Alert archive / Iowa / Severe Thunderstorm Warnings in 2002

Severe Thunderstorm Warning 194, NWS Des Moines, IA

August 17, 2002Sac County, Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at Aug 17, 2002, 2:24 AM CDT for Sac County, Iowa. It was in force for 51 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 17, 2002, 2:24 AM CDT (07:24 UTC)
Expired: Aug 17, 2002, 3:15 AM CDT
In force: 51 min
Issued by: NWS Des Moines, IA
Area: Counties, with a storm outline in the text

County Sac County, IA

The radar

The Des Moines radar (KDMX), 143 km from the middle of the area, began a volume at 07:24 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 17, 1:05 AM CDT	Severe Thunderstorm Watch	SPC	5 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 7.4 hours before the alert went out and 158 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: 3070 J/kg
Mixed-layer CIN: -50 J/kg
Mixed-layer LCL: 1356 m above ground
0-6 km bulk shear: 55 kt
0-1 km storm-relative helicity: 229 m²/s²
0-3 km storm-relative helicity: 597 m²/s²
Significant tornado parameter: 3.9
Supercell composite: 18.4

Open this sounding in Storm Lab

The text

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

550 
WUUS53 KDMX 170724
SVRDSM
IAC161-170815-

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE DES MOINES IA
223 AM CDT SAT AUG 17 2002

THE NATIONAL WEATHER SERVICE IN DES MOINES HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  SAC COUNTY IN WEST CENTRAL IOWA

* UNTIL 315 AM CDT

* AT 219 AM...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A LINE
  OF SEVERE THUNDERSTORMS FROM 6 MILES NORTH OF NEMAHA TO 16 MILES
  WEST OF ODEBOLT...OR FROM 38 MILES SOUTH OF SPENCER TO 46 MILES
  SOUTHEAST OF SIOUX CITY...MOVING EAST AT 55 MPH.

* SEVERE THUNDERSTORMS WILL BE...

  NEAR ODEBOLT AROUND 230 AM...
  NEAR SAC CITY AROUND 240 AM...
  NEAR LAKE VIEW AROUND 245 AM AND
  NEAR AUBURN AROUND 255 AM.

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

VERY STRONG WINDS UP TO 60 MPH ARE LIKELY IN THE WARNED AREA.

REPORT WIND IN EXCESS OF 50 MPH...HAIL LARGER THAN ONE HALF 
INCH...OR STORM DAMAGE TO YOUR LOCAL LAW ENFORCEMENT.

LAT...LON 4256 9537 4223 9538 4223 9488 4256 9491

31

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 17, 1:26 AM CDT, 58 minutes earlier.

Area forecast discussion, Aug 17, 1:26 AM CDT, 58 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
126 AM CDT SAT AUG 17 2002

SHORT TERM...
OMINOUS SQUALL LINE WILL BE RAGING THROUGH OUR CWA OVER NEXT FEW
HOURS WITH VERY IMPRESSIVE WIND FIELD FOR MID AUGUST.  OUTFLOW
BOUNDARY AND WARM FRONT CONNECTING UP TO THE LINE IN NW IA POSES A
HIGHER THREAT OF MESOS/ISOLATED TORNADOES EMBEDDED IN THE LINE.
ALSO A PERSISTENT AND INTRIGUING HIGH WIND EVENT OVER NORTH CENTRAL
IA WITH SEVERAL DAMAGE REPORTS LAST 3 HOURS.  REFERENCING THE IOWA
ENVIRONMENTAL MESONET, A STRONG MESOSCALE PRESSURE GRADIENT IS
ASSOCIATED WITH THIS WAVE.  RUC/META TIMING OF FRONT LOOKS
REASONABLE, WITH MOST IMPRESSIVE PUSH TO THE LINE THROUGH SE NEBR/SW
IA ASSOCIATED WITH STRONGER ISALLOBARIC COUPLET.  FOR NOW, WILL HOLD
OFF ON DAYTIME WIND ADVISORY, BUT GUSTS OVER 30 MPH LIKELY.  NOT
MANY CHANGES TO TEMPS NEEDED TODAY THROUGH TONIGHT.

LONGER TERM...
PATTERN SHAPING UP WELL FOR NOCTURNAL MCS/HEAVY RAIN EVENTS NEXT TWO
NIGHTS AND INTO MONDAY.  TONIGHT IS QUESTIONABLE WITH REGARD TO
BOUNDARY PLACEMENT, BUT META DEVELOPS A SOLID AREA OF 850-700 MB
THETA E ADVECTION UPON DEVELOPMENT OF WIDESPREAD LLJ ALONG FRONTAL
BOUNDARY.  WILL INCLUDE A LOW POP AFTER MIDNIGHT FOR POTENTIAL
TONIGHT INTO SUNDAY, WITH SHARP MOISTURE GRADIENT FURTHER N.  SHOULD
BE A PRETTY NICE DAY ACROSS NORTHERN IA N OF CI SHIELD.

HIGHER THREAT OF HEAVY RAIN AND POTENTIAL ELEVATED SEVERE CELLS
EXISTS SUNDAY NIGHT INTO MONDAY, WITH A STRONGER 700 MB SHORTWAVE,
LLJ AND STRONGER INSTABILITY ALONG PERSISTENT THERMAL BOUNDARY IN
VICINITY OF SOUTHERN IA / NORTHERN MO.  WILL INSERT MODERATE TO
LIKELY POPS DURING THIS PERIOD.  THIS MAY KEEP TEMPS RATHER COOL ON
MONDAY, SO WILL DROP HIGHS A BIT.

.DSM...NONE

KULA

In the hours before

Local storm report, Aug 16, 11:33 PM CDT, 2 hours 51 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1133 PM CDT FRI AUG 16 2002

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

1127 PM    EMMETSBURG                IA   WIND DAMAGE
08/16/02   PALO ALTO                      REPORTED BY LAW
                                          ENFORCEMENT OFFICIAL.
                                          NON THUNDERSTORM WIND
                                          GUSTS CAUSING NUMEROUS
                                          LARGE TREES TO
                                          FALL...DAMAGING
                                          POWERLINES.

Local storm report, Aug 16, 11:34 PM CDT, 2 hours 50 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1134 PM CDT FRI AUG 16 2002

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

0520 PM    3 S WALLINGFORD           IA   NON TSTM WINDS
08/16/02   EMMET                          REPORTED BY KICD RADIO.
                                          NUMEROUS TREES AND
                                          POWERLINES DOWN. BARN
                                          DESTROYED.

Local storm report, Aug 17, 12:31 AM CDT, 1 hour 53 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1231 AM CDT SAT AUG 17 2002

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

1210 AM    AYRSHIRE                  IA   1 INCH HAIL
08/17/02   PALOALTO                       REPORTED KICD RADIO.

Local storm report, Aug 17, 12:39 AM CDT, 1 hour 45 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1239 AM CDT SAT AUG 17 2002

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

1122 PM    SWEA CITY                 IA   WIND DAMAGE
08/16/02   KOSSUTH                        REPORTED BY LAW
                                          ENFORCEMENT OFFICIAL.
                                          LARGE TREES DOWN - NON
                                          THUNDERSTORM WINDS.

1144 PM    ALGONA                    IA   WIND DAMAGE
08/16/02   KOSSUTH                        REPORTED BY LAW
                                          ENFORCEMENT OFFICIAL.
                                          POWERLINES DOWN - NON
                                          THUNDERSTORM WINDS.

Local storm report, Aug 17, 12:45 AM CDT, 1 hour 39 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1245 AM CDT SAT AUG 17 2002

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

1227 AM    2 S EMMETSBURG            IA   1.75 INCH HAIL
08/17/02   PALOALTO                       REPORTED BY HAM RADIO
                                          OPERATOR.

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 17, 12:13 AM CDT	Severe Thunderstorm Warning	DMX	Palo Alto	47 min
Aug 17, 12:30 AM CDT	Severe Thunderstorm Warning	DMX	Kossuth	30 min
Aug 17, 1:44 AM CDT	Severe Thunderstorm Warning	DMX	Palo Alto	46 min
Aug 17, 3:05 AM CDT	Severe Thunderstorm Warning	DMX	Calhoun	40 min
Aug 17, 3:13 AM CDT	Severe Thunderstorm Warning	DMX	Webster	47 min
Aug 17, 3:33 AM CDT	Severe Thunderstorm Warning	DMX	Hamilton, Wright	57 min
Aug 17, 3:38 AM CDT	Severe Thunderstorm Warning	DMX	Boone	37 min
Aug 17, 3:45 AM CDT	Severe Thunderstorm Warning	DMX	Greene	30 min
Aug 17, 3:49 AM CDT	Severe Thunderstorm Warning	DMX	Adair, Adams	56 min
Aug 17, 3:52 AM CDT	Severe Thunderstorm Warning	DMX	Ringgold, Taylor, Union	53 min
Aug 17, 3:58 AM CDT	Severe Thunderstorm Warning	DMX	Franklin, Hardin	42 min
Aug 17, 4:00 AM CDT	Severe Thunderstorm Warning	DMX	Story	45 min
Aug 17, 4:06 AM CDT	Severe Thunderstorm Warning	DMX	Madison	39 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2002 Every severe thunderstorm warning in 2002

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.