Alert archive / Alabama / Tornado Watches in 2007

Tornado Watch 683

September 21, 200729 counties in Alabama; 12 counties in Florida

The Storm Prediction Center issued this tornado watch at Sep 21, 2007, 10:11 PM CDT for 29 counties in Alabama; 12 counties in Florida. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: Sep 21, 2007, 10:11 PM CDT (03:11 UTC)
Expired: Sep 22, 2007, 4:17 AM CDT
In force: 6 hr
Issued by: the Storm Prediction Center
Largest hail expected: 0.5 in
Strongest gust expected: 50 kt

All 41 counties

Autauga County, AL, Baldwin County, AL, Barbour County, AL, Bullock County, AL, Butler County, AL, Chambers County, AL, Clarke County, AL, Coffee County, AL, Conecuh County, AL, Covington County, AL, Crenshaw County, AL, Dale County, AL, Dallas County, AL, Elmore County, AL, Escambia County, AL, Geneva County, AL, Henry County, AL, Houston County, AL, Lee County, AL, Lowndes County, AL, Macon County, AL, Mobile County, AL, Monroe County, AL, Montgomery County, AL, Pike County, AL, Russell County, AL, Tallapoosa County, AL, Washington County, AL, Wilcox County, AL, Bay County, FL, Calhoun County, FL, Escambia County, FL, Franklin County, FL, Gulf County, FL, Holmes County, FL, Jackson County, FL, Liberty County, FL, Okaloosa County, FL, Santa Rosa County, FL, Walton County, FL, Washington County, FL

The radar

The Eglin Afb radar (KEVX), 90 km from the middle of the area, began a volume at 03:14 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.

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes: 30%
One or more EF2 to EF5 tornadoes: 5%
Ten or more severe wind reports: 10%
One or more gusts of 65 knots or more: 5%
Ten or more severe hail reports: 5%
One or more hailstones of 2 inches or more: 5%
Six or more combined severe hail and wind reports: 30%

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Tallahassee Rgnl, FL (KTLH), launched 00:00Z, 3.2 hours before the alert went out and 240 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: 1628 J/kg
Mixed-layer CIN: -7 J/kg
Mixed-layer LCL: 694 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: 75 m²/s²
0-3 km storm-relative helicity: 170 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 220318
SEL3  
SPC WW 220318
ALZ000-FLZ000-CWZ000-221100-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 683
NWS STORM PREDICTION CENTER NORMAN OK
1010 PM CDT FRI SEP 21 2007

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

       SOUTHERN AND CENTRAL ALABAMA
       THE WESTERN AND CENTRAL FLORIDA PANHANDLE
       COASTAL WATERS

EFFECTIVE THIS FRIDAY NIGHT AND SATURDAY MORNING FROM 1010 PM
UNTIL 600 AM CDT.

TORNADOES...HAIL TO 0.5 INCH IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 60 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 75 STATUTE
MILES EAST AND WEST OF A LINE FROM 50 MILES SOUTHEAST OF
PENSACOLA FLORIDA TO 20 MILES NORTH NORTHEAST OF MONTGOMERY
ALABAMA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).

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 679...WW 681...WW 682...

DISCUSSION...SCTD BANDS OF SHOWERS/STORMS WITH LOW-LVL ROTATION
EXPECTED TO PERSIST INVOF WEAKENING TROPICAL CIRCULATION NOW
CENTERED NEAR PNS AS ASSOCIATED SLY LLJ SPREADS N ACROSS AL.  AREA
VWP DATA IN ERN AND NERN PARTS OF CIRCULATION SHOW SUFFICIENT LOW
LVL DIRECTIONAL SHEAR TO FOSTER UPDRAFT ROTATION AND POSSIBLE BRIEF
TORNADOES GIVEN LOW LCLS PRESENT THERE.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 50 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
450. MEAN STORM MOTION VECTOR 17030.


...CORFIDI

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 21, 8:57 PM CDT	Mesoscale Discussion	SPC	Autauga, Bibb, Butler, Chilton, Choctaw, Clarke and 14 more	93 min
Sep 22, 2:00 AM CDT	Mesoscale Discussion	SPC	Baldwin, Clarke, Conecuh, Covington, Escambia, Mobile and 2 more	2 hr

Nearby

Tornado Watches in Alabama, 2007 Tornado Watches in Florida, 2007 Every tornado watch in 2007

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.