Alert archive / Illinois / Tornado Watches in 2014

Tornado Watch 412

July 12, 201427 counties in Illinois; 5 counties in Indiana

The Storm Prediction Center issued this tornado watch at Jul 12, 2014, 9:51 PM CDT for 27 counties in Illinois; 5 counties in Indiana. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Jul 12, 2014, 9:51 PM CDT (02:51 UTC)
Expired: Jul 13, 2014, 1:00 AM CDT
In force: 3 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1 in
Strongest gust expected: 60 kt

All 32 counties

Boone County, IL, Cook County, IL, DeKalb County, IL, DuPage County, IL, Ford County, IL, Fulton County, IL, Grundy County, IL, Iroquois County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, Knox County, IL, Lake County, IL, LaSalle County, IL, Lee County, IL, Livingston County, IL, Marshall County, IL, Mason County, IL, McHenry County, IL, McLean County, IL, Ogle County, IL, Peoria County, IL, Stark County, IL, Tazewell County, IL, Will County, IL, Winnebago County, IL, Woodford County, IL, Benton County, IN, Jasper County, IN, Lake County, IN, Newton County, IN, Porter County, IN

The radar

The Chicago radar (KLOT), 66 km from the middle of the area, began a volume at 02:53 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: 30%
One or more EF2 to EF5 tornadoes: 10%
Ten or more severe wind reports: 40%
One or more gusts of 65 knots or more: 5%
Ten or more severe hail reports: 20%
One or more hailstones of 2 inches or more: 5%
Six or more combined severe hail and wind reports: 70%

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
Jul 12, 9:53 PM CDT	Severe Thunderstorm Warning	LOT	DeKalb, Kane, Kendall, LaSalle, Lee, Ogle	52 min
Jul 12, 11:35 PM CDT	Flash Flood Warning	LOT	Cook, Will	6 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

Davenport, (KDVN), launched 00:00Z, 2.9 hours before the alert went out and 135 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: 2609 J/kg
Mixed-layer CIN: -4 J/kg
Mixed-layer LCL: 916 m above ground
0-6 km bulk shear: 38 kt
0-1 km storm-relative helicity: 129 m²/s²
0-3 km storm-relative helicity: 199 m²/s²
Significant tornado parameter: 2.0
Supercell composite: 13.9

Open this sounding in Storm Lab

The text

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

263 
WWUS20 KWNS 130254
SEL2  
SPC WW 130254
ILZ000-INZ000-LMZ000-130600-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 412
NWS STORM PREDICTION CENTER NORMAN OK
950 PM CDT SAT JUL 12 2014

THE NWS STORM PREDICTION CENTER HAS ISSUED A

* TORNADO WATCH FOR PORTIONS OF 
  NORTHERN ILLINOIS
  NORTHWEST INDIANA
  LAKE MICHIGAN

* EFFECTIVE THIS SATURDAY NIGHT AND SUNDAY MORNING FROM 950 PM
  UNTIL 100 AM CDT.

* PRIMARY THREATS INCLUDE...
  A COUPLE TORNADOES POSSIBLE
  SCATTERED DAMAGING WIND GUSTS TO 70 MPH POSSIBLE
  ISOLATED LARGE HAIL EVENTS TO 1 INCH IN DIAMETER POSSIBLE

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 85 STATUTE
MILES EAST AND WEST OF A LINE FROM 55 MILES WEST NORTHWEST OF
BENTON HARBOR MICHIGAN TO 40 MILES SOUTHWEST OF PEORIA ILLINOIS. 
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU2).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 411...

DISCUSSION...WDLY SCTD TSTMS/TSTM CLUSTERS IN NW IL EXPECTED TO
CONTINUE E ACROSS THE REMAINDER OF NRN IL THROUGH EARLY SUN. WHILE
MID-LVL LAPSE RATES WILL REMAIN MODEST...SUFFICIENT SFC-BASED
BUOYANCY APPEARS PRESENT TO SUPPORT CONTINUED REDEVELOPMENT OF STORM
UPDRAFTS EWD INTO THE CHICAGO AREA. STRENGTH OF LOW-LVL
SHEAR...QUALITY OF LOW-LVL MOISTURE...AND SMALL TEMPERATURE-DEWPOINT
SPREADS SUGGEST A RISK FOR OCCASIONAL LOW-LVL MESOCYCLONES/POSSIBLE
TORNADOES...IN ADDITION TO SMALL BOWING SEGMENTS WITH DMGG WIND.

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 500.
MEAN STORM MOTION VECTOR 28035.


...CORFIDI

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 12, 7:09 PM CDT	Mesoscale Discussion	SPC	Bureau, Fulton, Hancock, Henderson, Henry, Knox and 13 more	96 min
Jul 12, 9:09 PM CDT	Mesoscale Discussion	SPC	Boone, Bureau, Carroll, Cook, DeKalb, DuPage and 23 more	66 min
Jul 12, 11:44 PM CDT	Mesoscale Discussion	SPC	Grundy, Kendall, LaSalle, Will	31 min
Jul 13, 12:41 PM CDT	Mesoscale Discussion	SPC	Clay, Clinton, Crawford, Edwards, Franklin, Gallatin and 23 more	94 min
Jul 12, 10:32 PM CDT	Mesoscale Discussion	SPC	DeKalb, Elkhart, Kosciusko, LaGrange, LaPorte, Marshall and 5 more	118 min
Jul 13, 11:37 AM CDT	Mesoscale Discussion	SPC	Dearborn, Franklin, Ohio, Union	53 min
Jul 13, 12:17 PM CDT	Severe Thunderstorm Watch	SPC	Dearborn, Fayette, Franklin, Ohio, Ripley, Switzerland and 2 more	7 hr
Jul 13, 5:18 PM CDT	Mesoscale Discussion	SPC	Bartholomew, Clark, Dearborn, Decatur, Floyd, Franklin and 8 more	87 min

Nearby

Tornado Watches in Illinois, 2014 Tornado Watches in Indiana, 2014 Every tornado watch in 2014

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.