Alert archive / Iowa / Tornado Watches in 2003

Tornado Watch 779

July 20, 20034 states

The Storm Prediction Center issued this tornado watch at Jul 20, 2003, 8:50 PM CDT for 4 states. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued: Jul 20, 2003, 8:50 PM CDT (01:50 UTC)
Expired: Jul 21, 2003, 2:00 AM CDT
In force: 5 hr
Issued by: the Storm Prediction Center

All 59 counties

Adair County, IA, Adams County, IA, Audubon County, IA, Boone County, IA, Carroll County, IA, Cass County, IA, Crawford County, IA, Dallas County, IA, Fremont County, IA, Greene County, IA, Guthrie County, IA, Harrison County, IA, Madison County, IA, Mills County, IA, Montgomery County, IA, Page County, IA, Pottawattamie County, IA, Ringgold County, IA, Shelby County, IA, Taylor County, IA, Union County, IA, Webster County, IA, Brown County, KS, Clay County, KS, Cloud County, KS, Jewell County, KS, Lincoln County, KS, Marshall County, KS, Mitchell County, KS, Nemaha County, KS, Ottawa County, KS, Republic County, KS, Washington County, KS, Atchison County, MO, Holt County, MO, Nodaway County, MO, Worth County, MO, Butler County, NE, Cass County, NE, Clay County, NE, Douglas County, NE, Fillmore County, NE, Gage County, NE, Hamilton County, NE, Jefferson County, NE, Johnson County, NE, Lancaster County, NE, Nemaha County, NE, Nuckolls County, NE, Otoe County, NE, Pawnee County, NE, Richardson County, NE, Saline County, NE, Sarpy County, NE, Saunders County, NE, Seward County, NE, Thayer County, NE, Washington County, NE, York County, NE

The radar

The Omaha radar (KOAX), 70 km from the middle of the area, began a volume at 01:52 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

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

Issued	Product	Office	Counties	Lasted
Jul 20, 8:54 PM CDT	Severe Thunderstorm Warning	OAX	Johnson	36 min
Jul 20, 9:16 PM CDT	Severe Thunderstorm Warning	OAX	Pawnee	44 min
Jul 20, 9:19 PM CDT	Severe Thunderstorm Warning	OAX	Jefferson, Saline	41 min
Jul 20, 9:25 PM CDT	Severe Thunderstorm Warning	TOP	Brown, Marshall, Nemaha	65 min
Jul 20, 9:27 PM CDT	Severe Thunderstorm Warning	DMX	Cass	33 min
Jul 20, 9:29 PM CDT	Severe Thunderstorm Warning	OAX	Gage	31 min
Jul 20, 9:33 PM CDT	Severe Thunderstorm Warning	OAX	Mills, Montgomery	42 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, 1.8 hours before the alert went out and 70 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: 4827 J/kg
Mixed-layer CIN: -30 J/kg
Mixed-layer LCL: 1616 m above ground
0-6 km bulk shear: 43 kt
0-1 km storm-relative helicity: 92 m²/s²
0-3 km storm-relative helicity: 162 m²/s²
Significant tornado parameter: 1.4
Supercell composite: 28.6

Open this sounding in Storm Lab

The text

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

000 
WWUS20 KWNS 210150
SEL9  
SPC WW 210150
IAZ000-KSZ000-MOZ000-NEZ000-210700-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 779 
NWS STORM PREDICTION CENTER NORMAN OK 
850 PM CDT SUN JUL 20 2003

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

       WESTERN IOWA
       NORTHEAST KANSAS
       NORTHWEST MISSOURI
       SOUTHEAST NEBRASKA

EFFECTIVE THIS SUNDAY NIGHT AND MONDAY MORNING FROM 850 PM UNTIL
200 AM CDT.

TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS ALONG AND 75 STATUTE MILES NORTH AND
SOUTH OF A LINE FROM 40 MILES WEST NORTHWEST OF CONCORDIA KANSAS
TO 65 MILES NORTH OF LAMONI IOWA.

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 773...SEVERE THUNDERSTORM WATCH NUMBER 775. WATCH
NUMBER 773 775 WILL NOT BE IN EFFECT AFTER 850 PM CDT.
CONTINUE...WW 772...WW 773...WW 775...WW 776...WW 777...WW 778...


DISCUSSION...CLUSTERS OF SEVERE THUNDERSTORMS OVER SOUTHEAST NEB AND
WESTERN IA WILL CONTINUE TO TRACK SOUTHWARD INTO NORTHEAST KS AND
NORTHWEST MO.  ISOLATED TORNADO THREAT MAY PERSIST FOR A COUPLE OF
HOURS ACROSS NEB/IA PORTION OF WATCH.  HOWEVER...MAIN THREAT IS
EXPECTED TO BE LARGE HAIL AND DAMAGING WINDS.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500.
MEAN STORM MOTION VECTOR 24035.


...HART

405,0982 423,0935 402,0935 383,0982

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 20, 7:49 PM CDT	Mesoscale Discussion	SPC	Adair, Adams, Audubon, Calhoun, Carroll, Cass and 17 more	56 min
Jul 20, 8:08 PM CDT	Mesoscale Discussion	SPC	Appanoose, Benton, Black Hawk, Bremer, Buchanan, Cedar and 38 more	2 hr
Jul 20, 8:30 PM CDT	Tornado Watch	SPC	Allamakee, Appanoose, Benton, Black Hawk, Bremer, Buchanan and 42 more	6 hr
Jul 20, 11:14 PM CDT	Mesoscale Discussion	SPC	Appanoose, Benton, Cedar, Clinton, Davis, Delaware and 20 more	2 hr
Jul 20, 11:30 PM CDT	Severe Thunderstorm Watch	SPC	Lee	6 hr
Jul 20, 7:03 PM CDT	Mesoscale Discussion	SPC	Decatur, Norton, Phillips, Rawlins, Sheridan, Thomas	87 min
Jul 20, 10:16 PM CDT	Mesoscale Discussion	SPC	Chase, Coffey, Dickinson, Douglas, Franklin, Geary and 9 more	89 min
Jul 20, 10:43 PM CDT	Mesoscale Discussion	SPC	Brown, Clay, Cloud, Jewell, Marshall, Mitchell and 6 more	62 min
Jul 21, 2:24 PM CDT	Mesoscale Discussion	SPC	Cheyenne, Decatur, Graham, Norton, Phillips, Rawlins and 2 more	66 min
Jul 21, 4:50 PM CDT	Tornado Watch	SPC	Cheyenne, Decatur, Gove, Graham, Logan, Norton and 6 more	5 hr
Jul 20, 7:05 PM CDT	Severe Thunderstorm Watch	SPC	Douglas, Howell, Oregon, Ozark, Shannon	5 hr

Nearby

Tornado Watches in Iowa, 2003 Tornado Watches in Nebraska, 2003 Tornado Watches in Kansas, 2003 Every tornado watch in 2003

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.