Flash Flooding and Hail in Iowa, May 29, 2002

Name: Flash Flooding and Hail in Iowa, May 29, 2002
Start: 2002-05-29T15:46
End: 2002-05-29T20:45
Location: Iowa

May 29, 2002 · NWS DMX · 9 events in 6 counties and zones

In a weather pattern similar to the previous day, isolated thunderstorms developed around the state. A light southerly flow was in place with wind speeds at the 850 MB level were around 10 kts.

Where it happened

Every event with a place to put it; 4 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: $405,000
Crop damage: $103,000
Events: 9

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.

What happened

The episode as NWS DMX wrote it up.

In a weather pattern similar to the previous day, isolated thunderstorms developed around the state. A light southerly flow was in place with wind speeds at the 850 MB level were around 10 kts. Surface dew point temperatures were in the mid to upper 60s, with air temperatures in the low to mid 80s. Most of the stronger thunderstorms were the result of outflow boundary interaction. There was little in the way of severe weather actually. One inch diameter hail fell in Jasper County at Colfax. There were a few reports of high winds. The winds were likely microburst winds. Trees were downed in Woodward in northern Dallas County. High winds downed several trees west of Dallas Center as one cell produced a microburst there. Flooding was a significant problem with this situation. Several areas around the state approached flash flood criteria. Thunderstorm clusters dropped 2 to 4 inches of rain in under two hours in a few locations. A strong cluster of thunderstorms formed over Mahaska and Marion Counties. Flash flooding was reported in Mahaska County with trails and roads flooded. Low areas of Highway 92 were under water. In eastern Marion County, residential home damage was reported by the high water. For example, two home owners reported a total of $30,000 damage by the water. Two to 4 feet of water flowed over vehicles causing engine damage. The main railroad tracks through the area were out of commission for 3 days due to washouts. Flash flooding washed out the railroad tracks in 15 places. This damage occurred about 2 1/2 miles east of Knoxville near the town lf Flagler. The damage was quite localized however. Quite a few of the storms produce pea to marble size hail, but very few dropped severe hail. One inch diameter hail was reported with one storm in Jasper County at Colfax, while three quarter inch diameter hail fell south of Tripoli in Bremer County. During the thunderstorms that afternoon, lightning struck a tree at a farm house in rural Buffalo Center. The tree exploded, throwing pieces throughout the yard. Damage occurred to the roof, TV antenna, the vinyl siding on the south side of the house, the air conditioner, and satellite dish. The voltage surge from the lightning strike damaged phones and appliances in the home.

What forecasters said that day

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 May 29, 12:55 PM CST, 2 hours 51 minutes earlier.

Area forecast discussion, May 29, 12:55 PM CST, 2 hours 51 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
155 PM CDT WED MAY 29 2002

WEAK FORCING NEXT 24 HOURS WILL MAKE THE FORECAST OF COVERAGE AND
LOCATION OF TSRA DIFFICULT. AFTER A DRY DAY FRIDAY...MORE ORGANIZED
E/W BOUNDARY AND WNW FLOW ALOFT WILL MAKE FOR ACTIVE THUNDERSTORM
COMPLEXES SAT THRU TUE.

CURRENT ANALYSIS SHOWS WEAK SFC CONVERGENCE AND MDT-STG INSTABILITY
ACROSS MOST OF CENTRAL IOWA...BUT WEAK WINDS AND SHEAR. ACTIVITY NE
OF OTM APPEARS TO BE IN SOMEWHAT DEEPER MOISTURE AXIS.
MEANWHILE...WINDS IN WRN IA ARE BACKING A BIT AND DEWPOINTS POOLING.
EXPECT TSRA TO CONTINUE DEVELOPING THIS AFTERNOON ESPECIALLY FROM NW
INTO CENTRAL IA. MARGINAL PULSE SEVERE HAIL AND WIND THREAT...AND
LOCALLY HEAVY RAINS AS THE STORMS MOVE VERY SLOWLY EWD. ADDITIONAL
STORMS ARE LIKELY TO DEVELOP ALONG WHAT TURNS OUT TO BE A WARM FRONT
OVER THE ERN DAKS. THIS TROF WILL DROP INTO NRN IA TONIGHT AND THRU
STATE THU...BRINGING ANOTHER ROUND OF SCATTERED TSRA...ESPECIALLY
NRN HALF TONIGHT. LOW-LEVEL FLOW BECOMES NWLY THU AND SUBSIDENCE
BECOMES DRIVING FACTOR...BUT ENOUGH LOW-LEVEL MOISTURE AND
INSTABILITY SHOULD BE IN PLACE TO CONTINUE CHC THUNDERSTORMS TOWARD
OTM INTO EARLY AFTERNOON. COOL AIR FINALLY COMES IN BEHIND THIS
SYSTEM THU NIGHT.

FRIDAY LOOKS DRY AS WARM ADVECTION RETURNS TO WRN PLAINS...SETTING
UP E/W STATIONARY FRONT THAT EXTENDS INTO IA BY SAT. THUNDERSTORMS
WILL BE FAIRLY LIKELY ALONG AND NORTH OF THE BOUNDARY AS HEAT AND
INSTABILITY BUILD TO THE SOUTH. LLJ SHOULD PROVIDE PLENTY OF INFLOW
FOR NOCTURNAL MCS DEVELOPMENT AND BY SUNDAY AND MONDAY...DAYTIME
DEVELOPMENT IS ALSO POSSIBLE.  OBVIOUSLY LOCATION OF BOUNDARY WILL
MAKE BIG DIFFERENCE IN TEMPS AND POPS. LAST NIGHTS MRF WAS QUITE
FAR NORTH COMPARED TO 12Z AVN AND OTHER ENSEMBLE MEMBERS...SO WILL
STICK WITH CONSERVATIVE MORE SOUTHERN LOCATION FOR FRONT.  OUTFLOW
FROM STORMS WILL TEND TO HOLD BOUNDARY SOUTH AS WELL.

.DSM...NONE

JUNGBLUTH

The radar

The Des Moines radar (KDMX), 40 km away, was scanning. The volume nearest the first event began at 21:47 UTC.

Open the radar archive at this moment

Event by event

3 thunderstorm wind, 3 flash flood, 2 hail, 1 lightning. Local standard time, as filed.

Hail, Jasper

When: May 29, 3:46 PM CST
Where: Jasper County, Colfax
Measured: 1 in hail
Property damage: $5,000
Crop damage: $5,000
Reported by: BROADCAST MEDIA
Coordinates: 41.667, -93.250

Lightning, Winnebago

When: May 29, 3:50 PM CST
Where: Winnebago County, Buffalo Center
Property damage: $15,000
Reported by: NEWSPAPER
Coordinates: 43.378, -93.734 (the zone’s center; the record gives no point)

Thunderstorm Wind, Dallas

When: May 29, 4:00 PM CST
Where: Dallas County, 1 mi W of Granger
Measured: 61 kt (70 mph)
Property damage: $25,000
Reported by: AMATEUR RADIO
Coordinates: 41.767, -93.850

Flash Flood, Mahaska

When: May 29, 4:00 PM CST to 5:40 PM CST
Where: Mahaska County, Countywide
Property damage: $100,000
Crop damage: $25,000
Reported by: LAW ENFORCEMENT
Coordinates: 41.335, -92.641 (the zone’s center; the record gives no point)

Flash Flood, Marion

When: May 29, 4:00 PM CST to 5:40 PM CST
Where: Marion County, East Portion
Property damage: $100,000
Crop damage: $20,000
Reported by: EMERGENCY MANAGER
Coordinates: 41.334, -93.099 (the zone’s center; the record gives no point)

Thunderstorm Wind, Dallas

When: May 29, 4:07 PM CST
Where: Dallas County, Woodward
Measured: 52 kt (60 mph)
Property damage: $5,000
Reported by: EMERGENCY MANAGER
Coordinates: 41.850, -93.933

Thunderstorm Wind, Dallas

When: May 29, 4:55 PM CST
Where: Dallas County, 5 mi N of Dallas Center
Measured: 52 kt (60 mph)
Property damage: $5,000
Reported by: AMATEUR RADIO
Coordinates: 41.750, -93.967

Flash Flood, Dallas

When: May 29, 5:35 PM CST to 8:45 PM CST
Where: Dallas County, Countywide
Property damage: $150,000
Crop damage: $50,000
Reported by: EMERGENCY MANAGER
Coordinates: 41.685, -94.040 (the zone’s center; the record gives no point)

Hail, Bremer

When: May 29, 5:50 PM CST
Where: Bremer County, 3 mi S of Tripoli
Measured: 0.75 in hail
Crop damage: $3,000
Reported by: LAW ENFORCEMENT
Coordinates: 42.750, -92.250

What these are

Hail: Hail three-quarters of an inch or larger, or smaller hail that caused damage, filed with the largest stone measured.
Lightning: A lightning strike that killed, injured or caused damage.
Thunderstorm Wind: Winds from a thunderstorm of 50 knots (58 mph) or more, or lower winds that caused damage or casualties. Measured gusts are marked MG, estimated EG.
Flash Flood: Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Iowa in 2002 Every state in 2002 This day in weather history Warnings in Iowa, May 2002

Sources

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: 5292674, 5292682, 5292677, 5292678, 5292679, 5292675, 5292676, 5292680, 5292681.