Alert archive / Louisiana / Mesoscale Discussions in 2011

Mesoscale Discussion 71

February 1, 201118 parishes in Louisiana; 12 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Feb 1, 2011, 1:23 PM CST for 18 parishes in Louisiana; 12 counties in Mississippi. It was in force for 67 min.

The area

The outline as issued.

The facts

Issued: Feb 1, 2011, 1:23 PM CST (19:23 UTC)
Expired: Feb 1, 2011, 2:30 PM CST
In force: 67 min
Issued by: the Storm Prediction Center

All 30 counties

Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, Jefferson Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Plaquemines 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 Tammany Parish, LA, St. Mary Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Washington Parish, LA, Amite County, MS, Copiah County, MS, Hinds County, MS, Jefferson Davis County, MS, Lawrence County, MS, Lincoln County, MS, Madison County, MS, Marion County, MS, Pike County, MS, Rankin County, MS, Simpson County, MS, Walthall County, MS

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 7.4 hours before the alert went out and 32 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: 464 m above ground
0-6 km bulk shear: 56 kt
0-1 km storm-relative helicity: 437 m²/s²
0-3 km storm-relative helicity: 526 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2

Open this sounding in Storm Lab

The text

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

831 
ACUS11 KWNS 011923
SWOMCD
SPC MCD 011923 
LAZ000-MSZ000-012030-

MESOSCALE DISCUSSION 0071
NWS STORM PREDICTION CENTER NORMAN OK
0123 PM CST TUE FEB 01 2011

AREAS AFFECTED...SRN MS AND SERN LA

CONCERNING...TORNADO WATCH 9...

VALID 011923Z - 012030Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 9 CONTINUES.

TORNADO THREAT MAY BE GREATER THIS AFTERNOON ACROSS THE VALID PART
OF WW 9 IN SRN MS AND SERN LA.

AT 19Z...REGIONAL RADAR IMAGERY INDICATED THE STORMS LOCATED ALONG
THE PORTION OF THE ADVANCING LINE FROM FAR SOUTH CENTRAL MS /JUST
NW-SW OF MCB/ INTO SERN LA /INVOF BTR/ HAVE EVOLVED INTO MORE
DISCRETE STORMS.  THIS TREND IS LIKELY A RESULT OF STRONG FORCING
FOR ASCENT MOVING MORE NEWD AWAY FROM THIS REGION REDUCING THE
LINEAR FORCING.  A WARM FRONT HAD MOVED A LITTLE FARTHER N EARLY
THIS AFTERNOON AND EXTENDED EWD FROM LAKE PONTCHARTRAIN EWD INTO THE
FL PANHANDLE.  EFFECTIVE SRH VALUES INVOF THIS BOUNDARY RANGE FROM
400-800+ M2/S2...WITH THE SPECIAL 18Z SLIDELL SOUNDING VERIFYING
THESE VALUES SHOWING EFFECTIVE SRH CLOSE TO 900 M2/S2.  60 KT SLY
LLJ AND EFFECTIVE BULK SHEAR EXCEEDING 50 KT WILL MAINTAIN POTENTIAL
FOR SUPERCELLS WITH SURFACE BASED STORMS LIKELY ALONG AND S OF THE
WARM FRONT.

..PETERS.. 02/01/2011

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

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

LAT...LON   29129179 30659108 31809060 32599039 32908975 31808968
            31448965 30718980 30198956 30118916 29978878 29488910
            29098900 28868926 28648921 28628949 28868984 28739025
            28739103 29129179

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Feb 1, 6:46 AM CST	Mesoscale Discussion	SPC	Allen, Avoyelles, Bienville, Bossier, Caddo, Caldwell and 25 more	119 min
Feb 1, 8:40 AM CST	Tornado Watch	SPC	Acadia, Allen, Ascension, Assumption, Avoyelles, Beauregard and 46 more	6 hr
Feb 1, 12:00 PM CST	Mesoscale Discussion	SPC	Ascension, Assumption, East Baton Rouge, East Feliciana, Iberia, Iberville and 24 more	60 min
Feb 1, 1:03 PM CST	Tornado Watch	SPC	Clarke, Covington, Forrest, George, Greene, Hancock and 13 more	7 hr
Feb 1, 3:44 PM CST	Mesoscale Discussion	SPC	George, Greene, Hancock, Harrison, Jackson, Perry and 2 more	61 min

Nearby

Mesoscale Discussions in Louisiana, 2011 Mesoscale Discussions in Mississippi, 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.