Alert archive / Illinois / Mesoscale Discussions in 2004

Mesoscale Discussion 1871

August 3, 20049 counties in Illinois

The Storm Prediction Center issued this mesoscale discussion at Aug 3, 2004, 9:52 PM CDT for 9 counties in Illinois. It was in force for 53 min.

The area

The outline as issued.

The facts

Issued: Aug 3, 2004, 9:52 PM CDT (02:52 UTC)
Expired: Aug 3, 2004, 10:45 PM CDT
In force: 53 min
Issued by: the Storm Prediction Center

Counties Cook County, IL, DuPage County, IL, Grundy County, IL, Kane County, IL, Kendall County, IL, Lake County, IL, LaSalle County, IL, Putnam County, IL, Will County, IL

The radar

The Chicago radar (KLOT), 46 km from the middle of the area, began a volume at 02:54 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, 2.9 hours before the alert went out and 155 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: 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.

Issued	Product	Office	Counties	Lasted
Aug 3, 7:38 PM CDT	Mesoscale Discussion	SPC	Bureau, Cook, DeKalb, DuPage, Ford, Grundy and 14 more	67 min
Aug 3, 7:55 PM CDT	Severe Thunderstorm Watch	SPC	Boone, Bureau, Cook, DeKalb, DuPage, Ford and 21 more	5 hr
Aug 3, 8:19 PM CDT	Mesoscale Discussion	SPC	Carroll, Henry, Jo Daviess, Knox, Mercer, Rock Island and 2 more	56 min
Aug 3, 9:45 PM CDT	Severe Thunderstorm Watch	SPC	Fulton, Hancock, Henderson, Henry, Knox, McDonough and 3 more	5 hr
Aug 3, 10:38 PM CDT	Mesoscale Discussion	SPC	Adams, Brown, Calhoun, Cass, Greene, Jersey and 3 more	67 min
Aug 3, 11:30 PM CDT	Severe Thunderstorm Watch	SPC	Adams, Brown, Calhoun, Cass, Champaign, Christian and 32 more	6 hr
Aug 4, 1:42 AM CDT	Mesoscale Discussion	SPC	Fulton, Henderson, Jersey, Livingston, McDonough, Mason and 5 more	2 hr
Aug 4, 3:52 AM CDT	Mesoscale Discussion	SPC	Adams, Brown, Calhoun, Cass, Champaign, Christian and 32 more	53 min
Aug 4, 3:39 PM CDT	Mesoscale Discussion	SPC	Hardin, Massac, Pope	96 min

Nearby

Mesoscale Discussions in Illinois, 2004 Every 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.