Alert archive / Nebraska / Tornado Watches in 2002

Tornado Watch 450

June 20, 200225 counties in Iowa; 30 counties in Nebraska

The Storm Prediction Center issued this tornado watch at Jun 20, 2002, 4:00 PM CDT for 25 counties in Iowa; 30 counties in Nebraska. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: Jun 20, 2002, 4:00 PM CDT (21:00 UTC)
Expired: Jun 20, 2002, 10:00 PM CDT
In force: 6 hr
Issued by: the Storm Prediction Center

All 55 counties

Adair County, IA, Adams County, IA, Audubon County, IA, Boone County, IA, Calhoun 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, Ida County, IA, Madison County, IA, Mills County, IA, Monona County, IA, Montgomery County, IA, Page County, IA, Pottawattamie County, IA, Sac County, IA, Shelby County, IA, Union County, IA, Webster County, IA, Woodbury County, IA, Antelope County, NE, Boone County, NE, Burt County, NE, Butler County, NE, Cass County, NE, Clay County, NE, Colfax County, NE, Cuming County, NE, Dakota County, NE, Dodge County, NE, Douglas County, NE, Fillmore County, NE, Hamilton County, NE, Lancaster County, NE, Madison County, NE, Merrick County, NE, Nance County, NE, Otoe County, NE, Pierce County, NE, Platte County, NE, Polk County, NE, Saline County, NE, Sarpy County, NE, Saunders County, NE, Seward County, NE, Stanton County, NE, Thurston County, NE, Washington County, NE, Wayne County, NE, York County, NE

The radar

The Omaha radar (KOAX), 40 km from the middle of the area, began a volume at 20:59 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

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

Issued	Product	Office	Counties	Lasted
Jun 20, 5:49 PM CDT	Severe Thunderstorm Warning	OAX	Burt	26 min
Jun 20, 8:05 PM CDT	Severe Thunderstorm Warning	DMX	Calhoun, Webster	55 min
Jun 20, 8:30 PM CDT	Tornado Warning	DMX	Webster	45 min
Jun 20, 8:32 PM CDT	Tornado Warning	DMX	Webster	43 min
Jun 20, 8:56 PM CDT	Severe Thunderstorm Warning	FSD	Woodbury	34 min
Jun 20, 9:05 PM CDT	Tornado Warning	FSD	Woodbury	25 min
Jun 20, 9:23 PM CDT	Severe Thunderstorm Warning	DMX	Webster	47 min
Jun 20, 9:40 PM CDT	Severe Thunderstorm Warning	DMX	Crawford	50 min
Jun 20, 9:41 PM CDT	Flash Flood Warning	FSD	Woodbury	49 min
Jun 20, 9:54 PM CDT	Tornado Warning	DMX	Crawford	51 min

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 9.0 hours before the alert went out and 40 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: 203 J/kg
Mixed-layer CIN: -310 J/kg
Mixed-layer LCL: 957 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 121 m²/s²
0-3 km storm-relative helicity: 152 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.0

Open this sounding in Storm Lab

The text

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

000 
WWUS20 KWNS 202121
SEL0  
SPC WW 202038
IAZ000-NEZ000-210300-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 450
STORM PREDICTION CENTER NORMAN OK
338 PM CDT THU JUN 20 2002

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

   WESTERN IOWA                               
   EASTERN NEBRASKA                           

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 400 PM UNTIL
1000 PM 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 65 STATUTE MILES NORTH AND
SOUTH OF A LINE FROM 20 MILES NORTH OF GRAND ISLAND NEBRASKA TO 55
MILES SOUTH SOUTHEAST OF FORT DODGE 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...  CONTINUE...WW 447...WW 448...WW 449...


DISCUSSION...MCV WILL CONTINUE A SLOW EWD MOTION ACROSS ERN NEB
THIS EVENING...AND INTERACT WITH AN EXTREMELY UNSTABLE AIR MASS
ALONG AND SOUTH OF STATIONARY FRONT FROM CENTRAL IA INTO CENTRAL
NEB.  RAPID SEVERE THUNDERSTORM DEVELOPMENT IS THEREFORE EXPECTED
IN THE NEXT 1-2 HOURS.  NARROW ZONE OF DEEP LAYER SHEAR SHOULD
SUPPORT SUPERCELLS... WHILE ENHANCED ELY FLOW ALONG AND JUST NORTH
OF THE FRONT INDICATE AN ADDITIONAL THREAT OF A FEW TORNADOES.


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 25025.


...EVANS

421,0981 424,0934 405,0934 401,0981

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 19, 8:30 PM CDT	Severe Thunderstorm Watch	SPC	Adams, Butler, Clay, Fillmore, Franklin, Hall and 11 more	4 hr

Nearby

Tornado Watches in Nebraska, 2002 Tornado Watches in Iowa, 2002 Every tornado watch in 2002

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.