Alert archive / Iowa / Severe Thunderstorm Warnings in 1997

Severe Thunderstorm Warning 88, NWS Des Moines, IA

July 20, 1997Polk County, Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at Jul 20, 1997, 2:59 PM CDT for Polk 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 20, 1997, 2:59 PM CDT (19:59 UTC)
Expired
Jul 20, 1997, 3:30 PM CDT
In force
31 min
Issued by
NWS Des Moines, IA
Area
Whole counties

County Polk County, IA

The radar

The Des Moines radar (KDMX), 13 km from the middle of the area, began a volume at 19:59 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 12:00Z, 8.0 hours before the alert went out and 236 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-pSkew-T log-p diagram, Omaha, NE at 12:00Z on 1997-07-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1096 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Omaha, NE at 12:00Z on 1997-07-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -10 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
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
1096 J/kg
Mixed-layer CIN
-42 J/kg
Mixed-layer LCL
1035 m above ground
0-6 km bulk shear
7 kt
0-1 km storm-relative helicity
-10 m²/s²
0-3 km storm-relative helicity
12 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

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

000 
TTAA00 KDSM 201959 RRA
SVRDSM
IAC153-202030-

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE DES MOINES IA
259 PM CDT SUN JUL 20 1997

* SEVERE THUNDERSTORM WARNING FOR
  WESTERN POLK COUNTY - CENTRAL IOWA

* UNTIL 330 PM CDT
 
* SOME AREAS AFFECTED
    GRIMES
    URBANDALE
    POLK CITY

* AT 255 PM CDT STORM SPOTTERS REPORTED A SEVERE THUNDERSTORM JUST
  SOUTH OF THE DES MOINES METRO AREA MOVING NORTH AT 30 MPH.

* THE STORM WILL BE THROUGH GRIMES BY 315 PM CDT.

THIS IS A DANGEROUS STORM.  DO NOT GO OUTDOORS.

FAB
 

&

The office that day

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

IssuedProductOfficeCountiesLasted
Jul 19, 9:30 PM CDTFlash Flood WarningDMXKossuth3 hr
Jul 20, 4:50 PM CDTSevere Thunderstorm WarningDMXMonroe35 min

Nearby

Severe Thunderstorm Warnings in Iowa, 1997Every 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.