Alert archive / Mississippi / Mesoscale Discussions in 2012

Mesoscale Discussion 2161

December 16, 201213 parishes in Louisiana; 18 counties in Mississippi; 9 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Dec 16, 2012, 9:54 AM CST for 13 parishes in Louisiana; 18 counties in Mississippi; 9 counties in Texas. It was in force for 96 min.

The area

The outline as issued.

The facts

Issued: Dec 16, 2012, 9:54 AM CST (15:54 UTC)
Expired: Dec 16, 2012, 11:30 AM CST
In force: 96 min
Issued by: the Storm Prediction Center

All 40 counties

Acadia Parish, LA, Allen Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Concordia Parish, LA, East Feliciana Parish, LA, Evangeline Parish, LA, Jefferson Davis Parish, LA, Pointe Coupee Parish, LA, Saint Landry Parish, LA, West Feliciana Parish, LA, Adams County, MS, Amite County, MS, Claiborne County, MS, Copiah County, MS, Franklin County, MS, Hinds County, MS, Jefferson County, MS, Jefferson Davis County, MS, Lawrence County, MS, Leake County, MS, Lincoln County, MS, Newton County, MS, Pike County, MS, Rankin County, MS, Scott County, MS, Simpson County, MS, Smith County, MS, Wilkinson County, MS, Brazoria County, TX, Calhoun County, TX, Chambers County, TX, Galveston County, TX, Jackson County, TX, Jefferson County, TX, Matagorda County, TX, Orange County, TX, Victoria County, TX

The radar

The Lake Charles radar (KLCH), 59 km from the middle of the area, began a volume at 15:56 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

Lake Charles Mun, LA (KLCH), launched 12:00Z, 3.9 hours before the alert went out and 59 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: 739 J/kg
Mixed-layer CIN: -5 J/kg
Mixed-layer LCL: 536 m above ground
0-6 km bulk shear: 63 kt
0-1 km storm-relative helicity: 140 m²/s²
0-3 km storm-relative helicity: 178 m²/s²
Significant tornado parameter: 0.7
Supercell composite: 5.0

Open this sounding in Storm Lab

The text

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

993 
ACUS11 KWNS 161554
SWOMCD
SPC MCD 161554 
MSZ000-LAZ000-TXZ000-161730-

MESOSCALE DISCUSSION 2161
NWS STORM PREDICTION CENTER NORMAN OK
0954 AM CST SUN DEC 16 2012

AREAS AFFECTED...SE TX...SW/CENTRAL LA...SW/CENTRAL MS

CONCERNING...SEVERE THUNDERSTORM WATCH 682...

VALID 161554Z - 161730Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 682
CONTINUES.

SUMMARY...A PRE-FRONTAL BAND OF STRONG/SEVERE STORMS WILL PERSIST
FOR THE NEXT SEVERAL HOURS WITH THE POTENTIAL FOR ISOLATED DAMAGING
WINDS.  THE WIND THREAT MAY ALSO SPREAD INTO SW/CENTRAL MS BY MIDDAY
AS THE LOW LEVELS WARM/MOISTEN.

DISCUSSION...AN EXTENSIVE PRE-FRONTAL BAND OF THUNDERSTORMS IS
MOVING SLOWLY SEWD ON WEAK CONVECTIVE OUTFLOW...WHILE INDIVIDUAL
CELLS MOVE QUICKLY ENEWD ALONG THE LINE.  THE PRESENCE OF A MOIST
BOUNDARY LAYER /MID-UPPER 60S DEWPOINTS/ AHEAD OF THE STORMS FROM SE
TX INTO LA WILL SUPPORT REGENERATION OF STORMS ALONG THE COMPOSITE
OUTFLOW BOUNDARY THROUGH EARLY AFTERNOON.  ADDITIONALLY...A FEW
STORMS COULD DEVELOP WITHIN THE WARM SECTOR AS THE BOUNDARY LAYER
WARMS/MOISTENS...AND THE RIGHT ENTRANCE REGION OF A STRONG UPPER JET
DEVELOPS ENEWD FROM TX TOWARD LA/MS.  THE OVERALL SETUP STILL
APPEARS SUPPORTIVE OF PRIMARY EMBEDDED LINE SEGMENTS WITH AN
ATTENDANT RISK FOR ISOLATED DAMAGING WINDS...GIVEN MODEST
INSTABILITY S OF THE ONGOING STORMS AND LARGELY LINE-PARALLEL
DEEP-LAYER VERTICAL SHEAR.  WHILE LOW-LEVEL SHEAR IS NOT
PARTICULARLY STRONG...ANY MORE DISCRETE STORMS THAT HAPPEN TO FORM S
OF THE BAND MAY POSE A MARGINAL TORNADO RISK.

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

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

ATTN...WFO...JAN...LIX...LCH...SHV...HGX...CRP...

LAT...LON   29169441 28369663 28549724 28749726 29209642 29629540
            30279418 30879305 31419206 31929144 32239102 32459046
            32888935 32638902 32048910 31219023 30339200 29169441

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Dec 16, 5:00 AM CST	Mesoscale Discussion	SPC	Allen, Avoyelles, Beauregard, Bienville, Calcasieu, Caldwell and 23 more	90 min
Dec 16, 5:48 AM CST	Severe Thunderstorm Watch	SPC	Acadia, Allen, Avoyelles, Beauregard, Bienville, Calcasieu and 27 more	7 hr
Dec 16, 12:23 PM CST	Mesoscale Discussion	SPC	Ascension, Assumption, East Baton Rouge, East Feliciana, Iberia, Iberville and 18 more	67 min
Dec 16, 1:51 PM CST	Mesoscale Discussion	SPC	Aransas, Calhoun, Jackson, Matagorda, Refugio, Victoria	84 min

Nearby

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