Alert archive / Louisiana / Mesoscale Discussions in 2012
Mesoscale Discussion 2125
The Storm Prediction Center issued this mesoscale discussion at Nov 26, 2012, 6:44 PM CST for 4 states. It was in force for 91 min.
The area
The outline as issued.
The facts
- Issued
- Nov 26, 2012, 6:44 PM CST (00:44 UTC)
- Expired
- Nov 26, 2012, 8:15 PM CST
- In force
- 91 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 60%
All 56 counties
Union County, AR, Acadia Parish, LA, Allen Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Bienville Parish, LA, Bossier Parish, LA, Caddo Parish, LA, Calcasieu Parish, LA, Caldwell Parish, LA, Cameron Parish, LA, Catahoula Parish, LA, Claiborne Parish, LA, Concordia Parish, LA, De Soto Parish, LA, East Carroll Parish, LA, Evangeline Parish, LA, Franklin Parish, LA, Grant Parish, LA, Jackson Parish, LA, Jefferson Davis Parish, LA, LaSalle Parish, LA, Lincoln Parish, LA, Madison Parish, LA, Morehouse Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Rapides Parish, LA, Red River Parish, LA, Richland Parish, LA, Sabine Parish, LA, Saint Landry Parish, LA, Tensas Parish, LA, Union Parish, LA, Vernon Parish, LA, Webster Parish, LA, West Carroll Parish, LA, Winn Parish, LA, Adams County, MS, Angelina County, TX, Chambers County, TX, Hardin County, TX, Jasper County, TX, Jefferson County, TX, Liberty County, TX, Nacogdoches County, TX, Newton County, TX, Orange County, TX, Panola County, TX, Polk County, TX, Sabine County, TX, San Augustine County, TX, San Jacinto County, TX, Shelby County, TX, Trinity County, TX, Tyler County, TX
The nearest sounding before it
Shreveport, LA (KSHV), launched 00:00Z, 0.7 hours before the alert went out and 134 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.
- Mixed-layer CAPE
- 1013 J/kg
- Mixed-layer CIN
- -11 J/kg
- Mixed-layer LCL
- 1238 m above ground
- 0-6 km bulk shear
- 37 kt
- 0-1 km storm-relative helicity
- 120 m²/s²
- 0-3 km storm-relative helicity
- 187 m²/s²
- Significant tornado parameter
- 0.5
- Supercell composite
- 3.3
The text
As transmitted, in the capitals the NWS used until 2016.
625
ACUS11 KWNS 270044
SWOMCD
SPC MCD 270044
MSZ000-LAZ000-ARZ000-TXZ000-270215-
MESOSCALE DISCUSSION 2125
NWS STORM PREDICTION CENTER NORMAN OK
0644 PM CST MON NOV 26 2012
AREAS AFFECTED...ERN TX...NRN/CNTRL/WRN LA...FAR SRN
AR...SWRN/W-CNTRL MS
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 270044Z - 270215Z
PROBABILITY OF WATCH ISSUANCE...60 PERCENT
SUMMARY...CONVECTIVE DEVELOPMENT IS UNDERWAY ACROSS PARTS OF NERN TX
AND NWRN LA...AND THE ISSUANCE OF A SVR TSTM WATCH IS POSSIBLE.
DISCUSSION...OBSERVED SOUNDINGS FROM SHREVEPORT INDICATE COOLING
WITHIN THE 730-600-MB LAYER FROM 18Z TO 00Z...POTENTIALLY INDICATING
THE INCREASE IN LARGE-SCALE ASCENT DOWNSTREAM OF A MID-LEVEL VORT
MAX SOON TO EMERGE OVER CNTRL/SRN TX. THE ASCENT/COOLING HAS
CONTRIBUTED TO DESTABILIZATION...WITH THE 00Z SHREVEPORT RAOB
INDICATING AROUND 1100 J/KG OF MLCAPE WITH AROUND 20 J/KG MLCIN.
RADAR RETURNS HAVE BEEN NOTED FROM RUSK COUNTY TX TO BOSSIER PARISH
LA...WHICH IS THE MANIFESTATION OF ONGOING CONVECTIVE INITIATION AS
A COLD FRONT APPROACHES FROM THE NW...WITH MESOSCALE ASCENT ENHANCED
BY CONVERGENCE AROUND A WEAK SUB-SYNOPTIC-SCALE CYCLONE POSITIONED
NEAR SHREVEPORT. STORMS WILL LIKELY INCREASE IN NUMBER AND INTENSITY
DURING THE NEXT HOUR OR TWO...POTENTIALLY EVOLVING INTO ONE OR MORE
SQUALL LINES NEAR/JUST AHEAD OF THE FRONT AMIDST 20-35 KT OF
EFFECTIVE BULK SHEAR. SVR WINDS/HAIL WILL BE THE MAIN CONCERN WITH
THIS ACTIVITY...MAINLY TO THE W OF A NNW/SSE-ORIENTED CONFLUENCE
AXIS/WARM FRONT ACROSS THE WRN HALF OF LA. WEAKER INSTABILITY
FARTHER E TOWARD THE MS RIVER INTO WRN MS AND N INTO FAR SRN AR MAY
MITIGATE THE THREAT WITH TIME...WHERE WW ISSUANCE IS RELATIVELY LESS
LIKELY.
..COHEN/DARROW.. 11/27/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...JAN...LIX...LZK...LCH...SHV...HGX...
LAT...LON 29849303 29549484 30929543 32149468 33189347 33289272
33159198 32819123 31989096 31139139 30359203 29849303SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Nov 26, 10:14 PM CST | Mesoscale Discussion | SPC | Ashley, Chicot | 3 hr |
Nearby
Mesoscale Discussions in Louisiana, 2012Mesoscale Discussions in Texas, 2012Mesoscale Discussions in Arkansas, 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.