Alert archive / Louisiana / Mesoscale Discussions in 2016

Mesoscale Discussion 413

April 18, 2016Calcasieu Parish, Cameron Parish, Jefferson Davis Parish, Louisiana

The Storm Prediction Center issued this mesoscale discussion at Apr 18, 2016, 3:23 PM CDT for Calcasieu Parish, Cameron Parish, Jefferson Davis Parish, Louisiana. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Apr 18, 2016, 3:23 PM CDT (20:23 UTC)
Expired: Apr 18, 2016, 5:30 PM CDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 5%

Counties Calcasieu Parish, LA, Cameron Parish, LA, Jefferson Davis Parish, LA

The radar

The Lake Charles radar (KLCH), 16 km from the middle of the area, began a volume at 20:21 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 nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 12:00Z, 8.4 hours before the alert went out and 15 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: 283 J/kg
Mixed-layer CIN: -37 J/kg
Mixed-layer LCL: 517 m above ground
0-6 km bulk shear: 25 kt
0-1 km storm-relative helicity: 174 m²/s²
0-3 km storm-relative helicity: 231 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.6

Open this sounding in Storm Lab

The text

As transmitted.

674 
ACUS11 KWNS 182023
SWOMCD
SPC MCD 182023 
LAZ000-182230-

MESOSCALE DISCUSSION 0413
NWS STORM PREDICTION CENTER NORMAN OK
0323 PM CDT MON APR 18 2016

AREAS AFFECTED...A SMALL PART OF SWRN LA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 182023Z - 182230Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...THERE WILL EXIST VERY LIMITED POTENTIAL FOR A STRONG TSTM
OR TWO THIS AFTERNOON WITH A LINGERING CONVECTIVE BAND AFFECTING
PORTIONS OF SWRN LA. A WW IS NOT NEEDED.

DISCUSSION...A REMNANT LEADING CONVECTIVE LINE...ASSOCIATED WITH A
LONG-LIVED MCS...HAS STALLED OVER SWRN LA. THIS ACTIVITY HAS BECOME
ORIENTED NEARLY PARALLEL TO THE CLOUD-LAYER SLY FLOW SAMPLED BY THE
LCH VWP. WEAKLY UNSTABLE...MOIST...ESELY LOW-LEVEL INFLOW WILL ALLOW
THIS ACTIVITY TO GRADUALLY EDGE EWD THROUGH THE AFTERNOON. VERY
MODEST DIURNAL HEATING OF THIS INFLOW...AIDED BY FILTERED INSOLATION
AMIDST TRANSLUCENT CIRRUS/ANVIL...IS SUPPORTING MARGINAL INSTABILITY
GIVEN SFC DEWPOINTS IN THE UPPER 60S TO AROUND 70F. FURTHERMORE...
THE PRESENCE OF AROUND 25 KT OF BULK SHEAR IN THE 0-1-KM AND 0-6-KM
LAYERS SAMPLED BY THE LCH VWP IS SUPPORTING ORGANIZED LEWP
STRUCTURES/MESO-VORTICES EVIDENT FROM KLCH RADAR DATA. AN ISOLATED
SVR WIND GUST AND/OR WEAK/BRIEF TORNADO COULD ACCOMPANY THIS
ACTIVITY IN THE NEXT FEW HOURS -- CENTERED AROUND PEAK DIURNAL
HEATING. HOWEVER...GIVEN THE LACK OF STRONGER POLEWARD FLUXES OF
RICHER LOW-LEVEL MOISTURE...AND GIVEN THE LACK OF APPRECIABLE
LINE-ORTHOGONAL SHEAR...ANY SVR RISK SHOULD BE SPATIALLY RESTRICTED.
POOR TROPOSPHERIC LAPSE RATES WILL ALSO BE DETRIMENTAL TO SUPPORTING
A GREATER SVR RISK.

..COHEN/HART.. 04/18/2016

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

ATTN...WFO...LCH...

LAT...LON   29759337 30069338 30319338 30399318 30439304 30299281
            30039266 29729262 29709295 29759337

Nearby

Mesoscale Discussions in Louisiana, 2016 Every mesoscale discussion in 2016

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.