Alert archive / Iowa / Mesoscale Discussions in 2007

Mesoscale Discussion 1815

August 20, 200727 counties in Iowa; 8 counties in Minnesota; Burt County, Thurston County, Washington County, Nebraska

The Storm Prediction Center issued this mesoscale discussion at Aug 20, 2007, 9:34 AM CDT for 27 counties in Iowa; 8 counties in Minnesota; Burt County, Thurston County, Washington County, Nebraska. It was in force for 56 min.

The area

The outline as issued.

The facts

Issued
Aug 20, 2007, 9:34 AM CDT (14:34 UTC)
Expired
Aug 20, 2007, 10:30 AM CDT
In force
56 min
Issued by
the Storm Prediction Center
All 38 counties

Audubon County, IA, Buena Vista County, IA, Calhoun County, IA, Carroll County, IA, Cerro Gordo County, IA, Cherokee County, IA, Clay County, IA, Crawford County, IA, Dickinson County, IA, Emmet County, IA, Greene County, IA, Hancock County, IA, Harrison County, IA, Humboldt County, IA, Ida County, IA, Kossuth County, IA, Monona County, IA, O'Brien County, IA, Palo Alto County, IA, Pocahontas County, IA, Sac County, IA, Shelby County, IA, Webster County, IA, Winnebago County, IA, Woodbury County, IA, Worth County, IA, Wright County, IA, Blue Earth County, MN, Faribault County, MN, Freeborn County, MN, Jackson County, MN, Martin County, MN, Steele County, MN, Waseca County, MN, Watonwan County, MN, Burt County, NE, Thurston County, NE, Washington County, NE

The radar

The Des Moines radar (KDMX), 152 km from the middle of the area, began a volume at 14:33 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 12:00Z, 2.6 hours before the alert went out and 228 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, 3:03 PM CDTMesoscale DiscussionSPCCherokee, Crawford, Fremont, Harrison, Ida, Lyon and 8 more117 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

Nearby

Mesoscale Discussions in Iowa, 2007Mesoscale Discussions in Minnesota, 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.