Alert archive / Illinois / Tornado Watches in 2015

Tornado Watch 288

June 11, 201520 counties in Illinois

The Storm Prediction Center issued this tornado watch at Jun 11, 2015, 5:49 PM CDT for 20 counties in Illinois. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Jun 11, 2015, 5:49 PM CDT (22:49 UTC)
Expired
Jun 11, 2015, 7:52 PM CDT
In force
2 hr
Issued by
the Storm Prediction Center
Largest hail expected
2 in
Strongest gust expected
60 kt

Counties Bureau County, IL, Ford County, IL, Fulton County, IL, Grundy County, IL, Henry County, IL, Kendall County, IL, Knox County, IL, LaSalle County, IL, Lee County, IL, Livingston County, IL, Marshall County, IL, McDonough County, IL, McLean County, IL, Peoria County, IL, Putnam County, IL, Stark County, IL, Tazewell County, IL, Warren County, IL, Whiteside County, IL, Woodford County, IL

The radar

The Quad Cities radar (KDVN), 82 km from the middle of the area, began a volume at 22:52 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
30%
One or more gusts of 65 knots or more
10%
Ten or more severe hail reports
30%
One or more hailstones of 2 inches or more
30%
Six or more combined severe hail and wind reports
60%

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 12:00Z, 10.8 hours before the alert went out and 77 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, Davenport, at 12:00Z on 2015-06-11Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 20 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, Davenport, at 12:00Z on 2015-06-11The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 197 square meters per square second.193958Sfc1 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
20 J/kg
Mixed-layer CIN
-459 J/kg
Mixed-layer LCL
1808 m above ground
0-6 km bulk shear
34 kt
0-1 km storm-relative helicity
197 m²/s²
0-3 km storm-relative helicity
190 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

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

527 
WWUS20 KWNS 112248
SEL8  
SPC WW 112248
ILZ000-120500-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 288
NWS STORM PREDICTION CENTER NORMAN OK
550 PM CDT THU JUN 11 2015

THE NWS STORM PREDICTION CENTER HAS ISSUED A

* TORNADO WATCH FOR PORTIONS OF 
  NORTHERN AND CENTRAL ILLINOIS

* EFFECTIVE THIS THURSDAY AFTERNOON FROM 550 PM UNTIL MIDNIGHT
  CDT.

* PRIMARY THREATS INCLUDE...
  A COUPLE TORNADOES POSSIBLE
  ISOLATED VERY LARGE HAIL EVENTS TO 2 INCHES IN DIAMETER POSSIBLE
  ISOLATED DAMAGING WIND GUSTS TO 70 MPH POSSIBLE

SUMMARY...A SMALL AREA ALONG A STALLED SURFACE FRONT WILL REMAIN
FAVORABLE FOR SUPERCELLS CAPABLE OF A COUPLE OF TORNADOES IN
ADDITION TO ISOLATED LARGE HAIL AND DAMAGING OUTFLOW WINDS THROUGH
THIS EVENING.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 55 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 40 MILES SOUTH SOUTHWEST OF
MOLINE ILLINOIS TO 25 MILES EAST SOUTHEAST OF MARSEILLES
ILLINOIS.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU8).

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 284...WW 285...WW
286...WW 287...

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 26025.


...MEAD

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jun 11, 3:52 PM CDTMesoscale DiscussionSPCCook, DuPage, Grundy, Iroquois, Kankakee, Kendall and 2 more113 min
Jun 11, 1:01 PM CDTMesoscale DiscussionSPCAdams, Cass, Fremont, Mills, Montgomery, Page and 2 more119 min
Jun 11, 1:53 PM CDTTornado WatchSPCAdair, Adams, Appanoose, Cass, Clarke, Davis and 13 more7 hr
Jun 11, 5:48 PM CDTMesoscale DiscussionSPCDecatur, Fremont, Page, Ringgold, Taylor, Wayne87 min

Nearby

Tornado Watches in Illinois, 2015Every tornado watch in 2015

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.