Alert archive / Georgia / Mesoscale Discussions in 2012

Mesoscale Discussion 1485

July 17, 20125 counties in Alabama; 17 counties in Florida; 45 counties in Georgia

The Storm Prediction Center issued this mesoscale discussion at Jul 17, 2012, 2:45 PM CDT for 5 counties in Alabama; 17 counties in Florida; 45 counties in Georgia. It was in force for 90 min.

The area

The outline as issued.

The facts

Issued: Jul 17, 2012, 2:45 PM CDT (19:45 UTC)
Expired: Jul 17, 2012, 4:15 PM CDT
In force: 90 min
Issued by: the Storm Prediction Center

All 67 counties

Coffee County, AL, Dale County, AL, Geneva County, AL, Henry County, AL, Houston County, AL, Bay County, FL, Calhoun County, FL, Gadsden County, FL, Gulf County, FL, Hamilton County, FL, Holmes County, FL, Jackson County, FL, Jefferson County, FL, Lafayette County, FL, Leon County, FL, Liberty County, FL, Madison County, FL, Suwannee County, FL, Taylor County, FL, Wakulla County, FL, Walton County, FL, Washington County, FL, Appling County, GA, Atkinson County, GA, Bacon County, GA, Baker County, GA, Ben Hill County, GA, Berrien County, GA, Brooks County, GA, Calhoun County, GA, Clay County, GA, Clinch County, GA, Coffee County, GA, Colquitt County, GA, Cook County, GA, Crisp County, GA, Decatur County, GA, Dodge County, GA, Dooly County, GA, Dougherty County, GA, Early County, GA, Echols County, GA, Grady County, GA, Irwin County, GA, Jeff Davis County, GA, Lanier County, GA, Lee County, GA, Lowndes County, GA, Miller County, GA, Mitchell County, GA, Montgomery County, GA, Pierce County, GA, Pulaski County, GA, Randolph County, GA, Seminole County, GA, Sumter County, GA, Telfair County, GA, Terrell County, GA, Thomas County, GA, Tift County, GA, Toombs County, GA, Turner County, GA, Ware County, GA, Webster County, GA, Wheeler County, GA, Wilcox County, GA, Worth County, GA

The nearest sounding before it

Tallahassee Rgnl, FL (KTLH), launched 12:00Z, 7.8 hours before the alert went out and 103 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: 2058 J/kg
Mixed-layer CIN: -40 J/kg
Mixed-layer LCL: 906 m above ground
0-6 km bulk shear: 19 kt
0-1 km storm-relative helicity: 18 m²/s²
0-3 km storm-relative helicity: 38 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.

770 
ACUS11 KWNS 171946
SWOMCD
SPC MCD 171945
GAZ000-FLZ000-ALZ000-172115-

MESOSCALE DISCUSSION 1485
NWS STORM PREDICTION CENTER NORMAN OK
0245 PM CDT TUE JUL 17 2012

AREAS AFFECTED...FL...GA...AL

CONCERNING...SEVERE THUNDERSTORM WATCH 488...

VALID 171945Z - 172115Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 488
CONTINUES.

SUMMARY...SCATTERED TO NUMEROUS STRONG TO SEVERE TSTMS DRIFTING
SOUTH ACROSS THE WATCH AREA WITH A CONTINUING THREAT FOR OCCASIONAL
DAMAGING WINDS.

DISCUSSION...NUMEROUS PULSE AND MULTICELL STORM CLUSTERS HAVE
DEVELOPED ACROSS THE WATCH AREA IN THE PAST FEW HOURS. THIS
CONVECTION WAS BEING DRIVEN BY ABUNDANT INSTABILITY AND SUPPORTIVE
BACKGROUND ASCENT ASSOCIATED WITH A WWD MOVING UPPER DISTURBANCE.
ACTIVITY IS BEING STEERED BY DEEP-LAYER MEAN WIND OF 10-15 KT AND
STORMS SHOULD CONTINUE TO DRIFT GENERALLY SOUTH-SOUTHWEST THROUGH
THE REST OF THE AFTERNOON.

RECENT STORM AND OUTFLOW MERGERS AROUND THE TLH AREA HAVE POSSIBLY
PRODUCED LOCALIZED STRONG TO SEVERE WIND GUSTS/PERHAPS SOME
HAIL...AND VERY HEAVY RAIN. GIVEN WEAK SHEAR ENVIRONMENT...SOME
CELLS SHOW A BRIEF INCREASE IN INTENSITY WHILE OTHERS UNDERGO
DESTRUCTIVE INTERFERENCE AND COLLAPSE. NUMEROUS OUTFLOW BOUNDARIES
APPEAR TO BE CONVERGING ON TLH AND...IN ADDITION TO DOWNBURST WIND
POTENTIAL WITH THIS CONVECTION...TORRENTIAL RAINS APPEAR TO BE VERY
LIKELY ACROSS THE AREA IN THE NEXT HOUR OR SO. OVER THE NEXT FEW
HOURS...WIDESPREAD AIRMASS OVERTURNING AND LACK OF GREATER FORCING
AND SHEAR SHOULD BEGIN TO RESULT IN GENERAL DEMISE TO THE SEVERE
WIND AND HAIL POTENTIAL ACROSS SRN PORTIONS OF THE WATCH.
HOWEVER...CONVECTIVE OVERTURNING HAS BEEN LESS ACROSS NRN AREAS OF
THE WATCH AND MORE RECENT DEVELOPMENT IN CNTRL GA AND ERN AL MAY
DRIFT INTO THIS PORTION OF THE WATCH IN THE NEXT 1-2 HOURS.

..CARBIN.. 07/17/2012

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

ATTN...WFO...CHS...JAX...FFC...TAE...BMX...MOB...

LAT...LON   32288447 31718514 31618613 30998618 30948638 30098650
            29688573 29718322 29698298 30298276 30588271 30548223
            30758215 30798238 31048240 31028216 31898217 32338225
            32158289 32468314 32398346 32178421 32288447

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 17, 11:21 AM CDT	Mesoscale Discussion	SPC	Barbour, Bullock, Chambers, Dale, Geneva, Henry and 6 more	84 min
Jul 17, 11:49 AM CDT	Severe Thunderstorm Watch	SPC	Coffee, Dale, Geneva, Henry, Houston	7 hr

Nearby

Mesoscale Discussions in Georgia, 2012 Mesoscale Discussions in Florida, 2012 Mesoscale Discussions in Alabama, 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.