Alert archive / Illinois / Tornado Watches in 2012
Tornado Watch 601
The Storm Prediction Center issued this tornado watch at Aug 31, 2012, 3:53 PM CDT for 21 counties in Illinois. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 31, 2012, 3:53 PM CDT (20:53 UTC)
- Expired
- Aug 31, 2012, 9:02 PM CDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 0.5 in
- Strongest gust expected
- 60 kt
All 21 counties
Cass County, IL, Champaign County, IL, Christian County, IL, Clay County, IL, Coles County, IL, Cumberland County, IL, DeWitt County, IL, Douglas County, IL, Effingham County, IL, Jasper County, IL, Logan County, IL, Macon County, IL, Mason County, IL, Menard County, IL, Morgan County, IL, Moultrie County, IL, Piatt County, IL, Sangamon County, IL, Schuyler County, IL, Scott County, IL, Shelby County, IL
The radar
The Lincoln radar (KILX), 57 km from the middle of the area, began a volume at 20:53 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
- 40%
- 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
- 50%
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, 8.9 hours before the alert went out and 114 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.
- Mixed-layer CAPE
- 947 J/kg
- Mixed-layer CIN
- -143 J/kg
- Mixed-layer LCL
- 1049 m above ground
- 0-6 km bulk shear
- 20 kt
- 0-1 km storm-relative helicity
- -60 m²/s²
- 0-3 km storm-relative helicity
- -45 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- -0.3
The text
As transmitted, in the capitals the NWS used until 2016.
297
WWUS20 KWNS 312051
SEL1
SPC WW 312051
ILZ000-010300-
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 601
NWS STORM PREDICTION CENTER NORMAN OK
350 PM CDT FRI AUG 31 2012
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
CENTRAL ILLINOIS
EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 350 PM UNTIL
1000 PM CDT.
TORNADOES...HAIL TO 0.5 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 40 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 80 MILES WEST OF SPRINGFIELD
ILLINOIS TO 20 MILES EAST NORTHEAST OF MATTOON ILLINOIS. 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 600...
DISCUSSION...AREA OF TSTMS IN W CNTRL IL...SOME OF WHICH HAVE SHOWN
LOW-LVL ROTATION...EXPECTED TO MOVE/DEVELOP NNE INTO CNTRL IL A BIT
LATER THIS AFTN/EVE. STORMS MAY CONTINUE TO EXHIBIT LOW-LVL
ROTATION GIVEN PRESENCE OF DIFFUSE WNW-ESE WARM FRONT APPROACHING
SRN PART OF WW...AND CONTINUED NNE MOVEMENT OF REMNANT CIRCULATION
OF FORMER HRCN ISAAC.
AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 19030.
...CORFIDISPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 31, 1:26 PM CDT | Mesoscale Discussion | SPC | Alexander, Bond, Calhoun, Clinton, Franklin, Greene and 14 more | 64 min |
| Aug 31, 1:56 PM CDT | Tornado Watch | SPC | Alexander, Bond, Brown, Calhoun, Clinton, Fayette and 19 more | 8 hr |
| Aug 31, 6:01 PM CDT | Mesoscale Discussion | SPC | Alexander, Bond, Brown, Calhoun, Cass, Champaign and 40 more | 89 min |
Nearby
Tornado Watches in Illinois, 2012Every tornado watch in 2012
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.