A very warm, moist, and unstable airmass was in place over Iowa from 8th into the 9th. Surface temperatures on the 8th warmed into the upper 80s and 90s, with dew point readings in the 70s.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS DMX wrote it up.
A very warm, moist, and unstable airmass was in place over Iowa from 8th into the 9th. Surface temperatures on the 8th warmed into the upper 80s and 90s, with dew point readings in the 70s. A weak cold front moved into the state during the evening of the 8th and early morning of the 9th. There was little thunderstorm development initially as the airmass was capped. Temperatures at the 700 mb level were +14 to +17 C. During the early morning hours of the 9th, a short wave lifted northeast out of the southern Rockies. This resulted in cooling of the mid levels of the atmosphere, thus destabilizing the airmass. The cold front stall out during the morning of the 9th as a second short wave lifted northast. Eventually, the front moved south of the state on the night of the 9th. Overall lifted indices were in the -6 to -10 C range with CAPE values in the 3000 to 4000 J/kg range. Downdraft CAPE was in the 800 to 1400 J/kg range with 30 to 50 kts of shear available. CAOE available in the -10 to -30 C layer of the atmosphere was between 300 and 700 J/kg, with a freezing level of 14,000 to 14,500 feet. The LCL was relatively high across the area ranging from just below 1000 meters to about 1250 meters. Plenty of moisture was available with precipitable water values between 1.75 and 2.25 inches. Thunderstorms developed initially over Nebraska and tracked east-northeast into Iowa shortly after sunrise. One supercell continued to track across the state and produced a swath of wind and hail damage from Sac County east to Black Hawk County. Additional thunderstorms formed along the cold frontal boundary by mid morning and progressed into the state. The storms remained below severe levels for several hours, but did become severe by mid afternoon. A broken like of storms formed with two primary areas tracking east across central and southern Iowa. These two areas featured mini bow echoes. The predominant mode of severe weather in the afternoon was high winds. Several of the storms produced hail, but the hail was sub-severe. A long lived supercell Thunderstorm tracked across northern Iowa Sunday morning with the Highway 20 corridor receiving the brunt of the damage. Reports of quarter to golf ball sized hail were common with some hail stones reported to be in excess of two inches approaching the size of a tennis ball. The hail was wind blown as well, at speeds of 50 to 70 mph, making it extremely damaging and dangerous striping siding off houses and knocking out windows. A measured wind speed of 68 mph was recorded at a KCCI TV SchoolNet site near Jewell in Hamilton County. Significant hail damage was received all along the track with areas near Otho, Callender, Radcliffe, Eldora and Grundy Center hit particularly hard. In Eldora, many homes had windows broken out and tree and power line damage left the city without power. Winds of over 100 MPH toppled a communication tower in Eldora. A short time before the winds hit Eldora, a 102 MPH wind gust was recorded at the landfill northwest of town. Wind driven hail of 2 to 3 inches in diameter broke all siding and windows out on the north and west walls of most homes, with hail stones reported landing inside of houses. Damage in the town of Eldora was expected to be greater than the damage done in the town of Parkersburg by the EF5 tornado a year earlier. A 150 square mile area of crops was affected in Hardin County. Total losses were reported on 45,000 acres, with 60% or greater loss on another 55,000 acres. Hail damage in the Otho to Callender areas was described as the worst seen in 20 years. MODIS satellite pictures of the crop damage area included in this report. Estimates of crop damage from this one supercell were over $175,000,000. Governor Culver declared Hardin County a state disaster area within a day or two of the storm, and declared Webster County a disaster area about a week later. Formal paperwork was turned in to make 8 Iowa counties federal disaster areas, They were Calhoun, Grundy, Hamilton, Hardin, Ida, Sac, Webster, and Woodbury. Following the storms, a shelter was set up for those who felt they should not stay in their homes. Luckily the evening round of storms tracked south. Campers at nearby Pine Lake State Park, gathered for an archery event, were bruised by hail. There were 22 reports of injuries in Hardin County, 11 serious enough for people to be taken to hospital, but there are no known life threatening injuries. A second round of severe weather rolled roughly along I-80 between 1630 and 1800 CST, producing a lot of tree and power line damage but apparently little structural damage. As the storms moved through the metropolitan Des Moines area, winds damaged power lines and knocked out power to 12,000 homes. One storm produced a wet microburst in Union County. The winds took the roof and shingles off of a two story brick building near Afton. The afternoon round of storms produced some hail, but most of the hail was not severe as mentioned above, and was pea size or smaller. During the morning round of storms, lightning struck a building in Waverly. The lightning struck an antenna on the building and melted screws all the way down the side of the building, starting a small fire and blowing hole in the wall.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Des Moines, IA wrote its last area forecast discussion before the first event at Aug 9, 5:20 AM CST, 1 hour 45 minutes earlier.
AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE DES MOINES IA 620 AM CDT SUN AUG 9 2009 ...UPDATED 12Z AVIATION DISCUSSION... .SHORT TERM...TODAY COLD FRONT CURRENTLY SETTLING SOUTH THROUGH NORTH CENTRAL AND NORTHWEST IOWA. THE BOUNDARY WILL STALL OVER CENTRAL IOWA THIS MORNING AND EVENTUALLY WILL BECOME THE FOCUS FOR THUNDERSTORM DEVELOPMENT TODAY. LATEST WATER VAPOR IMAGERY SHOWING TWO PLUMES OF MOISTURE CONVERGING ON THE CENTRAL PLAINS AND MIDWEST WITH A TROPICAL CONNECTION FEEDING RIGHT INTO IOWA FROM THE SOUTHWEST AND GULF MOISTURE LIFTING NORTHWARD AS WELL. TIMING FOR CONVECTIVE INITIATION IS PROBLEMATIC TODAY. THE LATEST NAM AND 4 KM WRF RUNS ALONG WITH LOCAL WRF RUNS SUGGEST INITIATION WITH FIRST ROUND THIS MORNING OVER KS AND SOUTHEAST NEBRASKA THEN A NORTHEAST STORM MOVEMENT INTO CNTRL IA...PARALLEL TO THE STALLED BOUNDARY. THIS SCENARIO DOES SEEM PLAUSIBLE WITH NEW WAVE OF MOISTURE TRANSPORT NOW LIFTING NORTHEAST THROUGH CNTRL KS AND WILL BE PRIMED TO LIFT OVER THE BOUNDARY. MID LEVEL LAPSE RATES ALSO FAVORABLE AT AROUND 7.5 C/KM. WOULD EXPECT AT LEAST A FEW ELEVATED STORMS TO DEVELOP THIS MORNING ABOVE THE CAPPED LAYER...THEN CHANCES INCREASING DURING THE AFTERNOON. HOURS. POTENTIAL FOR HEAVY RAINFALL COULD BECOME REALITY BY LATE THIS AFTERNOON WITH STORM MOTIONS PARALLEL TO THE STALLED BOUNDARY AND PWATS EXCEEDING 2 INCHES FLOW INTO THE REGION. ANYTHING THAT DOES DEVELOP BY THIS AFTERNOON WILL BE EFFICIENT RAIN PRODUCERS. THE SEVERE POTENTIAL MAY BE CONDITIONAL BASED ON HOW MUCH CLOUD COVER DEVELOPS BEFORE PEAK HEATING. IF GOOD INSTABILITY IS OBTAINED...THEN SEVERE STORMS WILL BE POSSIBLE WITH POTENTIAL FOR LARGE HAIL EARLY EVENTUALLY EVOLVING INTO BOWING SEGMENTS LATE IN THE PERIOD AND BEYOND WITH GOOD POTENTIAL FOR COLD POOL DEVELOPMENT. .LONG TERM...TONIGHT THROUGH SATURDAY SOME DISCREPANCIES OVER FRONTAL PLACEMENT INTO THE BEGINNING OF THE PERIOD TONIGHT...WITH THE NAM SLIGHTLY FURTHER NORTH THAN THE GFS BUT ALL MODELS IN GENERAL AGREEMENT THAT FRONTAL BOUNDARY WILL BE DRAPED ACROSS THE CWA PROVIDING FOCUS FOR SCATTERED THUNDERSTORM DEVELOPMENT TONIGHT. STORMS MAY BE ONGOING ALREADY BY THIS EVENING...BUT MID LEVEL SHORTWAVE CURRENTLY OVER WY/CO TO MOVE ACROSS THE AREA TONIGHT. MUCAPE VALUES LARGEST LATE THIS AFTERNOON INTO THE EVENING HOURS...WITH ATMOSPHERE BEGINNING TO STABILIZE AS THE FRONT MOVES SOUTHEAST THROUGH THE CWA BY LATE TONIGHT. MOISTURE TRANSPORT INCREASING THROUGH THE EVENING HOURS...AND ORIENTED INTO CENTRAL/NE IOWA. PWATS CLIMB TO AROUND 2 BY TONIGHT. MID LEVEL FLOW PARALLEL TO THE FRONTAL BOUNDARY...SO COULD END UP SEEING SOME TRAINING OF ECHOES ALONG THE FRONT...AND POTENTIAL FOR LOCALIZED HEAVY RAINS. INCREASED POPS INTO THE LIKELY CATEGORY ACROSS CENTRAL IOWA THIS EVENING...AND TRANSLATED THAT TO THE SOUTHEASTERN CWA BY LATE TONIGHT AS THE FRONTAL BOUNDARY PROGRESSES THROUGH THE CWA. UNIDIRECTIONAL SHEAR PROFILE...WITH DECENT SPEED SHEAR WILL ALLOW THE THREAT OF SEVERE WEATHER TO CONTINUE FOR THE TONIGHT PERIOD...WITH HAIL AND HIGH WINDS THE MAIN SEVERE THREATS. FRONTAL BOUNDARY STALLS OUT ACROSS THE SOUTHERN CWA MONDAY INTO MONDAY NIGHT...WITH ANOTHER SHORTWAVE DROPPING SOUTHEASTWARD THROUGH THE CWA. LOOKS LIKE MAJORITY OF THE PRECIP WILL BE TO THE SOUTH OF THE CWA. OTHERWISE COOLER AIR TO MOVE IN BEHIND THE SYSTEM FOR MID TO LATE WEEK WITH H85 TEMPS HOVERING IN THE MID TEENS. THEREFORE EXPECT A SLIGHT COOLING TREND AS TEMPERATURES EXPECTED TO BE NEAR THE SEASONAL AVERAGES THROUGH THE END OF THE WEEK. AS UPPER RIDGE BUILDS IN TO THE AREA...DRY CONDITIONS WILL PERSIST TUESDAY THROUGH THE END OF THE WEEK. UPPER RIDGE LOOKS TO BREAK DOWN TOWARD THE END OF THE WEEK INTO NEXT WEEKEND...SO COULD SEE THE CHANCE FOR PRECIPITATION RETURN TO THE FORECAST JUST BEYOND THE CURRENT FORECAST PERIOD. && .AVIATION...09/12Z COLD FRONT WILL BE STALLED OVER CENTRAL IOWA MUCH OF TODAY AND INTO THIS EVENING. THE BOUNDARY WILL BE THE FOCUS FOR THUNDERSTORM DEVELOPMENT DURING THE PERIOD WITH KFOD/KALO/KDSM UNDER A PROLONGED THREAT AS THUNDERSTORMS REPEATEDLY ROLL THROUGH THE CENTRAL PORTION OF THE STATE. THE BOUNDARY WILL BEGIN TO SHIFT SOUTHEAST LATE IN THE PERIOD HOWEVER WILL HAVE NOT SHIFTED FAR YET BY 12Z. IFR STRATUS TO LOCAL LIFR CONDITIONS WILL BE IN PLACE NORTH OF THE BOUNDARY EARLY TODAY BUT SHOULD EVENTUALLY ERODE AWAY LATER THIS MORNING. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...DONAVON AVIATION...DONAVON LONG TERM...ALBRECHT
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DES MOINES IA 519 AM CDT SUN AUG 9 2009 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086- 092>097-101030- EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO- POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-SAC-CALHOUN- WEBSTER-HAMILTON-HARDIN-GRUNDY-BLACK HAWK-CRAWFORD-CARROLL-GREENE- BOONE-STORY-MARSHALL-TAMA-AUDUBON-GUTHRIE-DALLAS-POLK-JASPER- POWESHIEK-CASS-ADAIR-MADISON-WARREN-MARION-MAHASKA-ADAMS-UNION- CLARKE-LUCAS-MONROE-WAPELLO-TAYLOR-RINGGOLD-DECATUR-WAYNE-APPANOOSE- DAVIS- 519 AM CDT SUN AUG 9 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA. .DAY ONE...TODAY AND TONIGHT THUNDERSTORM CHANCES WILL INCREASE ACROSS THE AREA THROUGHOUT THE DAY...WITH THUNDERSTORMS EXPECTED TO INCREASE IN COVERAGE AND INTENSITY TOWARD THIS AFTERNOON AND EVENING. SOME OF THESE STORMS MAY BE SEVERE WITH LARGE HAIL...GOLF BALL SIZE OR GREATER...DAMAGING WINDS...AND LOCALLY HEAVY RAINS THE PRIMARY THREATS. AN ISOLATED TORNADO IS POSSIBLE AS WELL. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY A FEW THUNDERSTORMS WILL STILL BE POSSIBLE ACROSS THE SOUTHERN CWA MONDAY INTO MONDAY NIGHT...WITH A SLIGHT RISK OF SEVERE WEATHER. LARGE HAIL AND DAMAGING WINDS WILL BE THE PRIMARY SEVERE THREATS. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED TODAY INTO TONIGHT. MJA
The Omaha radar (KOAX), 138 km away, was scanning. The volume nearest the first event began at 13:06 UTC.
56 thunderstorm wind, 27 hail, 1 lightning. Local standard time, as filed.
Wind driven hail.
Quarter size hail driven by 60 MPH winds. Crops 50 to 100% damaged with hail on the ground 4 hours after it fell.
Wind driven hail with crops completly destroyed.
Hail broke out 2 windows of a house.
Three inch diameter branches broken.
A trained spotter reports extensive tree, window, roof, and crop damage fro high winds and large hail around somers.
Large trees blown down.
A modular home list part of a roof and west side of the house due to high winds.
Extensive tree, window, roof, and crop damage from high winds and inch diameter. Large hail remained on the ground in the Callender area for a few hours.
Trees were downed on a roof. Damage caused by combination of silver dollar size hail and high winds.
Hail of at least golf ball size resulted in broken windows.
Spotter reports larger than golf ball size hail. It fell at Nelson Ave and Woodmans Hollow Road north of Coalville. Small branches were also blown down by high winds.
Windows broken in houses.
Windshield broken by hail.
Extensive crop damage. Several houses with broken windows from the hail on the west sides of them. Crop damage swath a mile to mile and one half wide.
Tree branches up to a foot in diameter broken.
A wind gust of 102 MPH was recorded at the Landfill northwest of Eldora.
Many Residences in town have broken windows. The Red Cross set up a shelter and treated several injuries. A communications tower was toppled by the high wind.
Large hail brok windows out of a residence and caused considerable crop damage.
Four foot diameter tree blown down and some power lines.
Large trees blown down.
One inch hail reported in Pine Lake State Park.
Windows broken by hail.
Grain bins and metal outbuildings were destroyed by high wind.
Winds of up to 65 MPH took out the power in Grundy Center.
Two to three inch diameter branches blow down. Nickel size hail.
Shingle debris flying in the wind along with golf ball size hail.
Pea to quarter size hail.
One inch diameter hail in Washburn.
Windows broken by hain and high wind.
High winds and heavy rain.
Spotters reported the top of a chimney was blown off of a house. Small tree limbs down as well.
Tree limbs blown down by high winds.
Tree limbs up to 12 inches in diameter down.
Minor tree limb damage.
Winds of 60 to 70 MPH with pea size hail.
Some tree branch damage.
Tree branches down.
Winds of up to 65 MPH reported at Western Hills Drive between E. P. True and Ashworth Road.
A 12 inch wide Maple tree was blown down, snapped off just above the ground.
Minor tree limb damage.
Large tree limbs down.
Large tree down.
Straight line winds of 70 to 80 MPH with pea size hail.
Spotter reported pea size hail and winds of up to 65 MPH.
Eight to 10 inch diameter branches down. Some damage to door and roof of house.
Winds blow 12 inch limbs from a tree. Large branches blocked NE 5th and Grant in Ankeny.
Multiple 3-4 inch tree limbs down between Ankeny BLVD and Delaware Rd. A power pole was snapped off near Bel Aire Road.
Eight inch diameter branches blown down.
Pea size hail with high winds.
High winds and pea hail.
High winds and small hail reported.
Six to eight inch diameter tree limb down.
Numerous trees were downed 4 miles west and 4 miles southwest of Bedford.
Tree limbs and power lines were blown down in Bedford.
Two 18 inch diameter trees and one 30 inch diameter tree was blown down. Rainfall of 1.25 inches in an hour.
Tree branches down.
Trees were blown down and power was out.
Numerous trees were blown down west and southwest of Bedford.
A two-story brick building with wooden roof and shingles was damaged. Roof and shingles were blown off. A 4 foot diameter tree was uprooted in the city park and 3 air handling units were blown off of the East Union High School in Afton. Tin was blown off the feed mill.
On Highway 92 near Snyder Ave.
High winds and small hail reported.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2009Every state in 2009This day in weather historyWarnings in Iowa, August 2009
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 180094, 180092, 178732, 178734, 180093, 178735, 178738, 178736, 178668, 178737, 178674, 178672, 178740, 178673, 178675, 178599, 178671, 178755, 178729, 178746, 178743, 178744, 178615, 178745, 178701, 178677, 186731, 178603, 178607, 178602, 178696, 178702, 178747, 178749, 185408, 185409, 178617, 178698, 178619, 178748, and more.