Alert archive / Illinois / Tornado Warnings in 1991

Tornado Warning 13, NWS Chicago, IL

April 29, 1991McHenry County, Illinois

NWS Chicago, IL issued this tornado warning at Apr 29, 1991, 8:37 PM CDT for McHenry County, Illinois. It was in force for 68 min.

The area

The counties it named.

The facts

Issued
Apr 29, 1991, 8:37 PM CDT (01:37 UTC)
Expired
Apr 29, 1991, 9:45 PM CDT
In force
68 min
Issued by
NWS Chicago, IL
Area
Whole counties

County McHenry County, IL

The nearest sounding before it

Green Bay/Straub, WI (KGRB), launched 00:00Z, 1.6 hours before the alert went out and 241 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, Green Bay/Straub, WI at 00:00Z on 1991-04-30Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 22 joules per kilogram.LCLLFCEL10008507005003002001001 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, Green Bay/Straub, WI at 00:00Z on 1991-04-30The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 95 square meters per square second.1939587897117Sfc1 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
22 J/kg
Mixed-layer CIN
-124 J/kg
Mixed-layer LCL
956 m above ground
0-6 km bulk shear
40 kt
0-1 km storm-relative helicity
95 m²/s²
0-3 km storm-relative helicity
114 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 
TTAA00 KCHI 300137
TORCHI
ILC111-300245-

BULLETIN - IMMEDIATE BROADCAST REQUESTED/EBS ACTIVATION REQUESTED 
TORNADO WARNING 
NATIONAL WEATHER SERVICE CHICAGO IL
837 PM CDT MON APR 29 1991

THE NATIONAL WEATHER SERVICE HAS ISSUED A TORNADO WARNING 
EFFECTIVE UNTIL 945 PM CDT FOR PEOPLE IN THE FOLLOWING COUNTY

   IN THE NORTHEAST PART OF ILLINOIS
      MCHENRY

AT 8 30 PM CDT A TORNADO WAS REPORTED BY THE MC HENRY COUNTY
SHERIFF AT GARDEN PRAIRIE OR ABOUT 5 MILES WEST OF MARENGO...
OR 15 MILES WEST SOUTHWEST OF WOODSTOCK. THE STORM WAS MOVING
NORTHEAST AT 40 MPH. OTHER SEVERE STORMS WERE MOVING NORTHEAST
OUT OF NORTHERN KANE COUNTY TOWARD SOUTHEAST MC HENRY COUNTY.

IF YOU ARE IN THE PATH OF A TORNADO...THE SAFEST PLACE TO BE IS IN
A BASEMENT. GET UNDER A WORKBENCH OR PIECE OF STURDY FURNITURE.
IF NO BASEMENT IS AVAILABLE...FIND SHELTER IN AN INTERIOR ROOM
SUCH AS A CLOSET ON THE LOWEST FLOOR. USE BLANKETS...PILLOWS...
OR CUSHIONS TO COVER YOUR BODY. AVOID WINDOWS.

MORRISON
ATTN ISP  2 AND 15

The office that day

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

IssuedProductOfficeCountiesLasted
Apr 29, 7:23 PM CDTSevere Thunderstorm WarningLOTLaSalle, Livingston67 min
Apr 29, 7:29 PM CDTTornado WarningLOTLaSalle61 min
Apr 29, 8:03 PM CDTTornado WarningLOTGrundy, Kendall57 min
Apr 29, 8:03 PM CDTTornado WarningLOTKane57 min
Apr 29, 8:15 PM CDTSevere Thunderstorm WarningLOTGrundy, Livingston60 min
Apr 29, 8:15 PM CDTSevere Thunderstorm WarningLOTKendall60 min
Apr 29, 8:15 PM CDTSevere Thunderstorm WarningLOTMcHenry60 min

Nearby

Tornado Warnings in Illinois, 1991Every tornado warning in 1991Tornadoes in 1991

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.