Alert archive / Iowa / Severe Thunderstorm Warnings in 2002

Severe Thunderstorm Warning 23, NWS Des Moines, IA

April 18, 2002Boone County, Hamilton County, Story County, Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at Apr 18, 2002, 12:01 AM CDT for Boone County, Hamilton County, Story County, Iowa. It was in force for 59 min. 5 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Apr 18, 2002, 12:01 AM CDT (05:01 UTC)
Expired: Apr 18, 2002, 1:00 AM CDT
In force: 59 min
Issued by: NWS Des Moines, IA
Area: Counties, with a storm outline in the text

Counties Boone County, IA, Hamilton County, IA, Story County, IA

The radar

The Des Moines radar (KDMX), 57 km from the middle of the area, began a volume at 05:03 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
Apr 18, 12:10 AM CDT	Hail 0.75	Fraser, IA
Apr 18, 12:27 AM CDT	Hail 0.75	Ellsworth, IA
Apr 18, 12:40 AM CDT	Hail 0.88	Stanhope, IA
Apr 18, 12:45 AM CDT	Hail 0.75	Story City, IA
Apr 18, 1:06 AM CDT	Hail 1	Jewell, 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.

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 nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 5.0 hours before the alert went out and 230 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: 72 J/kg
Mixed-layer CIN: -91 J/kg
Mixed-layer LCL: 2122 m above ground
0-6 km bulk shear: 65 kt
0-1 km storm-relative helicity: 113 m²/s²
0-3 km storm-relative helicity: 361 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 2.6

Open this sounding in Storm Lab

The text

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

000 
WUUS53 KDMX 180501
SVRDSM
IAC015-079-169-180600-

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE DES MOINES IA
1201 AM CDT THU APR 18 2002

THE NATIONAL WEATHER SERVICE IN DES MOINES HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  NORTHERN BOONE COUNTY IN CENTRAL IOWA
  SOUTHERN HAMILTON COUNTY IN CENTRAL IOWA
  NORTHWESTERN STORY COUNTY IN CENTRAL IOWA

* UNTIL 100 AM CDT

* AT 1158 PM...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  SEVERE THUNDERSTORM 18 MILES WEST OF STORY CITY...OR ABOUT 31 MILES
  SOUTHEAST OF FORT DODGE...MOVING NORTHEAST AT 30 MPH.

* THE SEVERE THUNDERSTORM WILL BE...

  NEAR STORY CITY AROUND 1230 AM AND
  8 MILES SOUTHEAST OF JEWELL AROUND 1235 AM.

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

STAY AWAY FROM WINDOWS DURING A SEVERE STORM...WIND GUSTS OVER 70 MPH
COULD BLOW THEM OUT.

PLEASE REPORT SEVERE WEATHER TO THE NEAREST LAW ENFORCEMENT AGENCY
FOR RELAY TO THE NATIONAL WEATHER SERVICE OFFICE NEAR DES MOINES.

LAT...LON 4234 9395 4221 9394 4221 9417 4206 9416
          4207 9346 4236 9348

$$

JOHNSON

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 Apr 17, 6:40 PM CDT, 5 hours 21 minutes earlier.

Area forecast discussion, Apr 17, 6:40 PM CDT, 5 hours 21 minutes before

AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE DES MOINES IA
640 PM CDT WED APR 17 2002

SHORT TERM...
COULD BE AN ACTIVE SEVERE WX NIGHT AHEAD WITH PARAMETERS QUITE
FAVORABLE.  JUST NEED SOME FORCING WHICH IS PROGGED TO INCREASE THIS
EVENING AS SHORTWAVE IN WESTERN KS HEADS NE.  ALSO, LLJ PROGGED TO
INCREASE TO OVER 50KT, WITH 850 MB THETA E ADVECTION WING NOW JUST N
OF SURFACE WARM FRONT INCREASES IN MAGNITUDE WHILE SHIFTING
NORTHWARD.  SHEAR PROFILE AT FBY EXCELLENT WITH OVER 300 M2/S2 0-3KM
HELICITY.  OF COURSE, THE 00Z SOUNDINGS WILL HELP, BUT ACCAS FIELD
IN NW IA CERTAINLY CONFIRMS RUC2 SOUNDING STEEP LAPSE RATES IN
WESTERN IA AND NEBR SPREADING NE.  TRIPLE POINT AND REGION JUST E HAS
BEEN FAVORED ZONE OF MOISTURE CONVERGENCE, WITH CU FIELD BECOMING
MORE AND MORE AGITATED IN NEBR.  IN FACT, OAX 88D AND IR (-31C TOPS)
SHOWING MID LEVEL ECHO ALREADY IN EXPANDING AC FIELD N OF WARM
FRONT.  I THINK THIS AREA NEEDS TO BE WATCHED CLOSELY FOR RAPID
DEVELOPMENT, AS LATEST RUC2 SHOWING BEST MOISTURE CONVERGENCE THIS
AREA SHIFTING INTO NW IA BY 06Z. HWO HAS BEEN UPDATED.

.DSM...NONE

KULA

In the hours before

Local storm report, Apr 17, 10:30 PM CDT, 1 hour 31 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1030 PM CDT WED APR 17 2002

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

1028 PM    10 S CARROLL              IA   1.75 INCH HAIL
04/17/02   CARROLL                        REPORTED BY STORM
                                          SPOTTER.

Local storm report, Apr 17, 10:40 PM CDT, 1 hour 21 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1040 PM CDT WED APR 17 2002

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

1020 PM    3 SW MANNING              IA   1.75 INCH HAIL
04/17/02   CRAWFORD                       REPORTED BY STORM
                                          SPOTTER.

1025 PM    TEMPLETON                 IA   1 INCH HAIL
04/17/02   CARROLL                        REPORTED BY STORM
                                          SPOTTER.

Local storm report, Apr 17, 10:55 PM CDT, 1 hour 6 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1055 PM CDT WED APR 17 2002

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

1052 PM    4 NW COON RAPIDS          IA   .75 INCH HAIL
04/17/02   CARROLL                        REPORTED BY STORM
                                          SPOTTER.

Local storm report, Apr 17, 11:29 PM CDT, 32 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1129 PM CDT WED APR 17 2002

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

1101 PM    3 S SCRANTON              IA   1 INCH HAIL
04/17/02   GREENE                         REPORTED BY HAM RADIO
                                          OPERATOR.

1106 PM    4 S SCRANTON              IA   .88 INCH HAIL
04/17/02   GREENE                         REPORTED BY STORM
                                          SPOTTER.

Local storm report, Apr 17, 11:37 PM CDT, 24 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1137 PM CDT WED APR 17 2002

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

1132 PM    3 S GRAND JCT             IA   1 INCH HAIL
04/17/02   GREENE                         REPORTED BY HAM RADIO
                                          OPERATOR.

1135 PM    RIPPEY                    IA   2 INCH HAIL
04/17/02   GREENE                         REPORTED BY MEDIA.

Local storm report, Apr 17, 11:52 PM CDT, 9 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1152 PM CDT WED APR 17 2002

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

1145 PM    2 W MADRID                IA   TORNADO
04/17/02   BOONE                          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
Apr 17, 9:09 PM CDT	Severe Thunderstorm Warning	DMX	Audubon	66 min
Apr 17, 9:31 PM CDT	Severe Thunderstorm Warning	DMX	Carroll, Crawford	59 min
Apr 17, 10:15 PM CDT	Severe Thunderstorm Warning	DMX	Audubon	45 min
Apr 17, 10:24 PM CDT	Severe Thunderstorm Warning	DMX	Carroll, Greene	66 min
Apr 17, 10:27 PM CDT	Tornado Warning	DMX	Audubon	33 min
Apr 17, 10:39 PM CDT	Tornado Warning	DMX	Carroll	36 min
Apr 17, 10:58 PM CDT	Severe Thunderstorm Warning	DMX	Guthrie	47 min
Apr 17, 11:05 PM CDT	Tornado Warning	DMX	Greene	40 min
Apr 17, 11:34 PM CDT	Tornado Warning	DMX	Boone	41 min
Apr 17, 11:47 PM CDT	Severe Thunderstorm Warning	DMX	Palo Alto, Pocahontas	43 min
Apr 18, 12:20 AM CDT	Tornado Warning	DMX	Boone	25 min
Apr 18, 12:28 AM CDT	Severe Thunderstorm Warning	DMX	Palo Alto	47 min
Apr 18, 12:34 AM CDT	Severe Thunderstorm Warning	DMX	Kossuth	56 min
Apr 18, 12:59 AM CDT	Severe Thunderstorm Warning	DMX	Hamilton, Hardin	61 min
Apr 18, 1:34 AM CDT	Severe Thunderstorm Warning	DMX	Butler, Franklin	56 min
Apr 18, 2:19 AM CDT	Severe Thunderstorm Warning	DMX	Bremer	41 min
Apr 18, 5:00 PM CDT	Severe Thunderstorm Warning	DMX	Adams	45 min
Apr 18, 5:07 PM CDT	Severe Thunderstorm Warning	DMX	Guthrie	38 min
Apr 18, 5:10 PM CDT	Severe Thunderstorm Warning	DMX	Hamilton	35 min
Apr 18, 5:22 PM CDT	Severe Thunderstorm Warning	DMX	Dallas	53 min
Apr 18, 5:23 PM CDT	Severe Thunderstorm Warning	DMX	Hardin	37 min
Apr 18, 5:27 PM CDT	Severe Thunderstorm Warning	DMX	Boone	33 min
Apr 18, 5:34 PM CDT	Severe Thunderstorm Warning	DMX	Greene	26 min
Apr 18, 5:41 PM CDT	Severe Thunderstorm Warning	DMX	Story	34 min
Apr 18, 5:47 PM CDT	Severe Thunderstorm Warning	DMX	Boone	43 min
Apr 18, 5:53 PM CDT	Severe Thunderstorm Warning	DMX	Taylor	52 min
Apr 18, 6:00 PM CDT	Severe Thunderstorm Warning	DMX	Polk	60 min
Apr 18, 6:04 PM CDT	Tornado Warning	DMX	Grundy, Hardin	56 min
Apr 18, 6:06 PM CDT	Severe Thunderstorm Warning	DMX	Guthrie, Madison	24 min
Apr 18, 6:14 PM CDT	Tornado Warning	DMX	Dallas	61 min
Apr 18, 6:18 PM CDT	Severe Thunderstorm Warning	DMX	Story	42 min
Apr 18, 6:40 PM CDT	Severe Thunderstorm Warning	DMX	Ringgold	50 min
Apr 18, 6:45 PM CDT	Severe Thunderstorm Warning	DMX	Polk	60 min
Apr 18, 6:52 PM CDT	Tornado Warning	DMX	Polk	23 min
Apr 18, 6:55 PM CDT	Severe Thunderstorm Warning	DMX	Madison, Warren	65 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; verification from NCEI's Storm Data; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.