Alert archive / Alabama / Mesoscale Discussions in 2012

Mesoscale Discussion 797

May 12, 201216 counties in Alabama; 5 counties in Florida; 13 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at May 12, 2012, 5:16 PM CDT for 16 counties in Alabama; 5 counties in Florida; 13 counties in Mississippi. It was in force for 89 min.

The area

The outline as issued.

The facts

Issued: May 12, 2012, 5:16 PM CDT (22:16 UTC)
Expired: May 12, 2012, 6:45 PM CDT
In force: 89 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 34 counties

Butler County, AL, Choctaw County, AL, Clarke County, AL, Coffee County, AL, Conecuh County, AL, Covington County, AL, Crenshaw County, AL, Dale County, AL, Escambia County, AL, Geneva County, AL, Houston County, AL, Marengo County, AL, Monroe County, AL, Pike County, AL, Washington County, AL, Wilcox County, AL, Holmes County, FL, Okaloosa County, FL, Santa Rosa County, FL, Walton County, FL, Washington County, FL, Clarke County, MS, Covington County, MS, Forrest County, MS, Greene County, MS, Jasper County, MS, Jefferson Davis County, MS, Jones County, MS, Lauderdale County, MS, Newton County, MS, Perry County, MS, Simpson County, MS, Smith County, MS, Wayne County, MS

The radar

The Mobile radar (KMOB), 97 km from the middle of the area, began a volume at 22:17 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, 10.3 hours before the alert went out and 214 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 0 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 96 m²/s²
0-3 km storm-relative helicity: 263 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.

670 
ACUS11 KWNS 122217
SWOMCD
SPC MCD 122216
FLZ000-ALZ000-MSZ000-122345-

MESOSCALE DISCUSSION 0797
NWS STORM PREDICTION CENTER NORMAN OK
0516 PM CDT SAT MAY 12 2012

AREAS AFFECTED...SRN MS...SRN AL...FL PANHANDLE

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 122216Z - 122345Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...AN ISOLATED SEVERE THREAT WILL LIKELY CONTINUE FROM SCNTRL
MS EWD ACROSS SRN AL FROM LATE THIS AFTERNOON INTO EARLY THIS
EVENING. HOWEVER...THE THREAT IS EXPECTED TO REMAIN MARGINAL AND WW
ISSUANCE IS NOT ANTICIPATED.

DISCUSSION...THE LATEST SFC ANALYSIS SHOWS A LOW OVER FAR SW MS WITH
A WARM FRONT EXTENDING EWD ACROSS SCNTRL MS INTO SRN AL AND THE FL
PANHANDLE. NUMEROUS THUNDERSTORMS ARE ONGOING ALONG AND TO THE NORTH
OF THE WARM FRONT WHERE THE AIRMASS HAS BEEN WORKED OVER.
MESOANALYSIS SUGGESTS THE STRONGEST INSTABILITY IS LOCATED FROM THE
WARM FRONT SWD WHERE MLCAPE VALUES ARE ESTIMATED FROM 1000 TO 1500
J/KG. IN ADDITION TO THE INSTABILITY...REGIONAL WSR-88D VWPS SHOW 40
TO 50 KT OF DEEP LAYER SHEAR SUGGESTING THE STORMS MAY BE ABLE TO
ROTATE AND APPROACH SEVERE LEVELS. THE SEVERE THREAT MAY BE GREATEST
FROM AROUND HATTIESBURG MS EWD INTO SRN AL ALONG AND JUST NORTH OF
THE FRONT. A WIND DAMAGE AND HAIL THREAT MAY EXIST WITH THE STRONGER
CELLS. HOWEVER...THE STORMS SHOULD BE INCREASINGLY ELEVATED NORTH OF
THE WARM FRONT WITH THE SEVERE THREAT DROPPING OFF QUICKLY WITH NWD
EXTENT.

..BROYLES.. 05/12/2012

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

ATTN...WFO...TAE...BMX...MOB...JAN...

LAT...LON   30348599 30818762 31038856 31198929 31328974 31669001
            32068996 32328972 32528874 32318733 31928617 31498536
            31088523 30698539 30348599

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 12, 10:39 AM CDT	Mesoscale Discussion	SPC	Choctaw, Mobile, Washington	2 hr

Nearby

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