Alert archive / Iowa / Tornado Watches in 2002

Tornado Watch 158

April 27, 20024 states

The Storm Prediction Center issued this tornado watch at Apr 27, 2002, 3:30 PM CDT for 4 states. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued: Apr 27, 2002, 3:30 PM CDT (20:30 UTC)
Expired: Apr 27, 2002, 8:00 PM CDT
In force: 5 hr
Issued by: the Storm Prediction Center

All 61 counties

Adair County, IA, Adams County, IA, Appanoose County, IA, Audubon County, IA, Black Hawk County, IA, Boone County, IA, Carroll County, IA, Cass County, IA, Clarke County, IA, Crawford County, IA, Dallas County, IA, Davis County, IA, Decatur County, IA, Fremont County, IA, Greene County, IA, Grundy County, IA, Guthrie County, IA, Hamilton County, IA, Hardin County, IA, Harrison County, IA, Jasper County, IA, Lucas County, IA, Madison County, IA, Mahaska County, IA, Marion County, IA, Marshall County, IA, Mills County, IA, Monroe 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, Wapello County, IA, Warren County, IA, Wayne County, IA, Brown County, KS, Doniphan County, KS, Adair County, MO, Andrew County, MO, Atchison County, MO, Daviess County, MO, DeKalb County, MO, Gentry County, MO, Grundy County, MO, Harrison County, MO, Holt County, MO, Mercer County, MO, Nodaway County, MO, Putnam County, MO, Schuyler County, MO, Sullivan County, MO, Worth County, MO, Nemaha County, NE, Richardson County, NE

The radar

The Des Moines radar (KDMX), 76 km from the middle of the area, began a volume at 20:30 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
Apr 27, 3:36 PM CDT	Tornado Warning	TOP	Brown	24 min
Apr 27, 3:49 PM CDT	Severe Thunderstorm Warning	EAX	Doniphan	41 min
Apr 27, 4:42 PM CDT	Tornado Warning	OAX	Fremont, Mills	33 min
Apr 27, 4:45 PM CDT	Tornado Warning	EAX	Andrew, Buchanan	30 min
Apr 27, 6:36 PM CDT	Tornado Warning	DMX	Union	24 min
Apr 27, 6:58 PM CDT	Tornado Warning	DMX	Madison	32 min
Apr 27, 7:11 PM CDT	Severe Thunderstorm Warning	EAX	Adair, Sullivan	49 min

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 8.5 hours before the alert went out and 159 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: 471 m above ground
0-6 km bulk shear: 58 kt
0-1 km storm-relative helicity: 164 m²/s²
0-3 km storm-relative helicity: 277 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

000
WWUS20 KWNS 272011
SEL8  
SPC WW 272002
IAZ000-MOZ000-280100-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 158
STORM PREDICTION CENTER NORMAN OK
302 PM CDT SAT APR 27 2002

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

   SOUTHERN AND WESTERN IOWA                               
   NORTHERN MISSOURI                           

EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 330 PM UNTIL 800
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 90 STATUTE MILES NORTH AND
SOUTH OF A LINE FROM 30 MILES SOUTH OF OMAHA NEBRASKA TO 20 MILES
NORTH NORTHEAST OF OTTUMWA 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 156...WW 157...

DISCUSSION...AIR MASS IS BECOMING INCREASINGLY UNSTABLE AS WARM
FRONT IS LIFTING RAPIDLY NEWD TOWARD NRN MO AND SWRN IA. STORMS ARE
EXPECTED TO DEVELOP IN NERN KS/SERN NEB AND SPREAD INTO THE AREA
DURING THE NEXT SEVERAL HOURS. THE MAIN THREAT WILL BE LARGE
HAIL...THOUGH TORNADOES ARE POSSIBLE...ESPECIALLY NEAR THE WARM
FRONT WHERE THE LOW LEVEL SHEAR AND STORM RELATIVE HELICITY ARE
GREATEST. 

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 450. 
MEAN STORM MOTION VECTOR 24045.

...IMY

421,0955 424,0921 400,0921 393,0955

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 27, 12:30 PM CDT	Tornado Watch	SPC	Cloud, Jewell, Marshall, Mitchell, Nemaha, Osborne and 3 more	6 hr
Apr 27, 3:00 PM CDT	Tornado Watch	SPC	Anderson, Atchison, Coffey, Douglas, Franklin, Greenwood and 13 more	5 hr
Apr 27, 6:30 PM CDT	Tornado Watch	SPC	Adair, Audrain, Benton, Boone, Callaway, Camden and 49 more	6 hr

Nearby

Tornado Watches in Iowa, 2002 Tornado Watches in Missouri, 2002 Tornado Watches in Kansas, 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.