Alert archive / Iowa / Tornado Watches in 2004

Tornado Watch 89

April 18, 20044 states

The Storm Prediction Center issued this tornado watch at Apr 18, 2004, 9:45 PM CDT for 4 states. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued: Apr 18, 2004, 9:45 PM CDT (02:45 UTC)
Expired: Apr 19, 2004, 2:00 AM CDT
In force: 4 hr
Issued by: the Storm Prediction Center

All 84 counties

Adair County, IA, Adams County, IA, Allamakee County, IA, Audubon County, IA, Benton County, IA, Black Hawk County, IA, Boone County, IA, Bremer County, IA, Buchanan County, IA, Butler County, IA, Calhoun County, IA, Carroll County, IA, Cass County, IA, Cerro Gordo County, IA, Chickasaw County, IA, Clarke County, IA, Clayton County, IA, Crawford County, IA, Dallas County, IA, Delaware County, IA, Fayette County, IA, Floyd County, IA, Franklin County, IA, Fremont County, IA, Greene County, IA, Grundy County, IA, Guthrie County, IA, Hamilton County, IA, Hancock County, IA, Hardin County, IA, Harrison County, IA, Howard County, IA, Humboldt County, IA, Jasper County, IA, Madison County, IA, Marion County, IA, Marshall County, IA, Mills County, IA, Mitchell County, IA, Montgomery County, IA, Page County, IA, Polk County, IA, Pottawattamie County, IA, Poweshiek County, IA, Ringgold County, IA, Shelby County, IA, Story County, IA, Tama County, IA, Taylor County, IA, Union County, IA, Warren County, IA, Webster County, IA, Winneshiek County, IA, Worth County, IA, Wright County, IA, Fillmore County, MN, Houston County, MN, Mower County, MN, Olmsted County, MN, Wabasha County, MN, Winona County, MN, Cass County, NE, Douglas County, NE, Lancaster County, NE, Sarpy County, NE, Adams County, WI, Buffalo County, WI, Crawford County, WI, Eau Claire County, WI, Grant County, WI, Jackson County, WI, Juneau County, WI, La Crosse County, WI, Marquette County, WI, Monroe County, WI, Outagamie County, WI, Portage County, WI, Richland County, WI, Sauk County, WI, Trempealeau County, WI, Vernon County, WI, Waupaca County, WI, Waushara County, WI, Wood County, WI

The radar

The Des Moines radar (KDMX), 65 km from the middle of the area, began a volume at 02:46 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.

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
Apr 18, 10:19 PM CDT	Severe Thunderstorm Warning	ARX	Floyd, Mitchell	26 min
Apr 18, 11:55 PM CDT	Severe Thunderstorm Warning	DMX	Dallas, Guthrie	35 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, 2.8 hours before the alert went out and 254 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: 1099 J/kg
Mixed-layer CIN: -135 J/kg
Mixed-layer LCL: 1062 m above ground
0-6 km bulk shear: 64 kt
0-1 km storm-relative helicity: 334 m²/s²
0-3 km storm-relative helicity: 385 m²/s²
Significant tornado parameter: 1.2
Supercell composite: 5.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

000 
WWUS20 KWNS 190232
SEL9  
SPC WW 190230
IAZ000-MNZ000-NEZ000-WIZ000-190700-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 89
NWS STORM PREDICTION CENTER NORMAN OK
930 PM CDT SUN APR 18 2004

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF 

       LARGE PART OF IOWA
       SOUTHEASTERN MINNESOTA
       SOUTHEASTERN NEBRASKA
       SOUTHWESTERN WISCONSIN

EFFECTIVE THIS SUNDAY NIGHT AND MONDAY MORNING FROM 930 PM UNTIL
200 AM CDT.

TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS ALONG AND 90 STATUTE MILES EAST AND WEST
OF A LINE FROM 60 MILES NORTH NORTHEAST OF CAMP DOUGLAS WISCONSIN
TO 45 MILES SOUTH SOUTHEAST OF OMAHA NEBRASKA.

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH AREA.
PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR THREATENING
WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS AND POSSIBLE
WARNINGS.

OTHER WATCH INFORMATION...THIS TORNADO WATCH REPLACES TORNADO
WATCH NUMBER 85. WATCH NUMBER 85 WILL NOT BE IN EFFECT AFTER 930
PM CDT. CONTINUE...WW 87...WW 88...

DISCUSSION...LINE OF SEVERE THUNDERSTORMS CONTINUES EWD FROM WRN WI
SWWD TO SERN NEB.  GIVEN THE VERY STRONG VEERING SHEAR PROFILES
AHEAD OF VIGOROUS UPPER TROUGH...POTENTIAL WILL CONTINUE FOR
DAMAGING WINDS AND ISOLATED TORNADOES AS THE LINE MOVES ACROSS 
WATCH AREA.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500.
MEAN STORM MOTION VECTOR 24045.


...HALES

444,0875 404,0935 404,0971 444,0913

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 18, 7:05 PM CDT	Mesoscale Discussion	SPC	Audubon, Buena Vista, Calhoun, Carroll, Cass, Cherokee and 29 more	115 min
Apr 18, 11:12 PM CDT	Mesoscale Discussion	SPC	Adair, Adams, Allamakee, Audubon, Benton, Black Hawk and 48 more	93 min
Apr 18, 7:10 PM CDT	Mesoscale Discussion	SPC	Lincoln, Pipestone, Rock	65 min
Apr 18, 8:28 PM CDT	Mesoscale Discussion	SPC	Brown, Carver, Dakota, Goodhue, Hennepin, Le Sueur and 7 more	92 min
Apr 18, 8:45 PM CDT	Severe Thunderstorm Watch	SPC	Langlade, Marinette	4 hr

Nearby

Tornado Watches in Iowa, 2004 Tornado Watches in Wisconsin, 2004 Tornado Watches in Minnesota, 2004 Every tornado watch in 2004

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.