Alert archive / Illinois / Tornado Watches in 2009
Tornado Watch 745
The Storm Prediction Center issued this tornado watch at Sep 27, 2009, 8:22 PM CDT for 45 counties in Illinois; 5 counties in Indiana; 10 counties in Wisconsin. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 27, 2009, 8:22 PM CDT (01:22 UTC)
- Expired
- Sep 27, 2009, 11:43 PM CDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 60 kt
All 60 counties
Boone County, IL, Bureau County, IL, Cass County, IL, Champaign County, IL, Christian County, IL, Clark County, IL, Coles County, IL, Cook County, IL, Cumberland County, IL, DeKalb County, IL, DeWitt County, IL, Douglas County, IL, DuPage County, IL, Edgar County, IL, Ford County, IL, Grundy County, IL, Iroquois County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, Lake County, IL, LaSalle County, IL, Lee County, IL, Livingston County, IL, Logan County, IL, Macon County, IL, Marshall County, IL, Mason County, IL, McHenry County, IL, McLean County, IL, Menard County, IL, Morgan County, IL, Moultrie County, IL, Ogle County, IL, Peoria County, IL, Piatt County, IL, Putnam County, IL, Sangamon County, IL, Shelby County, IL, Stark County, IL, Tazewell County, IL, Vermilion 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, Dodge County, WI, Jefferson County, WI, Kenosha County, WI, Milwaukee County, WI, Ozaukee County, WI, Racine County, WI, Rock County, WI, Walworth County, WI, Washington County, WI, Waukesha County, WI
The radar
The Chicago radar (KLOT), 41 km from the middle of the area, began a volume at 01:23 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
- 40%
- One or more gusts of 65 knots or more
- 30%
- Ten or more severe hail reports
- 30%
- 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.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 27, 9:19 PM CDT | Severe Thunderstorm Warning | LOT | Cook, DuPage, Will | 41 min |
| Sep 27, 9:24 PM CDT | Severe Thunderstorm Warning | LOT | Cook, Kendall, Will | 66 min |
| Sep 27, 9:49 PM CDT | Tornado Warning | LOT | Cook, Will | 26 min |
| Sep 27, 10:03 PM CDT | Severe Thunderstorm Warning | LOT | Lake, Porter | 57 min |
| Sep 27, 10:26 PM CDT | Severe Thunderstorm Warning | LOT | Iroquois | 49 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
Davenport, (KDVN), launched 00:00Z, 1.4 hours before the alert went out and 164 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
- 495 J/kg
- Mixed-layer CIN
- -30 J/kg
- Mixed-layer LCL
- 1417 m above ground
- 0-6 km bulk shear
- 63 kt
- 0-1 km storm-relative helicity
- 158 m²/s²
- 0-3 km storm-relative helicity
- 140 m²/s²
- Significant tornado parameter
- 0.2
- Supercell composite
- 1.1
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 27, 11:04 PM CDT | Mesoscale Discussion | SPC | Champaign, DeWitt, Douglas, Edgar, Ford, Iroquois and 6 more | 86 min |
| Sep 27, 9:14 PM CDT | Mesoscale Discussion | SPC | Elkhart, LaGrange, Marshall, Noble, Saint Joseph | 2 hr |
| Sep 27, 9:46 PM CDT | Severe Thunderstorm Watch | SPC | Adams, Allen, Blackford, Cass, DeKalb, Elkhart and 18 more | 4 hr |
| Sep 27, 11:21 PM CDT | Severe Thunderstorm Watch | SPC | Bartholomew, Boone, Brown, Carroll, Clay, Clinton and 37 more | 3 hr |
| Sep 28, 1:25 AM CDT | Mesoscale Discussion | SPC | Dearborn, Franklin, Jennings, Ohio, Ripley, Union | 65 min |
Nearby
Tornado Watches in Illinois, 2009Tornado Watches in Wisconsin, 2009Tornado Watches in Indiana, 2009Every tornado watch in 2009
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.