Alert archive / Illinois / Mesoscale Discussions in 2012

Mesoscale Discussion 1851

September 1, 201257 counties in Illinois; 5 counties in Kentucky; 13 counties in Missouri

The Storm Prediction Center issued this mesoscale discussion at Sep 1, 2012, 3:30 PM CDT for 57 counties in Illinois; 5 counties in Kentucky; 13 counties in Missouri. It was in force for 60 min.

The area

The outline as issued.

The facts

Issued
Sep 1, 2012, 3:30 PM CDT (20:30 UTC)
Expired
Sep 1, 2012, 4:30 PM CDT
In force
60 min
Issued by
the Storm Prediction Center
All 75 counties

Alexander County, IL, Bond County, IL, Christian County, IL, Clark County, IL, Clay County, IL, Clinton County, IL, Coles County, IL, Crawford County, IL, Cumberland County, IL, DeWitt County, IL, Douglas County, IL, Edwards County, IL, Effingham County, IL, Fayette County, IL, Franklin County, IL, Fulton County, IL, Gallatin County, IL, Hamilton County, IL, Hardin County, IL, Jackson County, IL, Jasper County, IL, Jefferson County, IL, Johnson County, IL, Knox County, IL, Lawrence County, IL, Logan County, IL, Macon County, IL, Madison County, IL, Marion County, IL, Marshall County, IL, Mason County, IL, Massac County, IL, McLean County, IL, Menard County, IL, Monroe County, IL, Montgomery County, IL, Moultrie County, IL, Peoria County, IL, Perry County, IL, Piatt County, IL, Pope County, IL, Pulaski County, IL, Randolph County, IL, Richland County, IL, Saint Clair County, IL, Saline County, IL, Sangamon County, IL, Shelby County, IL, Tazewell County, IL, Union County, IL, Wabash County, IL, Warren County, IL, Washington County, IL, Wayne County, IL, White County, IL, Williamson County, IL, Woodford County, IL, Ballard County, KY, Carlisle County, KY, Graves County, KY, Hickman County, KY, McCracken County, KY, Bollinger County, MO, Butler County, MO, Cape Girardeau County, MO, Madison County, MO, Mississippi County, MO, New Madrid County, MO, Perry County, MO, Ripley County, MO, Saint Francois County, MO, Sainte Genevieve County, MO, Scott County, MO, Stoddard County, MO, Wayne County, MO

The radar

The St Louis radar (KLSX), 108 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 nearest sounding before it

Lincoln, IL (KILX), launched 12:00Z, 8.5 hours before the alert went out and 166 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 2012-09-01Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 443 joules per kilogram.LCLEL10008507005003002001001 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 2012-09-01The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 24 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
443 J/kg
Mixed-layer CIN
0 J/kg
Mixed-layer LCL
457 m above ground
0-6 km bulk shear
14 kt
0-1 km storm-relative helicity
24 m²/s²
0-3 km storm-relative helicity
36 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

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 31, 9:05 PM CDTMesoscale DiscussionSPCAlexander, Bond, Brown, Calhoun, Cass, Champaign and 39 more55 min
Sep 1, 12:41 PM CDTMesoscale DiscussionSPCBond, Cass, Champaign, Christian, Clay, Clinton and 36 more64 min
Sep 1, 12:46 PM CDTTornado WatchSPCCass, Champaign, Christian, Clark, Clay, Coles and 29 more7 hr
Sep 1, 1:19 PM CDTTornado WatchSPCAlexander, Bond, Clinton, Edwards, Fayette, Franklin and 20 more8 hr
Sep 1, 5:43 PM CDTMesoscale DiscussionSPCAlexander, Gallatin, Hamilton, Hardin, Johnson, Massac and 7 more92 min
Sep 1, 3:49 PM CDTTornado WatchSPCDunklin, Pemiscot7 hr

Nearby

Mesoscale Discussions in Illinois, 2012Mesoscale Discussions in Missouri, 2012Mesoscale Discussions in Kentucky, 2012Every mesoscale discussion in 2012

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.