Alert archive / Illinois / Mesoscale Discussions in 2004

Mesoscale Discussion 745

May 18, 200429 counties in Illinois; Jefferson County, Saint Louis County, City of Saint Louis, Missouri

The Storm Prediction Center issued this mesoscale discussion at May 18, 2004, 2:38 PM CDT for 29 counties in Illinois; Jefferson County, Saint Louis County, City of Saint Louis, Missouri. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
May 18, 2004, 2:38 PM CDT (19:38 UTC)
Expired
May 18, 2004, 4:45 PM CDT
In force
2 hr
Issued by
the Storm Prediction Center
All 32 counties

Bond County, IL, Champaign County, IL, Christian County, IL, Clark County, IL, Clay County, IL, Clinton County, IL, Coles County, IL, Cumberland County, IL, DeWitt County, IL, Douglas County, IL, Edgar County, IL, Effingham County, IL, Fayette County, IL, Jasper County, IL, Jersey County, IL, Logan County, IL, Macon County, IL, Macoupin County, IL, Madison County, IL, Marion County, IL, Monroe County, IL, Montgomery County, IL, Moultrie County, IL, Piatt County, IL, Saint Clair County, IL, Sangamon County, IL, Shelby County, IL, Vermilion County, IL, Washington County, IL, City of Saint Louis, MO, Jefferson County, MO, Saint Louis County, MO

The radar

The Lincoln radar (KILX), 82 km from the middle of the area, began a volume at 19:41 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

Lincoln, IL (KILX), launched 12:00Z, 7.6 hours before the alert went out and 104 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, Lincoln, IL at 12:00Z on 2004-05-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 989 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, Lincoln, IL at 12:00Z on 2004-05-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 124 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
989 J/kg
Mixed-layer CIN
-53 J/kg
Mixed-layer LCL
838 m above ground
0-6 km bulk shear
32 kt
0-1 km storm-relative helicity
124 m²/s²
0-3 km storm-relative helicity
85 m²/s²
Significant tornado parameter
0.3
Supercell composite
2.1

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
May 17, 7:15 PM CDTSevere Thunderstorm WatchSPCBoone, Carroll, DeKalb, Jo Daviess, Lee, McHenry and 6 more5 hr
May 17, 11:37 PM CDTMesoscale DiscussionSPCBureau, Cook, DeKalb, DuPage, Grundy, Kane and 8 more23 min
May 18, 12:41 AM CDTMesoscale DiscussionSPCGrundy, Kankakee, Will2 hr
May 18, 10:26 AM CDTMesoscale DiscussionSPCBond, Brown, Bureau, Calhoun, Cass, Champaign and 38 more3 hr
May 18, 12:00 PM CDTSevere Thunderstorm WatchSPCAdams, Bond, Brown, Calhoun, Cass, Champaign and 48 more7 hr
May 18, 6:09 PM CDTMesoscale DiscussionSPCCass, Champaign, Christian, Clark, Clay, Coles and 27 more96 min
May 17, 8:20 PM CDTMesoscale DiscussionSPCAndrew, Atchison, Daviess, DeKalb, Gentry, Grundy and 7 more55 min
May 18, 6:22 AM CDTMesoscale DiscussionSPCBuchanan, Caldwell, Cass, Clay, Clinton, DeKalb and 3 more113 min
May 18, 6:27 PM CDTMesoscale DiscussionSPCBates, Buchanan, Caldwell, Carroll, Cass, Clay and 9 more2 hr

Nearby

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