Alert archive / Illinois / Mesoscale Discussions in 2004
Mesoscale Discussion 1742
The Storm Prediction Center issued this mesoscale discussion at Jul 20, 2004, 5:35 PM CDT for 15 counties in Illinois; 5 counties in Iowa; 6 counties in Wisconsin. It was in force for 55 min.
The area
The outline as issued.
The facts
- Issued
- Jul 20, 2004, 5:35 PM CDT (22:35 UTC)
- Expired
- Jul 20, 2004, 6:30 PM CDT
- In force
- 55 min
- Issued by
- the Storm Prediction Center
All 26 counties
Clinton County, IA, Dubuque County, IA, Jackson County, IA, Jones County, IA, Scott County, IA, Boone County, IL, Bureau County, IL, Carroll County, IL, DeKalb County, IL, Henry County, IL, Jo Daviess County, IL, Kane County, IL, Kendall County, IL, Lee County, IL, McHenry County, IL, Ogle County, IL, Rock Island County, IL, Stephenson County, IL, Whiteside County, IL, Winnebago County, IL, Dane County, WI, Green County, WI, Iowa County, WI, Lafayette County, WI, Rock County, WI, Walworth County, WI
The radar
The Quad Cities radar (KDVN), 112 km from the middle of the area, began a volume at 22:39 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.
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Davenport, (KDVN), launched 12:00Z, 10.6 hours before the alert went out and 106 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
- 1569 J/kg
- Mixed-layer CIN
- -33 J/kg
- Mixed-layer LCL
- 769 m above ground
- 0-6 km bulk shear
- 28 kt
- 0-1 km storm-relative helicity
- 16 m²/s²
- 0-3 km storm-relative helicity
- 96 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.6
The text
As transmitted, in the capitals the NWS used until 2016.
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</html>SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 20, 6:00 PM CDT | Severe Thunderstorm Watch | SPC | Boone, Bureau, Carroll, DeKalb, Grundy, Henry and 13 more | 4 hr |
| Jul 20, 6:08 PM CDT | Mesoscale Discussion | SPC | Boone, Bureau, Carroll, DeKalb, Henry, Jo Daviess and 9 more | 2 hr |
| Jul 20, 2:16 PM CDT | Mesoscale Discussion | SPC | Lyon, Monona, Plymouth, Sioux, Woodbury | 119 min |
| Jul 20, 1:09 PM CDT | Mesoscale Discussion | SPC | Adams, Barron, Buffalo, Calumet, Chippewa, Clark and 30 more | 2 hr |
Nearby
Mesoscale Discussions in Illinois, 2004Mesoscale Discussions in Wisconsin, 2004Mesoscale Discussions in Iowa, 2004Every mesoscale discussion in 2004
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.