Alert archive / Louisiana / Mesoscale Discussions in 2012

Mesoscale Discussion 126

February 18, 20124 states

The Storm Prediction Center issued this mesoscale discussion at Feb 18, 2012, 11:21 AM CST for 4 states. It was in force for 54 min.

The area

The outline as issued.

The facts

Issued: Feb 18, 2012, 11:21 AM CST (17:21 UTC)
Expired: Feb 18, 2012, 12:15 PM CST
In force: 54 min
Issued by: the Storm Prediction Center

All 30 counties

Baldwin County, AL, Escambia County, AL, Mobile County, AL, Escambia County, FL, Okaloosa County, FL, Santa Rosa County, FL, Ascension Parish, LA, Assumption 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 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, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Pearl River County, MS, Perry County, MS, Stone County, MS

The radar

The Mobile radar (KMOB), 97 km from the middle of the area, began a volume at 17:22 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Tornado Watch 29Feb 18, 11:50 AM CST

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 5.4 hours before the alert went out and 57 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: 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.

531 
ACUS11 KWNS 181721
SWOMCD
SPC MCD 181721 
FLZ000-ALZ000-MSZ000-LAZ000-181815-

MESOSCALE DISCUSSION 0126
NWS STORM PREDICTION CENTER NORMAN OK
1121 AM CST SAT FEB 18 2012

AREAS AFFECTED...SERN LA...SRN MS...SWRN AL...WRN FL PANHANDLE

CONCERNING...TORNADO WATCH 28...

VALID 181721Z - 181815Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 28 CONTINUES.

A DOWNSTREAM TORNADO WATCH WILL LIKELY BE ISSUED FOR AREAS N/E OF WW
28 BY 18Z. OTHERWISE...DAMAGING WIND...ISOLATED TORNADO AND MARGINAL
HAIL THREATS PERSIST WITH LINEAR MCS PROPAGATING EWD ACROSS SERN LA.

NE TO SW ORIENTED SQUALL LINE FROM LIVINGSTON TO ST MARY PARISH AS
OF 1715Z HAS LARGELY BEEN PROGRESSING EWD AT AROUND 40 KT. 17Z
SURFACE ANALYSIS PLACED WARM FRONT EXTENDING EWD FROM THE NRN
PORTION OF THE LINE ACROSS FAR SRN MS/AL INTO THE FL PANHANDLE. AIR
MASS CONTINUES TO DESTABILIZE ALONG AND S OF THE FRONT WITH THE 65 F
ISODROSOTHERM HAVING NOW REACHED THE NEW ORLEANS METRO. ALTHOUGH
MODIFIED RUC SOUNDINGS STILL SUGGEST SURFACE-BASED BUOYANCY IS WEAK
/AOB 500 J/KG/...THE PRESENCE OF 0-1 SRH AOA 500 M2/S2 PER THE LIX
VWP...WILL REMAIN QUITE FAVORABLE FOR AT LEAST TRANSIENT SUPERCELL
STRUCTURES CAPABLE OF PRODUCING DAMAGING WINDS AND ISOLATED
TORNADOES...ALONG WITH MARGINALLY SEVERE HAIL.

..GRAMS.. 02/18/2012

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

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

LAT...LON   29619177 30269100 30809036 31178936 31398814 31408727
            31238646 30948628 30518637 30038680 28618898 28709101
            29089194 29619177

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Feb 18, 11:49 AM CST	Tornado Watch	SPC	Baldwin, Covington, Escambia, Mobile	5 hr
Feb 18, 1:03 PM CST	Mesoscale Discussion	SPC	Baldwin, Escambia, Mobile	57 min
Feb 18, 2:02 PM CST	Mesoscale Discussion	SPC	Baldwin, Coffee, Conecuh, Covington, Dale, Escambia and 3 more	58 min
Feb 18, 2:58 PM CST	Tornado Watch	SPC	Coffee, Dale, Geneva, Henry, Houston	5 hr
Feb 18, 3:41 PM CST	Mesoscale Discussion	SPC	Baldwin, Coffee, Conecuh, Covington, Crenshaw, Dale and 4 more	64 min
Feb 18, 4:29 PM CST	Mesoscale Discussion	SPC	Baldwin, Covington, Escambia, Mobile	31 min
Feb 18, 4:48 PM CST	Tornado Watch	SPC	Baldwin, Covington, Escambia, Mobile	4 hr
Feb 18, 4:35 AM CST	Mesoscale Discussion	SPC	Calcasieu, Cameron, Jefferson Davis, Vermilion	55 min
Feb 18, 4:46 AM CST	Severe Thunderstorm Watch	SPC	Acadia, Calcasieu, Cameron, Jefferson Davis, Vermilion	5 hr
Feb 18, 8:29 AM CST	Mesoscale Discussion	SPC	Acadia, Assumption, Cameron, Iberia, Iberville, Jefferson Davis and 4 more	31 min
Feb 18, 9:31 AM CST	Mesoscale Discussion	SPC	Ascension, Assumption, East Baton Rouge, Iberia, Iberville, Jefferson and 16 more	59 min
Feb 18, 9:55 AM CST	Tornado Watch	SPC	Ascension, Assumption, East Baton Rouge, Iberia, Iberville, Jefferson and 15 more	7 hr
Feb 18, 2:21 PM CST	Mesoscale Discussion	SPC	Jefferson, Lafourche, Plaquemines, Saint Bernard, St. Mary, Terrebonne	24 min

Nearby

Mesoscale Discussions in Louisiana, 2012 Mesoscale Discussions in Mississippi, 2012 Mesoscale Discussions in Alabama, 2012 Every 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; radar from the NEXRAD Level II archive.