)A cold front tracked into eastern Iowa during the afternoon hours. The boundary collided with a very moist and unstable airmass to produce a line of strong to severe thunderstorms.
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 DVN wrote it up.
Event Summary for 8/09/01: (For additional details, see individual entries for the date.)A cold front tracked into eastern Iowa during the afternoon hours. The boundary collided with a very moist and unstable airmass to produce a line of strong to severe thunderstorms. Straight-line thunderstorm winds estimated as high as 70 mph downed trees, and damaged buildings and grain bins over parts of Scott, Des Moines, Henry, and Lee counties.
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 Quad Cities, IA wrote its last area forecast discussion before the first event at Aug 9, 1:33 PM CST, 3 hours 27 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE QUAD CITIES IA IL 233 PM CDT THU AUG 9 2001 FORECAST CHALLENGES CENTER ON POPS THIS EVENING...THEN TEMPERATURES THROUGHOUT. STRONG MID LEVEL SHORTWAVE SEEN WATER VAPOR IMAGERY MOVING ACROSS ONTARIO AT MIDDAY HAS FLATTENED RIDGE OVER FORECAST AREA. RELATED COLD FRONT AT SURFACE EXTENDED FROM CENTRAL LAKE SUPERIOR SW TO A LINE FROM NEAR DBQ TO DSM AT 18Z. SO FAR ONLY NORTHERN END OF FRONT ACTIVE ACROSS NORTHEAST WI AND NORTHERN LAKE MICHIGAN WHERE THUNDERSTORMS ALONG FRONT ENHANCED BY STRONG UPPER DIVERGENCE ASSOCIATED WITH ENTRANCE REGION TO 100 KT H3 JET. SOME MID LEVEL TCU AND FEW SHRA SEEN ON KDVN 88D PART OF CU FIELD WELL AHEAD OF FRONT FROM NE MO TO SE WI...OTHERWISE 88DS AND VISIBLE SATELLITE IMAGERY SHOWS ONLY SC ALONG FRONT WITH FEW SHOWERS WELL NW INTO COOLER AIR. BIGGEST MODEL DIFFERENCE IN SHORT TERM IS ETA CONTINUING TO INDICATE DRY FROPA UNTIL THIS EVENING WHERE QPF INTRODUCED TO E AND SE. NGM AGAIN OVERDONE WITH WIDESPREAD RAIN ALONG FRONT TO NORTH AND AHEAD OF FRONT IN NE MO. AVN CLOSER TO MIDDLE OF ROAD AND CONSISTANT WITH PREVIOUS CYCLES WITH FRONTAL AND POST-FRONTAL QPF DEVELOPING THIS AFTERNOON AND EVENING AND GENERALLY FOLLOWED. 18Z RUC INDICATES SHOWERS SHOULD DEVELOP ANY MOMENT NOW ALONG FRONT AND MOVE EAST THROUGH EARLY EVENING. VERY UNSTABLE BUT CAPPED AIRMASS IS OVER CWA WITH DEWPOINTS IN MID 70S AND TEMPERATURES IN 90S TO FUEL STORMS... BUT DECENT UPPER FORCING STAYS WELL TO NORTH AND WEAK AND NEARLY UNIDIRECTIONAL SHEAR INDICATED BY AREA WIND PROFILES STRIKE AGAINST ORGANIZED CONVECTION. WILL WAIT UNTIL LAST MINUTE TO DETERMINE WHAT POPS WILL BE NEEDED IN EVENING PERIOD. LEANING TOWARD GRADIENT FROM ABOUT 20 PERCENT NW TO 30-40 PERCENT IN E-SE ZONES WITH FRONT EXPECTED TO EXTEND FROM ABOUT KRFD TO KAWG LINE BY 23Z...AND EXIT IL ZONES BY 03Z. POST FRONTAL SHOWERS IN NW IA APPEAR TO BE DIURNALLY DRIVEN...SO DO NOT EXPECT MUCH AFTER FROPA THIS EVENING. BEYOND... ONLY MINOR DIFFERENCES THROUGH DAY 2 AND AVN/ETA FOLLOWED. HIGH PRESSURE SETTLES SE FROM NORTHERN PLAINS TO UPPER MISS VALLEY BY FRIDAY EVENING. SIGNIFICANT DROP IN DEWPOINTS...TO 40S AND 50S...LAGS FRONT BY A COUPLE HUNDRED MILES AND WILL NOT REACH FORECAST AREA UNTIL FRIDAY. EVEN THEN...EXPECT SOME MODERATION OF AIRMASS. WILL STAY CLOSE TO SLIGHTLY WARMER MAV GUIDANCE FOR LOWS TONIGHT WITH 60 TO 65 RANGE. H85 TEMPERATURES DROP OVER 10 C FROM CURRENT VALUES AND SUPPORT HIGHS NEAR 80 FOR FRIDAY. FRIDAY NIGHT WILL BE COOLEST THROUGH FORECAST WITH H85 THERMAL TROUGH AND SURFACE HIGH JUST TO NORTH TO ALLOW WIDESPREAD 50S. KEPT DRY FORECAST THROUGH WEEKEND WITH AREA UNDER SURFACE HIGH PRESSURE AND ZONAL TO NW FLOW ALOFT. AVN INDICATES ANOTHER MID LEVEL TROUGH AND WEAK FRONT MAY BRING FEW SHOWERS LATE SUNDAY NIGHT AND MONDAY...BUT ENOUGH CERTAINTY TO LEAVE DRY FOR NOW. EXTENDED KEEPS UPPER RIDGE TO WEST WITH ANOTHER TROUGH TO BRING NEXT CHANCE RAIN WED AND THURSDAY. LITTLE CHANGE NEEDED TO EXTENDED...WITH TEMPERATURES NEAR SEASONAL NORMS FOR A CHANGE. .DVN... IA...NONE. IL...NONE. MO...NONE. SHEETS
The Quad Cities radar (KDVN), 25 km away, was scanning. The volume nearest the first event began at 23:00 UTC.
5 thunderstorm wind. Local standard time, as filed.
An estimated 60 mph thunderstorm wind gust downed four-inch branches. Reported by off-duty NWS employee.
Thunderstorm winds estimated at 70 mph pulled the windows out of several buildings, twisted the legs of a grain bin, downed and split several trees, and uprooted a tree and carried it across town. Reported by fire and rescue officials.
Thunderstorm winds blew the siding off a building. Reported by law enforcement.
Thunderstorm winds downed trees. Reported by trained spotter.
Thunderstorm winds damaged grain bins. Reported by trained spotter.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2001Every state in 2001This day in weather historyWarnings in Iowa, August 2001
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: 5265916, 5265917, 5265918, 5265919, 5265920.