A cold front advanced into Iowa in advance of a strong upper air low pressure that was over central South Dakota. Instability was marginal with CAPE values in the 1000 J/kg range and lifted indices in the -2 to -4 C.
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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 cold front advanced into Iowa in advance of a strong upper air low pressure that was over central South Dakota. Instability was marginal with CAPE values in the 1000 J/kg range and lifted indices in the -2 to -4 C. range. A weak shear environment was in place with 20 kts or less of shear in the 0-6 km layer. Much of the CAPE that was available was in the lowest levels of the atmosphere. Thunderstorms erupted along the initial surface boundary during peak heating. With LCL in the 600-1000 meter range, combined with the amount of low level CAPE, the thunderstorms produced numerous funnel clouds. There were three reported touchdowns. They were actually more of a landspout that a full fledged tornado. Little damage occurred as they touched down briefly in open farm files. The thunderstorms also produced some localized very heavy rainfall. Satellite pictures shows evidence of a strong tropical connection to Hurricane John in the east Pacific. Local rainfall of 3 to 4.5 inches in about an hour was reported on the west side of the Des Moines metropolitan area. There were several reports of 1 to 3 inch rainfall along the Interstate 35 corridor. Some local street flooding was reported through this area.
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 Sep 2, 1:30 AM CST, 12 hours 16 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 230 AM CDT SAT SEP 2 2006 .DISCUSSION... MAIN FOCUS IN SHORT TERM WILL UPPER TIMING OF UPPER LOW TRACKING ACROSS THE AREA FOR THE WEEKEND AND EARLY NEXT WEEK. SECONDARY FOCUS WILL BE TEMPERATURES WITH PLENTY OF CLOUDS AND RAIN. TODAY MODELS HAVE COME TOGETHER AND IN FAIR AGREEMENT CONCERNING SOLUTION FOR UPPER LOW AND RESULTING PCPN. SOME DIFFERENCES IN THE DETAILS AS USUAL HOWEVER MANY DETAILS/TRENDS POINTING TO THE SAME SOLUTION. APPEARS MODELS INITIALIZED WELL ON LOCATION OF UPPER LOW AND SURFACE FEATURES. TIMING AND COVERAGE OF RAIN HANDLED WELL. LEFT THUNDER IN THE FORECAST AS DYNAMICAL FIELDS SUGGEST ISOLATED STORMS POSSIBLE. CAPE AND LIS ALONG WITH SOUNDINGS SUGGEST ATMOSPHERE HAS ENOUGH INSTABILITY AND WITH ALITTLE DAYTIME HEATING SHOULD TRIGGER SOME THUNDERSTORMS THIS WEEKEND. SYSTEM DOES PROGRESS EVER SO SLOWLY ACROSS THE AREA PUSHING POPS TO CATEGORICAL FOR SEVERAL PERIODS OF THE FORECAST AS PATTERN REMAINS UNFAVORABLE FOR A QUICK MOVEMENT OF SYSTEMS TO THE EAST. TEMPERATURES WILL BE THE TRICKY PART AS THIS TIME OF YEAR A DAY WITHOUT SUNSHINE AND RAINING WILL LIKELY PRODUCE A SMALL DIURNAL RANGE. HAVE LEANED INTO LOWER MAV GUIDANCE ESPECIALLY ON HIGHS HOWEVER WITH ALL THE CLOUDINESS AND RAIN HAVE MIXED IN NAM TEMPERATURE GUIDANCE IN DEALING WITH OVERNIGHT LOWS. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && FORSTER
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DES MOINES IA 503 AM CDT SAT SEP 2 2006 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>086-092>097-031100- 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- 503 AM CDT SAT SEP 2 2006 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA. .DAY ONE...TODAY AND TONIGHT BY THIS AFTERNOON ISOLATED THUNDERSTORMS ARE EXPECTED TO DEVELOP AND CONTINUE INTO THE EVENING HOURS. SOME OF THESE STORMS COULD PRODUCE HAIL THREE QUARTERS OF AN INCH OR SMALLER. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY SHOWERS AND ISOLATED THUNDERSTORMS ARE LIKELY SUNDAY...SUNDAY NIGHT THEN AGAIN TUESDAY. A FEW OF THESE STORMS COULD PRODUCE HAIL THREE QUARTERS OF AN INCH OR SMALLER. .SPOTTER INFORMATION STATEMENT... SPOTTERS WILL LIKELY NOT BE NEEDED AS MOST OF THE STORMS WILL BE ISOLATED AND HAIL OF MARGINAL SIZE.
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DES MOINES IA 219 PM CDT SAT SEP 2 2006 IAZ005>007-016-017-024>027-035>038-047>049-059>061-072>074- 082>084-093>095-022230- KOSSUTH-WINNEBAGO-WORTH-HANCOCK-CERRO GORDO-HUMBOLDT-WRIGHT- FRANKLIN-BUTLER-WEBSTER-HAMILTON-HARDIN-GRUNDY-BOONE-STORY- MARSHALL-DALLAS-POLK-JASPER-MADISON-WARREN-MARION-UNION-CLARKE- LUCAS-RINGGOLD-DECATUR-WAYNE- INCLUDING THE CITIES OF...ALGONA...FOREST CITY...NORTHWOOD... GARNER...MASON CITY...HUMBOLDT...CLARION...HAMPTON...ALLISON... FORT DODGE...WEBSTER CITY...ELDORA...GRUNDY CENTER...BOONE... AMES...MARSHALLTOWN...ADEL...DES MOINES...NEWTON...WINTERSET... INDIANOLA...KNOXVILLE...CRESTON...OSCEOLA...CHARITON... MOUNT AYR...LEON...CORYDON 219 PM CDT SAT SEP 2 2006 ...CONDITIONS FAVORABLE FOR FUNNEL CLOUDS THIS AFTERNOON... CURRENT ATMOSPHERIC CONDITIONS SUPPORT THE DEVELOPMENT OF FUNNEL CLOUDS. USUALLY...THESE FUNNEL CLOUDS CAN FORM FROM SHOWERS AND WEAK THUNDERSTORMS. THESE FUNNELS ARE NORMALLY BRIEF...DROP ONLY A FEW HUNDRED FEET FROM THE CLOUD BASE...AND RARELY BECOME A TORNADO OR CAUSE DAMAGE. HOWEVER...IF ONE IS SPOTTED...PLEASE REPORT IT IMMEDIATELY TO LOCAL LAW ENFORCEMENT FOR RELAY TO THE NATIONAL WEATHER SERVICE. IF A TORNADO WARNING WOULD BECOME NECESSARY...TAKE APPROPRIATE ACTION. DONAVON
The Des Moines radar (KDMX), 111 km away, was scanning. The volume nearest the first event began at 19:46 UTC.
3 tornado. Local standard time, as filed.
Brief tornado touchdown in open fields.
Brief tornado touchdown in open fields.
Brief tornado touchdown in open fields.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2006Every state in 2006This day in weather historyThe tornado archive for Iowa, 2006Warnings in Iowa, September 2006
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: 5534777, 5534779, 5534778.