Alert archive / Nebraska / Mesoscale Discussions in 2007

Mesoscale Discussion 1818

August 20, 20074 states

The Storm Prediction Center issued this mesoscale discussion at Aug 20, 2007, 3:03 PM CDT for 4 states. It was in force for 117 min.

The area

The outline as issued.

The facts

Issued
Aug 20, 2007, 3:03 PM CDT (20:03 UTC)
Expired
Aug 20, 2007, 5:00 PM CDT
In force
117 min
Issued by
the Storm Prediction Center
All 55 counties

Cherokee County, IA, Crawford County, IA, Fremont County, IA, Harrison County, IA, Ida County, IA, Lyon County, IA, Mills County, IA, Monona County, IA, O'Brien County, IA, Plymouth County, IA, Pottawattamie County, IA, Shelby County, IA, Sioux County, IA, Woodbury County, IA, Atchison County, MO, Antelope County, NE, Boone County, NE, Burt County, NE, Butler County, NE, Cass County, NE, Cedar County, NE, Colfax County, NE, Cuming County, NE, Dakota County, NE, Dixon County, NE, Dodge County, NE, Douglas County, NE, Fillmore County, NE, Gage County, NE, Hamilton County, NE, Jefferson County, NE, Johnson County, NE, Knox County, NE, Lancaster County, NE, Madison County, NE, Merrick County, NE, Nance County, NE, Nemaha County, NE, Otoe County, NE, Pierce County, NE, Platte County, NE, Polk County, NE, Saline County, NE, Sarpy County, NE, Saunders County, NE, Seward County, NE, Stanton County, NE, Thurston County, NE, Washington County, NE, Wayne County, NE, York County, NE, Clay County, SD, Lincoln County, SD, Union County, SD, Yankton County, SD

The radar

The Omaha radar (KOAX), 80 km from the middle of the area, began a volume at 20:06 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, 8.1 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-pSkew-T log-p diagram, Omaha, NE at 12:00Z on 2007-08-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 768 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Omaha, NE at 12:00Z on 2007-08-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 68 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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
768 J/kg
Mixed-layer CIN
-216 J/kg
Mixed-layer LCL
1084 m above ground
0-6 km bulk shear
30 kt
0-1 km storm-relative helicity
68 m²/s²
0-3 km storm-relative helicity
129 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.3

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.

IssuedProductOfficeCountiesLasted
Aug 20, 9:34 AM CDTMesoscale DiscussionSPCAudubon, Buena Vista, Calhoun, Carroll, Cerro Gordo, Cherokee and 21 more56 min
Aug 20, 3:49 PM CDTTornado WatchSPCFremont, Harrison, Mills, Monona, Montgomery, Page and 2 more6 hr
Aug 20, 6:27 PM CDTMesoscale DiscussionSPCPage2 hr
Aug 20, 4:38 AM CDTMesoscale DiscussionSPCBarton, Christian, Dade, Douglas, Greene, Howell and 7 more97 min
Aug 20, 6:50 PM CDTSevere Thunderstorm WatchSPCAndrew, Atchison, Buchanan, Caldwell, Carroll, Cass and 16 more6 hr
Aug 19, 8:46 PM CDTMesoscale DiscussionSPCBennett, Butte, Harding, Jackson, Meade, Oglala Lakota and 1 more59 min
Aug 19, 9:37 PM CDTSevere Thunderstorm WatchSPCBennett, Butte, Custer, Fall River, Haakon, Harding and 11 more5 hr
Aug 19, 10:29 PM CDTMesoscale DiscussionSPCBennett, Butte, Harding, Jackson, Meade, Oglala Lakota and 1 more61 min
Aug 20, 2:03 AM CDTMesoscale DiscussionSPCBennett, Buffalo, Campbell, Corson, Dewey, Haakon and 12 more57 min

Nearby

Mesoscale Discussions in Nebraska, 2007Mesoscale Discussions in Iowa, 2007Mesoscale Discussions in South Dakota, 2007Every mesoscale discussion in 2007

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.