Alert archive / Iowa / Tornado Watches in 2004

Tornado Watch 236

May 21, 2004Rock Island County, Illinois; 65 counties in Iowa; Crawford County, Grant County, Richland County, Wisconsin

The Storm Prediction Center issued this tornado watch at May 21, 2004, 2:45 PM CDT for Rock Island County, Illinois; 65 counties in Iowa; Crawford County, Grant County, Richland County, Wisconsin. It was in force for 7 hr.

The area

The outline as issued.

The facts

Issued
May 21, 2004, 2:45 PM CDT (19:45 UTC)
Expired
May 21, 2004, 10:00 PM CDT
In force
7 hr
Issued by
the Storm Prediction Center
All 69 counties

Allamakee County, IA, Audubon County, IA, Benton County, IA, Black Hawk County, IA, Boone County, IA, Bremer County, IA, Buchanan County, IA, Buena Vista County, IA, Butler County, IA, Calhoun County, IA, Carroll County, IA, Cedar County, IA, Cerro Gordo County, IA, Cherokee County, IA, Chickasaw County, IA, Clay County, IA, Clayton County, IA, Clinton County, IA, Crawford County, IA, Dallas County, IA, Delaware County, IA, Dickinson County, IA, Dubuque County, IA, Emmet County, IA, Fayette County, IA, Floyd County, IA, Franklin County, IA, Greene County, IA, Grundy County, IA, Guthrie County, IA, Hamilton County, IA, Hancock County, IA, Hardin County, IA, Harrison County, IA, Howard County, IA, Humboldt County, IA, Ida County, IA, Iowa County, IA, Jackson County, IA, Jasper County, IA, Johnson County, IA, Jones County, IA, Kossuth County, IA, Linn County, IA, Marshall County, IA, Mitchell County, IA, Monona County, IA, Muscatine County, IA, O'Brien County, IA, Osceola County, IA, Palo Alto County, IA, Pocahontas County, IA, Polk County, IA, Poweshiek County, IA, Sac County, IA, Scott County, IA, Shelby County, IA, Story County, IA, Tama County, IA, Webster County, IA, Winnebago County, IA, Winneshiek County, IA, Woodbury County, IA, Worth County, IA, Wright County, IA, Rock Island County, IL, Crawford County, WI, Grant County, WI, Richland County, WI

The radar

The Des Moines radar (KDMX), 104 km from the middle of the area, began a volume at 19:48 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.

Warnings issued inside it

74 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
May 21, 2:45 PM CDTTornado WarningDMXGrundy45 min
May 21, 3:06 PM CDTSevere Thunderstorm WarningDMXButler39 min
May 21, 3:07 PM CDTSevere Thunderstorm WarningDMXTama23 min
May 21, 3:26 PM CDTTornado WarningDVNBuchanan64 min
May 21, 3:27 PM CDTTornado WarningDMXGrundy48 min
May 21, 3:27 PM CDTSevere Thunderstorm WarningDVNBenton48 min
May 21, 3:35 PM CDTTornado WarningDMXBlack Hawk40 min
May 21, 3:38 PM CDTFlash Flood WarningDMXBlack Hawk, Palo Alto, Pocahontas119 days
May 21, 3:38 PM CDTTornado WarningDVNBenton37 min
May 21, 3:44 PM CDTTornado WarningDMXMarshall, Tama31 min
May 21, 3:47 PM CDTSevere Thunderstorm WarningFSDWoodbury43 min
May 21, 4:11 PM CDTSevere Thunderstorm WarningFSDO'Brien49 min
May 21, 4:12 PM CDTTornado WarningDVNLinn63 min
May 21, 4:13 PM CDTSevere Thunderstorm WarningFSDCherokee32 min
May 21, 4:14 PM CDTTornado WarningDVNBenton31 min
May 21, 4:16 PM CDTTornado WarningDMXTama29 min
May 21, 4:18 PM CDTSevere Thunderstorm WarningFSDIda27 min
May 21, 4:32 PM CDTSevere Thunderstorm WarningFSDCherokee43 min
May 21, 4:43 PM CDTFlash Flood WarningDVNBenton, Buchanan, Delaware, Linn6 hr
May 21, 4:44 PM CDTSevere Thunderstorm WarningDVNBenton61 min
May 21, 4:46 PM CDTSevere Thunderstorm WarningFSDBuena Vista44 min
May 21, 4:48 PM CDTTornado WarningDVNBenton57 min
May 21, 4:48 PM CDTSevere Thunderstorm WarningFSDClay42 min
May 21, 4:51 PM CDTSevere Thunderstorm WarningDVNDelaware54 min
May 21, 4:58 PM CDTSevere Thunderstorm WarningFSDO'Brien32 min
May 21, 5:01 PM CDTSevere Thunderstorm WarningDMXWright44 min
May 21, 5:05 PM CDTTornado WarningDVNJones55 min
May 21, 5:14 PM CDTSevere Thunderstorm WarningFSDCherokee31 min
May 21, 5:21 PM CDTSevere Thunderstorm WarningDVNLinn54 min
May 21, 5:23 PM CDTSevere Thunderstorm WarningFSDClay37 min
May 21, 5:26 PM CDTSevere Thunderstorm WarningFSDBuena Vista34 min
May 21, 5:27 PM CDTFlash Flood WarningDMXPalo Alto, Pocahontas, Taylor120 days
May 21, 5:27 PM CDTSevere Thunderstorm WarningDMXCerro Gordo, Hancock48 min
May 21, 5:30 PM CDTSevere Thunderstorm WarningDMXPalo Alto45 min
May 21, 5:38 PM CDTTornado WarningDVNClinton, Jackson67 min
May 21, 5:47 PM CDTSevere Thunderstorm WarningDMXFranklin43 min
May 21, 5:48 PM CDTSevere Thunderstorm WarningARXFloyd, Mitchell57 min
May 21, 5:51 PM CDTFlash Flood WarningDVNJones6 hr
May 21, 5:52 PM CDTSevere Thunderstorm WarningDMXGrundy, Hardin53 min
May 21, 5:54 PM CDTTornado WarningDMXPalo Alto, Pocahontas51 min
May 21, 5:56 PM CDTSevere Thunderstorm WarningDVNCedar, Jones64 min
May 21, 5:59 PM CDTSevere Thunderstorm WarningFSDClay31 min
May 21, 6:09 PM CDTFlash Flood WarningDMXAdams, Cerro Gordo, Franklin, Hancock, Humboldt, Kossuth and 1 more120 days
May 21, 6:15 PM CDTSevere Thunderstorm WarningDMXCerro Gordo45 min
May 21, 6:15 PM CDTTornado WarningDMXHumboldt, Kossuth45 min
May 21, 6:22 PM CDTSevere Thunderstorm WarningDMXButler53 min
May 21, 6:36 PM CDTSevere Thunderstorm WarningDMXPocahontas24 min
May 21, 6:41 PM CDTTornado WarningDMXHumboldt34 min
May 21, 6:45 PM CDTSevere Thunderstorm WarningARXFloyd30 min
May 21, 6:54 PM CDTSevere Thunderstorm WarningDMXBremer36 min
May 21, 6:54 PM CDTSevere Thunderstorm WarningDMXWright51 min
May 21, 6:55 PM CDTSevere Thunderstorm WarningARXChickasaw50 min
May 21, 7:00 PM CDTFlash Flood WarningARXChickasaw, Floyd3 hr
May 21, 7:16 PM CDTTornado WarningDMXWright29 min
May 21, 7:25 PM CDTSevere Thunderstorm WarningARXClayton35 min
May 21, 7:31 PM CDTSevere Thunderstorm WarningDMXBremer44 min
May 21, 7:36 PM CDTSevere Thunderstorm WarningDMXFranklin54 min
May 21, 7:41 PM CDTFlash Flood WarningARXAllamakee, Winneshiek3 hr
May 21, 7:41 PM CDTFlash Flood WarningDMXBremer, Butler17 hr
May 21, 7:46 PM CDTSevere Thunderstorm WarningDMXWright14 min
May 21, 8:12 PM CDTTornado WarningDMXBremer48 min
May 21, 8:35 PM CDTFlash Flood WarningARXClayton, Fayette3 hr
May 21, 8:37 PM CDTSevere Thunderstorm WarningFSDClay, O'Brien23 min
May 21, 8:40 PM CDTFlash Flood WarningARXCrawford, Richland, Vernon3 hr
May 21, 8:59 PM CDTSevere Thunderstorm WarningDMXPalo Alto31 min
May 21, 9:08 PM CDTFlash Flood WarningARXHoward, Mitchell3 hr
May 21, 9:09 PM CDTSevere Thunderstorm WarningARXClayton51 min
May 21, 9:25 PM CDTSevere Thunderstorm WarningFSDCherokee35 min
May 21, 9:33 PM CDTSevere Thunderstorm WarningFSDClay27 min
May 21, 9:33 PM CDTSevere Thunderstorm WarningFSDO'Brien42 min
May 21, 9:38 PM CDTFlash Flood WarningARXGrant3 hr
May 21, 9:57 PM CDTFlash Flood WarningARXChickasaw, Floyd3 hr
May 21, 9:59 PM CDTSevere Thunderstorm WarningFSDBuena Vista, Cherokee, Woodbury31 min
May 21, 10:00 PM CDTFlash Flood WarningDMXKossuth, Winnebago, Worth18 hr

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Minneapolis, MN (KMPX), launched 12:00Z, 7.8 hours before the alert went out and 243 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, Minneapolis, MN at 12:00Z on 2004-05-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 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, Minneapolis, MN at 12:00Z on 2004-05-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 216 square meters per square second.1939587897Sfc1 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
732 m above ground
0-6 km bulk shear
43 kt
0-1 km storm-relative helicity
216 m²/s²
0-3 km storm-relative helicity
321 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 
WWUS20 KWNS 211945
SEL6  
SPC WW 211945
IAZ000-ILZ000-NEZ000-SDZ000-WIZ000-220300-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 236
NWS STORM PREDICTION CENTER NORMAN OK
245 PM CDT FRI MAY 21 2004

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF 

       NORTHERN AND CENTRAL IOWA
       EXTREME NORTHWEST ILLINOIS
       EXTREME NORTHEAST NEBRASKA
       EXTREME SOUTHEAST SOUTH DAKOTA
       SOUTHWEST WISCONSIN

EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 245 PM UNTIL 1000
PM CDT.

TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS ALONG AND 70 STATUTE MILES NORTH AND
SOUTH OF A LINE FROM 65 MILES SOUTHWEST OF SPENCER IOWA TO 20
MILES EAST OF DUBUQUE IOWA.

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH AREA.
PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR THREATENING
WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS AND POSSIBLE
WARNINGS.

OTHER WATCH INFORMATION...CONTINUE...WW 231...WW 232...WW 233...WW
234...WW 235...

DISCUSSION...AIRMASS CONTINUES TO DESTABILIZE ACROSS IA IN VICINITY
OF SURFACE COLD FRONT/OUTFLOW BOUNDARIES.  LOW LEVEL SHEAR/HELICITY
VALUES SUGGEST AN INCREASING THREAT OF TORNADIC SUPERCELLS OVER THIS
REGION THROUGH THE EVENING.  UPSTREAM DEVELOPMENT OVER NORTHWEST IA
IS LESS CERTAIN...BUT CONDITIONS ARE FAVORABLE FOR TORNADOES IN THIS
REGION AS WELL IF CONVECTIVE INITIATION CAN OCCUR.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500.
MEAN STORM MOTION VECTOR 27035.


...HART

432,0960 432,0901 412,0901 412,0960

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 20, 7:32 PM CDTMesoscale DiscussionSPCBoone, Bureau, Carroll, Cook, DeKalb, DuPage and 21 more88 min
May 20, 9:05 PM CDTSevere Thunderstorm WatchSPCBureau, Cook, DeKalb, DuPage, Ford, Fulton and 20 more5 hr
May 21, 4:34 AM CDTMesoscale DiscussionSPCJo Daviess56 min
May 21, 9:40 AM CDTMesoscale DiscussionSPCCook, DuPage, Kane, Kankakee, Lake, Will2 hr
May 21, 10:25 AM CDTSevere Thunderstorm WatchSPCBoone, Bureau, Carroll, DeKalb, Henry, Jo Daviess and 8 more6 hr
May 21, 5:35 PM CDTTornado WatchSPCBoone, Bureau, Carroll, Cook, DeKalb, DuPage and 21 more5 hr
May 20, 10:03 PM CDTMesoscale DiscussionSPCFremont, Harrison, Mills, Pottawattamie87 min
May 21, 1:11 AM CDTMesoscale DiscussionSPCAudubon, Boone, Buena Vista, Calhoun, Carroll, Cherokee and 27 more34 min
May 21, 1:20 AM CDTSevere Thunderstorm WatchSPCAudubon, Boone, Buena Vista, Calhoun, Carroll, Cherokee and 19 more6 hr
May 21, 2:22 AM CDTMesoscale DiscussionSPCAllamakee, Benton, Black Hawk, Boone, Bremer, Buchanan and 47 more23 min
May 21, 2:35 AM CDTSevere Thunderstorm WatchSPCAllamakee, Benton, Black Hawk, Bremer, Buchanan, Butler and 22 more4 hr
May 21, 6:23 AM CDTMesoscale DiscussionSPCAllamakee, Bremer, Butler, Cerro Gordo, Chickasaw, Clay and 20 more67 min
May 21, 9:44 AM CDTMesoscale DiscussionSPCAllamakee, Benton, Black Hawk, Bremer, Buchanan, Buena Vista and 38 more3 hr
May 21, 1:59 PM CDTMesoscale DiscussionSPCBenton, Black Hawk, Bremer, Buchanan, Butler, Cerro Gordo and 9 more2 hr
May 21, 6:33 PM CDTMesoscale DiscussionSPCLyon, Plymouth, Sioux, Woodbury57 min
May 21, 3:00 PM CDTSevere Thunderstorm WatchSPCAdams, Calumet, Columbia, Dane, Dodge, Fond du Lac and 19 more7 hr

Nearby

Tornado Watches in Iowa, 2004Tornado Watches in Wisconsin, 2004Tornado Watches in Illinois, 2004Every tornado watch in 2004

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.