Alert archive / Illinois / Tornado Watches in 2008

Tornado Watch 963

December 27, 200812 counties in Illinois; 5 counties in Indiana

The Storm Prediction Center issued this tornado watch at Dec 27, 2008, 12:30 PM CST for 12 counties in Illinois; 5 counties in Indiana. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued
Dec 27, 2008, 12:30 PM CST (18:30 UTC)
Expired
Dec 27, 2008, 4:43 PM CST
In force
4 hr
Issued by
the Storm Prediction Center
Largest hail expected
1 in
Strongest gust expected
60 kt

Counties Cook County, IL, DeKalb County, IL, DuPage County, IL, Ford County, IL, Grundy County, IL, Iroquois County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, LaSalle County, IL, Livingston County, IL, Will County, IL, Benton County, IN, Jasper County, IN, Lake County, IN, Newton County, IN, Porter County, IN

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes
30%
One or more EF2 to EF5 tornadoes
30%
Ten or more severe wind reports
50%
One or more gusts of 65 knots or more
40%
Ten or more severe hail reports
5%
One or more hailstones of 2 inches or more
5%
Six or more combined severe hail and wind reports
70%

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
Dec 27, 12:37 PM CSTFlash Flood WarningLOTBoone, DeKalb, LaSalle, Lee, Ogle, Winnebago8 hr
Dec 27, 1:00 PM CSTSevere Thunderstorm WarningLOTFord, Iroquois, Livingston75 min
Dec 27, 1:25 PM CSTSevere Thunderstorm WarningLOTCook, Ford, Grundy, Iroquois, Kankakee, Kendall and 3 more80 min
Dec 27, 1:51 PM CSTFlash Flood WarningLOTFord, Grundy, Iroquois, Kankakee, LaSalle, Livingston6 hr
Dec 27, 2:08 PM CSTSevere Thunderstorm WarningLOTIroquois, Kankakee67 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Lincoln, IL (KILX), launched 12:00Z, 6.5 hours before the alert went out and 165 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, Lincoln, IL at 12:00Z on 2008-12-27Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 87 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, Lincoln, IL at 12:00Z on 2008-12-27The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 451 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
87 J/kg
Mixed-layer CIN
-128 J/kg
Mixed-layer LCL
538 m above ground
0-6 km bulk shear
47 kt
0-1 km storm-relative helicity
451 m²/s²
0-3 km storm-relative helicity
455 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.3

Open this sounding in Storm Lab

The text

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

303 
WWUS20 KWNS 271829
SEL3  
SPC WW 271829
ILZ000-INZ000-LMZ000-280100-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 963
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CST SAT DEC 27 2008

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

       NORTHEAST ILLINOIS
       NORTHWEST INDIANA
       LAKE MICHIGAN

EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 1230 PM UNTIL
700 PM CST.

TORNADOES...HAIL TO 1 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 55 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 20 MILES NORTHWEST OF
MARSEILLES ILLINOIS TO 15 MILES SOUTH OF VALPARAISO INDIANA.  FOR
A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU3).

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 960...WW 961...WW 962...

DISCUSSION...NARROW LINE OF LOW-TOPPED STORMS CONTINUES TO RACE NEWD
ACROSS CENTRAL IL AND WILL LIKELY MOVE ACROSS AT LEAST THE SRN HALF
OF THE CHICAGO METRO AND INTO FAR NWRN IND OVER THE NEXT COUPLE
HOURS.  WIND DAMAGE WILL BE PRIMARY SEVERE THREAT FROM THE
STRONGLY-FORCED LINE...ALTHOUGH EXTREME LOW LEVEL SHEAR AND STRONG
PRESSURE FALLS AT THE SURFACE MAY SUPPORT A RISK OF ISOLATED
TORNADOES.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 300.
MEAN STORM MOTION VECTOR 23050.


...EVANS

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Dec 26, 11:15 PM CSTMesoscale DiscussionSPCAdams, Brown, Fulton, Hancock, Henderson, Knox and 6 more90 min
Dec 27, 1:35 AM CSTTornado WatchSPCAdams, Brown, Calhoun, Cass, Champaign, Christian and 26 more7 hr
Dec 27, 4:30 AM CSTTornado WatchSPCAdams, Bond, Brown, Calhoun, Clinton, Fayette and 11 more8 hr
Dec 27, 8:03 AM CSTMesoscale DiscussionSPCBond, Brown, Calhoun, Clinton, Greene, Jersey and 8 more117 min
Dec 27, 8:48 AM CSTMesoscale DiscussionSPCCass, Christian, DeWitt, Fulton, Knox, Logan and 9 more27 min
Dec 27, 9:34 AM CSTMesoscale DiscussionSPCAlexander, Bond, Calhoun, Clinton, Jackson, Jersey and 8 more56 min
Dec 27, 10:26 AM CSTMesoscale DiscussionSPCAdams, Alexander, Bond, Brown, Calhoun, Cass and 45 more94 min
Dec 27, 10:58 AM CSTTornado WatchSPCBrown, Bureau, Calhoun, Cass, Champaign, Christian and 43 more8 hr
Dec 27, 11:46 AM CSTMesoscale DiscussionSPCBureau, Calhoun, Cass, Christian, DeKalb, DeWitt and 32 more89 min
Dec 27, 12:45 PM CSTTornado WatchSPCBond, Clinton, Fayette, Jersey, Macoupin, Madison and 6 more5 hr
Dec 27, 1:52 PM CSTTornado WatchSPCAlexander, Edwards, Franklin, Gallatin, Hamilton, Hardin and 13 more5 hr
Dec 27, 1:54 PM CSTMesoscale DiscussionSPCBond, Champaign, Christian, Clark, Clay, Clinton and 29 more2 hr
Dec 27, 3:46 PM CSTMesoscale DiscussionSPCAlexander, Clark, Clay, Clinton, Coles, Crawford and 27 more89 min
Dec 27, 5:06 PM CSTMesoscale DiscussionSPCCrawford, Edwards, Gallatin, Hamilton, Hardin, Johnson and 10 more84 min

Nearby

Tornado Watches in Illinois, 2008Tornado Watches in Indiana, 2008Every tornado watch in 2008

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.