Alert archive / Illinois / Tornado Warnings in 2004

Tornado Warning 13, NWS Chicago, IL

April 20, 2004Grundy County, Illinois

NWS Chicago, IL issued this tornado warning at Apr 20, 2004, 7:34 PM CDT for Grundy County, Illinois. It was in force for 41 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: Apr 20, 2004, 7:34 PM CDT (00:34 UTC)
Expired: Apr 20, 2004, 8:15 PM CDT
In force: 41 min
Issued by: NWS Chicago, IL
Area: Counties, with a storm outline in the text

County Grundy County, IL

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

Lincoln, IL (KILX), launched 00:00Z, 0.6 hours before the alert went out and 117 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: 118 J/kg
Mixed-layer CIN: -27 J/kg
Mixed-layer LCL: 1737 m above ground
0-6 km bulk shear: 40 kt
0-1 km storm-relative helicity: 176 m²/s²
0-3 km storm-relative helicity: 261 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.7

Open this sounding in Storm Lab

The text

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

000 
WFUS53 KLOT 210034
TORLOT
ILC063-210115-

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

THE NATIONAL WEATHER SERVICE IN CHICAGO HAS ISSUED A

* TORNADO WARNING FOR...
  GRUNDY COUNTY IN NORTHEAST ILLINOIS

* UNTIL 815 PM CDT

* AT 733 PM CDT...DOPPLER RADAR INDICATED STRONG ROTATION IN A SEVERE
  THUNDERSTORM NEAR 13 MILES SOUTHWEST OF GARDNER...MOVING NORTHEAST
  AT 20 MPH.

* THE STORM WILL BE NEAR...
  GARDNER AROUND 750 PM CDT.

* THE STORM WILL AFFECT THE TOWNS OF...
  GARDNER...

DO NOT WAIT UNTIL YOU HEAR OR SEE THE TORNADO. TAKE SHELTER NOW.

LAT...LON 4113 8858 4113 8827 4115 8828 4128 8827
          4131 8838
$$

MARSILI

NNNN

The office that day

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

Issued	Product	Office	Counties	Lasted
Apr 20, 7:01 PM CDT	Tornado Warning	LOT	Grundy, Will	29 min
Apr 20, 7:13 PM CDT	Tornado Warning	LOT	Kankakee	32 min
Apr 20, 7:15 PM CDT	Tornado Warning	LOT	Iroquois	30 min
Apr 20, 7:17 PM CDT	Tornado Warning	LOT	Livingston	43 min
Apr 20, 7:17 PM CDT	Tornado Warning	LOT	DuPage, Kane, Kendall	28 min
Apr 20, 7:21 PM CDT	Tornado Warning	LOT	LaSalle	24 min
Apr 20, 7:31 PM CDT	Tornado Warning	LOT	Will	29 min
Apr 20, 7:44 PM CDT	Tornado Warning	LOT	Kendall	31 min
Apr 20, 7:44 PM CDT	Tornado Warning	LOT	Kankakee	46 min
Apr 20, 7:47 PM CDT	Tornado Warning	LOT	Kendall	28 min
Apr 20, 7:53 PM CDT	Special Marine Warning	LOT		82 min
Apr 20, 7:53 PM CDT	Special Marine Warning	LOT		82 min
Apr 20, 7:53 PM CDT	Special Marine Warning	LOT		82 min
Apr 20, 8:02 PM CDT	Tornado Warning	LOT	Cook, Will	28 min
Apr 20, 8:03 PM CDT	Flash Flood Warning	LOT	Cook, Will	3 hr
Apr 20, 8:12 PM CDT	Tornado Warning	LOT	DuPage, Kane, Kendall	33 min
Apr 20, 8:27 PM CDT	Tornado Warning	LOT	Cook, Will	48 min
Apr 20, 9:11 PM CDT	Severe Thunderstorm Warning	LOT	Cook	49 min
Apr 20, 9:16 PM CDT	Special Marine Warning	LOT		89 min
Apr 20, 9:16 PM CDT	Special Marine Warning	LOT		89 min
Apr 20, 9:16 PM CDT	Special Marine Warning	LOT		89 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; the sounding from the Mesonet's radiosonde archive.