Alert archive / Louisiana / Mesoscale Discussions in 2012

Mesoscale Discussion 2162

December 16, 20128 counties in Alabama; 24 parishes in Louisiana; 19 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Dec 16, 2012, 12:23 PM CST for 8 counties in Alabama; 24 parishes in Louisiana; 19 counties in Mississippi. It was in force for 67 min.

The area

The outline as issued.

The facts

Issued
Dec 16, 2012, 12:23 PM CST (18:23 UTC)
Expired
Dec 16, 2012, 1:30 PM CST
In force
67 min
Issued by
the Storm Prediction Center
Chance of a watch
80%
All 51 counties

Baldwin County, AL, Choctaw County, AL, Clarke County, AL, Escambia County, AL, Mobile County, AL, Monroe County, AL, Washington County, AL, Wilcox County, AL, Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Parish, LA, Lafayette Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint Helena Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Martin Parish, LA, Saint Tammany Parish, LA, St. Mary Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Vermilion Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, Clarke County, MS, Covington County, MS, Forrest County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Jefferson Davis County, MS, Jones County, MS, Lamar County, MS, Lawrence County, MS, Marion County, MS, Pearl River County, MS, Perry County, MS, Pike County, MS, Stone County, MS, Walthall County, MS, Wayne County, MS

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 6.4 hours before the alert went out and 67 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 12:00Z on 2012-12-16Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 4 joules per kilogram.LCLLFCEL10008507005003002001001 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 12:00Z on 2012-12-16The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 171 square meters per square second.1939587897Sfc1 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
4 J/kg
Mixed-layer CIN
-4 J/kg
Mixed-layer LCL
440 m above ground
0-6 km bulk shear
63 kt
0-1 km storm-relative helicity
171 m²/s²
0-3 km storm-relative helicity
262 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.1

Open this sounding in Storm Lab

The text

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

434 
ACUS11 KWNS 161823
SWOMCD
SPC MCD 161823 
ALZ000-FLZ000-MSZ000-LAZ000-161930-

MESOSCALE DISCUSSION 2162
NWS STORM PREDICTION CENTER NORMAN OK
1223 PM CST SUN DEC 16 2012

AREAS AFFECTED...SE LA...SRN MS...SW AL

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

VALID 161823Z - 161930Z

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...THE THREAT FOR ISOLATED DAMAGING WINDS WILL PERSIST THIS
AFTERNOON WITH THE PRE-FRONTAL SQUALL LINE.  ADDITIONAL/ISOLATED
STORM DEVELOPMENT MAY OCCUR ALONG WARM SECTOR CONFLUENCE AXES ACROSS
SE LA AND SW AL...WHERE THERE WILL BE SOME RISK FOR A TORNADO OR
TWO.  A NEW WATCH IS BEING CONSIDERED PRIOR TO 19Z.

DISCUSSION...THE PRE-FRONTAL SQUALL LINE APPEARS TO HAVE WEAKENED
SOME SINCE LATE MORNING.  HOWEVER...SURFACE HEATING IS BOOSTING
TEMPERATURES WELL INTO THE 70S AS MID-UPPER 60S BOUNDARY LAYER
DEWPOINTS SPREAD INLAND.  THE RESULTANT DESTABILIZATION COULD
SUPPORT AN UPSWING IN STORM INTENSITY THIS AFTERNOON...WHERE LARGELY
UNIDIRECTIONAL/LINE-PARALLEL SHEAR WILL SUPPORT A FEW LINE SEGMENTS
WITH DAMAGING WIND POTENTIAL.  OTHERWISE...SURFACE OBS AND VISIBLE
IMAGERY SHOW WARM SECTOR CONFLUENCE AXES ACROSS SE LA AND SW
AL...WITH DEEPENING CONVECTIVE SHOWERS ALONG EACH BAND.  THE MOIST
ENVIRONMENT WITH MODEST INSTABILITY AND DEEP-LAYER VERTICAL SHEAR
COULD SUPPORT MORE DISCRETE STORM DEVELOPMENT...WITH AND ATTENDANT
RISK FOR AN ISOLATED TORNADO OR TWO.

..THOMPSON/CORFIDI.. 12/16/2012

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

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

LAT...LON   32238740 32068697 30828709 30288780 29299032 29369205
            29539280 29889293 30499181 31059094 31659008 32248846
            32238740

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Dec 16, 5:00 AM CSTMesoscale DiscussionSPCAllen, Avoyelles, Beauregard, Bienville, Calcasieu, Caldwell and 23 more90 min
Dec 16, 5:48 AM CSTSevere Thunderstorm WatchSPCAcadia, Allen, Avoyelles, Beauregard, Bienville, Calcasieu and 27 more7 hr
Dec 16, 9:54 AM CSTMesoscale DiscussionSPCAcadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 7 more96 min

Nearby

Mesoscale Discussions in Louisiana, 2012Mesoscale Discussions in Mississippi, 2012Mesoscale Discussions in Alabama, 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.