Alert archive / Iowa / Mesoscale Discussions in 2003

Mesoscale Discussion 1876

July 18, 20035 counties in Illinois; 25 counties in Iowa

The Storm Prediction Center issued this mesoscale discussion at Jul 18, 2003, 2:26 AM CDT for 5 counties in Illinois; 25 counties in Iowa. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Jul 18, 2003, 2:26 AM CDT (07:26 UTC)
Expired: Jul 18, 2003, 5:00 AM CDT
In force: 3 hr
Issued by: the Storm Prediction Center

All 30 counties

Benton County, IA, Cedar County, IA, Dallas County, IA, Des Moines County, IA, Henry County, IA, Iowa County, IA, Jasper County, IA, Jefferson County, IA, Johnson County, IA, Keokuk County, IA, Louisa County, IA, Madison County, IA, Mahaska County, IA, Marion County, IA, Marshall County, IA, Monroe County, IA, Muscatine County, IA, Polk County, IA, Poweshiek County, IA, Scott County, IA, Story County, IA, Tama County, IA, Wapello County, IA, Warren County, IA, Washington County, IA, Henderson County, IL, Knox County, IL, Mercer County, IL, Rock Island County, IL, Warren County, IL

The radar

The Des Moines radar (KDMX), 115 km from the middle of the area, began a volume at 07:27 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 756Jul 18, 4:30 AM CDT

The nearest sounding before it

Davenport, (KDVN), launched 00:00Z, 7.4 hours before the alert went out and 158 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: 2939 J/kg
Mixed-layer CIN: -65 J/kg
Mixed-layer LCL: 1455 m above ground
0-6 km bulk shear: 36 kt
0-1 km storm-relative helicity: 29 m²/s²
0-3 km storm-relative helicity: 86 m²/s²
Significant tornado parameter: 0.7
Supercell composite: 11.6

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 17, 9:40 PM CDT	Severe Thunderstorm Watch	SPC	Bureau, Champaign, DeWitt, Ford, Grundy, Henry and 13 more	5 hr
Jul 17, 11:41 PM CDT	Mesoscale Discussion	SPC	Bureau, Champaign, Ford, Grundy, Henry, Iroquois and 12 more	94 min
Jul 18, 2:01 AM CDT	Mesoscale Discussion	SPC	Champaign, Clark, Coles, Cumberland, DeWitt, Douglas and 13 more	59 min
Jul 18, 4:30 AM CDT	Severe Thunderstorm Watch	SPC	Adams, Bond, Brown, Calhoun, Cass, Christian and 38 more	6 hr
Jul 18, 6:15 AM CDT	Mesoscale Discussion	SPC	Adams, Alexander, Bond, Brown, Calhoun, Clinton and 18 more	60 min
Jul 18, 6:50 AM CDT	Severe Thunderstorm Watch	SPC	Alexander, Franklin, Jackson, Johnson, Monroe, Perry and 6 more	5 hr
Jul 18, 9:06 AM CDT	Mesoscale Discussion	SPC	Alexander, Bond, Calhoun, Clinton, Franklin, Greene and 16 more	84 min
Jul 18, 9:55 AM CDT	Severe Thunderstorm Watch	SPC	Alexander, Clinton, Franklin, Gallatin, Hamilton, Hardin and 15 more	5 hr
Jul 18, 3:23 PM CDT	Mesoscale Discussion	SPC	Adams, Calhoun, Jersey, Monroe, Pike, Randolph	97 min
Jul 18, 3:45 PM CDT	Severe Thunderstorm Watch	SPC	Calhoun, Greene, Jersey, Monroe	5 hr

Nearby

Mesoscale Discussions in Iowa, 2003 Mesoscale Discussions in Illinois, 2003 Every mesoscale discussion in 2003

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.