Damaging Winds in Iowa, August 12, 2002

Name: Damaging Winds in Iowa, August 12, 2002
Start: 2002-08-12T20:25
End: 2002-08-12T22:12
Location: Iowa

August 12, 2002 · NWS DMX · 3 events in 3 counties and zones

A cold front moved into Iowa slowly from the northwest. The airmass in front of the cold front was quite unstable with temperatures in the low to mid 80s and dew point temperatures around 70.

Where it happened

Every event with a place to put it. 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: $30,000
Crop damage: $20,000
Events: 3

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.

A cold front moved into Iowa slowly from the northwest. The airmass in front of the cold front was quite unstable with temperatures in the low to mid 80s and dew point temperatures around 70. Thunderstorms erupted during the late afternoon and evening hours as the front moved into the state and strong forcing in the way of jet stream dynamics moved into the state. An unseasonably strong upper level trough of low pressure was approaching from the west. Most of the thunderstorms remained below severe levels with winds in the 40 to 50 MPH range. A storm became severe as it organized over Taylor County. Some damage occurred west of Lenox with 60 to 70 MPH reported. Severe thunderstorms were also reported in Adams County, with 60 MPH winds in the Corning area. As the night progressed, the thunderstorms formed into a line extending northeast to southwest across the state. During the late evening hours one of the storms produced winds around 65 MPH in the Waterloo area. Several trees were downed and there was power line damage around the city.

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 Aug 12, 1:00 PM CST, 7 hours 25 minutes earlier.

Area forecast discussion, Aug 12, 1:00 PM CST, 7 hours 25 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
200 PM CDT MON AUG 12 2002

AFD COMPOSED EARLY.  THERE MAY BE LAST MINUTE CHANGES TO FORECAST
THINKING.

CDFNT FM SRN MN SW INTO EARN NE AT 18Z.  SE SFC WINDS OVER WRN IA
INCREASED EARLY THIS AFTERNOON AND VSBY SATELLITE PICS SHOWING
MID/HI CLOUDS THINNING ATTM.  TEMPS RECOVERED INTO THE LOWER 80S
EARLY THIS AFTERNOON.  THINKING ATTM IS THAT AMS SHUD DESTABILIZE
ENOUGH TO SUPPORT TSTMS WHICH SHOULD INCREASE IN COVERAGE OVER WRN
IA AND THEN SPREAD ACRS FA THIS EVENING.  SE SFC FLOW AHEAD OF FRONT
INTO FRONTAL BOUNDARY AIDING IN AREA OF STRONG MOISTURE FLUX CNVG
NEAR BOUNDARY.  THIS SHOULD BE THE MOST LIKELY AREA OF DEVELOPMENT
THIS AFTERNOON. WILL GO WITH HI POPS TONIGHT.

CDFNT SE OF IA BY 12Z TUESDAY. AVN PRINTS SOME PCPN OVER SRN FA
TUESDAY DUE TO S/WV ROTATING THROUGH THE TROF CREATING SOME PCPN
NORTH OF THE BOUNDARY.  ETA LESS AGGRESSIVE WITH THIS FEATURE.  WILL
KEEP CURRENT FCST OF MORNING POPS SRN FA FOR NOW DUE TO THIS.

DRY WX REST OF SHORT TERM FORECAST AND LESS HUMID.  NEW GUIDANCE IN
LINE WITH CURRENT TEMP GRIDS AND ONLY MADE MINOR ADJUSTMENTS.

12Z AVN DIFFERENT THAN 00Z MRF WITH RESPECT TO FROPA FRIDAY NIGHT.
12Z AVN DRIVES FRONT THROUGH FA FRIDAY NIGHT WHILE OLD MRF KEEPS
BOUNDARY N.  IN EITHER CASE...EXPECT BOUNDARY NEAR IA THIS WEEKEND
GIVEN WSW FLOW ALOFT AND IA NEAR SRN EDGE OF WESTERLIES.  WILL TIME
PCPN BASED ON 12Z AVN AND KEEP CHANCES IN DAY 6 AND 7 BASED ON
ABOVE.  NEAR OR SLIGHTLY BLO NORMAL TEMPS.

.DSM...NONE

JOHNSON

The radar

The Des Moines radar (KDMX), 121 km away, was scanning. The volume nearest the first event began at 02:25 UTC.

Open the radar archive at this moment

Event by event

3 thunderstorm wind. Local standard time, as filed.

Thunderstorm Wind, Taylor

When: August 12, 8:25 PM CST
Where: Taylor County, 4 mi W of Lenox
Measured: 56 kt (64 mph)
Property damage: $5,000
Crop damage: $10,000
Reported by: TRAINED SPOTTER
Coordinates: 40.883, -94.633

Thunderstorm Wind, Adams

When: August 12, 8:30 PM CST
Where: Adams County, Corning
Measured: 52 kt (60 mph)
Property damage: $5,000
Crop damage: $5,000
Reported by: TRAINED SPOTTER
Coordinates: 40.983, -94.733

Thunderstorm Wind, Black Hawk

When: August 12, 10:12 PM CST
Where: Black Hawk County, Waterloo
Measured: 56 kt (64 mph)
Property damage: $20,000
Crop damage: $5,000
Reported by: LAW ENFORCEMENT
Coordinates: 42.500, -92.350

What these are

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.

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, August 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: 5311777, 5311778, 5311779.