Alert archive / Louisiana / Mesoscale Discussions in 2012

Mesoscale Discussion 2102

November 5, 201228 parishes in Louisiana

The Storm Prediction Center issued this mesoscale discussion at Nov 5, 2012, 4:43 PM CST for 28 parishes in Louisiana. It was in force for 92 min.

The area

The outline as issued.

The facts

Issued: Nov 5, 2012, 4:43 PM CST (22:43 UTC)
Expired: Nov 5, 2012, 6:15 PM CST
In force: 92 min
Issued by: the Storm Prediction Center
Chance of a watch: 80%

All 28 counties

Acadia Parish, LA, Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Evangeline Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Parish, LA, Lafayette Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Pointe Coupee Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, Saint Tammany Parish, LA, St. Mary Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Vermilion Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 674Nov 5, 5:30 PM CST

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 10.7 hours before the alert went out and 97 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: 1067 m above ground
0-6 km bulk shear: 36 kt
0-1 km storm-relative helicity: -24 m²/s²
0-3 km storm-relative helicity: 12 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.

592 
ACUS11 KWNS 052243
SWOMCD
SPC MCD 052243 
LAZ000-MSZ000-060015-

MESOSCALE DISCUSSION 2102
NWS STORM PREDICTION CENTER NORMAN OK
0443 PM CST MON NOV 05 2012

AREAS AFFECTED...S-CNTRL AND SERN LA

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

VALID 052243Z - 060015Z

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...THE THREAT FOR SEVERE THUNDERSTORMS INCLUDING SUPERCELLS
IS INCREASING...AND THE ISSUANCE OF A WW IS LIKELY.

DISCUSSION...DCVA ACCOMPANYING AN APPROACHING COMPACT SHORTWAVE
TROUGH IS BECOMING MANIFEST AS DEEPENING CONVECTION INVOF THE
SRN-LA/SWRN-MS BORDER. MODIFIED FORECAST SOUNDINGS TO ACCOUNT FOR
CURRENT SFC OBSERVATIONS SUGGEST THAT 500-1000 J/KG OF MLCAPE
CHARACTERIZES THE WARM SECTOR SOUTH OF A DIFFUSE FRONT THAT LIES
FROM A MESO-LOW 30 SSE ALEXANDRIA TO LAKE PONTCHARTRAIN TO THE GULF
WATERS SOUTH OF GULFPORT MS. LITTLE INHIBITION EXISTS ACROSS THE
WARM SECTOR FOR PARCELS EMANATING WITHIN THE BOUNDARY LAYER...AND
STORMS WILL LIKELY INCREASE IN NUMBER AND INTENSITY NEAR THE FRONT
WHILE DEEP FORCING FOR ASCENT INCREASES. THE ACTIVITY WILL SHIFT
ESEWD THROUGH THE EVENING. SLIDELL VWP DATA SUGGEST THAT 51 KT OF
0-6-KM BULK SHEAR WITH DEEP UNIDIRECTIONAL WLY FLOW ABOVE 1 KM AGL
WILL YIELD SPLITTING SUPERCELL STRUCTURES AND LINE SEGMENTS CAPABLE
OF SVR HAIL AND DMGG WIND GUSTS. WEAK SPLITTING SUPERCELLS HAVE
ALREADY BEEN NOTED NEAR AND ON LAKE PONTCHARTRAIN PER SLIDELL RADAR
DATA. SOME DIRECTIONAL SHEAR IN THE LOWEST 1 KM MAY ALSO SUPPORT A
TORNADO...PARTICULARLY NEAR THE SFC BOUNDARY.

..COHEN/CORFIDI.. 11/05/2012

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

ATTN...WFO...LIX...LCH...

LAT...LON   28999003 29029082 29389171 29619223 30339264 30899241
            30989152 30719032 30528982 30078912 29718879 29128893
            28938950 28999003

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Nov 5, 1:19 PM CST	Mesoscale Discussion	SPC	Acadia, Allen, Ascension, Assumption, Avoyelles, Beauregard and 21 more	86 min
Nov 5, 2:08 PM CST	Severe Thunderstorm Watch	SPC	Beauregard, Calcasieu, Cameron	7 hr
Nov 5, 5:25 PM CST	Mesoscale Discussion	SPC	Allen, Beauregard, Calcasieu, Cameron, Jefferson Davis	95 min
Nov 5, 5:29 PM CST	Severe Thunderstorm Watch	SPC	Acadia, Allen, Ascension, Assumption, East Baton Rouge, East Feliciana and 26 more	6 hr

Nearby

Mesoscale Discussions in Louisiana, 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.