Alert archive / Illinois / Mesoscale Discussions in 2008

Mesoscale Discussion 1820

July 19, 20085 states

The Storm Prediction Center issued this mesoscale discussion at Jul 19, 2008, 11:24 PM CDT for 5 states. It was in force for 96 min.

The area

The outline as issued.

The facts

Issued: Jul 19, 2008, 11:24 PM CDT (04:24 UTC)
Expired: Jul 20, 2008, 1:00 AM CDT
In force: 96 min
Issued by: the Storm Prediction Center

All 59 counties

Davis County, IA, Des Moines County, IA, Henry County, IA, Jefferson County, IA, Lee County, IA, Louisa County, IA, Van Buren County, IA, Wapello County, IA, Boone County, IL, Bureau County, IL, Cook County, IL, DeKalb County, IL, DeWitt County, IL, DuPage County, IL, Ford County, IL, Fulton County, IL, Grundy County, IL, Hancock County, IL, Henderson County, IL, Henry County, IL, Iroquois County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, Knox County, IL, Lake County, IL, LaSalle County, IL, Lee County, IL, Livingston County, IL, Logan County, IL, Marshall County, IL, Mason County, IL, McDonough County, IL, McHenry County, IL, McLean County, IL, Mercer County, IL, Peoria County, IL, Putnam County, IL, Stark County, IL, Tazewell County, IL, Warren County, IL, Will County, IL, Woodford County, IL, Elkhart County, IN, Jasper County, IN, LaGrange County, IN, Lake County, IN, LaPorte County, IN, Marshall County, IN, Newton County, IN, Porter County, IN, Pulaski County, IN, Saint Joseph County, IN, Starke County, IN, Allegan County, MI, Berrien County, MI, Cass County, MI, Van Buren County, MI, Kenosha County, WI

The radar

The Chicago radar (KLOT), 80 km from the middle of the area, began a volume at 04:26 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, 4.4 hours before the alert went out and 122 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: 633 J/kg
Mixed-layer CIN: -121 J/kg
Mixed-layer LCL: 1040 m above ground
0-6 km bulk shear: 29 kt
0-1 km storm-relative helicity: -8 m²/s²
0-3 km storm-relative helicity: 144 m²/s²
Significant tornado parameter: -0.0
Supercell composite: -0.2

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 19, 7:59 PM CDT	Tornado Watch	SPC	Carroll, Jo Daviess, Mercer, Rock Island, Stephenson, Whiteside	4 hr
Jul 19, 9:35 PM CDT	Severe Thunderstorm Watch	SPC	Boone, DeKalb, Kane, Lee, McHenry, Ogle and 1 more	3 hr
Jul 20, 12:43 PM CDT	Mesoscale Discussion	SPC	Cass, Champaign, Christian, Clark, Coles, Cumberland and 12 more	92 min
Jul 20, 2:10 PM CDT	Severe Thunderstorm Watch	SPC	Champaign, Clark, Clay, Coles, Crawford, Cumberland and 12 more	8 hr
Jul 20, 5:33 PM CDT	Mesoscale Discussion	SPC	Bartholomew, Brown, Clark, Dearborn, Decatur, Fayette and 12 more	87 min
Jul 20, 10:04 AM CDT	Mesoscale Discussion	SPC	Adams, Audubon, Cass, Crawford, Fremont, Harrison and 8 more	86 min

Nearby

Mesoscale Discussions in Illinois, 2008 Mesoscale Discussions in Indiana, 2008 Mesoscale Discussions in Iowa, 2008 Every mesoscale discussion in 2008

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.