Alert archive / Alabama / Mesoscale Discussions in 2012

Mesoscale Discussion 1692

August 3, 201218 counties in Alabama; 4 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Aug 3, 2012, 3:33 PM CDT for 18 counties in Alabama; 4 counties in Mississippi. It was in force for 57 min.

The area

The outline as issued.

The facts

Issued: Aug 3, 2012, 3:33 PM CDT (20:33 UTC)
Expired: Aug 3, 2012, 4:30 PM CDT
In force: 57 min
Issued by: the Storm Prediction Center

All 22 counties

Autauga County, AL, Bibb County, AL, Chilton County, AL, Coosa County, AL, Dallas County, AL, Elmore County, AL, Greene County, AL, Hale County, AL, Jefferson County, AL, Lowndes County, AL, Marengo County, AL, Montgomery County, AL, Perry County, AL, Pickens County, AL, Shelby County, AL, Sumter County, AL, Tuscaloosa County, AL, Wilcox County, AL, Clay County, MS, Kemper County, MS, Lowndes County, MS, Noxubee County, MS

The radar

The Birmingham radar (KBMX), 66 km from the middle of the area, began a volume at 20:33 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 nearest sounding before it

Birmingham, AL (KBMX), launched 12:00Z, 8.6 hours before the alert went out and 66 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: 1920 J/kg
Mixed-layer CIN: -25 J/kg
Mixed-layer LCL: 586 m above ground
0-6 km bulk shear: 11 kt
0-1 km storm-relative helicity: -22 m²/s²
0-3 km storm-relative helicity: 19 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.

650 
ACUS11 KWNS 032034
SWOMCD
SPC MCD 032033
ALZ000-MSZ000-032130-

MESOSCALE DISCUSSION 1692
NWS STORM PREDICTION CENTER NORMAN OK
0333 PM CDT FRI AUG 03 2012

AREAS AFFECTED...CENTRAL AL AND CENTRAL MS

CONCERNING...SEVERE THUNDERSTORM WATCH 552...

VALID 032033Z - 032130Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 552
CONTINUES.

SUMMARY...GREATEST POTENTIAL FOR ADDITIONAL TSTM DEVELOPMENT SHOULD
REMAIN CONFINED TO THE AL PORTION OF WW 552 INTO FAR ERN MS.
FARTHER WEST INTO CENTRAL MS...THE LACK OF LOW LEVEL CONVERGENCE
APPEARS TO LIMITING DEEP MOIST CONVECTIVE FORMATION THUS FAR.
ISOLATED STRONG TO SEVERE STORMS WILL REMAIN POSSIBLE IN CENTRAL
AL...THOUGH THIS WW MAY BE CANCELLED EARLY DUE TO THE LACK OF
GREATER STORM ORGANIZATION POTENTIAL.

DISCUSSION...THE ENVIRONMENT ACROSS MUCH OF THE AL PORTION OF WW 552
HAS BEEN CONVECTIVELY OVERTURNED REDUCING THE CONTINUED THREAT FOR
SEVERE STORMS.  THE EXCEPTION RESIDES ALONG THE SRN BOUNDARY OF THIS
WATCH IN SWRN AL WHERE STEEPER LOW LEVEL LAPSE RATES COULD ENHANCE
LOCALIZED DOWNDRAFTS FOR STRONGER WIND GUSTS.  20-30 KT OF EFFECTIVE
BULK SHEAR AND MLCAPE OF 2500 J/KG SUGGEST MULTICELL STORM
DEVELOPMENT REMAINS POSSIBLE.  HOWEVER...THIS OVERALL SEVERE WEATHER
THREAT IS SOMEWHAT LIMITED BY WEAK MIDLEVEL LAPSE RATES WHICH WILL
TEND TO LIMIT THE DEVELOPMENT OF ROBUST...SUSTAINED UPDRAFTS.

..PETERS.. 08/03/2012

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

ATTN...WFO...BMX...MOB...MEG...JAN...

LAT...LON   32008810 32088848 33788892 33568819 33578730 33828675
            33348638 33088643 33048596 32008601 31868650 31958766
            32008810

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 3, 11:56 AM CDT	Mesoscale Discussion	SPC	Bibb, Choctaw, Dallas, Fayette, Greene, Hale and 8 more	64 min
Aug 3, 12:14 PM CDT	Severe Thunderstorm Watch	SPC	Autauga, Bibb, Chilton, Coosa, Dallas, Elmore and 11 more	6 hr

Nearby

Mesoscale Discussions in Alabama, 2012 Mesoscale Discussions in Mississippi, 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; radar from the NEXRAD Level II archive.