Alert archive / Georgia / Tornado Watches in 2011

Tornado Watch 865

October 10, 201111 counties in Florida; 16 counties in Georgia

The Storm Prediction Center issued this tornado watch at Oct 10, 2011, 4:26 AM EDT for 11 counties in Florida; 16 counties in Georgia. It was in force for 9 hr.

The area

The outline as issued.

The facts

Issued: Oct 10, 2011, 4:26 AM EDT (08:26 UTC)
Expired: Oct 10, 2011, 1:00 PM EDT
In force: 9 hr
Issued by: the Storm Prediction Center
Strongest gust expected: 60 kt

All 27 counties

Alachua County, FL, Baker County, FL, Bradford County, FL, Clay County, FL, Columbia County, FL, Duval County, FL, Hamilton County, FL, Nassau County, FL, Putnam County, FL, Saint Johns County, FL, Union County, FL, Appling County, GA, Bacon County, GA, Brantley County, GA, Bryan County, GA, Camden County, GA, Charlton County, GA, Chatham County, GA, Clinch County, GA, Echols County, GA, Glynn County, GA, Liberty County, GA, Long County, GA, McIntosh County, GA, Pierce County, GA, Ware County, GA, Wayne County, GA

The radar

The Jacksonville radar (KJAX), 77 km from the middle of the area, began a volume at 08:26 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: 40%
One or more EF2 to EF5 tornadoes: 20%
Ten or more severe wind reports: 10%
One or more gusts of 65 knots or more: 30%
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: 50%

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
Oct 10, 6:41 AM EDT	Tornado Warning	JAX	Nassau	23 min

Discussions around it

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

The nearest sounding before it

Jacksonville, FL (KJAX), launched 00:00Z, 8.4 hours before the alert went out and 75 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: 277 J/kg
Mixed-layer CIN: 0 J/kg
Mixed-layer LCL: 665 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: -74 m²/s²
0-3 km storm-relative helicity: -46 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.

337 
WWUS20 KWNS 100832
SEL5
SPC WW 100832
FLZ000-GAZ000-CWZ000-101700-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 865
NWS STORM PREDICTION CENTER NORMAN OK
425 AM EDT MON OCT 10 2011

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

       NORTHERN FLORIDA
       SOUTHERN AND EASTERN GEORGIA
       COASTAL WATERS

EFFECTIVE THIS MONDAY MORNING AND AFTERNOON FROM 425 AM UNTIL 100
PM EDT.

TORNADOES...THUNDERSTORM WIND GUSTS TO 70 MPH...AND DANGEROUS
LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 50 STATUTE
MILES EITHER SIDE OF A LINE FROM 60 MILES NORTH NORTHEAST OF
WAYCROSS GEORGIA TO 30 MILES EAST OF GAINESVILLE FLORIDA.  FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU5).

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.

DISCUSSION...SFC LOW NOW NEAR OCALA FL EXPECTED TO CONTINUE MOVING
SLOWLY WNW THROUGH LATE THIS MORNING.  THIS WILL ALLOW ATTENDANT
WEDGE OF HIGH THETA-E AIR IN NERN QUADRANT OF SYSTEM...AND MARITIME
BOUNDARY ON ITS LEADING EDGE...TO ADVANCE FARTHER WNW ACROSS FAR NRN
FL...AND INTO SRN/ERN GA.  50 KT ESELY LLJ AND BAND OF STRONGLY
ENHANCED LOW LVL SRH IN NE QUADRANT OF LOW IS CO-LOCATED WITH AXIS
OF HIGHEST THETA-E /WITH PW ABOVE 2 INCHES/.  GIVEN CONFLUENT NATURE
OF LOW LVL FLOW...SCTD SHOWERS/STORMS MAY CONTINUE TO FORM WITHIN
THE LLJ AND POSE A RISK FOR BRIEF TORNADOES.  THIS RISK SHOULD BE
GREATEST WHERE THE JET INTERSECTS SLOWLY-ADVANCING MARITIME
BOUNDARY.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH EXTREME
TURBULENCE AND SURFACE WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI
WITH MAXIMUM TOPS TO 500. MEAN STORM MOTION VECTOR 12040.


...CORFIDI

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Oct 10, 3:52 AM EDT	Mesoscale Discussion	SPC	Alachua, Baker, Bradford, Clay, Columbia, Duval and 6 more	83 min
Oct 10, 8:30 AM EDT	Mesoscale Discussion	SPC	Alachua, Baker, Bradford, Clay, Columbia, Duval and 5 more	90 min
Oct 10, 12:12 PM EDT	Mesoscale Discussion	SPC	Appling, Bacon, Brantley, Bryan, Camden, Charlton and 10 more	63 min

Nearby

Tornado Watches in Georgia, 2011 Tornado Watches in Florida, 2011 Every tornado watch in 2011

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.