Alert archive / Louisiana / Mesoscale Discussions in 2012

Mesoscale Discussion 124

February 18, 201210 parishes in Louisiana; Galveston County, Texas

The Storm Prediction Center issued this mesoscale discussion at Feb 18, 2012, 8:29 AM CST for 10 parishes in Louisiana; Galveston County, Texas. It was in force for 31 min.

The area

The outline as issued.

The facts

Issued: Feb 18, 2012, 8:29 AM CST (14:29 UTC)
Expired: Feb 18, 2012, 9:00 AM CST
In force: 31 min
Issued by: the Storm Prediction Center

Counties Acadia Parish, LA, Assumption Parish, LA, Cameron Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, Saint Martin Parish, LA, St. Mary Parish, LA, Vermilion Parish, LA, Galveston County, TX

The radar

The Lake Charles radar (KLCH), 72 km from the middle of the area, began a volume at 14:32 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 28Feb 18, 9:55 AM CST

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 12:00Z, 2.5 hours before the alert went out and 71 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: 564 m above ground
0-6 km bulk shear: 75 kt
0-1 km storm-relative helicity: 359 m²/s²
0-3 km storm-relative helicity: 635 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 2.0

Open this sounding in Storm Lab

The text

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

834 
ACUS11 KWNS 181430
SWOMCD
SPC MCD 181429
LAZ000-TXZ000-181500-

MESOSCALE DISCUSSION 0124
NWS STORM PREDICTION CENTER NORMAN OK
0829 AM CST SAT FEB 18 2012

AREAS AFFECTED...SRN LA...SERN TX

CONCERNING...SEVERE THUNDERSTORM WATCH 27...

VALID 181429Z - 181500Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 27
CONTINUES.

SQUALL LINE ALONG PRIMARILY COASTAL SECTIONS OF SWRN LA TO SERN TX
SHOULD POSE A THREAT FOR ISOLATED DAMAGING WINDS ALONG THE SRN LA
COAST THIS MORNING. WW 27 MAY BE SPATIOTEMPORALLY EXTENDED ACROSS
PARTS OF SWRN LA. A DOWNSTREAM WW IS NOT ANTICIPATED WITHIN THE HOUR
FOR SERN LA...BUT WILL BE MONITORED FOR ONE LATER THIS MORNING.

14Z SURFACE ANALYSIS PLACED 1006 MB CYCLONE AROUND 30 S BPT...WITH
QUASI-STATIONARY WARM FRONT EXTENDING EWD ALONG THE SRN LA COAST.
MODIFIED 12Z LCH RAOB WOULD INFER THAT PORTION OF SQUALL LINE ACROSS
SWRN LA IS ELEVATED WITH MINIMAL SURFACE-BASED INSTABILITY. GIVEN
ORIENTATION EVOLVING FROM A N-S TO MORE OF AN W-E STRUCTURE SUGGEST
DOWNSTREAM DAMAGING WIND THREAT SHOULD REMAIN MARGINAL IN THE
NEAR-TERM.../RECENT OBSERVED GUSTS OF 37 AND 40 KT MEASURED AT KCWF
AND KUXL/. STILL PRESENCE OF 50 KT EFFECTIVE SHEAR MAY POSE AN
ISOLATED RISK FOR DAMAGING WINDS...PRIMARILY ALONG COASTAL SWRN LA.

..GRAMS.. 02/18/2012

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

ATTN...WFO...LIX...LCH...HGX...

LAT...LON   28369572 28989563 29599460 29749399 30219322 30579259
            30519175 30269110 29869077 29609081 29179102 29089150
            29169238 29389350 28369572

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
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, 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, 11:21 AM CST	Mesoscale Discussion	SPC	Ascension, Assumption, Jefferson, Lafourche, Livingston, Orleans and 10 more	54 min
Feb 18, 1:03 PM CST	Mesoscale Discussion	SPC	Orleans, Saint Bernard, Saint Charles	57 min
Feb 18, 2:21 PM CST	Mesoscale Discussion	SPC	Jefferson, Lafourche, Plaquemines, Saint Bernard, St. Mary, Terrebonne	24 min
Feb 18, 3:41 PM CST	Mesoscale Discussion	SPC	Jefferson, Plaquemines, Saint Bernard	64 min
Feb 18, 4:29 PM CST	Mesoscale Discussion	SPC	Jefferson, Lafourche, Orleans, Plaquemines, Saint Bernard, Saint Charles and 1 more	31 min
Feb 18, 4:48 PM CST	Tornado Watch	SPC	Lafourche, Plaquemines, Terrebonne	4 hr
Feb 17, 11:15 PM CST	Mesoscale Discussion	SPC	Atascosa, Austin, Bandera, Bastrop, Bell, Bexar and 54 more	90 min

Nearby

Mesoscale Discussions in Louisiana, 2012 Mesoscale Discussions in Texas, 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.