Alert archive / Illinois / Mesoscale Discussions in 2008

Mesoscale Discussion 731

April 25, 200813 counties in Illinois; Clinton County, Louisa County, Scott County, Iowa

The Storm Prediction Center issued this mesoscale discussion at Apr 25, 2008, 3:28 PM CDT for 13 counties in Illinois; Clinton County, Louisa County, Scott County, Iowa. It was in force for 62 min.

The area

The outline as issued.

The facts

Issued: Apr 25, 2008, 3:28 PM CDT (20:28 UTC)
Expired: Apr 25, 2008, 4:30 PM CDT
In force: 62 min
Issued by: the Storm Prediction Center

Counties Clinton County, IA, Louisa County, IA, Scott County, IA, Bureau County, IL, Carroll County, IL, Henry County, IL, Jo Daviess County, IL, Knox County, IL, Lee County, IL, Mercer County, IL, Ogle County, IL, Putnam County, IL, Rock Island County, IL, Stark County, IL, Warren County, IL, Whiteside County, IL

The radar

The Quad Cities radar (KDVN), 31 km from the middle of the area, began a volume at 20:30 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.

Tornado Watch 234Apr 25, 3:40 PM CDT

The nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 8.5 hours before the alert went out and 26 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 1215 J/kg
Mixed-layer CIN: -45 J/kg
Mixed-layer LCL: 678 m above ground
0-6 km bulk shear: 44 kt
0-1 km storm-relative helicity: 157 m²/s²
0-3 km storm-relative helicity: 204 m²/s²
Significant tornado parameter: 1.1
Supercell composite: 7.5

Open this sounding in Storm Lab

The text

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

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 25, 4:22 AM CDT	Mesoscale Discussion	SPC	Henderson, Mercer, Rock Island	23 min
Apr 25, 4:51 AM CDT	Severe Thunderstorm Watch	SPC	Adams, Brown, Carroll, Hancock, Henderson, Henry and 8 more	5 hr
Apr 25, 9:10 AM CDT	Mesoscale Discussion	SPC	Boone, Carroll, Jo Daviess, Lee, Ogle, Rock Island and 3 more	65 min
Apr 25, 12:21 PM CDT	Mesoscale Discussion	SPC	Adams, Brown, Carroll, Fulton, Hancock, Henderson and 10 more	54 min
Apr 25, 1:27 PM CDT	Severe Thunderstorm Watch	SPC	Adams, Boone, Brown, Bureau, Calhoun, Carroll and 38 more	7 hr
Apr 25, 3:41 PM CDT	Tornado Watch	SPC	Boone, Bureau, Carroll, Cass, DeKalb, Fulton and 34 more	4 hr
Apr 25, 5:18 PM CDT	Mesoscale Discussion	SPC	Bureau, Carroll, Henry, Jo Daviess, Knox, Lee and 7 more	57 min
Apr 25, 6:01 PM CDT	Mesoscale Discussion	SPC	Bureau, Carroll, Henry, Jo Daviess, Knox, Lee and 7 more	59 min
Apr 25, 12:07 AM CDT	Severe Thunderstorm Watch	SPC	Adair, Adams, Cass, Clarke, Dallas, Decatur and 15 more	7 hr
Apr 25, 12:55 AM CDT	Mesoscale Discussion	SPC	Page	35 min
Apr 25, 1:13 AM CDT	Tornado Watch	SPC	Fremont, Montgomery, Page	5 hr
Apr 25, 2:24 AM CDT	Mesoscale Discussion	SPC	Adair, Adams, Cass, Clarke, Dallas, Decatur and 14 more	66 min
Apr 25, 3:18 AM CDT	Mesoscale Discussion	SPC	Fremont, Montgomery, Page	57 min

Nearby

Mesoscale Discussions in Illinois, 2008 Mesoscale Discussions in Iowa, 2008 Every mesoscale discussion 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.