Alert archive / Louisiana / Mesoscale Discussions in 2011

Mesoscale Discussion 2213

September 28, 201132 parishes in Louisiana; 13 counties in Mississippi; Jasper County, Newton County, Orange County, Texas

The Storm Prediction Center issued this mesoscale discussion at Sep 28, 2011, 5:19 PM CDT for 32 parishes in Louisiana; 13 counties in Mississippi; Jasper County, Newton County, Orange County, Texas. It was in force for 86 min.

The area

The outline as issued.

The facts

Issued: Sep 28, 2011, 5:19 PM CDT (22:19 UTC)
Expired: Sep 28, 2011, 6:45 PM CDT
In force: 86 min
Issued by: the Storm Prediction Center

All 48 counties

Acadia Parish, LA, Allen Parish, LA, Ascension Parish, LA, Assumption Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Concordia Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Evangeline Parish, LA, Iberville Parish, LA, Jefferson Davis Parish, LA, Jefferson Parish, LA, Lafayette 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, Tangipahoa Parish, LA, Vernon Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Adams County, MS, Amite County, MS, Franklin County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Lamar County, MS, Marion County, MS, Pearl River County, MS, Pike County, MS, Stone County, MS, Walthall County, MS, Wilkinson County, MS, Jasper 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.

Severe Thunderstorm Watch 858Sep 28, 5:50 PM CDT

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 10.3 hours before the alert went out and 163 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: 3518 J/kg
Mixed-layer CIN: 0 J/kg
Mixed-layer LCL: 461 m above ground
0-6 km bulk shear: 23 kt
0-1 km storm-relative helicity: 57 m²/s²
0-3 km storm-relative helicity: 66 m²/s²
Significant tornado parameter: 0.4
Supercell composite: 2.5

Open this sounding in Storm Lab

The text

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

329 
ACUS11 KWNS 282220
SWOMCD
SPC MCD 282219
ALZ000-MSZ000-LAZ000-TXZ000-282345-

MESOSCALE DISCUSSION 2213
NWS STORM PREDICTION CENTER NORMAN OK
0519 PM CDT WED SEP 28 2011

AREAS AFFECTED...SE LA...SRN MS

CONCERNING...SEVERE THUNDERSTORM WATCH 857...

VALID 282219Z - 282345Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 857
CONTINUES.

THE SEVERE THREAT ACROSS WW 857 WILL LIKELY CONTINUE FOR SEVERAL
MORE HOURS WITH WIND DAMAGE AND HAIL POSSIBLE WITH THE STRONGER
CELLS. THE AREA WWD ACROSS SW LA AND SE TX IS BEING MONITORED FOR
POSSIBLE WATCH ISSUANCE.

A CLUSTER OF STRONG TO SEVERE THUNDERSTORMS IS CURRENTLY ONGOING IN
SE LA AND SRN MS ALONG THE ERN EDGE IF MODERATE INSTABILITY WHERE
MLCAPE VALUES ARE ESTIMATED IN THE 2000 TO 3000 J/KG RANGE. THE
STORMS ARE LOCATED JUST SOUTH OF A COLD FRONT IN A VERY MOIST
AIRMASS WITH SFC DEWPOINTS IN THE LOWER TO MID 70S F. A POOL OF
COOLER AIR IS LOCATED JUST BEHIND THE STORMS. THIS COLD POOL WILL
SAG SWD OVER THE NEXT FEW HOURS INCREASING THE POTENTIAL FOR WET
DOWNBURSTS SWD INTO AREAS AROUND LAKE PONTCHARTRAIN...NEW ORLEANS
AND BATON ROUGE. HAIL WILL ALSO BE POSSIBLE BUT THIS SHOULD BE THE
LESSER OF THE TWO THREATS.

FURTHER WEST ACROSS SE TX AND SW LA...MODERATE TO STRONG INSTABILITY
IS PRESENT BUT THE AIRMASS APPEARS TO BE SLIGHTLY CAPPED. AS A
VORTICITY MAX EVIDENT ON WATER VAPOR OVER NE TX APPROACHES THIS
EVENING...INCREASING LARGE-SCALE ASCENT MAY BE ENOUGH TO INITIATE
SCATTERED THUNDERSTORMS IN SE TX AND SW LA. IF STORMS INITIATE AND
PERSIST...THE STRONG INSTABILITY AND VERY MOIST AIRMASS MAY BE
ENOUGH FOR DAMAGING WIND GUSTS ESPECIALLY IF A LINE CAN DEVELOP THIS
EVENING.

..BROYLES.. 09/28/2011

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

ATTN...WFO...MOB...JAN...LIX...LCH...SHV...

LAT...LON   30728838 31408989 31569112 31469224 31119326 30629437
            30159436 29949371 29889306 29809178 29599054 29388956
            29268881 30728838

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 28, 12:10 PM CDT	Mesoscale Discussion	SPC	Acadia, Allen, Ascension, Assumption, Avoyelles, Beauregard and 30 more	2 hr
Sep 28, 1:59 PM CDT	Severe Thunderstorm Watch	SPC	Ascension, Assumption, East Baton Rouge, East Feliciana, Iberville, Jefferson and 16 more	6 hr
Sep 28, 5:48 PM CDT	Severe Thunderstorm Watch	SPC	Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 15 more	6 hr

Nearby

Mesoscale Discussions in Louisiana, 2011 Mesoscale Discussions in Mississippi, 2011 Mesoscale Discussions in Texas, 2011 Every mesoscale discussion in 2011

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.