Alert archive / Iowa / Tornado Watches in 2009

Tornado Watch 191

April 26, 200939 counties in Iowa; 7 counties in Missouri; 11 counties in Nebraska

The Storm Prediction Center issued this tornado watch at Apr 26, 2009, 12:48 PM CDT for 39 counties in Iowa; 7 counties in Missouri; 11 counties in Nebraska. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued: Apr 26, 2009, 12:48 PM CDT (17:48 UTC)
Expired: Apr 26, 2009, 5:05 PM CDT
In force: 4 hr
Issued by: the Storm Prediction Center
Largest hail expected: 3 in
Strongest gust expected: 60 kt

All 57 counties

Adair County, IA, Adams County, IA, Audubon County, IA, Boone County, IA, Butler County, IA, Calhoun County, IA, Carroll County, IA, Cass County, IA, Clarke County, IA, Crawford County, IA, Dallas County, IA, Decatur County, IA, Franklin County, IA, Fremont County, IA, Greene County, IA, Grundy County, IA, Guthrie County, IA, Hamilton County, IA, Hardin County, IA, Harrison County, IA, Humboldt County, IA, Jasper County, IA, Madison County, IA, Marshall County, IA, Mills County, IA, Montgomery County, IA, Page County, IA, Pocahontas County, IA, Polk County, IA, Pottawattamie County, IA, Ringgold County, IA, Sac County, IA, Shelby County, IA, Story County, IA, Taylor County, IA, Union County, IA, Warren County, IA, Webster County, IA, Wright County, IA, Andrew County, MO, Atchison County, MO, Gentry County, MO, Harrison County, MO, Holt County, MO, Nodaway County, MO, Worth County, MO, Cass County, NE, Douglas County, NE, Gage County, NE, Jefferson County, NE, Johnson County, NE, Lancaster County, NE, Nemaha County, NE, Otoe County, NE, Pawnee County, NE, Richardson County, NE, Sarpy County, NE

The radar

The Omaha radar (KOAX), 83 km from the middle of the area, began a volume at 17:48 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: 60%
One or more EF2 to EF5 tornadoes: 30%
Ten or more severe wind reports: 50%
One or more gusts of 65 knots or more: 30%
Ten or more severe hail reports: 70%
One or more hailstones of 2 inches or more: 30%
Six or more combined severe hail and wind reports: 90%

Warnings issued inside it

12 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
Apr 26, 1:12 PM CDT	Severe Thunderstorm Warning	OAX	Gage, Jefferson	63 min
Apr 26, 1:49 PM CDT	Severe Thunderstorm Warning	OAX	Mills, Montgomery, Pottawattamie	41 min
Apr 26, 1:52 PM CDT	Severe Thunderstorm Warning	OAX	Gage, Johnson, Lancaster, Otoe	38 min
Apr 26, 2:09 PM CDT	Severe Thunderstorm Warning	DMX	Cass	51 min
Apr 26, 2:17 PM CDT	Severe Thunderstorm Warning	OAX	Cass, Otoe	58 min
Apr 26, 3:01 PM CDT	Severe Thunderstorm Warning	OAX	Mills, Montgomery, Pottawattamie	59 min
Apr 26, 3:42 PM CDT	Severe Thunderstorm Warning	DMX	Audubon, Cass	48 min
Apr 26, 3:45 PM CDT	Severe Thunderstorm Warning	OAX	Nemaha, Richardson	22 min
Apr 26, 4:34 PM CDT	Severe Thunderstorm Warning	OAX	Montgomery	28 min
Apr 26, 4:40 PM CDT	Flash Flood Warning	DMX	Adair, Audubon, Cass, Guthrie	6 hr
Apr 26, 4:58 PM CDT	Severe Thunderstorm Warning	DMX	Adair, Audubon, Cass, Guthrie	47 min
Apr 26, 5:05 PM CDT	Tornado Warning	EAX	Atchison, Nodaway	15 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 12:00Z, 5.8 hours before the alert went out and 83 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 538 m above ground
0-6 km bulk shear: 51 kt
0-1 km storm-relative helicity: 457 m²/s²
0-3 km storm-relative helicity: 572 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.0

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 25, 7:17 PM CDT	Mesoscale Discussion	SPC	Appanoose, Davis, Wapello, Wayne	58 min
Apr 25, 9:23 PM CDT	Mesoscale Discussion	SPC	Davis, Des Moines, Henry, Lee, Van Buren	67 min
Apr 25, 10:09 PM CDT	Severe Thunderstorm Watch	SPC	Fremont, Page	6 hr
Apr 26, 9:18 AM CDT	Mesoscale Discussion	SPC	Audubon, Crawford, Harrison, Mills, Monona, Pottawattamie and 2 more	27 min
Apr 26, 9:34 AM CDT	Severe Thunderstorm Watch	SPC	Audubon, Buena Vista, Calhoun, Carroll, Cass, Cherokee and 29 more	6 hr
Apr 26, 12:30 PM CDT	Mesoscale Discussion	SPC	Adair, Adams, Audubon, Boone, Cass, Dallas and 13 more	60 min
Apr 26, 2:41 PM CDT	Mesoscale Discussion	SPC	Adair, Adams, Audubon, Boone, Buena Vista, Calhoun and 35 more	3 hr
Apr 26, 5:02 PM CDT	Tornado Watch	SPC	Adair, Adams, Allamakee, Appanoose, Benton, Black Hawk and 41 more	6 hr
Apr 26, 5:14 PM CDT	Mesoscale Discussion	SPC	Clayton, Delaware, Dubuque, Jackson	61 min
Apr 26, 6:14 PM CDT	Mesoscale Discussion	SPC	Adams, Appanoose, Benton, Black Hawk, Bremer, Buchanan and 40 more	61 min
Apr 26, 2:10 AM CDT	Mesoscale Discussion	SPC	Andrew, Atchison, Bates, Buchanan, Caldwell, Carroll and 23 more	95 min
Apr 26, 12:27 PM CDT	Mesoscale Discussion	SPC	Gage, Jefferson, Johnson, Nemaha, Otoe, Pawnee and 1 more	2 hr

Nearby

Tornado Watches in Iowa, 2009 Tornado Watches in Nebraska, 2009 Tornado Watches in Missouri, 2009 Every tornado watch in 2009

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.