Alert archive / Alabama / Mesoscale Discussions in 2012

Mesoscale Discussion 2011

September 30, 20129 counties in Alabama; Escambia County, Santa Rosa County, Florida; George County, Greene County, Jackson County, Mississippi

The Storm Prediction Center issued this mesoscale discussion at Sep 30, 2012, 9:48 PM CDT for 9 counties in Alabama; Escambia County, Santa Rosa County, Florida; George County, Greene County, Jackson County, Mississippi. It was in force for 87 min.

The area

The outline as issued.

The facts

Issued: Sep 30, 2012, 9:48 PM CDT (02:48 UTC)
Expired: Sep 30, 2012, 11:15 PM CDT
In force: 87 min
Issued by: the Storm Prediction Center

Counties Baldwin County, AL, Choctaw County, AL, Clarke County, AL, Conecuh County, AL, Escambia County, AL, Mobile County, AL, Monroe County, AL, Washington County, AL, Wilcox County, AL, Escambia County, FL, Santa Rosa County, FL, George County, MS, Greene County, MS, Jackson County, MS

The radar

The Mobile radar (KMOB), 51 km from the middle of the area, began a volume at 02:51 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

Slidell Radar S, LA (KSIL), launched 00:00Z, 2.8 hours before the alert went out and 188 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: 1860 J/kg
Mixed-layer CIN: 0 J/kg
Mixed-layer LCL: 486 m above ground
0-6 km bulk shear: 36 kt
0-1 km storm-relative helicity: 235 m²/s²
0-3 km storm-relative helicity: 248 m²/s²
Significant tornado parameter: 1.8
Supercell composite: 12.4

Open this sounding in Storm Lab

The text

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

865 
ACUS11 KWNS 010249
SWOMCD
SPC MCD 010248
ALZ000-FLZ000-MSZ000-010415-

MESOSCALE DISCUSSION 2011
NWS STORM PREDICTION CENTER NORMAN OK
0948 PM CDT SUN SEP 30 2012

AREAS AFFECTED...PARTS OF SERN MS...SRN AL AND THE WRN FL PNHDL

CONCERNING...TORNADO WATCH 657...

VALID 010248Z - 010415Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 657 CONTINUES.

SUMMARY...PROBABILISTICALLY...THE SEVERE STORM THREAT MAY REMAIN
RELATIVELY LOW TONIGHT.  BUT...IT IS NOT NEGLIGIBLE...AND DOES
INCLUDE THE RISK FOR A POTENTIALLY DAMAGING TORNADO OR
TWO...PARTICULARLY ACROSS PARTS OF SOUTHWESTERN ALABAMA AND THE
WESTERN FLORIDA PANHANDLE BETWEEN NOW AND 07-09Z.

DISCUSSION...DESPITE THE HIGH BOUNDARY LAYER MOISTURE CONTENT...DEEP
LAYER SATURATED/NEAR MOIST ADIABATIC THERMODYNAMIC PROFILES AHEAD OF
A PRE-FRONTAL WIND SHIFT NOW ADVANCING EASTWARD TOWARD THE
MISSISSIPPI/ALABAMA BORDER AREA HAVE LIMITED CONVECTIVE POTENTIAL
THIS EVENING.  THUNDERSTORM ACTIVITY HAS GENERALLY BECOME CONFINED
TO THE COOL SIDE OF THE WARM FRONT ACROSS PARTS OF NORTH CENTRAL
MISSISSIPPI...AND ALONG THE PRE-FRONTAL WIND SHIFT SOUTH OF THE
MISSISSIPPI GULF COAST.  HOWEVER...SOUTHERLY 850 MB FLOW IS
STRENGTHENING ALONG AN AXIS NEAR THE MISSISSIPPI/ALABAMA BORDER...
AND THE LATEST RAPID REFRESH SUGGESTS THE JET COULD INTENSIFY IN
EXCESS OF 50 KT AS IT SHIFTS INTO WESTERN ALABAMA DURING THE 04-06Z
TIME FRAME.  CLOCKWISE CURVED LOW-LEVEL HODOGRAPHS LIKELY WILL
BECOME QUITE LARGE ACROSS SOUTHWESTERN ALABAMA AND ADJACENT AREAS OF
THE WESTERN FLORIDA PANHANDLE AS THIS OCCURS.  AND...AS AN UPSTREAM
SHORT WAVE IMPULSE PIVOTS INTO THE CENTRAL GULF COAST
REGION...FORCING COULD STILL SUPPORT INTENSIFICATION ALONG/AHEAD OF
THE PRE-FRONTAL WIND SHIFT.  IF THIS OCCURS...THE ENVIRONMENT WILL
BE CONDUCIVE TO THE RISK FOR AT LEAST AN ISOLATED SUPERCELL OR
TWO...CAPABLE OF PRODUCING TORNADOES...PERHAPS BRIEFLY STRONG.

..KERR.. 10/01/2012

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

ATTN...WFO...BMX...MOB...JAN...LIX...

LAT...LON   30748888 31978854 32258806 32118686 30808685 30198721
            29838861 30748888

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Oct 1, 1:45 AM CDT	Mesoscale Discussion	SPC	Baldwin, Coffee, Conecuh, Covington, Dale, Escambia and 5 more	2 hr
Oct 1, 5:51 AM CDT	Mesoscale Discussion	SPC	Barbour, Bullock, Calhoun, Chambers, Clay, Cleburne and 20 more	114 min
Oct 1, 12:52 PM CDT	Mesoscale Discussion	SPC	Barbour, Blount, Calhoun, Chambers, Cherokee, Clay and 13 more	53 min
Oct 1, 1:16 PM CDT	Tornado Watch	SPC	Blount, Bullock, Calhoun, Chambers, Cherokee, Clay and 19 more	7 hr
Oct 1, 3:00 PM CDT	Mesoscale Discussion	SPC	Blount, Calhoun, Chambers, Cherokee, Clay, Cleburne and 12 more	2 hr
Oct 1, 5:40 PM CDT	Mesoscale Discussion	SPC	Chambers, Cherokee, Cleburne, Lee, Randolph	95 min

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.