Alert archive / Iowa / Mesoscale Discussions in 2007

Mesoscale Discussion 1841

August 21, 20074 states

The Storm Prediction Center issued this mesoscale discussion at Aug 21, 2007, 10:49 PM CDT for 4 states. It was in force for 86 min.

The area

The outline as issued.

The facts

Issued
Aug 21, 2007, 10:49 PM CDT (03:49 UTC)
Expired
Aug 22, 2007, 12:15 AM CDT
In force
86 min
Issued by
the Storm Prediction Center
All 61 counties

Allamakee County, IA, Audubon County, IA, Benton County, IA, Black Hawk County, IA, Boone County, IA, Bremer County, IA, Buchanan County, IA, Butler County, IA, Calhoun County, IA, Carroll County, IA, Cedar County, IA, Chickasaw County, IA, Clayton County, IA, Clinton County, IA, Dallas County, IA, Delaware County, IA, Dubuque County, IA, Fayette County, IA, Franklin County, IA, Greene County, IA, Grundy County, IA, Guthrie County, IA, Hamilton County, IA, Hardin County, IA, Iowa County, IA, Jackson County, IA, Jasper County, IA, Johnson County, IA, Jones County, IA, Keokuk County, IA, Linn County, IA, Mahaska County, IA, Marion County, IA, Marshall County, IA, Muscatine County, IA, Polk County, IA, Poweshiek County, IA, Scott County, IA, Shelby County, IA, Story County, IA, Tama County, IA, Webster County, IA, Winneshiek County, IA, Carroll County, IL, Jo Daviess County, IL, Stephenson County, IL, Whiteside County, IL, Houston County, MN, Adams County, WI, Columbia County, WI, Crawford County, WI, Dane County, WI, Grant County, WI, Green County, WI, Iowa County, WI, Juneau County, WI, Lafayette County, WI, Monroe County, WI, Richland County, WI, Sauk County, WI, Vernon County, WI

The radar

The Quad Cities radar (KDVN), 146 km from the middle of the area, began a volume at 03:50 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 00:00Z, 3.8 hours before the alert went out and 150 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-pSkew-T log-p diagram, Davenport, at 00:00Z on 2007-08-22Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 4094 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Davenport, at 00:00Z on 2007-08-22The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 114 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
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
4094 J/kg
Mixed-layer CIN
-7 J/kg
Mixed-layer LCL
915 m above ground
0-6 km bulk shear
29 kt
0-1 km storm-relative helicity
114 m²/s²
0-3 km storm-relative helicity
101 m²/s²
Significant tornado parameter
1.4
Supercell composite
8.0

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.

IssuedProductOfficeCountiesLasted
Aug 22, 2:13 AM CDTMesoscale DiscussionSPCBoone, Jo Daviess, Lake, McHenry, Stephenson, Winnebago62 min
Aug 22, 4:53 AM CDTMesoscale DiscussionSPCKankakee, Will67 min
Aug 22, 3:17 PM CDTMesoscale DiscussionSPCBoone, Bureau, Carroll, DeKalb, DuPage, Ford and 28 more2 hr
Aug 21, 8:14 PM CDTSevere Thunderstorm WatchSPCAllamakee, Buchanan, Chickasaw, Clayton, Delaware, Dubuque and 5 more8 hr
Aug 22, 6:45 AM CDTMesoscale DiscussionSPCBuena Vista, Calhoun, Carroll, Cherokee, Clay, Crawford and 13 more60 min
Aug 22, 10:12 AM CDTMesoscale DiscussionSPCBuena Vista, Calhoun, Cherokee, Clay, Crawford, Humboldt and 8 more93 min
Aug 22, 2:37 PM CDTMesoscale DiscussionSPCAdair, Adams, Appanoose, Audubon, Benton, Black Hawk and 40 more83 min
Aug 22, 3:20 PM CDTSevere Thunderstorm WatchSPCFremont, Harrison, Mills, Montgomery, Page, Pottawattamie and 1 more6 hr
Aug 22, 6:33 PM CDTMesoscale DiscussionSPCFremont, Harrison, Mills, Montgomery, Page, Pottawattamie and 1 more87 min
Aug 22, 12:09 AM CDTSevere Thunderstorm WatchSPCColumbia, Dane, Dodge, Fond du Lac, Green, Green Lake and 11 more3 hr

Nearby

Mesoscale Discussions in Iowa, 2007Mesoscale Discussions in Wisconsin, 2007Mesoscale Discussions in Illinois, 2007Every mesoscale discussion in 2007

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.