Alert archive / Louisiana / Mesoscale Discussions in 2011

Mesoscale Discussion 33

January 18, 201123 parishes in Louisiana; Hancock County, Harrison County, Mississippi

The Storm Prediction Center issued this mesoscale discussion at Jan 18, 2011, 3:33 PM CST for 23 parishes in Louisiana; Hancock County, Harrison County, Mississippi. It was in force for 87 min.

The area

The outline as issued.

The facts

Issued: Jan 18, 2011, 3:33 PM CST (21:33 UTC)
Expired: Jan 18, 2011, 5:00 PM CST
In force: 87 min
Issued by: the Storm Prediction Center

All 25 counties

Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Iberia Parish, LA, Iberville 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 Martin Parish, LA, Saint Tammany Parish, LA, St. Mary Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, Hancock County, MS, Harrison County, MS

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 9.6 hours before the alert went out and 90 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: 1147 m above ground
0-6 km bulk shear: 76 kt
0-1 km storm-relative helicity: 145 m²/s²
0-3 km storm-relative helicity: 140 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

129 
ACUS11 KWNS 182133
SWOMCD
SPC MCD 182133 
MSZ000-LAZ000-182300-

MESOSCALE DISCUSSION 0033
NWS STORM PREDICTION CENTER NORMAN OK
0333 PM CST TUE JAN 18 2011

AREAS AFFECTED...SERN LA...FAR SERN MS

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 182133Z - 182300Z

MARGINAL THREAT FOR STRONG WIND GUSTS TO 50 KT WILL EXIST OVER SERN
LA AND FAR SERN MS DURING THE REMAINDER OF THE AFTERNOON. WW DOES
NOT APPEAR NECESSARY.

SURFACE WAVE HAS DEVELOPED ALONG THE LA GULF COAST...WITH
TEMPERATURES OVER SERN LA WARMING INTO THE LOW 70S F AND DEWPOINTS
INCREASING INTO THE LOW 60S F. CONVECTION OCCURRING COINCIDENT WITH
WEAK SURFACE LOW PRESSURE OVER SRN LA HAS ORGANIZED INTO A LINE WITH
EMBEDDED BOW STRUCTURE. AIRMASS AHEAD OF THIS CONVECTION IS
CHARACTERIZED BY MLCAPE VALUES AROUND 250 J/KG...WITH POSITIVE CAPE
AREA LOCATED BELOW MIXED PHASE REGION SUGGESTING LIGHTNING IS
UNLIKELY. NEVERTHELESS...STEEPENING LOW-LEVEL LAPSE RATES OVER SERN
LA COMBINED WITH VERY STRONG UNIDIRECTIONAL LOW/MIDLEVEL WIND FIELDS
WILL FAVOR RAPID FORWARD PROGRESSION /AROUND 40 KT/ AND THE
POTENTIAL FOR MOMENTUM TRANSPORT TO THE SURFACE. THIS MAY LEAD TO A
MARGINAL THREAT FOR LOCALLY STRONG WIND GUSTS TO 50 KT. THE THREAT
IS EXPECTED TO SUBSIDE BY EVENING AS BOUNDARY LAYER STABILIZES WITH
LOSS OF HEATING.

..GARNER.. 01/18/2011

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

ATTN...WFO...MOB...LIX...LCH...

LAT...LON   30549183 30919087 30848973 30418883 29208919 29089078
            29549192 30549183

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.