Alert archive / Illinois / Tornado Warnings in 2004

Tornado Warning 2, NWS Chicago, IL

April 20, 2004LaSalle County, Illinois

NWS Chicago, IL issued this tornado warning at Apr 20, 2004, 6:11 PM CDT for LaSalle County, Illinois. It was in force for 34 min. 8 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 20, 2004, 6:11 PM CDT (23:11 UTC)
Expired: Apr 20, 2004, 6:45 PM CDT
In force: 34 min
Issued by: NWS Chicago, IL
Area: Counties, with a storm outline in the text

County LaSalle County, IL

What was reported inside it

Time	Report	Where	Remark
Apr 20, 6:12 PM CDT	TORNADO	La Salle, IL	INTERSTATE 80 MILE MARKER 75
Apr 20, 6:12 PM CDT	TORNADO	La Salle, IL	INTERSTATE 80 MILE MARKER 75
Apr 20, 6:20 PM CDT	TORNADO	9 W Ottawa, IL	TONADO WITH MULTIPLE VORTEX MOVING NORTHEAST.
Apr 20, 6:20 PM CDT	TORNADO	9 W Ottawa, IL	TONADO WITH MULTIPLE VORTEX MOVING NORTHEAST.
Apr 20, 6:37 PM CDT	HAIL 1.75	9 N Ottawa, IL
Apr 20, 6:48 PM CDT	TORNADO	3 Ne Ottawa, IL	SOUTH OF SERENA ON ILLINOIS ROUTE 52
Apr 20, 6:52 PM CDT	TORNADO	8 N Marseilles, IL	2 TORNADOES NEAR ROUTE 52 AND 71.
Apr 20, 6:55 PM CDT	TORNADO	3 S Sheridan, IL	REPORTED IN NORWAY SUBDIVISION AT INTERSECTION OF ROUTE 52 AND STATE HWY 71 MOVING EAST.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The watch it was issued in

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

Issued	Product	Office	Lasted
Apr 20, 5:40 PM CDT	Tornado Watch	SPC	5 hr

The nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 11.2 hours before the alert went out and 139 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1073 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 118 m²/s²
0-3 km storm-relative helicity: 192 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 
WFUS53 KLOT 202311
TORLOT
ILC099-202345-

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE CHICAGO IL
612 PM CDT TUE APR 20 2004

THE NATIONAL WEATHER SERVICE IN CHICAGO HAS ISSUED A

* TORNADO WARNING FOR...
  LA SALLE COUNTY IN NORTH CENTRAL ILLINOIS

* UNTIL 645 PM CDT

* AT 608 PM CDT...THE PUBLIC REPORTED A TORNADO AND RADAR INDICATED
  ROTATION 2 MILES NORTHEAST OF LA SALLE...MOVING NORTHEAST AT 30    
  MPH.

* THE STORM WILL BE NEAR...
  NAPLATE AROUND 615 PM CDT.
  OTTAWA AROUND 620 PM CDT.
  SHERIDAN AROUND 645 PM CDT.

THIS EXTENDS THE PREVIOUS TORNADO WARNING.

TWO LARGE AND DESTRUCTIVE TORNADOES ARE ON THE GROUND. ONE NEAR 
UTICA AND ONE NEAR LASALLE. TAKE IMMEDIATE SHELTER. IF NO BASEMENT 
IS AVAILABLE...SEEK SHELTER IN AN INTERIOR CLOSET...BATHROOM...OR 
HALLWAY ON THE LOWEST FLOOR. STAY AWAY FROM WINDOWS.

LAT...LON 4156 8861 4143 8860 4126 8906 4138 8915
          4142 8915 4165 8869
$$

BRUMER

The office that day

Everything else NWS Chicago, IL issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 20, 5:33 PM CDT	Tornado Warning	LOT	LaSalle	42 min
Apr 20, 6:04 PM CDT	Severe Thunderstorm Warning	LOT	Ford, Iroquois, Livingston	56 min
Apr 20, 6:26 PM CDT	Tornado Warning	LOT	Grundy	34 min
Apr 20, 6:37 PM CDT	Tornado Warning	LOT	Ford, Iroquois, Livingston	38 min
Apr 20, 6:43 PM CDT	Tornado Warning	LOT	Kendall, LaSalle	32 min

Nearby

Tornado Warnings in Illinois, 2004 Every tornado warning in 2004 Tornadoes 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive.