Alert archive / Illinois / Mesoscale Discussions in 2011

Mesoscale Discussion 1900

August 8, 201125 counties in Illinois; 17 counties in Iowa

The Storm Prediction Center issued this mesoscale discussion at Aug 8, 2011, 1:06 PM CDT for 25 counties in Illinois; 17 counties in Iowa. It was in force for 84 min.

The area

The outline as issued.

The facts

Issued: Aug 8, 2011, 1:06 PM CDT (18:06 UTC)
Expired: Aug 8, 2011, 2:30 PM CDT
In force: 84 min
Issued by: the Storm Prediction Center

All 42 counties

Benton County, IA, Cedar County, IA, Clinton County, IA, Des Moines County, IA, Dubuque County, IA, Henry County, IA, Iowa County, IA, Jackson County, IA, Johnson County, IA, Jones County, IA, Keokuk County, IA, Linn County, IA, Louisa County, IA, Muscatine County, IA, Poweshiek County, IA, Scott County, IA, Washington County, IA, Boone County, IL, Bureau County, IL, Carroll County, IL, DeKalb County, IL, Grundy County, IL, Henderson County, IL, Henry County, IL, Jo Daviess County, IL, Kane County, IL, Kendall County, IL, Knox County, IL, LaSalle County, IL, Lee County, IL, Marshall County, IL, Mercer County, IL, Ogle County, IL, Peoria County, IL, Putnam County, IL, Rock Island County, IL, Stark County, IL, Stephenson County, IL, Warren County, IL, Whiteside County, IL, Winnebago County, IL, Woodford County, IL

The radar

The Quad Cities radar (KDVN), 10 km from the middle of the area, began a volume at 18:10 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 12:00Z, 6.1 hours before the alert went out and 13 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: 610 J/kg
Mixed-layer CIN: -47 J/kg
Mixed-layer LCL: 783 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 44 m²/s²
0-3 km storm-relative helicity: 55 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.1

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

373 
ACUS11 KWNS 081806
SWOMCD
SPC MCD 081806 
ILZ000-WIZ000-IAZ000-081930-

MESOSCALE DISCUSSION 1900
NWS STORM PREDICTION CENTER NORMAN OK
0106 PM CDT MON AUG 08 2011

AREAS AFFECTED...ERN IA...NRN IL

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 081806Z - 081930Z

WHILE SOME MARGINALLY SEVERE HAIL/GUSTY WINDS WILL BE POSSIBLE IN
STRONGER STORMS THIS AFTERNOON...THE NEED FOR A WW IS NOT CURRENTLY
ANTICIPATED.  BUT TRENDS WILL CONTINUE TO BE MONITORED FOR THE
POSSIBILITY OF AN INCREASING SEVERE THREAT.

VIGOROUS STORM DEVELOPMENT IS NOW WELL UNDERWAY NEAR A WEAK SURFACE
LOW LOCATED WEST OF CEDAR RAPIDS IOWA...AND NEAR A FRONTAL ZONE
EXTENDING EAST SOUTHEASTWARD INTO NORTH CENTRAL ILLINOIS.  THE LOW
APPEARS ASSOCIATED WITH A DISTINCT LOWER/MID TROPOSPHERIC CYCLONIC
CIRCULATION CENTER...WITHIN A SHORT WAVE TROUGH WHICH IS EXPECTED TO
SHIFT EAST OF THE MISSISSIPPI RIVER BETWEEN NOW AND 20-22Z.  IN THE
PRESENCE OF A MOIST ENVIRONMENT WITH MODERATELY LARGE CAPE /UP TO
2000 J PER KG/...LARGE-SCALE FORCING IS EXPECTED TO SUPPORT A
FURTHER INCREASE IN NUMBER/COVERAGE OF STORMS...WITH CONSOLIDATION
AND UPSCALE GROWTH INTO AN ORGANIZED STORM CLUSTER POSSIBLE ACROSS
NORTHERN ILLINOIS BY LATE AFTERNOON.  LOW-LEVEL FLOW FIELDS ARE
FAIRLY WEAK...BUT 30-35 KT WESTERLY DEEP LAYER MEAN FLOW WILL
CONTRIBUTE TO STORM MOTION...AND PERHAPS THE RISK FOR STRONG GUSTY
WINDS THAT COULD AT LEAST APPROACH SEVERE LIMITS ON THE LEADING EDGE
OF AN ASSOCIATED DEVELOPING SURFACE COLD POOL.

..KERR.. 08/08/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...LOT...ILX...MKX...DVN...ARX...DMX...

LAT...LON   42409178 42539065 42438922 42188829 41418818 40818884
            40499041 40729136 41229216 41669259 42029229 42409178

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 7, 8:27 PM CDT	Mesoscale Discussion	SPC	Alexander, Jackson, Johnson, Massac, Pulaski, Randolph and 1 more	2 hr
Aug 7, 10:54 PM CDT	Mesoscale Discussion	SPC	Alexander, Massac, Pulaski	96 min
Aug 8, 5:23 PM CDT	Mesoscale Discussion	SPC	Bureau, Cass, Champaign, Christian, DeWitt, Ford and 21 more	67 min
Aug 8, 5:38 PM CDT	Severe Thunderstorm Watch	SPC	Bureau, Champaign, DeWitt, Ford, Fulton, Grundy and 19 more	5 hr
Aug 7, 7:49 PM CDT	Severe Thunderstorm Watch	SPC	Ida, Woodbury	7 hr
Aug 7, 10:28 PM CDT	Mesoscale Discussion	SPC	Audubon, Calhoun, Carroll, Cass, Cherokee, Crawford and 10 more	2 hr
Aug 7, 11:34 PM CDT	Severe Thunderstorm Watch	SPC	Adair, Adams, Audubon, Calhoun, Carroll, Cass and 15 more	4 hr

Nearby

Mesoscale Discussions in Illinois, 2011 Mesoscale Discussions in Iowa, 2011 Every mesoscale discussion in 2011

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.