Alert archive / Illinois / Mesoscale Discussions in 2011

Mesoscale Discussion 1769

July 27, 201115 counties in Illinois; 6 counties in Iowa

The Storm Prediction Center issued this mesoscale discussion at Jul 27, 2011, 9:43 PM CDT for 15 counties in Illinois; 6 counties in Iowa. It was in force for 62 min.

The area

The outline as issued.

The facts

Issued: Jul 27, 2011, 9:43 PM CDT (02:43 UTC)
Expired: Jul 27, 2011, 10:45 PM CDT
In force: 62 min
Issued by: the Storm Prediction Center

All 21 counties

Cedar County, IA, Clinton County, IA, Delaware County, IA, Dubuque County, IA, Jackson County, IA, Jones County, IA, Boone County, IL, Carroll County, IL, Cook County, IL, DeKalb County, IL, DuPage County, IL, Jo Daviess County, IL, Kane County, IL, Kendall County, IL, Lake County, IL, Lee County, IL, McHenry County, IL, Ogle County, IL, Stephenson County, IL, Whiteside County, IL, Winnebago County, IL

The radar

The Quad Cities radar (KDVN), 86 km from the middle of the area, began a volume at 02:44 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, 2.7 hours before the alert went out and 80 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: 4556 J/kg
Mixed-layer CIN: -8 J/kg
Mixed-layer LCL: 962 m above ground
0-6 km bulk shear: 32 kt
0-1 km storm-relative helicity: 141 m²/s²
0-3 km storm-relative helicity: 316 m²/s²
Significant tornado parameter: 3.9
Supercell composite: 19.4

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
Jul 27, 7:43 PM CDT	Tornado Watch	SPC	Boone, Carroll, Cook, DeKalb, DuPage, Jo Daviess and 10 more	5 hr
Jul 28, 12:36 AM CDT	Mesoscale Discussion	SPC	Boone, Carroll, Cook, DeKalb, DuPage, Jo Daviess and 10 more	84 min
Jul 28, 5:40 PM CDT	Mesoscale Discussion	SPC	Bureau, Hancock, Henderson, Henry, Knox, Lee and 9 more	95 min
Jul 28, 2:47 PM CDT	Mesoscale Discussion	SPC	Buena Vista, Calhoun, Carroll, Cerro Gordo, Cherokee, Crawford and 18 more	118 min

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.