Alert archive / Tennessee / Severe Thunderstorm Watches in 2002

Severe Thunderstorm Watch 694

September 20, 200230 counties in Tennessee

The Storm Prediction Center issued this severe thunderstorm watch at Sep 20, 2002, 12:10 PM CDT for 30 counties in Tennessee. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued: Sep 20, 2002, 12:10 PM CDT (17:10 UTC)
Expired: Sep 20, 2002, 5:00 PM CDT
In force: 5 hr
Issued by: the Storm Prediction Center

All 30 counties

Benton County, TN, Carroll County, TN, Cheatham County, TN, Chester County, TN, Davidson County, TN, Decatur County, TN, Dickson County, TN, Giles County, TN, Hardeman County, TN, Hardin County, TN, Henderson County, TN, Hickman County, TN, Houston County, TN, Humphreys County, TN, Lawrence County, TN, Lewis County, TN, Macon County, TN, Marshall County, TN, Maury County, TN, McNairy County, TN, Montgomery County, TN, Perry County, TN, Robertson County, TN, Rutherford County, TN, Stewart County, TN, Sumner County, TN, Trousdale County, TN, Wayne County, TN, Williamson County, TN, Wilson County, TN

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
Sep 20, 2:55 PM CDT	Severe Thunderstorm Warning	OHX	Montgomery	50 min
Sep 20, 3:10 PM CDT	Severe Thunderstorm Warning	OHX	Robertson	35 min

The nearest sounding before it

Nashville Metro, TN (KBNA), launched 12:00Z, 5.2 hours before the alert went out and 120 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: 719 J/kg
Mixed-layer CIN: -36 J/kg
Mixed-layer LCL: 749 m above ground
0-6 km bulk shear: 38 kt
0-1 km storm-relative helicity: 203 m²/s²
0-3 km storm-relative helicity: 175 m²/s²
Significant tornado parameter: 0.7
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 201709
SEL4  
SPC WW 201710
TNZ000-202200-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 694
STORM PREDICTION CENTER NORMAN OK
1210 PM CDT FRI SEP 20 2002

THE STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

   WESTERN AND MIDDLE TENNESSEE                          

EFFECTIVE THIS FRIDAY AFTERNOON FROM 1210 PM UNTIL 500 PM CDT.

HAIL TO 1 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS ALONG AND 65 STATUTE MILES
EAST AND WEST OF A LINE FROM 105 MILES SOUTHWEST OF NASHVILLE
TENNESSEE TO 35 MILES NORTH NORTHWEST OF NASHVILLE TENNESSEE.

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR 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.  SEVERE THUNDERSTORMS CAN AND OCCASIONALLY DO PRODUCE
TORNADOES.

OTHER WATCH INFORMATION...  CONTINUE...WW 693...

DISCUSSION...COLD FRONT MOVING INTO WRN TN PRECEEDED BY A VERY
MOIST AND UNSTABLE AIRMASS. WITH UPPER TROUGH MOVING NEWD INTO OH
VALLEY...WIND SHEAR PROFILES WILL REMAIN STRONG THROUGH THE
AFTERNOON WRN/MID TN.  STORMS WILL CONTINUE TO INTENSIFY
ALONG/AHEAD OF COLD FRONT WITH DAMAGING WIND THREAT DEVELOPING.


AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 1 INCH EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60 KNOTS. 
A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550.  MEAN STORM MOTION
VECTOR 22035.


...HALES

363,0854 350,0865 350,0890 363,0880

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 20, 5:05 PM CDT	Severe Thunderstorm Watch	SPC	Anderson, Bedford, Bledsoe, Bradley, Campbell, Cannon and 38 more	5 hr

Nearby

Severe Thunderstorm Watches in Tennessee, 2002 Every severe thunderstorm 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.