Alert archive / Illinois / Severe Thunderstorm Watches in 2008
Severe Thunderstorm Watch 809
The Storm Prediction Center issued this severe thunderstorm watch at Aug 5, 2008, 2:55 AM CDT for 24 counties in Illinois; 7 counties in Iowa. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 5, 2008, 2:55 AM CDT (07:55 UTC)
- Expired
- Aug 5, 2008, 7:10 AM CDT
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
All 31 counties
Cedar County, IA, Des Moines County, IA, Henry County, IA, Lee County, IA, Louisa County, IA, Muscatine County, IA, Scott County, IA, Bureau County, IL, Ford County, IL, Fulton County, IL, Grundy County, IL, Hancock County, IL, Henderson County, IL, Henry County, IL, Iroquois County, IL, Kankakee County, IL, Knox County, IL, LaSalle County, IL, Livingston County, IL, Marshall County, IL, McDonough County, IL, McLean County, IL, Mercer County, IL, Peoria County, IL, Putnam County, IL, Rock Island County, IL, Stark County, IL, Tazewell County, IL, Warren County, IL, Will County, IL, Woodford County, IL
The radar
The Quad Cities radar (KDVN), 50 km from the middle of the area, began a volume at 07:57 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
- 50%
- One or more gusts of 65 knots or more
- 40%
- Ten or more severe hail reports
- 30%
- One or more hailstones of 2 inches or more
- 20%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
11 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 5, 3:25 AM CDT | Severe Thunderstorm Warning | DVN | Henderson, Mercer, Rock Island, Warren | 72 min |
| Aug 5, 3:52 AM CDT | Severe Thunderstorm Warning | ILX | Fulton, Knox, Marshall, Peoria, Stark, Tazewell and 1 more | 53 min |
| Aug 5, 4:00 AM CDT | Severe Thunderstorm Warning | DVN | Bureau, Henry, Putnam | 73 min |
| Aug 5, 4:10 AM CDT | Severe Thunderstorm Warning | LOT | LaSalle, Lee | 50 min |
| Aug 5, 4:42 AM CDT | Severe Thunderstorm Warning | ILX | McLean, Mason, Peoria, Tazewell, Woodford | 48 min |
| Aug 5, 4:57 AM CDT | Severe Thunderstorm Warning | LOT | Grundy, Kendall, LaSalle | 63 min |
| Aug 5, 5:24 AM CDT | Severe Thunderstorm Warning | ILX | Champaign, McLean | 24 min |
| Aug 5, 5:29 AM CDT | Severe Thunderstorm Warning | LOT | Ford, Iroquois, Kankakee, Livingston | 49 min |
| Aug 5, 6:04 AM CDT | Tornado Warning | LOT | Iroquois, Kankakee | 26 min |
| Aug 5, 6:08 AM CDT | Severe Thunderstorm Warning | DVN | Henry, Mercer, Rock Island | 22 min |
| Aug 5, 6:20 AM CDT | Severe Thunderstorm Warning | DVN | Mercer | 40 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, 7.9 hours before the alert went out and 48 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
- 6781 J/kg
- Mixed-layer CIN
- -3 J/kg
- Mixed-layer LCL
- 790 m above ground
- 0-6 km bulk shear
- 48 kt
- 0-1 km storm-relative helicity
- 163 m²/s²
- 0-3 km storm-relative helicity
- 239 m²/s²
- Significant tornado parameter
- 7.9
- Supercell composite
- 32.9
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 4, 7:17 PM CDT | Severe Thunderstorm Watch | SPC | Cook, DuPage, Ford, Grundy, Iroquois, Kane and 5 more | 7 hr |
| Aug 4, 8:50 PM CDT | Mesoscale Discussion | SPC | Grundy, Kankakee, Will | 85 min |
| Aug 5, 1:53 AM CDT | Mesoscale Discussion | SPC | Bureau, Carroll, Henry, Mercer, Rock Island, Whiteside | 97 min |
| Aug 5, 7:07 AM CDT | Mesoscale Discussion | SPC | Bureau, Champaign, Ford, Grundy, Henry, Iroquois and 13 more | 53 min |
| Aug 5, 12:56 PM CDT | Mesoscale Discussion | SPC | Bond, Clay, Clinton, Edwards, Fayette, Franklin and 17 more | 94 min |
| Aug 5, 2:59 PM CDT | Severe Thunderstorm Watch | SPC | Bond, Calhoun, Cass, Christian, Clay, Clinton and 30 more | 9 hr |
Nearby
Severe Thunderstorm Watches in Illinois, 2008Severe Thunderstorm Watches in Iowa, 2008Every severe thunderstorm watch in 2008
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.