Alert archive / Illinois / Tornado Warnings in 1998

Tornado Warning 8, NWS Chicago, IL

June 18, 1998DeKalb County, LaSalle County, Illinois

NWS Chicago, IL issued this tornado warning at Jun 18, 1998, 7:31 PM CDT for DeKalb County, LaSalle County, Illinois. It was in force for 29 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Jun 18, 1998, 7:31 PM CDT (00:31 UTC)
Expired: Jun 18, 1998, 8:00 PM CDT
In force: 29 min
Issued by: NWS Chicago, IL
Area: Whole counties

Counties DeKalb County, IL, LaSalle County, IL

The radar

The Chicago radar (KLOT), 62 km from the middle of the area, began a volume at 00:40 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.

The watch it was issued in

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

Issued	Product	Office	Lasted
Jun 18, 4:00 PM CDT	Severe Thunderstorm Watch	SPC	5 hr

The nearest sounding before it

Lincoln, IL (KILX), launched 00:00Z, 0.5 hours before the alert went out and 164 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: 2675 J/kg
Mixed-layer CIN: -8 J/kg
Mixed-layer LCL: 1092 m above ground
0-6 km bulk shear: 27 kt
0-1 km storm-relative helicity: 115 m²/s²
0-3 km storm-relative helicity: 219 m²/s²
Significant tornado parameter: 1.7
Supercell composite: 17.5

Open this sounding in Storm Lab

The text

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

000 
TTAA00 KCHI 190030 RRA
TORCHI
ILC037-099-190126-

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE CHICAGO IL
731 PM CDT THU JUN 18 1998

THE NATIONAL WEATHER SERVICE IN CHICAGO HAS ISSUED A

* TORNADO WARNING FOR...
  SOUTHERN DEKALB COUNTY IN NORTH CENTRAL ILLINOIS
  NORTHERN LASALLE COUNTY IN NORTH CENTRAL ILLINOIS

* UNTIL 800 PM CDT

* AT 727 PM CDT DOPPLER RADAR INDICATED A POSSIBLE TORNADO
  NEAR TROY GROVE...OR 10 MILES NORTH OF LA SALLE. THE
  STORM WAS MOVING TO THE NORTHEAST AT 35 MPH.

* THE STORM WILL BE NEAR EARLVILLE...LELAND...AND HINCKLEY   
  BY 800 PM CDT.

GO TO THE BASEMENT OR A SMALL INTERIOR ROOM ON THE LOWEST
FLOOR!

IF YOU ARE IN A CAR...GO INSIDE A NEARBY STxURDY BUILDING!
AS A LAST RESORT LIE FLAT IN A DITCH AND COVE R YOUR HEAD.

$$
RATZER

The office that day

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

Issued	Product	Office	Counties	Lasted
Jun 18, 7:00 PM CDT	Severe Thunderstorm Warning	LOT	DeKalb, Grundy, Kane, Kendall, LaSalle	60 min
Jun 18, 7:00 PM CDT	Severe Thunderstorm Warning	LOT	Boone, McHenry	60 min
Jun 18, 7:00 PM CDT	Severe Thunderstorm Warning	LOT	Livingston	60 min
Jun 18, 7:55 PM CDT	Severe Thunderstorm Warning	LOT	Cook, DuPage, Will	65 min
Jun 18, 7:55 PM CDT	Severe Thunderstorm Warning	LOT	Lake	65 min

Nearby

Tornado Warnings in Illinois, 1998 Every tornado warning in 1998 Tornadoes in 1998

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.