Alert archive / Louisiana / Mesoscale Discussions in 2012
Mesoscale Discussion 2210
The Storm Prediction Center issued this mesoscale discussion at Dec 25, 2012, 12:19 PM CST for 41 parishes in Louisiana; 29 counties in Mississippi; 7 counties in Texas. It was in force for 71 min.
The area
The outline as issued.
The facts
- Issued
- Dec 25, 2012, 12:19 PM CST (18:19 UTC)
- Expired
- Dec 25, 2012, 1:30 PM CST
- In force
- 71 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 692...694
All 77 counties
Acadia Parish, LA, Allen Parish, LA, Ascension Parish, LA, Assumption Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Evangeline Parish, LA, Grant Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Davis Parish, LA, Jefferson Parish, LA, Lafayette Parish, LA, Lafourche Parish, LA, LaSalle Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Pointe Coupee Parish, LA, Rapides 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 Landry Parish, LA, Saint Martin Parish, LA, Saint Tammany Parish, LA, St. Mary Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Vermilion Parish, LA, Vernon Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Adams County, MS, Amite County, MS, Clarke County, MS, Copiah County, MS, Covington County, MS, Forrest County, MS, Franklin County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Jasper County, MS, Jefferson County, MS, Jefferson Davis County, MS, Jones County, MS, Lamar County, MS, Lawrence County, MS, Lincoln County, MS, Marion County, MS, Pearl River County, MS, Perry County, MS, Pike County, MS, Simpson County, MS, Smith County, MS, Stone County, MS, Walthall County, MS, Wayne County, MS, Wilkinson County, MS, Chambers County, TX, Galveston County, TX, Hardin County, TX, Jasper County, TX, Jefferson County, TX, Newton County, TX, Orange County, TX
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Slidell Radar S, LA (KSIL), launched 12:00Z, 6.3 hours before the alert went out and 159 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
- 790 J/kg
- Mixed-layer CIN
- -14 J/kg
- Mixed-layer LCL
- 576 m above ground
- 0-6 km bulk shear
- 46 kt
- 0-1 km storm-relative helicity
- 181 m²/s²
- 0-3 km storm-relative helicity
- 237 m²/s²
- Significant tornado parameter
- 1.1
- Supercell composite
- 10.0
The text
As transmitted, in the capitals the NWS used until 2016.
933
ACUS11 KWNS 251819
SWOMCD
SPC MCD 251819 COR
ALZ000-MSZ000-LAZ000-TXZ000-251930-
MESOSCALE DISCUSSION 2210
NWS STORM PREDICTION CENTER NORMAN OK
1219 PM CST TUE DEC 25 2012
AREAS AFFECTED...E/SE TX...CENTRAL/SRN LA AND CENTRAL/SRN MS
CONCERNING...TORNADO WATCH 692...694...
VALID 251819Z - 251930Z
CORRECTED FOR STATES LISTED IN AREAS AFFECTED SECTION OF TEXT
PRODUCT AND WEB GRAPHIC.
THE SEVERE WEATHER THREAT FOR TORNADO WATCH 692...694...CONTINUES.
SUMMARY...TORNADO THREAT WILL CONTINUE TO INCREASE ACROSS SE TX INTO
SWRN AND CENTRAL LA ACROSS WW 694...WITH A TORNADO POTENTIAL ALSO
INTO THE FAR SRN EXTENT OF SVR WW 693.
A NEW TORNADO WATCH WILL BE NEEDED TO REPLACE CURRENT WW 692 PRIOR
TO 19Z...WITH THE POTENTIAL FOR THIS NEW WW TO BE A PDS GIVEN A
SIGNIFICANT INCREASE IN EFFECTIVE SRH THIS AFTERNOON AS THE LLJ
STRENGTHENS ACROSS THE LOWER MS VALLEY.
DISCUSSION...LATE THIS MORNING...THERE HAS BEEN AN INCREASE IN CG
LIGHTNING STRIKES ACROSS SE THROUGH EAST CENTRAL TX TO NWRN LA INVOF
A SURFACE LOW NOW LOCATED IN FAR EAST CENTRAL TX /NEAR JASPER TX/.
THIS LIGHTNING AND SIMILAR INCREASE IN REFLECTIVITIES EXTENDED SSWWD
ALONG A DRY LINE/PACIFIC FRONT THROUGH SE TX/UPPER TX COAST /TO THE
N-SW OF THE HOUSTON METRO AREA/. TSTMS /MAINLY ELEVATED/ ALSO
EXTENDED NEWD OF THE SURFACE LOW INTO NWRN LA. THIS INCREASE IN TSTM
DEVELOPMENT IS LIKELY INDICATIVE OF THE ARRIVAL OF STRONG FORCING
FOR ASCENT WITHIN THE EXIT REGION OF A 90-100 KT MIDLEVEL JET
ACCOMPANYING THE POWERFUL SRN PLAINS SHORTWAVE TROUGH. SUBSEQUENT
AND EXPECTED STRENGTHENING OF A SSWLY LLJ WAS EVIDENT OVER
SWRN-CENTRAL LA PER 17Z LCH WSR-88D VAD SHOWING 60 KT AT 1 KM AGL.
THE STRONG VERTICALLY VEERING WINDS HAVE GREATLY ENHANCED THE
EFFECTIVE SRH VALUES UP TO 400-600 M2/S2 TO SUPPORT AN INCREASED
TORNADO THREAT...EXPECTED TO SPREAD EWD THIS AFTERNOON INTO THE SRN
PART OF THE LOWER MS VALLEY...WITHIN THE WARM SECTOR.
LATE MORNING SURFACE ANALYSES SHOWED THE LOW HAS CONTINUED TO DEEPEN
AND AT 17Z WAS LOCATED INVOF JASPER TX. A WARM FRONT HAS MOVED
STEADILY NWD AND EXTENDED EWD THROUGH CENTRAL LA...SRN MS /N OF
KMCB/...TO THE N OF KMOB AND INTO THE WRN FL PANHANDLE. GIVEN THE
LOCATION OF THE WARM FRONT...THE SRN EXTENT OF SVR WATCH 693 WILL
ALSO HAVE A TORNADO POTENTIAL AS STORMS WILL BE SFC-BASED OR NEAR
SFC-BASED.
MEANWHILE...THE WARM FRONT HAS MOVED N OF WW 692...THOUGH THE WARM
SECTOR ACROSS THIS WW HAS ONLY SLOWLY DESTABILIZED THUS FAR DUE TO
THE MIXING RELATED DECREASE IN THE DEWPOINTS. 18Z SLIDELL SPECIAL
SOUNDING INDICATED AN INVERSION LOCATED BETWEEN 700-800 MB AND THIS
SHOULD CONTINUE TO INHIBIT DEEPER CU DEVELOPMENT UNTIL THE ARRIVAL
OF GREATER ASCENT WITH THE EXIT REGION OF THE IMMEDIATELY UPSTREAM
MIDLEVEL JET. SOME VEERING OF LOW LEVEL WINDS ACROSS SWRN LA SHOULD
ADVECT RICHER MOISTURE INTO SERN LA/SRN MS SUPPORTING STRONGER
DESTABILIZATION TO SUPPORT AN ENVIRONMENT FAVORABLE FOR
SUSTAINED...DEEP UPDRAFTS.
..PETERS/EDWARDS.. 12/25/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...MOB...JAN...LIX...LCH...SHV...HGX...
LAT...LON 28859514 29869488 31269374 31809285 31719159 31949054
32129009 32198915 32258860 32198850 31578843 30318844
29628962 29139007 29119092 28929128 29139235 29169380
28859514SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Dec 25, 1:01 AM CST | Mesoscale Discussion | SPC | Allen, Beauregard, Sabine, Vernon | 59 min |
| Dec 25, 1:37 AM CST | Severe Thunderstorm Watch | SPC | Acadia, Allen, Avoyelles, Beauregard, Calcasieu, De Soto and 9 more | 7 hr |
| Dec 25, 5:56 AM CST | Mesoscale Discussion | SPC | Acadia, Allen, Avoyelles, Beauregard, Calcasieu, De Soto and 10 more | 94 min |
| Dec 25, 7:00 AM CST | Mesoscale Discussion | SPC | Acadia, Allen, Ascension, Assumption, Beauregard, Calcasieu and 24 more | 60 min |
| Dec 25, 7:28 AM CST | Tornado Watch | SPC | Acadia, Ascension, Assumption, East Baton Rouge, East Feliciana, Iberia and 19 more | 6 hr |
| Dec 25, 8:46 AM CST | Mesoscale Discussion | SPC | Allen, Avoyelles, Beauregard, Bienville, Calcasieu, Caldwell and 21 more | 59 min |
| Dec 25, 9:02 AM CST | Severe Thunderstorm Watch | SPC | Bienville, Bossier, Caddo, Caldwell, Catahoula, Claiborne and 20 more | 7 hr |
| Dec 25, 9:17 AM CST | Tornado Watch | SPC | Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 10 more | 8 hr |
| Dec 25, 12:23 PM CST | Mesoscale Discussion | SPC | Bienville, Caldwell, Catahoula, Concordia, East Carroll, Franklin and 13 more | 67 min |
| Dec 25, 12:58 PM CST | Tornado Watch | SPC | Ascension, Assumption, Catahoula, Concordia, East Baton Rouge, East Feliciana and 20 more | 9 hr |
| Dec 25, 3:22 PM CST | Mesoscale Discussion | SPC | Caldwell, East Carroll, Morehouse, Richland, West Carroll | 53 min |
| Dec 25, 3:44 PM CST | Mesoscale Discussion | SPC | Ascension, Assumption, East Baton Rouge, East Feliciana, Iberia, Iberville and 19 more | 91 min |
| Dec 25, 9:31 AM CST | Mesoscale Discussion | SPC | Archer, Baylor, Clay, Cooke, Denton, Hood and 10 more | 5 hr |
| Dec 25, 11:02 AM CST | Mesoscale Discussion | SPC | Wichita, Wilbarger | 4 hr |
| Dec 25, 1:00 PM CST | Mesoscale Discussion | SPC | Bowie, Camp, Cass, Collin, Dallas, Delta and 16 more | 5 hr |
| Dec 25, 2:50 PM CST | Mesoscale Discussion | SPC | Clay, Wichita, Wilbarger | 4 hr |
Nearby
Mesoscale Discussions in Louisiana, 2012Mesoscale Discussions in Mississippi, 2012Mesoscale Discussions in Texas, 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.