Alert archive / Iowa / Severe Thunderstorm Warnings in 1997

Severe Thunderstorm Warning 90, NWS Des Moines, IA

July 23, 1997Crawford County, Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at Jul 23, 1997, 5:24 AM CDT for Crawford County, Iowa. It was in force for 31 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Jul 23, 1997, 5:24 AM CDT (10:24 UTC)
Expired: Jul 23, 1997, 5:55 AM CDT
In force: 31 min
Issued by: NWS Des Moines, IA
Area: Whole counties

County Crawford County, IA

The radar

The Omaha radar (KOAX), 114 km from the middle of the area, began a volume at 10:25 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 10.4 hours before the alert went out and 114 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 1353 J/kg
Mixed-layer CIN: -40 J/kg
Mixed-layer LCL: 1400 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: 54 m²/s²
0-3 km storm-relative helicity: 148 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 2.9

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

000 
TTAA00 KDSM 231024 RRA
SVRDSM
IAC047-231055-

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE DES MOINES IA
524 AM CDT WED JUL 23 1997

* SEVERE THUNDERSTORM WARNING FOR
  WESTERN CRAWFORD COUNTY - WEST CENTRAL IOWA

* UNTIL 555 AM CDT
 
* SOME AREAS AFFECTED
    CHARTER OAK
    RICKETTS
    DOW CITY
    ARION

* AT 522 AM CDT RADAR INDICATED A SEVERE THUNDERSTORM 60 MILES NORTH OF
  OMAHA MOVING SOUTHEAST AT 25 MPH.

* THZE STORM WILL BE WEST OF DOW CITY BY 535 AM CDT.

THIS IS A DANGEROUS STORM.  DO NOT GO OUTDOORS.




77

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

In the hours before

Special weather statement, Jul 23, 4:43 AM CDT, 41 minutes before

IAZ044-045-057-070-081-092-232150-

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
443 AM CDT WED JUL 23 1997

HAZARD--ISOLATED THUNDERSTORMS WITH HEAVY RAINFALL.  THERE IS A SMALL
THREAT OF SEVERE WEATHER.

AREA OF CONCERN--ALONG AND WEST OF A DENISON--ATLANTIC--BEDFORD LINE.

TIMING DETAILS--THROUGH 900 AM.

METEOROLOGICAL COMMENTS--A STRONG WARM ADVECTION ZONE HAS SET UP ALONG
THE WESTERN PART OF IOWA.  SOUTHWESTERLY INFLOW OF 20 TO 25 KTS
THROUGH THE LOWEST 5000 FT HAS INCREASED CONVERGENCE ALONG THIS
BOUNDARY.  STORM RELATIVE MOVEMENT WAS BETWEEN 330 AND 360 AT 25 KTS
WHICH DRAMATICALLY INCREASES THE WIND SHEAR PROFILE AND HELICITY
VALUES FOR INDIVIDUAL STORMS.  THE ATMOSPHERE IS QUITE UNSTABLE ABOVE
THE BOUNDARY LAYER...BUT MID-LEVEL TEMPERATURES ARE QUITE WARM.  THE
THREAT FOR LARGE HAIL IS MINIMAL DUE TO THIS FACTOR...BUT THE MAGNITUDE
OF THE SHEAR PROFILE IS FAVORABLE FOR ISOLATED SUPERCELL
STORMS...ESPECIALLY ALONG THE MISSOURI RIVER.

PRECAUTIONS--SPOTTER ACTIVATION MAY BE NEEDED EARLY THIS MORNING WITHIN
THE AREA OF CONCERN.  STAY TUNED TO FURTHER SHORT TERM FORECASTS FOR
ADDITIONAL INFORMATION.

KULA

The office that day

Everything else NWS Des Moines, IA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 23, 8:01 AM CDT	Flash Flood Warning	DMX	Crawford	34 min
Jul 23, 8:01 AM CDT	Severe Thunderstorm Warning	DMX	Crawford	34 min
Jul 23, 8:02 AM CDT	Flash Flood Warning	DMX	Crawford	33 min
Jul 23, 8:02 AM CDT	Severe Thunderstorm Warning	DMX	Crawford	33 min

Nearby

Severe Thunderstorm Warnings in Iowa, 1997 Every severe thunderstorm warning in 1997

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.