tornado touchdown 2 NNW of Lytton in Sac county and was on the ground until 4 W of Jolley in Calhoun county. The tornado was in open country and was a small EF0 tornado. One inch diameter hail fell in Sac County, with numerous reports of pea to marble size hail.
42.81999-04-08241°31'N / 93°20'W41°40'N / 93°15'W11.00 Miles175 Yards011.0M0Jasper
 Brief Description: broken track As mentioned in the narrative above, an intense low pressure formed to the southwest of Iowa. The low tracked northeast and lifted into eastern Nebraska. Ahead of the low, a strong low level jet of around 60 knots continued through the day. A nearly stationary frontal boundary extended east from the low. It lifted into southeast Nebraska during the day, but made little progress into southern Iowa. Lines of thunderstorms formed along the boundary through the day and lifted north rapidly. These storms were elevated in nature and as a result produced most of their severe weather in the form of hail. As the day unfolded, a sharp dry line was clearly evident on the satellite as early as 1600 UTC across Kansas. This line raced east during the day. By afternoon, a speed max had rotated around the upper low to the southwest with wind speeds measured by the Lathrop wind profiler at 100 knots at 500 mb by mid afternoon. Jet stream winds were in excess of 120 knots at the same time. Combined with the dynamic situation mentioned above, considerable moisture convergence took place near the triple point between the warm front and the dry line. Surface dew points pooled into to the mid 60s to even a few 70 degree F. dew point readings over northwest Missouri, southeast Nebraska, and southwest Iowa. Meanwhile, dew points fell into the upper 20s over northeast Kansas and south central Nebraska behind the dry line, with teens over central and south central Kansas. Thunderstorms erupted along the dry line by mid day and advanced east through the afternoon. Low level helicity values topped out between 500 and 600 (m/s)**2 just before the first tornadoes formed. Most of the storms in the warm sector became tornadic quickly. The northern limit of the tornado tracks extended about 10 miles or so north of the warm front. Tracks became intermittent very quickly as soon as the storms crossed the surface warm front due to the layer of very cold air just north of the front. Surface temperatures on the cold side of the front were only in the upper 40s to mid 50s. The entire day was very active. Initially, warm air advection thunderstorms produced hail at many locations of central and northern Iowa. Most of is was just below severe levels however. The activity that developed during the afternoon was a combination of warm air advection and the approach of the dryline. At the beginning of the event, the main weather feature was in the form of hail. There were numerous reports of hail three quarters to one and three quarters inch in diameter. The largest hail fell in Guthrie and Dallas Counties with reports of golf ball size hail. One of the storms in the initial wave of afternoon activity became stronger as it moved into southern Story County. Initially, high winds of 60 MPH or more swept through Sheldahl area of Boone County. Greene County was also affected by high winds from the storms. A tornado dropped out of the storm as it moved into the Slater area and was on the ground for about 2 miles. Initial estimates showed 44 homes and businesses damaged in Story County, one was destroyed with major damage to another. Thirty six homes and four businesses were damaged in the town of Slater. Two people were injured during the passage of the tornado. One of the injuries involved a 70 year old man who was picked up by the tornadoes winds and thrown about 10 feet before he latched on to something. His shoulder was dislocated and he required 6 stitches due to his injuries in his hand. High winds northeast of Slater knocked several cars of a Burlington Northern freight train off the tracks after they were blown more than one quarter mile down the track. It was not possible to determine of the cars were knocked off by the tornado or high winds however. This band of storms continue to race and develop northeast through the afternoon. Damage became more sporadic, however high winds occurred as far northeast as Hardin County, with 70 MPH winds reported near New Providence. Hail reports came in from as far northeast as Grundy and Black Hawk Counties, though it was only three quarters of an inch in diameter. Attention then shifted to the tornadic storms that formed near the dry line. During the afternoon, six more tornadoes touched down in Iowa, several of which were long track tornadoes. The first touched down in Taylor County and tracked through Adams, Cass, and Adair Counties. This tornado had was an F4 intensity tornado in parts of Adair and Adams Counties. Damage was extensive with $1,000,000 damage reported in both Adams and Adair Counties. Entire farmsteads were swept clean by the tornado. At one time this tornado was a mile wide wedge with a damage path nearly two miles wide due to the circulation around the tornado. Eyewitness reports indicated that the tornado split into two distinct tornadoes at times, similar to what occurred with the intense F4 tornado in Adair County of 27 May 1995. One of the farmsteads hit near Nodaway was levelled. Reports indicated that a check was blown from the house nearly 100 miles and was found in the town of Jefferson in Greene County. Other checks and papers were found strewn along the path, stretching from Jefferson all the way back to northwest Taylor County. In Adair County, one account indicated pieces of sheet metal from one farm was lifted and deposited six miles away from the farm. Two people were injured by this tornado, one in Adams County with the other in Adair County. One of the injuries Adair County was serious as a man suffered a broken back when the tornado lifted his semi-tractortrailer truck from the Interstate and threw it into a nearby field. The other injuries from this tornado were minor enough that the people were taken to the hospital, treated, and released. There was one account of a horse being picked up by the tornado. It was lifted into the air and thrown through a stand of pine trees 40 feet high. The horse suffered serious injuries and required significant medical attention do to lacerations. The horse amazingly did survive against all odds, though was said would likely lose sight in one eye. The next tornado touched down in Union County and tracked across Madison and Dallas Counties. This tornado had an F4 strength in Union and decreased to a strong F2 in Madison Counties before intensifying again to near F3 strength as it headed into Dallas County. Damage in Union County was around $2,000,000, and around $350,000 in Madison County. There was one person injured by this tornado in Union County. In an amazing account, the Union County Sheriff reported watching as the tornado lifted the car in front of him 35 feet in the air and throwing it 250 feet. The driver was inside during this time and came out of the situation uninjured. Five coal cars were knocked off the tracks in Union County by the tornado as well. This tornado also had a double structure. From eye witness accounts, which also can be shown on Doppler radar imagery, suggest a small rope like tornado passed through the Twelve Mile Lake area shortly before the passage of the main tornado. The next tornado was a weak tornado which touched down about 4 miles west of downtown Des Moines. The tornado did little damage, but did affect one house and several trees. The tornado was seen by a local television sky camera. A short time later, an F2 tornado touched down in Warren County and tracked into southeast Polk County. The track was over rural areas and damage from it was relatively minor. A more significant F3 tornado tracked from northern Lucas County, and weakened to an F2 as it moved across Warren, part of marion, and into Jasper County. One house was destroyed in Lucas County with the four people inside sustaining minor injuries. Once again, this tornado tracked across mostly rural areas, though it did hit a business and two homes in Jasper County and did $1,000,000 in damage. One person was injured in Jasper County. The last tornado touched down in Davis County at Bloomfield and tracked northeast into Wapello County with a maximum strength of F3. Damage in Davis County was over $500,000 as 64 homes and businesses were damaged in the Bloomfield area. To the northeast, the area of the tornado track was mostly rural and damage was limited to outbuildings for the most part. One farmstead reported severe damage near Floris in Davis County. The house was nearly levelled and several outbuildings were completely destroyed. Parts of the house and outbuildings were found as far as 5 miles away from the farmstead. As the storms moved north, high winds were produced over Story County east of Story City. High winds toppled a tractor semi-trailer truck east of Story City on Interstate 35, injuring the driver. Two cars and a truck were also blown off Interstate 35 in Hamilton County. Four people were injured. Two were taken to the hospital, treated, and released. Two were listed in serious condition, one with a neck fracture, the other with a shoulder fracture. The later incident appeared to be from the rear flank downdraft behind the storm and not the initial gust front. From the preliminary data, 178 homes and business were damaged or destroyed by the tornadic storms as well as countless outbuildings. There were several reports of livestock loss as well. It is truly amazing that there was no loss of life during this event and even more amazing is the fact that the injuries that did occur were all minor. Twenty counties in Iowa experienced serious damage from the storms of the day. Iowa Governor Vilsack declared several counties in Iowa disaster areas. These included Taylor, Union, Adams, and Adair Counties. High winds accompanied the storms as the moved through Appanoose County. A local gas station recorded an 81 MPH wind gust as the storms cut a half mile wide swath of destruction west of Moravia. There were numerous reports of cattle killed by the storms. Some were killed by the tornadoes and flying debris, others by lightning. Reports in Adair County, northwest of Fontanelle indicated about 25 head of cattle were struck by lightning shortly before a tornado moved through that area. As the area of storms that produced the high winds north of Ames in central Iowa moved north, they lost their punch. A few of the storms did remain quite strong however. As the area of thunderstorms moved through Cerro Gordo County, high winds blew down a 60 foot corn crib and did some other damage on a farm near Rockwell.
42.91998-06-27242°40'N / 92°34'W42°42'N / 92°29'W5.00 Miles75 Yards003K1KBremer
 Brief Description: Iowa was located in the warm sector of a developing storm system to the west. The warm front had moved to the northern Iowa border during the afternoon of the 27th with dew point temperatures in the mid 70s to around 80 blanketing the state in the warm sector. Initially, the airmass was capped, preventing thunderstorms from forming during the afternoon. Slightly cooler air moved in during the evening hours. In addition to the slightly cooler air moving in aloft, a cold front was poised over eastern Nebraska ready to move east into the state. Thunderstorms erupted rapidly by early evening with hail and high winds reported over northern Iowa. There were numerous reports of hail of an inch or larger in diameter, with a few reports of golf ball size hail. High winds were also a problem with many of the storms producing 60 to 70 MPH wind gusts. Reports of tree and power line damage were widespread. There were a few tornadoes as well. One tracked across open country in Cerro Gordo County before damaging a house south of Clear Lake. Another tornado touched down near Swaledale in Cerro Gordo County and passed southeast of Mason City. Much of the track was over open country, however one house was destroyed near Swaledale by this tornado. The longest track tornado moved across Butler and Bremer Counties. It also passed through open country, causing damage to crops and out buildings. In addition to these, there were a few brief touchdowns reported. Iowa soil remained very saturated with numerous rivers at or near flood stage. Heavy rainfall of near 4 inches in a couple hours time caused flash flooding in Cerro Gordo County. A widespread area of north central into northeast Iowa received heavy rainfall. Many areas picked up two to four inches of rain in a few hour period. This resulted in urban and small stream flooding, and ultimately general river flooding in the days that followed. As the storms moved through Worth County, lightning struck an outbuilding west of Kensett. The building was set on fire and destroyed.
43.61974-06-22242°18'N / 93°39'W42°19'N / 93°36'W00250K0Hamilton
45.32000-05-11242°34'N / 92°10'W42°30'N / 92°08'W5.00 Miles150 Yards00300K2KBlack Hawk
 Brief Description: Two houses destroyed The seasons first tornado outbreak took place during the late afternoon and early evening hours of the 11th. During the day, very strong warm air advection took place. Temperatures warmed rapidly during the day with highs reaching the mid to upper 90s over about the southwest half of the state. Dew point temperatures were in the upper 60s to low 70s. This combination produced CAPE values in excess of 8000 J/kg. During the afternoon, a strong cap was in place with 700 mb temperatures around +16 C. This prevented convection from firing during the afternoon. Toward evening, thunderstorms broke through the cap over northeast Iowa. The storms went from initial echo to tornadic storms in less than 50 minutes. A supercell formed west of the Waterloo area. This cell became a splitting cell and produced a brief tornado in Grundy County as the right moving cell split off, and golf ball size hail in Bremer County from the left moving cell. The cell moved off quickly, however additional supercells back developed over the same area. the strongest tornado developed in the Cedar Falls area and tracked across the northern portions of Waterloo. This cell produced a strong tornado which was actually a multi-vortex tornado based on reports from storm chasers in the area. At one point, west of Dunkerton, three tornadoes each one quarter mile wide were on the ground with this storm. The tornado damaged several houses and a few farmsteads along the way. Reports indicated between 5 and 10 houses in Black Hawk County were totally destroyed, and another 15 to 20 sustained significant damage. A total of at least 41 structures sustained at least some damage. In addition to the tornado, damage also occurred south of the track as RFD winds estimated as high as 100 MPH were observed. Dunkerton was hard hit as the tornado moved through. Heavy damage was reported at a coop elevator in Dunkerton, with 10 of 16 grain elevators damaged. A roof was removed from a church as well, resulting in about $500,000 damage. The City Hall building was destroyed in Dunkerton. The City Hall was housed in a series of double wide trailers since ironically the former City Hall building was destroyed just last year in the floods of '99. As the tornado moved through the fairly densely populated area, numerous injuries were reported. Some of the injuries were severe with limbs being cut off by flying debris. One woman lost both one arm and one hand, and had her back broken. She passed away 17 days after her injuries occurred. Six of the injuries occurred at a nursing home that was hit by the tornado. They occurred as the 139 residents were being evacuated. Reports indicated the width of the tornado was up to three-quarters of a mile at its widest. The damage path from the storm was around one and one half miles wide. The tornado continued moving east and crossed into Buchanan County, about 4 miles northeast of Dunkerton. A short time later, another cell developed in the Dunkerton area and dropped a tornado. That tornado struck a farm northwest of town, destroying the farm house and seven outbuildings. In addition to the damage that occurred to the structures, the family dog and one of the five horses on the farm were killed. Reports indicate a letter from one of the farm houses destroyed was found 60 miles away from Dunkerton in the town of Monona in Clayton County. Polly Mill's rural Dunkerton farmhouse was shredded by the tornado. She lost some of her late husband's military medals, pages out of the family Bible, and part of her collection of letters and first-issue stamps. Sixty miles away, on a farm east of Monona, the letter was found in an envelope carrying a first-day issue, 5-cent stamp commemorating the Battle of New Orleans. There was yet a third round of tornadic storms in the Dunkerton area. The last tornado touched down near Dunkerton and developed southward. Two houses in the town of Dunkerton were destroyed by this tornado. In addition to the tornadoes, very heavy rain fell in a narrow area of Black Hawk County. Reports of 3 inches or more of rain was received from the area. Soil conditions were very dry at the time. The dry soil conditions helped preclude any significant flooding. By the afternoon of the 12th, Iowa Governor Vilsack had declared Black Hawk County a state disaster area.
45.41952-05-23242°45'N / 92°58'W000K0Butler
45.51974-06-18241°57'N / 93°41'W2.00 Miles200 Yards00250K0Story
45.92000-05-11242°34'N / 92°14'W42°36'N / 92°10'W3.60 Miles120 Yards00350K5KBlack Hawk
 Brief Description: Farm and several outbuildings destroyed The seasons first tornado outbreak took place during the late afternoon and early evening hours of the 11th. During the day, very strong warm air advection took place. Temperatures warmed rapidly during the day with highs reaching the mid to upper 90s over about the southwest half of the state. Dew point temperatures were in the upper 60s to low 70s. This combination produced CAPE values in excess of 8000 J/kg. During the afternoon, a strong cap was in place with 700 mb temperatures around +16 C. This prevented convection from firing during the afternoon. Toward evening, thunderstorms broke through the cap over northeast Iowa. The storms went from initial echo to tornadic storms in less than 50 minutes. A supercell formed west of the Waterloo area. This cell became a splitting cell and produced a brief tornado in Grundy County as the right moving cell split off, and golf ball size hail in Bremer County from the left moving cell. The cell moved off quickly, however additional supercells back developed over the same area. the strongest tornado developed in the Cedar Falls area and tracked across the northern portions of Waterloo. This cell produced a strong tornado which was actually a multi-vortex tornado based on reports from storm chasers in the area. At one point, west of Dunkerton, three tornadoes each one quarter mile wide were on the ground with this storm. The tornado damaged several houses and a few farmsteads along the way. Reports indicated between 5 and 10 houses in Black Hawk County were totally destroyed, and another 15 to 20 sustained significant damage. A total of at least 41 structures sustained at least some damage. In addition to the tornado, damage also occurred south of the track as RFD winds estimated as high as 100 MPH were observed. Dunkerton was hard hit as the tornado moved through. Heavy damage was reported at a coop elevator in Dunkerton, with 10 of 16 grain elevators damaged. A roof was removed from a church as well, resulting in about $500,000 damage. The City Hall building was destroyed in Dunkerton. The City Hall was housed in a series of double wide trailers since ironically the former City Hall building was destroyed just last year in the floods of '99. As the tornado moved through the fairly densely populated area, numerous injuries were reported. Some of the injuries were severe with limbs being cut off by flying debris. One woman lost both one arm and one hand, and had her back broken. She passed away 17 days after her injuries occurred. Six of the injuries occurred at a nursing home that was hit by the tornado. They occurred as the 139 residents were being evacuated. Reports indicated the width of the tornado was up to three-quarters of a mile at its widest. The damage path from the storm was around one and one half miles wide. The tornado continued moving east and crossed into Buchanan County, about 4 miles northeast of Dunkerton. A short time later, another cell developed in the Dunkerton area and dropped a tornado. That tornado struck a farm northwest of town, destroying the farm house and seven outbuildings. In addition to the damage that occurred to the structures, the family dog and one of the five horses on the farm were killed. Reports indicate a letter from one of the farm houses destroyed was found 60 miles away from Dunkerton in the town of Monona in Clayton County. Polly Mill's rural Dunkerton farmhouse was shredded by the tornado. She lost some of her late husband's military medals, pages out of the family Bible, and part of her collection of letters and first-issue stamps. Sixty miles away, on a farm east of Monona, the letter was found in an envelope carrying a first-day issue, 5-cent stamp commemorating the Battle of New Orleans. There was yet a third round of tornadic storms in the Dunkerton area. The last tornado touched down near Dunkerton and developed southward. Two houses in the town of Dunkerton were destroyed by this tornado. In addition to the tornadoes, very heavy rain fell in a narrow area of Black Hawk County. Reports of 3 inches or more of rain was received from the area. Soil conditions were very dry at the time. The dry soil conditions helped preclude any significant flooding. By the afternoon of the 12th, Iowa Governor Vilsack had declared Black Hawk County a state disaster area.
45.91953-06-07241°25'N / 93°55'W41°42'N / 92°45'W63.30 Miles200 Yards000K0Madison
46.01976-06-13342°05'N / 93°44'W42°05'N / 93°42'W0025K0Boone
46.21976-06-12242°32'N / 92°13'W42°38'N / 92°10'W6.90 Miles100 Yards0225K0Black Hawk
46.21964-06-22241°24'N / 92°54'W41°28'N / 92°48'W6.40 Miles200 Yards0025K0Marion
46.41988-05-08241°32'N / 92°24'W41°31'N / 92°19'W4.00 Miles60 Yards002.5M0Poweshiek
46.61966-06-11241°34'N / 93°33'W41°40'N / 93°21'W12.20 Miles150 Yards0025K0Polk
47.22001-09-06242°42'N / 92°34'W42°47'N / 92°25'W10.00 Miles100 Yards00100K10KBremer
 Brief Description: Tornado moved in from Butler County and touched down again, mostly in open field. A car and garage was damaged in Bremer County. A strong upper level low pressure lifted northeast out of the southern Plains during the afternoon of the 6th. During the heating of the afternoon, thunderstorms erupted in the unstable air. The freezing level was around 15,000 feet, so hail was not a great threat. Surface dew point temperatures were in the upper 60s to low 70s with precipitable water values around 1.75 inches. Thunderstorms fired southwest of the Des Moines metropolitan area. A tornado touched down in rural Madison County. The tornado was about 60 feet wide and produced a half mile long path of damage in open country. As the storms moved northeast they continued to intensity. One cell dropped a tornado at the Glen Oaks Golf Course in West Des Moines, causing some minor damage there. The tornado tracked northeast and flipped a semi tractor-trailer truck in Interstate 35 resulting in one injury. It continued northeast and hit an apartment complex causing damage to the building and destroying an 8-car garage. The path was more intermittent as it continued northeast into the city. There were numerous reports of trees and power lines being downed. The tornado lifted as the event transitioned into a high wind event. The storms produced wind damage in Johnston as it moved through the area. High winds of 80 to 85 MPH occurred in northern Polk and southern Story Counties before they weakened. A grain bin was flattened, along with tree and crop damage, as the storm moved through the Elkhart area. Just northwest of that, in Slater, high winds took the roof off of a house in southern Story County. One person in the house was injured. The storms continued to track northeast, eventually dropping another tornado in Butler and Bremer Counties. The tornado had a somewhat intermittent track touching down south of Shell Rock and lifting northeast of Waverly. For the most part the tornado tracked through corn fields there. One farmstead was hit in Butler County. A grain bin was destroyed and blown one quarter of a mile across a field, another was blown off its foundation, a shed was destroyed, and crops were damaged. In Bremer County, one car and a garage were damaged along the tornadoes path. Another farmstead was hit north of Waverly. Part of a machine garage was destroyed and blown about 30 feet off of its foundation.
47.71960-04-16342°28'N / 92°05'W42°30'N / 92°00'W3.80 Miles800 Yards00250K0Buchanan
48.81976-07-28241°31'N / 93°21'W1.20 Miles100 Yards0025K0Polk
49.61956-08-18241°23'N / 92°36'W41°28'N / 92°24'W11.50 Miles33 Yards0025K0Mahaska
50.01961-09-01442°47'N / 93°00'W42°52'N / 92°33'W23.30 Miles27 Yards072.5M0Butler


* The information on this page is based on the global volcano database, the U.S. earthquake database of 1638-1985, and the U.S. Tornado and Weather Extremes database of 1950-2010.


 
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