Alert archive / Georgia / Mesoscale Discussions in 2009

Mesoscale Discussion 21

January 6, 20094 states

The Storm Prediction Center issued this mesoscale discussion at Jan 6, 2009, 7:02 PM CST for 4 states. It was in force for 118 min.

The area

The outline as issued.

The facts

Issued: Jan 6, 2009, 7:02 PM CST (01:02 UTC)
Expired: Jan 6, 2009, 9:00 PM CST
In force: 118 min
Issued by: the Storm Prediction Center

All 44 counties

Baldwin County, AL, Bullock County, AL, Butler County, AL, Chambers County, AL, Conecuh County, AL, Crenshaw County, AL, Escambia County, AL, Lee County, AL, Macon County, AL, Montgomery County, AL, Banks County, GA, Barrow County, GA, Clarke County, GA, Clayton County, GA, Coweta County, GA, DeKalb County, GA, Elbert County, GA, Fayette County, GA, Franklin County, GA, Fulton County, GA, Gwinnett County, GA, Habersham County, GA, Hall County, GA, Harris County, GA, Hart County, GA, Heard County, GA, Henry County, GA, Jackson County, GA, Madison County, GA, Meriwether County, GA, Newton County, GA, Oconee County, GA, Pike County, GA, Rockdale County, GA, Spalding County, GA, Stephens County, GA, Troup County, GA, Walton County, GA, Henderson County, NC, Transylvania County, NC, Anderson County, SC, Greenville County, SC, Oconee County, SC, Pickens County, SC

The radar

The Atlanta radar (KFFC), 52 km from the middle of the area, began a volume at 01:02 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.

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Tornado Watch 5Jan 6, 10:50 PM CST

The nearest sounding before it

Peachtre/Fal Fld, GA (KFFC), launched 00:00Z, 1.0 hours before the alert went out and 57 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: 41 J/kg
Mixed-layer CIN: -14 J/kg
Mixed-layer LCL: 1003 m above ground
0-6 km bulk shear: 89 kt
0-1 km storm-relative helicity: 406 m²/s²
0-3 km storm-relative helicity: 492 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 
ACUS11 KWNS 070103
SWOMCD
SPC MCD 070102 
NCZ000-SCZ000-GAZ000-ALZ000-FLZ000-070300-

MESOSCALE DISCUSSION 0021
NWS STORM PREDICTION CENTER NORMAN OK
0702 PM CST TUE JAN 06 2009

AREAS AFFECTED...SRN AL THROUGH N CNTRL GA...WRN SC AND EXTREME SW
NC

CONCERNING...TORNADO WATCH 3...4...

VALID 070102Z - 070300Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 3...4...CONTINUES.

THREAT FOR ISOLATED DAMAGING WIND AND AN ISOLATED TORNADO OR TWO
WILL PERSIST FROM SRN AL NEWD THROUGH N CNTRL GA AND EXTREME SW NC
NEXT COUPLE HOURS. OVERALL THREAT IS SOMEWHAT CONDITIONAL AND WW 3
HAS BEEN ALLOWED TO EXPIRE AT 01Z...BUT AREA WILL CONTINUE TO BE
MONITORED.

A LINE OF STORMS WITH OCCASIONAL EMBEDDED BOWING SEGMENTS AND
MESOCYCLONES EXTENDS FROM NE GA SWWD THROUGH SW AL. THE LINE IS
MOVING EAST AT AROUND 20 KT...WHILE INDIVIDUAL STORMS MOVE MORE
RAPIDLY NE. OVERALL TREND HAS BEEN FOR STORMS TO DECREASE IN
INTENSITY...AND LIGHTNING HAS ALSO DIMINISHED DURING THE PAST HOUR.
A STRONG 50-60 KT SWLY LOW LEVEL JET WILL PERSIST IN WARM SECTOR
WITHIN ZONE OF HEIGHT FALLS AHEAD OF EWD ADVANCING UPPER TROUGH. THE
STRONG VERTICAL SHEAR AND LARGE LOW LEVEL HODOGRAPHS WILL PROMOTE A
THREAT OF BOWING SEGMENTS...LOW LEVEL MESOCYCLONES AND POSSIBLY AN
ISOLATED TORNADO OR TWO. HOWEVER...PRIMARY LIMITING FACTOR HAS BEEN
AND WILL CONTINUE TO BE THE MARGINAL THERMODYNAMIC ENVIRONMENT EAST
OF THE ADVANCING LINE. THE 00Z RAOB FROM ATLANTA SHOWS VERY LIMITED
INSTABILITY...5.6 C/KM 850-500 MB LAPSE RATES AND A PRONOUNCED
INVERSION PRESENT NEAR 700 MB. THIS ENVIRONMENT SUGGEST IT WILL
PROBABLY REMAIN DIFFICULT FOR THE SHALLOW CONVECTION DEVELOPING
AHEAD OF THE LINE TO DEEPEN AND INTENSIFY. THE DEEPER CONVECTION
WILL PROBABLY REMAIN CONFINED TO THE ZONE OF STRONGER FORCING ALONG
THE LINE.

IF TRENDS BEGIN TO SUGGEST CONVECTION WILL REINTENSIFY...ANOTHER WW
COULD BE NEEDED ACROSS SRN AL GIVEN THE FAVORABLE HODOGRAPHS AND
BULK SHEAR. OTHERWISE...AREA WILL CONTINUE TO BE MONITORED.

..DIAL.. 01/07/2009

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

ATTN...WFO...GSP...FFC...BMX...MOB...

LAT...LON   34308235 33388400 32558508 31558626 30598755 30728826
            31368764 32658601 34108419 35108310 35458228 34308235

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jan 6, 9:04 PM CST	Mesoscale Discussion	SPC	Barbour, Coffee, Covington, Dale, Geneva, Henry and 1 more	116 min
Jan 6, 10:51 PM CST	Tornado Watch	SPC	Barbour, Bullock, Coffee, Covington, Crenshaw, Dale and 8 more	6 hr
Jan 7, 1:32 AM CST	Mesoscale Discussion	SPC	Baker, Baldwin, Bibb, Bleckley, Calhoun, Clay and 42 more	118 min
Jan 7, 3:29 AM CST	Mesoscale Discussion	SPC	Appling, Atkinson, Bacon, Ben Hill, Berrien, Brantley and 42 more	91 min

Nearby

Mesoscale Discussions in Georgia, 2009 Mesoscale Discussions in Alabama, 2009 Mesoscale Discussions in South Carolina, 2009 Every mesoscale discussion in 2009

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.