Alert archive / Illinois / Tornado Watches in 2004

Tornado Watch 95

April 20, 200426 counties in Illinois; 24 counties in Indiana; Scott County, Iowa

The Storm Prediction Center issued this tornado watch at Apr 20, 2004, 5:40 PM CDT for 26 counties in Illinois; 24 counties in Indiana; Scott County, Iowa. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued
Apr 20, 2004, 5:40 PM CDT (22:40 UTC)
Expired
Apr 20, 2004, 11:00 PM CDT
In force
5 hr
Issued by
the Storm Prediction Center
All 51 counties

Scott County, IA, Bureau County, IL, Champaign County, IL, DeWitt County, IL, Ford County, IL, Fulton County, IL, Grundy County, IL, Henry County, IL, Iroquois County, IL, Kankakee County, IL, Knox County, IL, LaSalle County, IL, Livingston County, IL, Logan County, IL, Marshall County, IL, Mason County, IL, McDonough County, IL, McLean County, IL, Peoria County, IL, Piatt County, IL, Putnam County, IL, Rock Island County, IL, Stark County, IL, Tazewell County, IL, Vermilion County, IL, Warren County, IL, Woodford County, IL, Benton County, IN, Boone County, IN, Carroll County, IN, Cass County, IN, Clinton County, IN, Fountain County, IN, Fulton County, IN, Hamilton County, IN, Hendricks County, IN, Howard County, IN, Jasper County, IN, Johnson County, IN, Marion County, IN, Miami County, IN, Montgomery County, IN, Newton County, IN, Parke County, IN, Pulaski County, IN, Putnam County, IN, Tippecanoe County, IN, Tipton County, IN, Vermillion County, IN, Warren County, IN, White County, IN

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
Apr 20, 5:49 PM CDTTornado WarningILXKnox, Stark41 min
Apr 20, 5:51 PM CDTTornado WarningILXMarshall9 min
Apr 20, 5:55 PM CDTSevere Thunderstorm WarningILXMcLean35 min
Apr 20, 5:55 PM CDTTornado WarningILXMarshall35 min
Apr 20, 6:04 PM CDTSevere Thunderstorm WarningLOTFord, Iroquois, Livingston56 min
Apr 20, 6:05 PM CDTTornado WarningILXWoodford55 min
Apr 20, 6:11 PM CDTTornado WarningLOTLaSalle34 min
Apr 20, 6:13 PM CDTTornado WarningIWXMiami, Wabash62 min
Apr 20, 6:19 PM CDTTornado WarningINDHamilton, Tipton56 min
Apr 20, 6:26 PM CDTTornado WarningLOTGrundy34 min
Apr 20, 6:36 PM CDTSevere Thunderstorm WarningINDTippecanoe39 min
Apr 20, 6:37 PM CDTTornado WarningLOTFord, Iroquois, Livingston38 min
Apr 20, 6:43 PM CDTTornado WarningLOTKendall, LaSalle32 min
Apr 20, 7:00 PM CDTTornado WarningINDMadison, Tipton60 min
Apr 20, 7:01 PM CDTTornado WarningLOTGrundy, Will29 min
Apr 20, 7:12 PM CDTSevere Thunderstorm WarningINDCarroll33 min
Apr 20, 7:13 PM CDTTornado WarningLOTKankakee32 min
Apr 20, 7:15 PM CDTTornado WarningLOTIroquois30 min
Apr 20, 7:17 PM CDTTornado WarningLOTLivingston43 min
Apr 20, 7:21 PM CDTTornado WarningLOTLaSalle24 min
Apr 20, 7:27 PM CDTSevere Thunderstorm WarningIWXCass48 min
Apr 20, 7:34 PM CDTTornado WarningLOTGrundy41 min
Apr 20, 7:44 PM CDTTornado WarningLOTKankakee46 min

Discussions around it

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

The nearest sounding before it

Lincoln, IL (KILX), launched 12:00Z, 10.7 hours before the alert went out and 85 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, Lincoln, IL at 12:00Z on 2004-04-20Temperature 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, Lincoln, IL at 12:00Z on 2004-04-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 111 square meters per square second.19395878Sfc1 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
1297 m above ground
0-6 km bulk shear
33 kt
0-1 km storm-relative helicity
111 m²/s²
0-3 km storm-relative helicity
169 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 202242
SEL5  
SPC WW 202240
ILZ000-INZ000-210400-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 95
NWS STORM PREDICTION CENTER NORMAN OK
540 PM CDT TUE APR 20 2004

CORRECTED FOR ADD DUPAGE COUNTY

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

       NORTHERN AND CENTRAL ILLINOIS
       NORTHERN AND CENTRAL INDIANA

EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 540 PM UNTIL
1100 PM CDT.

TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS ALONG AND 55 STATUTE MILES NORTH AND
SOUTH OF A LINE FROM 30 MILES SOUTH SOUTHWEST OF MOLINE ILLINOIS
TO 40 MILES NORTH NORTHEAST OF INDIANAPOLIS INDIANA.

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 93...WW 94...

DISCUSSION...FAVORABLE SHEAR PROFILES ON NWD MOVING WARM FRONT FOR
TORNADIC SUPERCELLS.  STORMS WILL CONTINUE TO DEVELOP AS THE WARM
FRONT SHIFTS NWD INTO NRN IL/IND.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 400.
MEAN STORM MOTION VECTOR 23035.


...HALES

415,0904 410,0855 392,0855 401,0904

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 20, 6:00 PM CDTMesoscale DiscussionSPCBureau, Champaign, DeWitt, Ford, Fulton, Grundy and 20 more2 hr
Apr 20, 4:40 PM CDTSevere Thunderstorm WatchSPCAppanoose, Clarke, Davis, Decatur, Henry, Jefferson and 13 more5 hr
Apr 20, 6:25 PM CDTSevere Thunderstorm WatchSPCFremont, Harrison, Mills, Monona, Montgomery, Page and 2 more5 hr

Nearby

Tornado Watches in Illinois, 2004Tornado Watches in Indiana, 2004Tornado Watches in Iowa, 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.