Alert archive / Indiana / Tornado Watches in 2008

Tornado Watch 901

September 13, 200813 counties in Illinois; 37 counties in Indiana

The Storm Prediction Center issued this tornado watch at Sep 13, 2008, 1:46 AM CDT for 13 counties in Illinois; 37 counties in Indiana. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued
Sep 13, 2008, 1:46 AM CDT (06:46 UTC)
Expired
Sep 13, 2008, 7:49 AM CDT
In force
6 hr
Issued by
the Storm Prediction Center
Largest hail expected
0.5 in
Strongest gust expected
50 kt
All 50 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, Lee County, IL, Livingston County, IL, Will County, IL, Adams County, IN, Allen County, IN, Benton County, IN, Blackford County, IN, Carroll County, IN, Cass County, IN, Clinton County, IN, DeKalb County, IN, Delaware County, IN, Elkhart County, IN, Fulton County, IN, Grant County, IN, Howard County, IN, Huntington County, IN, Jasper County, IN, Jay County, IN, Kosciusko County, IN, LaGrange County, IN, Lake County, IN, LaPorte County, IN, Madison County, IN, Marshall County, IN, Miami County, IN, Newton County, IN, Noble County, IN, Porter County, IN, Pulaski County, IN, Randolph County, IN, Saint Joseph County, IN, Starke County, IN, Steuben County, IN, Tippecanoe County, IN, Tipton County, IN, Wabash County, IN, Wells County, IN, White County, IN, Whitley County, IN

The radar

The Chicago radar (KLOT), 59 km from the middle of the area, began a volume at 06:47 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.

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
20%
Ten or more severe wind reports
10%
One or more gusts of 65 knots or more
5%
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
40%

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
Sep 13, 2:12 AM CDTFlash Flood WarningLOTDeKalb, Kane, Kendall, LaSalle, Lee3 hr
Sep 13, 3:34 AM CDTFlash Flood WarningLOTCook, DuPage, Kane, Will4 hr
Sep 13, 4:14 AM CDTFlash Flood WarningLOTPorter3 hr
Sep 13, 4:26 AM CDTFlash Flood WarningIWXLaPorte4 hr
Sep 13, 4:29 AM CDTSevere Thunderstorm WarningLOTBoone, DeKalb, Grundy, Kane, Kendall, LaSalle and 4 more1 min
Sep 13, 4:33 AM CDTFlash Flood WarningLOTBoone, Cook, DeKalb, DuPage, Grundy, Kane and 7 more6 hr
Sep 13, 5:06 AM CDTFlash Flood WarningIWXSaint Joseph4 hr
Sep 13, 5:26 AM CDTFlash Flood WarningLOTCook, Kane, Lake, McHenry5 hr
Sep 13, 7:26 AM CDTFlash Flood WarningLOTCook, Grundy, Kankakee, Kendall, LaSalle, Livingston and 1 more3 hr
Sep 13, 7:35 AM CDTFlash Flood WarningLOTCook, DuPage, Kane, Will3 hr

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 00:00Z, 6.8 hours before the alert went out and 163 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 00:00Z on 2008-09-13Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 197 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 00:00Z on 2008-09-13The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 156 square meters per square second.19395878Sfc1 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
197 J/kg
Mixed-layer CIN
-60 J/kg
Mixed-layer LCL
604 m above ground
0-6 km bulk shear
49 kt
0-1 km storm-relative helicity
156 m²/s²
0-3 km storm-relative helicity
231 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.3

Open this sounding in Storm Lab

The text

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

926 
WWUS20 KWNS 130645
SEL1  
SPC WW 130645
ILZ000-INZ000-LMZ000-131500-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 901
NWS STORM PREDICTION CENTER NORMAN OK
145 AM CDT SAT SEP 13 2008

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

       NORTHERN ILLINOIS
       NORTHERN INDIANA
       LAKE MICHIGAN

EFFECTIVE THIS SATURDAY MORNING FROM 145 AM UNTIL 1000 AM CDT.

TORNADOES...HAIL TO 0.5 INCH IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 60 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 45 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 30 MILES WEST NORTHWEST OF
MARSEILLES ILLINOIS TO 25 MILES SOUTHEAST OF FORT WAYNE INDIANA. 
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU1).

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 900...

DISCUSSION...INCREASED LOW LVL VEERING WIND PROFILES ALONG NE-MOVING
WARM FRONT...ALONG WITH FAIRLY RICH LOW LVL MOISTURE AND
STRENGTHENING WAA BENEATH ENTRANCE REGION OF HIGH LVL JET STREAK
OVER THE GRT LKS ...SUGGEST CONTINUE THREAT FOR STORMS WITH LOW LVL
ROTATION OVER PARTS OF NRN IL/IND /REF MCD 2258/.  ISOLD TORNADOES
WILL BE POSSIBLE WITH ANY MORE SUSTAINED/DISCRETE STORMS.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 50 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
450. MEAN STORM MOTION VECTOR 26030.


...CORFIDI

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Sep 12, 11:44 PM CDTMesoscale DiscussionSPCFord, Grundy, Iroquois, Kankakee, Knox, LaSalle and 9 more91 min
Sep 13, 1:29 AM CDTMesoscale DiscussionSPCFord, Grundy, Iroquois, Kankakee, Kendall, LaSalle and 2 more91 min
Sep 13, 3:28 AM CDTMesoscale DiscussionSPCCook, DeKalb, DuPage, Ford, Grundy, Iroquois and 11 more92 min
Sep 13, 5:27 PM CDTMesoscale DiscussionSPCBrown, Calhoun, Cass, Christian, DeWitt, Greene and 13 more2 hr
Sep 13, 2:28 PM CDTMesoscale DiscussionSPCDeKalb, Elkhart, Kosciusko, LaGrange, LaPorte, Marshall and 5 more2 hr

Nearby

Tornado Watches in Indiana, 2008Tornado Watches in Illinois, 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; radar from the NEXRAD Level II archive.