Alert archive / Oklahoma / Tornado Watches in 2001

Tornado Watch 260

May 20, 200111 counties in Oklahoma

The Storm Prediction Center issued this tornado watch at May 20, 2001, 9:00 PM CDT for 11 counties in Oklahoma. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: May 20, 2001, 9:00 PM CDT (02:00 UTC)
Expired: May 20, 2001, 11:00 PM CDT
In force: 2 hr
Issued by: the Storm Prediction Center

Counties Adair County, OK, Cherokee County, OK, Delaware County, OK, Haskell County, OK, Latimer County, OK, LeFlore County, OK, Mayes County, OK, Muskogee County, OK, Pushmataha County, OK, Sequoyah County, OK, Wagoner County, OK

The radar

The Western Arkansas radar (KSRX), 68 km from the middle of the area, began a volume at 02:04 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

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

Issued	Product	Office	Counties	Lasted
May 20, 9:00 PM CDT	Tornado Warning	TSA	LeFlore	60 min
May 20, 9:19 PM CDT	Severe Thunderstorm Warning	TSA	Latimer	41 min
May 20, 9:50 PM CDT	Severe Thunderstorm Warning	TSA	Haskell	40 min
May 20, 9:59 PM CDT	Severe Thunderstorm Warning	TSA	LeFlore	46 min
May 20, 10:04 PM CDT	Severe Thunderstorm Warning	TSA	Muskogee	56 min
May 20, 10:13 PM CDT	Severe Thunderstorm Warning	TSA	Latimer, Pushmataha	62 min
May 20, 10:25 PM CDT	Severe Thunderstorm Warning	TSA	Latimer	50 min
May 20, 10:46 PM CDT	Severe Thunderstorm Warning	TSA	LeFlore	59 min
May 20, 10:52 PM CDT	Flash Flood Warning	TSA	Haskell, LeFlore, Sequoyah	113 min

The nearest sounding before it

Norman, OK (KOUN), launched 00:00Z, 2.0 hours before the alert went out and 209 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: 2068 J/kg
Mixed-layer CIN: -4 J/kg
Mixed-layer LCL: 1431 m above ground
0-6 km bulk shear: 46 kt
0-1 km storm-relative helicity: 127 m²/s²
0-3 km storm-relative helicity: 175 m²/s²
Significant tornado parameter: 1.3
Supercell composite: 13.3

Open this sounding in Storm Lab

The text

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

000 
WWUS9 KMKC 210139
SEL0  

SEL0  
MKC WW 210135
OKZ000-210400-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 260
STORM PREDICTION CENTER NORMAN OK
835 PM CDT SUN MAY 20 2001

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

   EASTERN OKLAHOMA                           

EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 900 PM UNTIL 1100
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 35 STATUTE MILES EAST AND WEST
OF A LINE FROM 30 MILES SOUTHWEST OF PAGE OKLAHOMA TO 60 MILES
NORTH NORTHEAST OF MUSKOGEE OKLAHOMA.

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 255...SEVERE THUNDERSTORM WATCH NUMBER 256.  WATCH NUMBER
255...256 WILL NOT BE IN EFFECT AFTER 900 PM CDT.  CONTINUE...WW
257...WW 258...WW 259...

DISCUSSION...SUPERCELL THUNDERSTORMS CONTINUE TO MOVE EWD ACROSS
EAST CENTRAL OK...WITH OTHER SEVERE STORMS MOVING ACROSS NERN OK. 
STORMS WILL CONTINUE EWD TOWARD THE AR BORDER DURING THE NEXT TWO
HOURS.


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.


...WEISS

;342,0953 362,0953 362,0941 342,03942;

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 20, 11:00 PM CDT	Tornado Watch	SPC	Adair, Cherokee, Delaware, Haskell, Latimer, LeFlore and 2 more	4 hr
May 20, 11:15 PM CDT	Severe Thunderstorm Watch	SPC	Beckham, Custer, Ellis, Greer, Harmon, Harper and 2 more	5 hr

Nearby

Tornado Watches in Oklahoma, 2001 Every tornado watch in 2001

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.