Alert archive / Illinois / Severe Thunderstorm Watches in 2009
Severe Thunderstorm Watch 620
The Storm Prediction Center issued this severe thunderstorm watch at Jul 24, 2009, 9:51 PM CDT for 24 counties in Illinois; 5 counties in Iowa; 6 counties in Missouri. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 24, 2009, 9:51 PM CDT (02:51 UTC)
- Expired
- Jul 25, 2009, 1:32 AM CDT
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 60 kt
All 35 counties
Des Moines County, IA, Henry County, IA, Jefferson County, IA, Lee County, IA, Van Buren County, IA, Adams County, IL, Brown County, IL, Cass County, IL, DeWitt County, IL, Fulton County, IL, Hancock County, IL, Henderson County, IL, Knox County, IL, Logan County, IL, Marshall County, IL, Mason County, IL, McDonough County, IL, McLean County, IL, Menard County, IL, Morgan County, IL, Peoria County, IL, Pike County, IL, Sangamon County, IL, Schuyler County, IL, Scott County, IL, Stark County, IL, Tazewell County, IL, Warren County, IL, Woodford County, IL, Clark County, MO, Knox County, MO, Lewis County, MO, Marion County, MO, Scotland County, MO, Shelby County, MO
The radar
The Quad Cities radar (KDVN), 93 km from the middle of the area, began a volume at 02:52 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
- 10%
- One or more EF2 to EF5 tornadoes
- 5%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 30%
- Ten or more severe hail reports
- 20%
- One or more hailstones of 2 inches or more
- 10%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
9 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 24, 10:19 PM CDT | Severe Thunderstorm Warning | ILX | Fulton, Knox, McLean, Marshall, Peoria, Stark and 2 more | 56 min |
| Jul 24, 10:42 PM CDT | Severe Thunderstorm Warning | ILX | McLean, Mason, Peoria, Tazewell, Woodford | 48 min |
| Jul 24, 11:00 PM CDT | Severe Thunderstorm Warning | DVN | McDonough, Warren | 37 min |
| Jul 24, 11:01 PM CDT | Severe Thunderstorm Warning | ILX | Fulton, Mason, Peoria, Tazewell | 44 min |
| Jul 24, 11:16 PM CDT | Severe Thunderstorm Warning | ILX | DeWitt, Logan, McLean, Mason, Menard, Piatt and 2 more | 59 min |
| Jul 24, 11:46 PM CDT | Severe Thunderstorm Warning | ILX | Champaign, DeWitt, McLean, Piatt, Vermilion | 59 min |
| Jul 24, 11:46 PM CDT | Severe Thunderstorm Warning | ILX | Cass, Fulton, Mason, Menard, Morgan, Schuyler | 44 min |
| Jul 25, 12:06 AM CDT | Severe Thunderstorm Warning | ILX | Christian, DeWitt, Logan, Macon, Menard, Moultrie and 1 more | 39 min |
| Jul 25, 12:37 AM CDT | Severe Thunderstorm Warning | ILX | Christian, Macon, Moultrie, Piatt, Sangamon, Shelby | 53 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, 2.9 hours before the alert went out and 97 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
- 1164 J/kg
- Mixed-layer CIN
- -72 J/kg
- Mixed-layer LCL
- 1266 m above ground
- 0-6 km bulk shear
- 52 kt
- 0-1 km storm-relative helicity
- 87 m²/s²
- 0-3 km storm-relative helicity
- 321 m²/s²
- Significant tornado parameter
- 1.1
- Supercell composite
- 12.3
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 24, 7:20 PM CDT | Mesoscale Discussion | SPC | Bureau, Carroll, DeKalb, Henderson, Henry, Jo Daviess and 16 more | 85 min |
| Jul 24, 9:22 PM CDT | Mesoscale Discussion | SPC | Bureau, DeWitt, Fulton, Hancock, Henderson, Henry and 18 more | 53 min |
| Jul 24, 11:00 PM CDT | Severe Thunderstorm Watch | SPC | Champaign, Christian, Coles, Douglas, Edgar, Iroquois and 6 more | 3 hr |
| Jul 24, 11:46 PM CDT | Mesoscale Discussion | SPC | Adams, Brown, Cass, Champaign, Christian, Clark and 26 more | 89 min |
| Jul 25, 1:26 AM CDT | Severe Thunderstorm Watch | SPC | Bond, Clark, Clay, Clinton, Crawford, Cumberland and 16 more | 4 hr |
| Jul 25, 3:09 AM CDT | Mesoscale Discussion | SPC | Edwards, Franklin, Gallatin, Hamilton, Hardin, Johnson and 8 more | 96 min |
| Jul 25, 2:17 AM CDT | Mesoscale Discussion | SPC | Audrain, Barton, Bates, Benton, Boone, Caldwell and 32 more | 88 min |
Nearby
Severe Thunderstorm Watches in Illinois, 2009Severe Thunderstorm Watches in Missouri, 2009Severe Thunderstorm Watches in Iowa, 2009Every severe thunderstorm 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.