Alert archive / Iowa / Mesoscale Discussions in 2003

Mesoscale Discussion 1918

July 20, 200323 counties in Iowa; 17 counties in Nebraska

The Storm Prediction Center issued this mesoscale discussion at Jul 20, 2003, 5:29 PM CDT for 23 counties in Iowa; 17 counties in Nebraska. It was in force for 91 min.

The area

The outline as issued.

The facts

Issued: Jul 20, 2003, 5:29 PM CDT (22:29 UTC)
Expired: Jul 20, 2003, 7:00 PM CDT
In force: 91 min
Issued by: the Storm Prediction Center

All 40 counties

Adair County, IA, Adams County, IA, Audubon County, IA, Carroll County, IA, Cass County, IA, Cherokee County, IA, Crawford County, IA, Decatur County, IA, Fremont County, IA, Guthrie County, IA, Harrison County, IA, Ida County, IA, Mills County, IA, Monona County, IA, Montgomery County, IA, Page County, IA, Pottawattamie County, IA, Ringgold County, IA, Sac County, IA, Shelby County, IA, Taylor County, IA, Union County, IA, Woodbury County, IA, Burt County, NE, Cass County, NE, Colfax County, NE, Cuming County, NE, Dakota County, NE, Dodge County, NE, Douglas County, NE, Lancaster County, NE, Madison County, NE, Otoe County, NE, Pierce County, NE, Sarpy County, NE, Saunders County, NE, Stanton County, NE, Thurston County, NE, Washington County, NE, Wayne County, NE

The radar

The Omaha radar (KOAX), 44 km from the middle of the area, began a volume at 22:31 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.

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 10.5 hours before the alert went out and 44 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: 1371 J/kg
Mixed-layer CIN: -314 J/kg
Mixed-layer LCL: 1243 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 67 m²/s²
0-3 km storm-relative helicity: 88 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.4

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 20, 4:14 AM CDT	Mesoscale Discussion	SPC	Howard, Mitchell, Winnebago, Winneshiek, Worth	3 hr
Jul 20, 6:45 AM CDT	Severe Thunderstorm Watch	SPC	Buena Vista, Butler, Calhoun, Cerro Gordo, Cherokee, Clay and 22 more	5 hr
Jul 20, 10:07 AM CDT	Mesoscale Discussion	SPC	Buena Vista, Calhoun, Cherokee, Clay, Dickinson, Emmet and 13 more	53 min
Jul 20, 2:09 PM CDT	Mesoscale Discussion	SPC	Crawford, Harrison, Monona, Plymouth, Pottawattamie, Shelby and 2 more	66 min
Jul 20, 2:50 PM CDT	Tornado Watch	SPC	Adair, Adams, Audubon, Buena Vista, Carroll, Cass and 20 more	6 hr
Jul 20, 1:25 PM CDT	Mesoscale Discussion	SPC	Arthur, Blaine, Brown, Chase, Cheyenne, Custer and 13 more	95 min
Jul 20, 4:32 PM CDT	Mesoscale Discussion	SPC	Adams, Arthur, Boone, Buffalo, Chase, Cheyenne and 32 more	58 min
Jul 20, 4:50 PM CDT	Severe Thunderstorm Watch	SPC	Adams, Boone, Buffalo, Butler, Chase, Clay and 35 more	4 hr

Nearby

Mesoscale Discussions in Iowa, 2003 Mesoscale Discussions in Nebraska, 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.