Alert archive / Iowa / Mesoscale Discussions in 2004

Mesoscale Discussion 1876

August 4, 200411 counties in Illinois; 23 counties in Iowa; 21 counties in Missouri

The Storm Prediction Center issued this mesoscale discussion at Aug 4, 2004, 1:42 AM CDT for 11 counties in Illinois; 23 counties in Iowa; 21 counties in Missouri. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Aug 4, 2004, 1:42 AM CDT (06:42 UTC)
Expired
Aug 4, 2004, 3:45 AM CDT
In force
2 hr
Issued by
the Storm Prediction Center
All 55 counties

Adams County, IA, Appanoose County, IA, Clarke County, IA, Davis County, IA, Decatur County, IA, Des Moines County, IA, Henry County, IA, Jefferson County, IA, Keokuk County, IA, Lee County, IA, Louisa County, IA, Lucas County, IA, Mahaska County, IA, Monroe County, IA, Montgomery County, IA, Page County, IA, Ringgold County, IA, Taylor County, IA, Union County, IA, Van Buren County, IA, Wapello County, IA, Washington County, IA, Wayne County, IA, Fulton County, IL, Henderson County, IL, Jersey County, IL, Livingston County, IL, Mason County, IL, McDonough County, IL, Mercer County, IL, Peoria County, IL, Schuyler County, IL, Tazewell County, IL, Woodford County, IL, Andrew County, MO, Audrain County, MO, Boone County, MO, Caldwell County, MO, Callaway County, MO, Carroll County, MO, Cooper County, MO, Daviess County, MO, Gentry County, MO, Livingston County, MO, Marion County, MO, Mercer County, MO, Montgomery County, MO, Nodaway County, MO, Pettis County, MO, Putnam County, MO, Saline County, MO, Schuyler County, MO, Scotland County, MO, Shelby County, MO, Worth County, MO

The radar

The St Louis radar (KLSX), 186 km from the middle of the area, began a volume at 06:42 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 nearest sounding before it

Davenport, (KDVN), launched 00:00Z, 6.7 hours before the alert went out and 240 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 2004-08-04Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 2771 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 2004-08-04The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 54 square meters per square second.193958Sfc1 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
2771 J/kg
Mixed-layer CIN
-73 J/kg
Mixed-layer LCL
1163 m above ground
0-6 km bulk shear
35 kt
0-1 km storm-relative helicity
54 m²/s²
0-3 km storm-relative helicity
163 m²/s²
Significant tornado parameter
1.6
Supercell composite
16.5

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.

IssuedProductOfficeCountiesLasted
Aug 3, 7:38 PM CDTMesoscale DiscussionSPCBureau, Cook, DeKalb, DuPage, Ford, Grundy and 14 more67 min
Aug 3, 7:55 PM CDTSevere Thunderstorm WatchSPCBoone, Bureau, Cook, DeKalb, DuPage, Ford and 21 more5 hr
Aug 3, 8:19 PM CDTMesoscale DiscussionSPCCarroll, Henry, Jo Daviess, Knox, Mercer, Rock Island and 2 more56 min
Aug 3, 9:45 PM CDTSevere Thunderstorm WatchSPCFulton, Hancock, Henderson, Henry, Knox, McDonough and 3 more5 hr
Aug 3, 9:52 PM CDTMesoscale DiscussionSPCCook, DuPage, Grundy, Kane, Kendall, Lake and 3 more53 min
Aug 3, 10:38 PM CDTMesoscale DiscussionSPCAdams, Brown, Calhoun, Cass, Greene, Jersey and 3 more67 min
Aug 3, 11:30 PM CDTSevere Thunderstorm WatchSPCAdams, Brown, Calhoun, Cass, Champaign, Christian and 32 more6 hr
Aug 4, 3:52 AM CDTMesoscale DiscussionSPCAdams, Brown, Calhoun, Cass, Champaign, Christian and 32 more53 min
Aug 4, 3:39 PM CDTMesoscale DiscussionSPCHardin, Massac, Pope96 min
Aug 3, 9:16 PM CDTMesoscale DiscussionSPCAdair, Adams, Audubon, Cass, Fremont, Guthrie and 9 more59 min
Aug 3, 11:34 PM CDTMesoscale DiscussionSPCAppanoose, Davis, Lee86 min

Nearby

Mesoscale Discussions in Iowa, 2004Mesoscale Discussions in Missouri, 2004Mesoscale Discussions in Illinois, 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.