Alert archive / Iowa / Severe Thunderstorm Warnings in 1997

Severe Thunderstorm Warning 105, NWS Des Moines, IA

August 23, 1997Black Hawk County, Grundy County, Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at Aug 23, 1997, 10:36 PM CDT for Black Hawk County, Grundy County, Iowa. It was in force for 34 min. 2 reports came from inside the area while it was in force.

The area

The counties it named, with what was reported inside it.

The facts

Issued: Aug 23, 1997, 10:36 PM CDT (03:36 UTC)
Expired: Aug 23, 1997, 11:10 PM CDT
In force: 34 min
Issued by: NWS Des Moines, IA
Area: Whole counties

Counties Black Hawk County, IA, Grundy County, IA

The radar

The Des Moines radar (KDMX), 125 km from the middle of the area, began a volume at 03:36 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.

What was reported inside it

Time	Report	Where	Remark
Aug 23, 10:40 PM CDT	Thunderstorm Wind 52	Dike, IA
Aug 23, 10:54 PM CDT	Hail 0.75	Hudson, IA

NCEI Storm Data entries that began inside the alert's area while it was in force. Before 2003 the local storm report archive is thin, so this is the record of what happened rather than what was phoned in.

The nearest sounding before it

Davenport, (KDVN), launched 00:00Z, 3.6 hours before the alert went out and 192 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: 128 J/kg
Mixed-layer CIN: -77 J/kg
Mixed-layer LCL: 1030 m above ground
0-6 km bulk shear: 44 kt
0-1 km storm-relative helicity: 151 m²/s²
0-3 km storm-relative helicity: 267 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.4

Open this sounding in Storm Lab

The text

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

000 
TTAA00 KDSM 240336 RRA
SVRDSM
IAC013-075-240410-

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE DES MOINES IA
1036 PM CDT SAT AUG 23 1997

* SEVERE THUNDERSTORM WARNING FOR
  WESTERN BLACK HAWK COUNTY - NORTHEASTERN IOWA
  EASTERN GRUNDY COUNTY - NORTHEASTERN IOWA

* UNTIL 1110 PM CDT
 
* SOME AREAS AFFECTED
    WATERLOO
    REMBECK
    HUDSON

* AT 1033 PM CDT RADAR INDICATED A SEVERE THUNDERSTORM 10 MILES WEST OF
  WATER[LOO MOVING SOUTHEAST AT 25 MPH.

* THE STORM WILL BE IN HUDSON BY 1045 PM CDT.

THIS IS A DANGEROUS STORM.  DO NOT GO OUTDOORS.




FORSTER/SMITH

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, Aug 23, 7:51 PM CDT, 2 hours 45 minutes before

IAZ004>007-015>017-023>028-033>039-044>050-057>062-240455-

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
751 PM CDT SAT AUG 23 1997

HAZARD--ISOLATED SEVERE THUNDERSTORMS CAPABLE OF PRODUCING WIND
GUSTS TO 60 MPH AND LARGE HAIL.

AREA OF CONCERN--NORTHEAST OF A MASON CITY TO WATERLOO LINE.

TIMING DETAILS--BETWEEN 800 PM AND MIDNIGHT.

METEOROLOGICAL COMMENTS--A WARM FRONT OVER EASTERN IOWA THIS EVENING
WILL BE THE PRIMARY FOCUS FOR THUNDERSTORMS TO DEVELOP ALONG. THE
ATMOSPHERE ALONG THE WARM FRONTAL BOUNDARY IS VERY UNSTABLE WITH
SURFACE DEW POINTS APPROACHING 70 DEGREES. WIND PROFILES ACROSS THE
STATE INDICATE A HIGH SHEAR PROFILE WITH LOW LEVEL SOUTHWESTERLY
WINDS FEEDING THE HIGHER DEW POINT AIR INTO THE WARM FRONTAL
BOUNDARY WHILE WINDS AT THE UPPER LEVELS ARE OUT OF THE NORTHWEST.
THIS WOULD INDICATE THE POTENTIAL FOR A FEW ROTATING UPDRAFTS WITH
THE THUNDERSTORMS THIS EVENING IN NORTHEAST IOWA.  THE STORMS WILL
CONTINUE TO DEVELOP AND MOVE ALONG THE WARM FRONT OVER NORTHEAST
IOWA THIS EVENING AND EARLY TONIGHT BEFORE THE THREAT FOR SEVERE
WEATHER THREAT SHIFTS INTO ILLINOIS.

PRECAUTIONS--PRESENT INDICATIONS SUGGEST SPOTTER ACTIVATION MAY BE
REQUIRED EARLY TONIGHT IN AREAS EAST OF I35 AND NORTH OF HIGHWAY 20.
PERSONS WITH OUTDOOR ACTIVITIES THIS EVENING SHOULD KEEP ABREAST OF
THE LATEST SHORT TERM FORECASTS IN THIS AREA.

SMITH

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 23, 9:13 PM CDT	Severe Thunderstorm Warning	DMX	Bremer	32 min
Aug 23, 11:07 PM CDT	Severe Thunderstorm Warning	DMX	Tama	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; verification from NCEI's Storm Data; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.