Alert archive / Iowa / Severe Thunderstorm Watches in 2007
Severe Thunderstorm Watch 540
The Storm Prediction Center issued this severe thunderstorm watch at Jul 18, 2007, 10:39 PM CDT for 29 counties in Iowa; 4 counties in Nebraska. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 18, 2007, 10:39 PM CDT (03:39 UTC)
- Expired
- Jul 19, 2007, 3:43 AM CDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 60 kt
All 33 counties
Adair County, IA, Audubon County, IA, Black Hawk County, IA, Boone County, IA, Calhoun County, IA, Carroll County, IA, Cass County, IA, Crawford County, IA, Dallas County, IA, Greene County, IA, Grundy County, IA, Guthrie County, IA, Hamilton County, IA, Hardin County, IA, Harrison County, IA, Jasper County, IA, Madison County, IA, Mahaska County, IA, Marion County, IA, Marshall County, IA, Polk County, IA, Pottawattamie County, IA, Poweshiek County, IA, Sac County, IA, Shelby County, IA, Story County, IA, Tama County, IA, Warren County, IA, Webster County, IA, Douglas County, NE, Sarpy County, NE, Saunders County, NE, Washington County, NE
The radar
The Des Moines radar (KDMX), 61 km from the middle of the area, began a volume at 03:39 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.
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 10%
- One or more EF2 to EF5 tornadoes
- 5%
- Ten or more severe wind reports
- 70%
- One or more gusts of 65 knots or more
- 30%
- Ten or more severe hail reports
- 40%
- One or more hailstones of 2 inches or more
- 20%
- Six or more combined severe hail and wind reports
- 95%
Warnings issued inside it
4 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 18, 10:40 PM CDT | Severe Thunderstorm Warning | DMX | Crawford | 50 min |
| Jul 18, 11:45 PM CDT | Severe Thunderstorm Warning | OAX | Washington | 45 min |
| Jul 19, 12:03 AM CDT | Severe Thunderstorm Warning | OAX | Harrison, Monona | 42 min |
| Jul 19, 12:35 AM CDT | Severe Thunderstorm Warning | OAX | Pottawattamie, Shelby | 40 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Omaha, NE (KOAX), launched 00:00Z, 3.7 hours before the alert went out and 179 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.
- Mixed-layer CAPE
- 2155 J/kg
- Mixed-layer CIN
- -38 J/kg
- Mixed-layer LCL
- 2120 m above ground
- 0-6 km bulk shear
- 27 kt
- 0-1 km storm-relative helicity
- 15 m²/s²
- 0-3 km storm-relative helicity
- 69 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 4.1
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 18, 8:39 PM CDT | Severe Thunderstorm Watch | SPC | Buena Vista, Cherokee, Ida, Monona, Plymouth, Woodbury | 7 hr |
| Jul 18, 9:06 PM CDT | Mesoscale Discussion | SPC | Clinton, Des Moines, Henry, Lee, Louisa, Scott | 84 min |
| Jul 18, 10:23 PM CDT | Mesoscale Discussion | SPC | Adair, Adams, Appanoose, Audubon, Benton, Black Hawk and 60 more | 97 min |
| Jul 18, 11:07 PM CDT | Severe Thunderstorm Watch | SPC | Cedar, Clinton, Des Moines, Henry, Iowa, Jefferson and 8 more | 4 hr |
| Jul 19, 1:41 AM CDT | Mesoscale Discussion | SPC | Adair, Audubon, Black Hawk, Boone, Calhoun, Carroll and 23 more | 94 min |
| Jul 18, 7:15 PM CDT | Mesoscale Discussion | SPC | Adams, Antelope, Arthur, Blaine, Boone, Box Butte and 45 more | 90 min |
Nearby
Severe Thunderstorm Watches in Iowa, 2007Severe Thunderstorm Watches in Nebraska, 2007Every severe thunderstorm watch 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.