Alert archive / Iowa / Severe Thunderstorm Warnings in 2003

Severe Thunderstorm Warning 241, NWS Des Moines, IA

August 20, 2003Mahaska County, Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at Aug 20, 2003, 3:40 PM CDT for Mahaska County, Iowa. It was in force for 50 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Aug 20, 2003, 3:40 PM CDT (20:40 UTC)
Expired: Aug 20, 2003, 4:30 PM CDT
In force: 50 min
Issued by: NWS Des Moines, IA
Area: Counties, with a storm outline in the text

County Mahaska County, IA

The radar

The Des Moines radar (KDMX), 96 km from the middle of the area, began a volume at 20:42 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.

Did it verify

Not verified. The Iowa Environmental Mesonet's Cow found no qualifying storm report inside this severe thunderstorm warning while it was in force. That is not proof nothing happened: reports are thin where few people live.

Cow counts a report within 15 km of the polygon while the warning was in force: a tornado for a tornado warning; hail of 1 inch or more, a gust of 58 mph or more or wind damage for a severe thunderstorm warning; a flash flood report for a flash flood warning.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Aug 20, 2:50 PM CDT	Severe Thunderstorm Watch	SPC	5 hr

The nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 8.7 hours before the alert went out and 183 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: 641 J/kg
Mixed-layer CIN: -231 J/kg
Mixed-layer LCL: 1398 m above ground
0-6 km bulk shear: 14 kt
0-1 km storm-relative helicity: 96 m²/s²
0-3 km storm-relative helicity: 102 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 
WUUS53 KDMX 202040
SVRDMX
IAC123-202130-

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE DES MOINES IA
340 PM CDT WED AUG 20 2003

THE NATIONAL WEATHER SERVICE IN DES MOINES HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  MAHASKA COUNTY IN SOUTH CENTRAL IOWA

* UNTIL 430 PM CDT

* AT 337 PM...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A LINE
  OF SEVERE THUNDERSTORMS FROM 6 MILES NORTHEAST OF NEW SHARON TO
  BEACON...OR FROM 35 MILES NORTH OF OTTUMWA TO 24 MILES NORTHWEST OF
  OTTUMWA...MOVING EAST AT 20 MPH.

* SEVERE THUNDERSTORMS WILL BE...

  NEAR OSKALOOSA AROUND 345 PM...
  NEAR UNIVERSITY PARK AROUND 350 PM...
  NEAR KEOMAH VILLAGE AROUND 355 PM...
  NEAR OSKALOOSA MUNICIPAL AIRPORT AROUND 400 PM AND
  NEAR FREMONT AROUND 410 PM.

HAIL UP TO THE SIZE OF NICKELS IS LIKELY IN THE WARNED AREA.

DAMAGING WINDS OF 60 TO 70 MILES AN HOUR ARE LIKELY IN THE WARNED
AREA.

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 800 PM WEDNESDAY
EVENING FOR EASTERN IOWA.

LAT...LON 4150 9286 4134 9286 4117 9286 4118 9243
          4134 9242 4150 9244

KINNEY

$$

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.

NWS Des Moines, IA wrote its last area forecast discussion before this severe thunderstorm warning went out at Aug 20, 11:33 AM CDT, 4 hours 7 minutes earlier.

Area forecast discussion, Aug 20, 11:33 AM CDT, 4 hours 7 minutes before

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
1133 AM CDT WED AUG 20 2003

UPDATED TODAY/S FORECAST FOR TEMPS...CLOUDS AND SUNSHINE.  SFC
BOUNDARY NORTH OF IA WITH FA IN WARM SECTOR AND SW BOUNDARY LAYER
FLOW.  21Z MESO ETA SOUNDINGS SUPPORT RAISING TEMPS.  AGREE SINCE
AMS SHUD MIX VERY WELL.  MID-LVL S/WV ON WATER VAPOR IMAGERY
SUPPORTS LEAVING SMALL POPS SRN IA LATE.  DEVELOPMENT...IF IT
OCCURS...SHOULD BE HIGH BASED AND ELEVATED.  AS FOR NORTHERN
FA...FORCING BEST NORTH OF STATE. FORECAST SOUNDINGS NOT SUPPORTIVE
OF TSTM DEVELOPMENT WITH A DECENT NEGATIVE AREA.  WILL DROP
AFTERNOON POPS NORTH.

.DSM...NONE.

JOHNSON

Hazardous weather outlook, Aug 20, 3:15 PM CDT, 25 minutes before

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-211100-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
315 PM CDT WED AUG 20 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL IOWA.

.DAY ONE...TODAY AND TONIGHT

SCATTERED THUNDERSTORMS ARE EXPECTED EARLY THIS EVENING FOR EASTERN
CENTRAL IOWA...EAST OF I35. A FEW OF THESE STORMS MAY BE SEVERE WITH
DAMAGING WINDS BEING THE PRIMARY THREAT.  LOCALLY HEAVY RAIN AND
HAIL UP TO 1 INCH ARE ALSO POSSIBLE.

ISOLATED STORMS CANNOT BE RULED OUT WEST OF I35 BUT THEY SHOULD BE
NON SEVERE.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS POSSIBLE EAST OF I35.

&&

MORE INFORMATION CAN BE OBTAINED AT WWW.CRH.NOAA.GOV/DMX (ALL LOWER
CASE).

JOHNSON

In the hours before

Local storm report, Aug 20, 3:18 PM CDT, 22 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
0318 PM CDT WED AUG 20 2003

TIME(CDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0250 PM    HUMESTON                  IA   WIND DAMAGE
08/20/03   WAYNE                          UP TO 10 INCH DIAMETER
                                          TREE LIMBS DOWN.

MR

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 20, 3:06 PM CDT	Severe Thunderstorm Warning	DMX	Lucas	39 min
Aug 20, 3:09 PM CDT	Severe Thunderstorm Warning	DMX	Marion	51 min
Aug 20, 3:23 PM CDT	Severe Thunderstorm Warning	DMX	Wayne	52 min
Aug 20, 3:51 PM CDT	Severe Thunderstorm Warning	DMX	Poweshiek	39 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2003 Every severe thunderstorm warning in 2003

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.