Alert archive / Illinois / Tornado Watches in 1998

Tornado Watch 360

May 15, 199821 counties in Illinois; 7 counties in Wisconsin

The Storm Prediction Center issued this tornado watch at May 15, 1998, 8:45 PM CDT for 21 counties in Illinois; 7 counties in Wisconsin. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued: May 15, 1998, 8:45 PM CDT (01:45 UTC)
Expired: May 16, 1998, 1:00 AM CDT
In force: 4 hr
Issued by: the Storm Prediction Center

All 28 counties

Boone County, IL, Champaign County, IL, Cook County, IL, DeKalb County, IL, DeWitt County, IL, DuPage County, IL, Ford County, IL, Grundy County, IL, Iroquois County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, Lake County, IL, LaSalle County, IL, Livingston County, IL, McHenry County, IL, McLean County, IL, Vermilion County, IL, Will County, IL, Winnebago County, IL, Woodford County, IL, Jefferson County, WI, Kenosha County, WI, Milwaukee County, WI, Racine County, WI, Rock County, WI, Walworth County, WI, Waukesha County, WI

The radar

The Chicago radar (KLOT), 51 km from the middle of the area, began a volume at 01:48 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.

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
May 15, 8:58 PM CDT	Severe Thunderstorm Warning	MKX	Green, Rock	62 min
May 15, 9:06 PM CDT	Severe Thunderstorm Warning	ILX	Marshall, Woodford	39 min
May 15, 9:20 PM CDT	Tornado Warning	LOT	Ogle, Winnebago	50 min
May 15, 9:46 PM CDT	Severe Thunderstorm Warning	MKX	Dodge, Jefferson, Walworth	59 min
May 15, 10:06 PM CDT	Severe Thunderstorm Warning	ILX	McLean	39 min
May 15, 10:38 PM CDT	Severe Thunderstorm Warning	MKX	Fond du Lac, Washington, Waukesha	62 min
May 15, 10:38 PM CDT	Severe Thunderstorm Warning	MKX	Kenosha, Racine	62 min

The nearest sounding before it

Lincoln, IL (KILX), launched 00:00Z, 1.8 hours before the alert went out and 213 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: 3559 J/kg
Mixed-layer CIN: -11 J/kg
Mixed-layer LCL: 821 m above ground
0-6 km bulk shear: 45 kt
0-1 km storm-relative helicity: 183 m²/s²
0-3 km storm-relative helicity: 254 m²/s²
Significant tornado parameter: 3.7
Supercell composite: 20.9

Open this sounding in Storm Lab

The text

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

197 
WWUS9 KMKC 160108
SEL0  
MKC WW 160108
WIZ000-ILZ000-160600-

BULLETIN - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 360
STORM PREDICTION CENTER NORMAN OK
808 PM CDT FRI MAY 15 1998

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

   SOUTHEAST WISCONSIN                          
   EASTERN ILLINOIS                           

EFFECTIVE THIS FRIDAY NIGHT AND SATURDAY MORNING FROM 845 PM UNTIL
100 AM CDT.

TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS ALONG AND 45 STATUTE MILES EITHER SIDE OF
A LINE FROM 40 MILES NORTHWEST OF MILWAUKEE WISCONSIN TO 40 MILES
SOUTHEAST OF BLOOMINGTON ILLINOIS.

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 354...WW 355...WW
356...WW 357...WW 358...WW 359...

DISCUSSION...INTENSE SQUALL LINE WESTERN IL WILL CONTINUE RAPIDLY
NEWD WHERE 00Z RAOB FROM ILX INDICATES VERY UNSTABLE AIRMASS AND
STRONGLY SHEARED WIND PROFILE.  SUPER CELLS AND TORNADOES ARE STILL
POSSIBLE WITH THIS LINE.


AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2 INCHES.  EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 70 KNOTS.  A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 520. 
MEAN STORM MOTION VECTOR 22040.


...HALES

432,0873 400,0873 400,0891 432,0892

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 15, 7:30 PM CDT	Tornado Watch	SPC	Adams, Brown, Calumet, Columbia, Dodge, Florence and 26 more	6 hr

Nearby

Tornado Watches in Illinois, 1998 Tornado Watches in Wisconsin, 1998 Every tornado watch 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.