Grinnell, IA Natural Disasters and Weather Extremes
Hot Rankings
The chance of earthquake damage in Grinnell is about the same as Iowa average and is much lower than the national average. The risk of tornado damage in Grinnell is higher than Iowa average and is much higher than the national average.
Earthquake Index, #492
| Grinnell, 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
| Grinnell, 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, #266
| Grinnell, IA | 258.01 |
| 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 4,397 other weather extremes events within 50 miles of Grinnell, IA were recorded from 1950 to 2010. The following is a break down of these events:
| Type | Count | Type | Count | Type | Count | Type | Count | Type | Count |
| Avalanche: | 0 | Blizzard: | 33 | Cold: | 49 | Dense Fog: | 13 | Drought: | 16 |
| Dust Storm: | 0 | Flood: | 609 | Hail: | 1,320 | Heat: | 18 | Heavy Snow: | 73 |
| High Surf: | 0 | Hurricane: | 0 | Ice Storm: | 45 | Landslide: | 0 | Strong Wind: | 86 |
| Thunderstorm Winds: | 1,693 | Tropical Storm: | 0 | Wildfire: | 0 | Winter Storm: | 103 | Winter Weather: | 57 |
| Other: | 282 | ||||||||
Volcanos Nearby
No volcano is found in or near Grinnell, IA.
Historical Earthquake Events
No historical earthquake events that had recorded magnitudes of 3.5 or above found in or near Grinnell, IA.
No historical earthquake events found in or near Grinnell, IA.
Historical Tornado Events
A total of 93 historical tornado events that had recorded magnitude of 2 or above found in or near Grinnell, IA.
| Distance (miles) | Date | Magnitude | Start Lat/Log | End Lat/Log | Length | Width | Fatalities | Injuries | Property Damage | Crop Damage | Affected County |
| 4.4 | 1978-09-16 | 3 | 41°42'N / 92°46'W | 41°39'N / 92°42'W | 4.10 Miles | 200 Yards | 4 | 43 | 2.5M | 0 | Poweshiek |
| 7.2 | 1969-06-11 | 2 | 41°50'N / 92°47'W | 1.00 Mile | 100 Yards | 0 | 0 | 25K | 0 | Marshall | |
| 7.7 | 2007-09-30 | 2 | 41°34'N / 92°45'W | 41°42'N / 92°36'W | 12.00 Miles | 1250 Yards | 0 | 0 | 2.5M | 1.0M | Poweshiek |
| 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. | |||||||||||
| 7.7 | 1969-06-29 | 2 | 41°48'N / 92°36'W | 1.00 Mile | 250 Yards | 0 | 0 | 25K | 0 | Poweshiek | |
| 8.3 | 1966-04-19 | 3 | 41°51'N / 92°43'W | 41°52'N / 92°42'W | 0 | 0 | 250K | 0 | Poweshiek | ||
| 8.7 | 1978-09-16 | 3 | 41°52'N / 93°00'W | 41°42'N / 92°46'W | 16.40 Miles | 200 Yards | 2 | 2 | 250K | 0 | Jasper |
| 9.4 | 1962-05-28 | 2 | 41°52'N / 92°47'W | 0 | 5 | 250K | 0 | Marshall | |||
| 9.4 | 1969-06-06 | 2 | 41°52'N / 92°47'W | 0 | 0 | 25K | 0 | Marshall | |||
| 12.4 | 1956-08-12 | 3 | 41°32'N / 92°45'W | 41°35'N / 92°40'W | 5.10 Miles | 200 Yards | 0 | 8 | 25K | 0 | Poweshiek |
| 14.5 | 2007-09-30 | 2 | 41°30'N / 92°49'W | 41°34'N / 92°45'W | 6.00 Miles | 1250 Yards | 0 | 0 | 1.0M | 500K | Jasper |
| 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. | |||||||||||
| 14.6 | 1978-06-26 | 2 | 41°35'N / 92°32'W | 0.70 Mile | 100 Yards | 0 | 1 | 2.5M | 0 | Poweshiek | |
| 16.0 | 1973-06-04 | 2 | 41°42'N / 93°03'W | 41°44'N / 93°01'W | 1.30 Miles | 250 Yards | 0 | 0 | 250K | 0 | Jasper |
| 17.3 | 1953-05-10 | 2 | 41°53'N / 92°27'W | 0 | 0 | 25K | 0 | Tama | |||
| 17.4 | 1953-03-21 | 2 | 41°53'N / 92°37'W | 42°03'N / 92°33'W | 11.70 Miles | 100 Yards | 0 | 0 | 25K | 0 | Tama |
| 18.6 | 2007-09-30 | 2 | 41°28'N / 92°52'W | 41°30'N / 92°49'W | 3.00 Miles | 1250 Yards | 0 | 0 | 500K | 250K | Mahaska |
| 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. | |||||||||||
| 18.9 | 1966-04-19 | 3 | 41°52'N / 92°42'W | 42°02'N / 92°17'W | 24.10 Miles | 400 Yards | 0 | 4 | 250K | 0 | Tama |
| 19.2 | 1968-04-03 | 2 | 41°34'N / 93°05'W | 41°37'N / 93°00'W | 5.20 Miles | 150 Yards | 0 | 0 | 25K | 0 | Jasper |
| 22.0 | 1964-06-22 | 2 | 41°24'N / 92°54'W | 41°28'N / 92°48'W | 6.40 Miles | 200 Yards | 0 | 0 | 25K | 0 | Marion |
| 22.4 | 1961-04-23 | 3 | 42°02'N / 92°55'W | 42°04'N / 92°46'W | 7.40 Miles | 800 Yards | 0 | 6 | 2.5M | 0 | Marshall |
| 22.5 | 1978-09-16 | 3 | 41°58'N / 93°11'W | 41°52'N / 93°00'W | 11.30 Miles | 200 Yards | 0 | 0 | 0K | 0 | Marshall |
| 22.7 | 1965-06-27 | 2 | 42°03'N / 92°35'W | 0 | 0 | 3K | 0 | Tama | |||
| 22.8 | 1986-09-28 | 4 | 41°46'N / 93°20'W | 41°46'N / 93°00'W | 14.00 Miles | 250 Yards | 0 | 0 | 2.5M | 0 | Jasper |
| 23.7 | 1991-04-27 | 2 | 41°42'N / 92°18'W | 41°44'N / 92°14'W | 4.50 Miles | 50 Yards | 0 | 0 | 250K | 0 | Iowa |
| 24.0 | 1988-05-08 | 2 | 41°32'N / 92°24'W | 41°31'N / 92°19'W | 4.00 Miles | 60 Yards | 0 | 0 | 2.5M | 0 | Poweshiek |
| 24.0 | 1981-04-10 | 2 | 41°53'N / 93°10'W | 41°57'N / 93°05'W | 5.60 Miles | 500 Yards | 0 | 9 | 2.5M | 0 | Marshall |
| 24.5 | 1956-08-18 | 2 | 41°23'N / 92°36'W | 41°28'N / 92°24'W | 11.50 Miles | 33 Yards | 0 | 0 | 25K | 0 | Mahaska |
| 24.7 | 1953-06-07 | 2 | 41°42'N / 92°45'W | 41°52'N / 91°45'W | 52.70 Miles | 200 Yards | 0 | 0 | 0K | 0 | Poweshiek |
| 24.7 | 1951-06-01 | 3 | 42°04'N / 92°55'W | 1.50 Miles | 880 Yards | 0 | 7 | 0K | 0 | Marshall | |
| 25.8 | 1953-06-27 | 2 | 41°24'N / 92°36'W | 41°20'N / 92°44'W | 7.80 Miles | 100 Yards | 0 | 1 | 3K | 0 | Mahaska |
| 26.7 | 1965-08-26 | 2 | 41°52'N / 93°15'W | 41°49'N / 93°12'W | 3.00 Miles | 100 Yards | 0 | 0 | 25K | 0 | Jasper |
| 27.9 | 1974-08-12 | 4 | 41°45'N / 92°11'W | 2.00 Miles | 100 Yards | 0 | 2 | 250K | 0 | Iowa | |
| 28.1 | 1965-05-25 | 2 | 41°20'N / 92°40'W | 2.00 Miles | 300 Yards | 0 | 0 | 3K | 0 | Mahaska | |
| 28.4 | 1956-04-26 | 2 | 42°00'N / 92°20'W | 42°00'N / 92°16'W | 2.30 Miles | 440 Yards | 0 | 0 | 3K | 0 | Tama |
| 30.0 | 1965-08-26 | 2 | 41°54'N / 93°18'W | 41°52'N / 93°15'W | 1.90 Miles | 100 Yards | 0 | 2 | 25K | 0 | Story |
| 30.0 | 1959-05-09 | 2 | 42°06'N / 92°24'W | 0 | 0 | 25K | 0 | Tama | |||
| 30.9 | 1999-04-08 | 2 | 41°31'N / 93°20'W | 41°40'N / 93°15'W | 11.00 Miles | 175 Yards | 0 | 1 | 1.0M | 0 | Jasper |
| 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. | |||||||||||
| 31.4 | 1989-05-24 | 4 | 42°11'N / 92°45'W | 42°12'N / 92°37'W | 8.00 Miles | 150 Yards | 0 | 0 | 25.0M | 0 | Tama |
| 31.6 | 1962-05-07 | 2 | 41°54'N / 93°18'W | 0 | 0 | 250K | 0 | Story | |||
| 31.9 | 2001-05-10 | 2 | 42°13'N / 92°45'W | 42°11'N / 92°42'W | 4.00 Miles | 750 Yards | 0 | 0 | 35K | 0 | Tama |
| 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. | |||||||||||
| 32.1 | 1984-06-07 | 4 | 41°10'N / 92°40'W | 41°25'N / 92°26'W | 14.00 Miles | 250 Yards | 1 | 30 | 25.0M | 0 | Mahaska |
| 32.2 | 1989-05-24 | 4 | 42°12'N / 93°00'W | 42°11'N / 92°45'W | 13.50 Miles | 150 Yards | 0 | 0 | 25.0M | 0 | Marshall |
| 32.6 | 1966-04-19 | 3 | 42°02'N / 92°17'W | 42°05'N / 92°14'W | 3.00 Miles | 400 Yards | 0 | 0 | 250K | 0 | Benton |
| 33.3 | 1984-06-07 | 4 | 41°25'N / 92°26'W | 41°31'N / 91°57'W | 29.00 Miles | 250 Yards | 1 | 33 | 25.0M | 0 | Keokuk |
| 33.8 | 1953-06-07 | 2 | 41°25'N / 93°55'W | 41°42'N / 92°45'W | 63.30 Miles | 200 Yards | 0 | 0 | 0K | 0 | Madison |
| 33.9 | 1958-07-14 | 2 | 42°12'N / 92°30'W | 0 | 0 | 25K | 0 | Tama | |||
| 35.1 | 1988-05-08 | 2 | 41°31'N / 92°19'W | 41°42'N / 91°49'W | 28.00 Miles | 60 Yards | 0 | 0 | 2.5M | 0 | Iowa |
| 35.7 | 1976-07-28 | 2 | 41°31'N / 93°21'W | 1.20 Miles | 100 Yards | 0 | 0 | 25K | 0 | Polk | |
| 36.0 | 2001-05-10 | 2 | 42°15'N / 92°55'W | 42°14'N / 92°54'W | 1.70 Miles | 200 Yards | 0 | 0 | 150K | 0 | Grundy |
| 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. | |||||||||||
| 36.1 | 2001-05-10 | 2 | 42°17'N / 92°49'W | 42°14'N / 92°46'W | 4.00 Miles | 875 Yards | 0 | 0 | 35K | 0 | Grundy |
| 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. | |||||||||||
| 36.5 | 1966-10-14 | 3 | 41°32'N / 93°06'W | 41°07'N / 93°14'W | 29.50 Miles | 200 Yards | 0 | 0 | 25K | 0 | Jasper |
| 37.0 | 1971-05-18 | 3 | 41°54'N / 92°05'W | 41°57'N / 92°01'W | 4.30 Miles | 300 Yards | 0 | 0 | 25K | 0 | Benton |
| 37.5 | 2008-05-30 | 2 | 41°13'N / 93°07'W | 41°15'N / 92°52'W | 12.00 Miles | 900 Yards | 0 | 10 | 750K | 25K | Marion |
| Brief Description: EVENT NARRATIVE: Several homes were damaged or destroyed, two mobile homes were destroyed. Considerable tree damage was reported. The EF2 damage occurred in the Attica area, along with 10 injuries. The tornado moved out of Marion County into Mahaska County. EPISODE NARRATIVE: A very unstable airmass moved into Iowa during the day on the 29th as a warm front lifted north into the state during the afternoon. Low pressure approached from the west, along with a cold front so that the triple point was near the western Iowa, eastern Nebraska area by late afternoon. Thunderstorms erupted quickly during the late afternoon and evening hours in the unstable airmass. By evening, the low level jet was in the 40 to 60 kt range, feeding moisture into the state and pushing precipitable water values to around 200% of normal, in the 1.5 to 1.8 inch range. MUCAPE reached 3000 to 3500 J/kg over western Iowa, with lifted indices in the -6 to -10 C. range. The freezing level was quite high, limiting the hail size somewhat with this event, at 14,300 feet. The available CAPE in the -10 to -30 C. layer of the atmosphere was in the 300 to 500 J/kg range. The DCAPE was between 800 and 1000 J/kg. The environment was highly sheared with 50 to 65 kts of shear available during the event. The LCL was also quite low, in the 750 to 1250 meter range. Thunderstorms erupted over western Iowa stretching into north central Iowa first. It did not take long for the storms to become severe with hail and high winds. Most of the hail reported was in the pea to marble size, with the larger stones in the nickel to quarter size range. The primary mode of severe weather was high winds and several tornadoes. The secondary, but significant threat, was heavy rainfall. A band of 3 to 5 inches of rain fell between U.S. Highway 30 and U.S. Highway 20 during the event. The heaviest rainfall total was in Greene County at Jefferson, with 5.90 inches. Tornadoes began to touch down in western Iowa in Crawford County with two brief touchdowns. One was west of Dow City, causing roof and shingle damage to a farmhouse there. The next was east of Denison where a barn roof was removed and a trailer house was destroyed. A tornado in Carroll County caused damage to 3 farmsteads southeast of Templeton. A machine shed was completely destroyed and numerous other buildings sustained damage. Trees also had substantial damage. Two tornadoes touched down in Calhoun County. One near Farnhamville, tore the roof off of a home and downed power lines. The second caused damage to trees, outbuildings, and power lines on four farmsteads. Farther south, a brief touchdown was reported in Dallas County in open fields west of Minburn. Another tornado touched down in Dallas County later on, west of Adel, and was on the ground for about 4 miles. A more substantial tornado touched down near Murray in Clarke County with one reported on the ground for about 9 miles. As the storms moved east, another tornado was on the ground for over 10 miles in Warren and Marion Counties. The most significant tornado occurred in Marion and Mahaska Counties where an EF2 tornado was on the ground for about 18 miles. Several homes were damaged along its path, two mobile homes were destroyed, and considerable damage was done to trees in the area. Up to 10 people were injured with this tornado, mainly in Attica. The official damage count from this tornado included 5 homes destroyed, 15 with major damage, and another 25 with minor damage. Many of the storms produced high winds with several reports of winds in the 65 to 75 MPH range. Considerable tree damage was reported and some structural damage, mainly outbuildings and shingle damage. Two cars were blown off of the road east of Manning by the high winds. Building debris was blown onto Highway D60 near Gowrie, causing a brief closure. High winds in Butler County blew down a machine shed and barn southwest of Aplington, very near to where an EF5 tornado struck just days before. Extensive damage was done to a farmstead there with some damage done to the house itself as well. Lightning struck a man in Carroll. The lightning bolt hit his driveway, blowing out a chunk of concrete out of the driveway and also injured the man. He was taken to hospital, treated, and released with minor injuries. Flooding became a significant issue after the heavy rainfall of the previous few days. Extensive river flooding occurred across the central third of the state. Record crests were recorded on the Iowa River at Marshalltown. | |||||||||||
| 37.6 | 1989-05-30 | 4 | 42°14'N / 92°59'W | 42°16'N / 92°58'W | 2.00 Miles | 200 Yards | 0 | 0 | 2.5M | 0 | Grundy |
| 38.0 | 1989-05-24 | 4 | 42°13'N / 93°13'W | 42°12'N / 93°00'W | 12.50 Miles | 150 Yards | 0 | 0 | 25.0M | 0 | Hardin |
| 38.0 | 1971-05-31 | 3 | 42°06'N / 92°18'W | 42°12'N / 92°10'W | 9.40 Miles | 600 Yards | 0 | 0 | 250K | 0 | Tama |
| 38.3 | 1966-06-11 | 2 | 41°34'N / 93°33'W | 41°40'N / 93°21'W | 12.20 Miles | 150 Yards | 0 | 0 | 25K | 0 | Polk |
| 38.7 | 1986-09-28 | 4 | 41°45'N / 93°36'W | 41°46'N / 93°21'W | 6.00 Miles | 250 Yards | 0 | 0 | 2.5M | 0 | Polk |
| 39.0 | 1965-09-20 | 3 | 41°20'N / 92°12'W | 1.00 Mile | 100 Yards | 0 | 4 | 250K | 0 | Keokuk | |
| 39.0 | 1991-03-22 | 2 | 42°16'N / 93°00'W | 42°16'N / 92°59'W | 1.00 Mile | 50 Yards | 0 | 0 | 250K | 0 | Hardin |
| 39.1 | 1990-03-13 | 2 | 41°56'N / 93°30'W | 41°53'N / 93°24'W | 3.00 Miles | 60 Yards | 0 | 0 | 2.5M | 0 | Story |
| 39.3 | 1990-03-13 | 3 | 42°01'N / 93°23'W | 42°08'N / 93°18'W | 9.00 Miles | 100 Yards | 0 | 1 | 250K | 0 | Story |
| 39.5 | 1972-06-05 | 2 | 41°13'N / 93°00'W | 41°11'N / 92°58'W | 1.90 Miles | 200 Yards | 0 | 0 | 25K | 0 | Marion |
| 40.2 | 1989-05-30 | 4 | 42°17'N / 93°10'W | 42°14'N / 92°59'W | 9.00 Miles | 200 Yards | 0 | 3 | 2.5M | 0 | Hardin |
| 40.5 | 1979-03-29 | 2 | 41°26'N / 93°30'W | 41°31'N / 93°21'W | 9.30 Miles | 60 Yards | 0 | 0 | 250K | 0 | Warren |
| 40.5 | 1988-05-08 | 2 | 41°26'N / 92°10'W | 41°28'N / 91°55'W | 12.00 Miles | 60 Yards | 0 | 0 | 250K | 0 | Keokuk |
| 40.5 | 1959-05-31 | 2 | 42°03'N / 93°26'W | 42°13'N / 93°11'W | 17.00 Miles | 440 Yards | 0 | 0 | 250K | 0 | Story |
| 40.5 | 1962-05-28 | 2 | 41°10'N / 93°12'W | 41°18'N / 93°03'W | 11.70 Miles | 200 Yards | 0 | 0 | 250K | 0 | Marion |
| 42.3 | 1967-06-08 | 2 | 42°00'N / 93°36'W | 42°02'N / 93°19'W | 14.40 Miles | 100 Yards | 0 | 0 | 250K | 0 | Story |
| 43.0 | 1983-05-06 | 2 | 41°35'N / 93°32'W | 1.00 Mile | 60 Yards | 0 | 0 | 2.5M | 0 | Polk | |
| 43.1 | 1960-04-16 | 3 | 42°20'N / 92°35'W | 42°22'N / 92°32'W | 2.30 Miles | 800 Yards | 0 | 0 | 250K | 0 | Grundy |
| 43.4 | 1990-03-13 | 2 | 41°44'N / 93°37'W | 41°56'N / 93°30'W | 12.00 Miles | 60 Yards | 0 | 15 | 2.5M | 0 | Polk |
| 44.5 | 1984-06-07 | 4 | 41°31'N / 91°57'W | 41°35'N / 91°51'W | 7.00 Miles | 250 Yards | 0 | 0 | 25.0M | 0 | Iowa |
| 44.5 | 1973-04-21 | 2 | 41°35'N / 91°55'W | 41°40'N / 91°50'W | 6.60 Miles | 33 Yards | 0 | 6 | 0K | 0 | Iowa |
| 44.5 | 1974-06-18 | 4 | 41°44'N / 93°37'W | 41°31'N / 93°32'W | 15.30 Miles | 400 Yards | 2 | 50 | 25.0M | 0 | Polk |
| 44.6 | 1989-05-24 | 4 | 42°11'N / 93°27'W | 42°13'N / 93°13'W | 13.00 Miles | 150 Yards | 0 | 0 | 25.0M | 0 | Story |
| 44.7 | 1991-03-22 | 2 | 42°16'N / 92°59'W | 42°29'N / 92°47'W | 19.00 Miles | 50 Yards | 0 | 0 | 250K | 0 | Grundy |
| 45.1 | 1950-06-15 | 3 | 41°59'N / 93°36'W | 41°58'N / 93°29'W | 5.60 Miles | 300 Yards | 0 | 5 | 0K | 0 | Story |
| 45.8 | 1991-03-22 | 3 | 41°54'N / 93°38'W | 42°14'N / 93°22'W | 27.00 Miles | 70 Yards | 0 | 0 | 2.5M | 0 | Story |
| 46.1 | 1999-04-08 | 2 | 41°09'N / 93°31'W | 41°31'N / 93°21'W | 22.50 Miles | 150 Yards | 0 | 0 | 70K | 0 | Warren |
| Brief Description: intermittent 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. | |||||||||||
| 46.1 | 1959-05-10 | 2 | 41°36'N / 93°36'W | 0.30 Mile | 50 Yards | 0 | 0 | 3K | 0 | Polk | |
| 46.5 | 1984-06-07 | 2 | 41°28'N / 92°00'W | 41°28'N / 91°48'W | 10.00 Miles | 200 Yards | 0 | 1 | 2.5M | 0 | Keokuk |
| 47.2 | 1965-07-18 | 2 | 42°18'N / 92°12'W | 0.50 Mile | 50 Yards | 0 | 0 | 0K | 0 | Black Hawk | |
| 47.5 | 1965-08-26 | 4 | 42°18'N / 92°12'W | 42°18'N / 92°11'W | 0 | 0 | 2.5M | 0 | Black Hawk | ||
| 47.5 | 1961-04-23 | 3 | 42°04'N / 92°46'W | 42°15'N / 91°13'W | 80.30 Miles | 800 Yards | 1 | 6 | 2.5M | 0 | Tama |
| 47.6 | 1975-06-18 | 2 | 41°22'N / 93°30'W | 0 | 0 | 3K | 0 | Warren | |||
| 47.6 | 1965-08-26 | 4 | 42°18'N / 92°11'W | 42°15'N / 92°06'W | 4.70 Miles | 200 Yards | 1 | 17 | 2.5M | 0 | Benton |
| 47.7 | 1966-10-14 | 2 | 42°23'N / 92°56'W | 42°26'N / 92°58'W | 2.70 Miles | 100 Yards | 0 | 0 | 3K | 0 | Grundy |
| 47.8 | 1971-05-31 | 2 | 42°24'N / 92°27'W | 1.00 Mile | 200 Yards | 0 | 0 | 25K | 0 | Black Hawk | |
| 48.4 | 1991-03-22 | 3 | 42°14'N / 93°22'W | 42°24'N / 93°09'W | 16.00 Miles | 70 Yards | 0 | 0 | 2.5M | 0 | Hardin |
| 48.7 | 1988-05-08 | 2 | 41°28'N / 91°55'W | 41°31'N / 91°46'W | 11.00 Miles | 60 Yards | 0 | 0 | 2.5M | 0 | Washington |
| 49.4 | 1988-11-15 | 2 | 41°04'N / 92°20'W | 41°08'N / 92°15'W | 6.00 Miles | 63 Yards | 0 | 0 | 250K | 0 | Wapello |
| 49.9 | 1960-06-16 | 2 | 41°23'N / 93°34'W | 2.00 Miles | 150 Yards | 0 | 0 | 25K | 0 | Warren | |
| 49.9 | 1971-05-18 | 3 | 42°00'N / 91°52'W | 42°03'N / 91°48'W | 4.30 Miles | 200 Yards | 0 | 0 | 250K | 0 | Benton |
* 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.