Damaging Wind in Iowa, July 20, 2001

Name: Damaging Wind in Iowa, July 20, 2001
Start: 2001-07-20T12:07
End: 2001-07-20T12:07
Location: Iowa

July 20, 2001 · NWS DMX · 1 event in 1 county or zone

Very unstable conditions were in place across Iowa. Surface dew point temperatures were in the mid 70s across the northern part of the state with a warm front approaching from the south.

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: $2,000
Crop damage: None recorded
Events: 1

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.

Very unstable conditions were in place across Iowa. Surface dew point temperatures were in the mid 70s across the northern part of the state with a warm front approaching from the south. At the same time, an old outflow boundary moved into the northern part of the state from convection that had taken place during the previous night in Minnesota. Thunderstorms erupted along the boundary. As they moved through the Mason City area, winds gusted to 52 MPH in the city, causing some minor damage. One small tree was blown over and a few power lines were taken down by branches.

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 Jul 20, 9:25 AM CST, 2 hours 42 minutes earlier.

Area forecast discussion, Jul 20, 9:25 AM CST, 2 hours 42 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1025 AM CDT FRI JUL 20 2001

WILL NEED TO UPDATE ZONES SHORTLY FOR FIRST PD  CHANGES.  TWO AREAS
OF CONCERN...NRN AND SOUTHERN IA.

SRN ZONES...SHOWERS AND A FEW THUNDERSTORMS OVR FAR SRN IA ATTM SHUD
DECREASE AND END AS LOW LVL JET CONTINUES TO DECREASE.  EXPECT
PLENTIFUL CLOUD COVER FM CONVECTIVE DEBRIS TDY.  MAY HAVE WDLY SCT
TSTMS SW ZONES NEAR SUBTLE BOUNDARY AND A MOISTURE AND INSTIBILITY
AXIS.

NRN ZONES...AREA UNDER UVV FM ISENT LIFT AND APPROACHING S/WV AS PER
WATER VAPOR IMAGERY.  MCS NORTH OF IA MAY HAVE ENOUGH PUSH TO REACH
NRN IA THIS AFTERNOON.  ANOTHER BOUNDARY WAS NEAR NRN IA IN SRN MN.
UVV AND PLENTIFUL MOISTURE AND CAPE SHUD RESULT IN SCT TSTMS OVR NRN
ZONES.  WL WORD ACCORDINGLY.

NO CHANGES TO OUT PDS.
.DSM...NONE
JOHNSON

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

1 thunderstorm wind. Local standard time, as filed.

Thunderstorm Wind, Cerro Gordo

When: July 20, 12:07 PM CST
Where: Cerro Gordo County, Mason City
Measured: 50 kt (58 mph)
Property damage: $2,000
Reported by: LAW ENFORCEMENT
Coordinates: 43.150, -93.200

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 2001 Every state in 2001 This day in weather history Warnings in Iowa, July 2001

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: 5252285.