Alert archive / Iowa / Mesoscale Discussions in 2007

Mesoscale Discussion 1797

August 18, 20074 states

The Storm Prediction Center issued this mesoscale discussion at Aug 18, 2007, 11:10 PM CDT for 4 states. It was in force for 110 min.

The area

The outline as issued.

The facts

Issued
Aug 18, 2007, 11:10 PM CDT (04:10 UTC)
Expired
Aug 19, 2007, 1:00 AM CDT
In force
110 min
Issued by
the Storm Prediction Center
All 60 counties

Buena Vista County, IA, Calhoun County, IA, Cerro Gordo County, IA, Cherokee County, IA, Clay County, IA, Dickinson County, IA, Emmet County, IA, Franklin County, IA, Hamilton County, IA, Hancock County, IA, Hardin County, IA, Humboldt County, IA, Ida County, IA, Kossuth County, IA, Lyon County, IA, O'Brien County, IA, Osceola County, IA, Palo Alto County, IA, Plymouth County, IA, Pocahontas County, IA, Sac County, IA, Sioux County, IA, Webster County, IA, Winnebago County, IA, Woodbury County, IA, Worth County, IA, Wright County, IA, Jackson County, MN, Nobles County, MN, Rock County, MN, Boyd County, NE, Brown County, NE, Cedar County, NE, Dakota County, NE, Dixon County, NE, Holt County, NE, Keya Paha County, NE, Knox County, NE, Rock County, NE, Aurora County, SD, Bon Homme County, SD, Brule County, SD, Charles Mix County, SD, Clay County, SD, Davison County, SD, Douglas County, SD, Gregory County, SD, Hanson County, SD, Hutchinson County, SD, Jerauld County, SD, Lake County, SD, Lincoln County, SD, McCook County, SD, Miner County, SD, Minnehaha County, SD, Moody County, SD, Sanborn County, SD, Turner County, SD, Union County, SD, Yankton County, SD

The radar

The Sioux Falls radar (KFSD), 89 km from the middle of the area, began a volume at 04:12 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

Omaha, NE (KOAX), launched 00:00Z, 4.2 hours before the alert went out and 226 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 00:00Z on 2007-08-19Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1801 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 00:00Z on 2007-08-19The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 12 square meters per square second.1939Sfc1 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
1801 J/kg
Mixed-layer CIN
-25 J/kg
Mixed-layer LCL
1509 m above ground
0-6 km bulk shear
14 kt
0-1 km storm-relative helicity
12 m²/s²
0-3 km storm-relative helicity
60 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

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 18, 8:03 PM CDTMesoscale DiscussionSPCAllamakee, Dickinson, Emmet, Howard, Mitchell, Winnebago and 2 more3 hr
Aug 19, 6:12 AM CDTMesoscale DiscussionSPCBlack Hawk, Bremer, Buchanan, Butler, Chickasaw, Clayton and 8 more93 min
Aug 19, 1:20 PM CDTMesoscale DiscussionSPCAppanoose, Benton, Cedar, Chickasaw, Clarke, Clayton and 33 more3 hr

Nearby

Mesoscale Discussions in Iowa, 2007Mesoscale Discussions in South Dakota, 2007Mesoscale Discussions in Nebraska, 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.