Alert archive / Georgia / Mesoscale Discussions in 2012

Mesoscale Discussion 1835

August 29, 201212 counties in Alabama; 4 counties in Florida; 15 counties in Georgia

The Storm Prediction Center issued this mesoscale discussion at Aug 29, 2012, 5:45 PM CDT for 12 counties in Alabama; 4 counties in Florida; 15 counties in Georgia. It was in force for 90 min.

The area

The outline as issued.

The facts

Issued: Aug 29, 2012, 5:45 PM CDT (22:45 UTC)
Expired: Aug 29, 2012, 7:15 PM CDT
In force: 90 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 31 counties

Barbour County, AL, Bullock County, AL, Butler County, AL, Coffee County, AL, Covington County, AL, Crenshaw County, AL, Dale County, AL, Geneva County, AL, Henry County, AL, Houston County, AL, Montgomery County, AL, Pike County, AL, Gadsden County, FL, Jackson County, FL, Jefferson County, FL, Leon County, FL, Baker County, GA, Calhoun County, GA, Clay County, GA, Decatur County, GA, Dougherty County, GA, Early County, GA, Grady County, GA, Miller County, GA, Mitchell County, GA, Quitman County, GA, Randolph County, GA, Seminole County, GA, Stewart County, GA, Terrell County, GA, Thomas County, GA

The nearest sounding before it

Tallahassee Rgnl, FL (KTLH), launched 12:00Z, 10.8 hours before the alert went out and 134 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: 1779 J/kg
Mixed-layer CIN: -2 J/kg
Mixed-layer LCL: 468 m above ground
0-6 km bulk shear: 12 kt
0-1 km storm-relative helicity: 19 m²/s²
0-3 km storm-relative helicity: 42 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.9

Open this sounding in Storm Lab

The text

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

306 
ACUS11 KWNS 292245
SWOMCD
SPC MCD 292245 
FLZ000-GAZ000-ALZ000-300015-

MESOSCALE DISCUSSION 1835
NWS STORM PREDICTION CENTER NORMAN OK
0545 PM CDT WED AUG 29 2012

AREAS AFFECTED...SE AL...SW GA...FL PANHANDLE

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 292245Z - 300015Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...AN ISOLATED TORNADO THREAT MAY CONTINUE ACROSS SE AL...SW
GA AND THE FL PANHANDLE FOR AN HOUR OR TWO. HOWEVER...THE THREAT IS
EXPECTED TO BE TOO ISOLATED AND BRIEF TO WARRANT WW ISSUANCE.

DISCUSSION...A CLUSTER OF STRONG THUNDERSTORMS WITH SOME SHOWING
ROTATION...IS LOCATED JUST TO THE NORTHWEST OF TALLAHASSEE NEAR THE
STATE-LINE INTERSECTION OF AL...GA AND FL. ACCORDING TO SFC
ANALYSIS...THE STORMS ARE LOCATED NEAR AN EAST TO WEST ZONE OF
CONFLUENCE WHERE WINDS TO THE SOUTH OF THE BOUNDARY ARE SLY AND
WINDS ON THE NRN SIDE ARE BACKED TO THE SOUTHEAST. THIS IS CREATING
SOME DIRECTIONAL SHEAR IN THE BOUNDARY LAYER EVIDENT ON THE FORT
RUCKER WSR-88 VWP. THIS IS DIRECTIONAL SHEAR IS HELPING TO CREATE
0-1 KM HELICITY AROUND 150 M2/S2. AS ROTATING CELLS INTERACT WITH
THE BOUNDARY WHERE LOW-LEVEL SHEAR IS ENHANCED...A TORNADO OR TWO
WILL BE POSSIBLE OVER THE NEXT HOUR OR TWO. THE AREAL EXTENT OF THE
TORNADO THREAT IS EXPECTED TO BE CONFINED TO THE BOUNDARY AND AS THE
CELLS MOVE TO THE NORTH...THE TORNADO THREAT IS EXPECTED TO
DECREASE.

..BROYLES/MEAD.. 08/29/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...FFC...TAE...BMX...MOB...

LAT...LON   31158662 31108658 30898561 30368446 30158392 30288373
            30738356 31508397 32168486 32498611 32088668 31528684
            31158662

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 29, 1:55 AM CDT	Mesoscale Discussion	SPC	Baldwin, Mobile, Washington	2 hr
Aug 29, 5:46 AM CDT	Mesoscale Discussion	SPC	Baldwin, Mobile, Washington	89 min
Aug 29, 6:36 AM CDT	Tornado Watch	SPC	Baldwin, Mobile, Washington	9 hr
Aug 29, 11:48 AM CDT	Mesoscale Discussion	SPC	Baldwin, Mobile, Washington	117 min
Aug 29, 3:17 PM CDT	Mesoscale Discussion	SPC	Baldwin, Mobile, Washington	28 min
Aug 29, 3:53 PM CDT	Tornado Watch	SPC	Baldwin, Mobile, Washington	8 hr

Nearby

Mesoscale Discussions in Georgia, 2012 Mesoscale Discussions in Alabama, 2012 Mesoscale Discussions in Florida, 2012 Every mesoscale discussion in 2012

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.