Alert archive / Iowa / Mesoscale Discussions in 2007

Mesoscale Discussion 1823

August 20, 20074 states

The Storm Prediction Center issued this mesoscale discussion at Aug 20, 2007, 7:03 PM CDT for 4 states. It was in force for 117 min.

The area

The outline as issued.

The facts

Issued
Aug 20, 2007, 7:03 PM CDT (00:03 UTC)
Expired
Aug 20, 2007, 9:00 PM CDT
In force
117 min
Issued by
the Storm Prediction Center
All 31 counties

Adair County, IA, Adams County, IA, Audubon County, IA, Buena Vista County, IA, Calhoun County, IA, Carroll County, IA, Cass County, IA, Cherokee County, IA, Clay County, IA, Dickinson County, IA, Emmet County, IA, Greene County, IA, Guthrie 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, Taylor County, IA, Union County, IA, Nobles County, MN, Rock County, MN, Cedar County, NE, Clay County, SD, Lincoln County, SD, Minnehaha County, SD, Turner County, SD, Union County, SD

The radar

The Omaha radar (KOAX), 140 km from the middle of the area, began a volume at 00:03 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 00:00Z, 0.1 hours before the alert went out and 141 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 2007-08-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 4337 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 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 2007-08-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 86 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
4337 J/kg
Mixed-layer CIN
-31 J/kg
Mixed-layer LCL
1029 m above ground
0-6 km bulk shear
30 kt
0-1 km storm-relative helicity
86 m²/s²
0-3 km storm-relative helicity
274 m²/s²
Significant tornado parameter
3.9
Supercell composite
21.2

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, 7:35 PM CDTMesoscale DiscussionSPCAdair, Adams, Audubon, Calhoun, Carroll, Cass and 15 more85 min
Aug 20, 8:10 PM CDTSevere Thunderstorm WatchSPCAdair, Adams, Appanoose, Audubon, Black Hawk, Boone and 50 more5 hr
Aug 20, 10:06 PM CDTMesoscale DiscussionSPCAdair, Adams, Appanoose, Boone, Buena Vista, Calhoun and 43 more84 min
Aug 21, 4:50 PM CDTMesoscale DiscussionSPCDickinson, Emmet, Howard, Mitchell, Osceola, Winnebago and 1 more85 min
Aug 21, 6:17 PM CDTMesoscale DiscussionSPCBuena Vista, Cherokee, Clay, Crawford, Ida, Lyon and 6 more88 min
Aug 21, 6:47 PM CDTTornado WatchSPCAudubon, Black Hawk, Boone, Bremer, Buena Vista, Butler and 34 more7 hr
Aug 20, 10:23 PM CDTSevere Thunderstorm WatchSPCAnoka, Blue Earth, Brown, Carver, Chippewa, Cottonwood and 25 more5 hr
Aug 21, 2:16 AM CDTMesoscale DiscussionSPCAnoka, Carver, Dakota, Hennepin, Isanti, McLeod and 6 more59 min
Aug 21, 2:47 PM CDTMesoscale DiscussionSPCAntelope, Blaine, Boone, Boyd, Brown, Buffalo and 44 more118 min
Aug 21, 3:45 PM CDTTornado WatchSPCAntelope, Boone, Boyd, Cedar, Colfax, Cuming and 14 more6 hr
Aug 21, 3:50 PM CDTSevere Thunderstorm WatchSPCAdams, Buffalo, Custer, Dawson, Franklin, Frontier and 16 more6 hr
Aug 21, 5:53 PM CDTMesoscale DiscussionSPCBuffalo, Dawson, Frontier, Furnas, Gosper, Harlan and 5 more97 min

Nearby

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