Alert archive / Louisiana / Mesoscale Discussions in 2012

Mesoscale Discussion 131

February 18, 20124 states

The Storm Prediction Center issued this mesoscale discussion at Feb 18, 2012, 4:29 PM CST for 4 states. It was in force for 31 min.

The area

The outline as issued.

The facts

Issued
Feb 18, 2012, 4:29 PM CST (22:29 UTC)
Expired
Feb 18, 2012, 5:00 PM CST
In force
31 min
Issued by
the Storm Prediction Center

Counties Baldwin County, AL, Covington County, AL, Escambia County, AL, Mobile County, AL, Escambia County, FL, Okaloosa County, FL, Santa Rosa County, FL, Jefferson Parish, LA, Lafourche Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Terrebonne Parish, LA, Hancock County, MS, Harrison County, MS, Jackson County, MS

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, 10.5 hours before the alert went out and 61 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-pSkew-T log-p diagram, Slidell Radar S, LA at 12:00Z on 2012-02-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Slidell Radar S, LA at 12:00Z on 2012-02-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 160 square meters per square second.1939587897117Sfc1 km3 km6 km9 kmRMLM
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
449 m above ground
0-6 km bulk shear
57 kt
0-1 km storm-relative helicity
160 m²/s²
0-3 km storm-relative helicity
177 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.

064 
ACUS11 KWNS 182229
SWOMCD
SPC MCD 182229 
FLZ000-ALZ000-MSZ000-LAZ000-182300-

MESOSCALE DISCUSSION 0131
NWS STORM PREDICTION CENTER NORMAN OK
0429 PM CST SAT FEB 18 2012

AREAS AFFECTED...SERN LA/FAR SERN MS/PARTS OF SWRN AL AND WRN FL
PANHANDLE

CONCERNING...TORNADO WATCH 29...

VALID 182229Z - 182300Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 29 CONTINUES.

NEW REPLACEMENT TORNADO WATCH WILL BE COORDINATED SHORTLY FOR WW/S
28 AND 29...AS INDICATED BY SPC MESOSCALE DISCUSSION 130.

IN ADDITION TO THE CONTINUED SEVERE WEATHER THREAT WITH ACTIVITY
ALONG AND INVOF THE LEADING EFFECTIVE OUTFLOW BOUNDARY...TSTMS
FARTHER WWD EXTENDING NNE-SSW FROM SOUTH CENTRAL LA INTO THE GULF
WILL INTERSECT WWD EXTENSION OF LEADING OUTFLOW BOUNDARY...AS THIS
NNE-SSW LINE ADVANCES EWD ACROSS COASTAL AREAS OF SOUTH CENTRAL/SERN
LA.  DESPITE MUCAPE AROUND 500 J/KG...STRONG LOW LEVEL SHEAR VALUES
/EFFECTIVE SRH 300-400 M2 PER S2/ INVOF OF SURFACE BOUNDARIES AND
WITHIN THE WARM SECTOR...COMBINED WITH STRONG DEEP LAYER SHEAR WILL
MAINTAIN LIKELIHOOD FOR ORGANIZED STORMS PRODUCING DAMAGING WINDS
AND A TORNADO THREAT INTO THE EVENING.

..PETERS.. 02/18/2012

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

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

LAT...LON   29529127 30009068 30218968 30578946 30798840 31278737
            31508620 30038647 29768818 29108887 28708915 28688997
            28659134 28729162 29529127

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Feb 18, 11:21 AM CSTMesoscale DiscussionSPCBaldwin, Escambia, Mobile54 min
Feb 18, 11:49 AM CSTTornado WatchSPCBaldwin, Covington, Escambia, Mobile5 hr
Feb 18, 1:03 PM CSTMesoscale DiscussionSPCBaldwin, Escambia, Mobile57 min
Feb 18, 2:02 PM CSTMesoscale DiscussionSPCBaldwin, Coffee, Conecuh, Covington, Dale, Escambia and 3 more58 min
Feb 18, 2:58 PM CSTTornado WatchSPCCoffee, Dale, Geneva, Henry, Houston5 hr
Feb 18, 3:41 PM CSTMesoscale DiscussionSPCBaldwin, Coffee, Conecuh, Covington, Crenshaw, Dale and 4 more64 min
Feb 18, 4:48 PM CSTTornado WatchSPCBaldwin, Covington, Escambia, Mobile4 hr
Feb 18, 4:35 AM CSTMesoscale DiscussionSPCCalcasieu, Cameron, Jefferson Davis, Vermilion55 min
Feb 18, 4:46 AM CSTSevere Thunderstorm WatchSPCAcadia, Calcasieu, Cameron, Jefferson Davis, Vermilion5 hr
Feb 18, 8:29 AM CSTMesoscale DiscussionSPCAcadia, Assumption, Cameron, Iberia, Iberville, Jefferson Davis and 4 more31 min
Feb 18, 9:31 AM CSTMesoscale DiscussionSPCAscension, Assumption, East Baton Rouge, Iberia, Iberville, Jefferson and 16 more59 min
Feb 18, 9:55 AM CSTTornado WatchSPCAscension, Assumption, East Baton Rouge, Iberia, Iberville, Jefferson and 15 more7 hr
Feb 18, 2:21 PM CSTMesoscale DiscussionSPCJefferson, Lafourche, Plaquemines, Saint Bernard, St. Mary, Terrebonne24 min

Nearby

Mesoscale Discussions in Louisiana, 2012Mesoscale Discussions in Alabama, 2012Mesoscale Discussions in Florida, 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.