Alert archive / Alabama / Mesoscale Discussions in 2012

Mesoscale Discussion 2012

October 1, 201211 counties in Alabama; 10 counties in Florida; George County, Greene County, Jackson County, Mississippi

The Storm Prediction Center issued this mesoscale discussion at Oct 1, 2012, 1:45 AM CDT for 11 counties in Alabama; 10 counties in Florida; George County, Greene County, Jackson County, Mississippi. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Oct 1, 2012, 1:45 AM CDT (06:45 UTC)
Expired
Oct 1, 2012, 3:45 AM CDT
In force
2 hr
Issued by
the Storm Prediction Center
All 24 counties

Baldwin County, AL, Coffee County, AL, Conecuh County, AL, Covington County, AL, Dale County, AL, Escambia County, AL, Geneva County, AL, Houston County, AL, Mobile County, AL, Monroe County, AL, Washington County, AL, Bay County, FL, Calhoun County, FL, Escambia County, FL, Gulf County, FL, Holmes County, FL, Jackson County, FL, Okaloosa County, FL, Santa Rosa County, FL, Walton County, FL, Washington County, FL, George County, MS, Greene County, MS, Jackson County, MS

The radar

The Mobile radar (KMOB), 101 km from the middle of the area, began a volume at 06:46 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, 6.8 hours before the alert went out and 246 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-pSkew-T log-p diagram, Slidell Radar S, LA at 00:00Z on 2012-10-01Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1860 joules per kilogram.LCLEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Slidell Radar S, LA at 00:00Z on 2012-10-01The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 235 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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.

582 
ACUS11 KWNS 010645
SWOMCD
SPC MCD 010645 
FLZ000-ALZ000-MSZ000-010845-

MESOSCALE DISCUSSION 2012
NWS STORM PREDICTION CENTER NORMAN OK
0145 AM CDT MON OCT 01 2012

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

CONCERNING...TORNADO WATCH 657...

VALID 010645Z - 010845Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 657 CONTINUES.

SUMMARY...THE SEVERE THREAT IS CURRENTLY MARGINAL...AND THE WATCH
WILL BE ALLOWED TO EXPIRE.  WE WILL CONTINUE TO MONITOR FOR ANY
CHANGES THAT WOULD WARRANT AN ADDITIONAL WATCH.

DISCUSSION...A WARM AND MOIST LOW LEVEL AIR MASS IS SITUATED ACROSS
THE NRN GULF OF MEXICO...E OF THE SURFACE COLD FRONT WHICH WAS
ACROSS SRN MS AND SERN LA AS OF 645Z. A PRE-FRONTAL BATCH OF RAIN
AND OCCASIONAL THUNDERSTORMS HAS BEEN SLOWLY DRIFTING EWD...NOW OVER
AL AND THE WRN FL PANHANDLE.

A 30-40 KT LOW LEVEL JET IS HELPING TO MAINTAIN INSTABILITY ALONG
THE COAST...BUT MIDLEVEL DRY AIR AND WARM TEMPERATURES ALOFT ARE
HAMPERING VERTICAL GROWTH...DESPITE OTHERWISE FAVORABLE LOW LEVELS
FOR SOME ROTATION.

SOME GUIDANCE SUGGESTS NEW STORMS COULD FORM ALONG THE COLD
FRONT...AND THERE MAY BE A MARGINAL TORNADO OR WIND THREAT MAINLY
ALONG THE COAST. UNTIL RADAR TRENDS SHOW STRONGER EVIDENCE OF
ROTATION OR STRONG WINDS...A WATCH IS UNLIKELY.

..JEWELL.. 10/01/2012

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

ATTN...WFO...TAE...BMX...MOB...LIX...

LAT...LON   30008872 30098891 30398908 31038902 31398875 31528825
            31708706 31648611 31468533 31218517 30928501 30368492
            29608527 30268655 30248726 30158807 30008872

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Sep 30, 9:48 PM CDTMesoscale DiscussionSPCBaldwin, Choctaw, Clarke, Conecuh, Escambia, Mobile and 3 more87 min
Oct 1, 5:51 AM CDTMesoscale DiscussionSPCBarbour, Bullock, Calhoun, Chambers, Clay, Cleburne and 20 more114 min
Oct 1, 12:52 PM CDTMesoscale DiscussionSPCBarbour, Blount, Calhoun, Chambers, Cherokee, Clay and 13 more53 min
Oct 1, 1:16 PM CDTTornado WatchSPCBlount, Bullock, Calhoun, Chambers, Cherokee, Clay and 19 more7 hr
Oct 1, 3:00 PM CDTMesoscale DiscussionSPCBlount, Calhoun, Chambers, Cherokee, Clay, Cleburne and 12 more2 hr
Oct 1, 5:40 PM CDTMesoscale DiscussionSPCChambers, Cherokee, Cleburne, Lee, Randolph95 min

Nearby

Mesoscale Discussions in Alabama, 2012Mesoscale Discussions in Florida, 2012Mesoscale Discussions in Mississippi, 2012Every 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.