Alert archive / Louisiana / Mesoscale Discussions in 2012

Mesoscale Discussion 2074

October 18, 201218 parishes in Louisiana

The Storm Prediction Center issued this mesoscale discussion at Oct 18, 2012, 1:16 AM CDT for 18 parishes in Louisiana. It was in force for 59 min.

The area

The outline as issued.

The facts

Issued: Oct 18, 2012, 1:16 AM CDT (06:16 UTC)
Expired: Oct 18, 2012, 2:15 AM CDT
In force: 59 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

Counties Acadia Parish, LA, Allen Parish, LA, Ascension Parish, LA, Assumption Parish, LA, Calcasieu Parish, LA, East Baton Rouge Parish, LA, Evangeline Parish, LA, Iberville Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, Livingston Parish, LA, Pointe Coupee Parish, LA, Saint James Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, Vermilion Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA

The radar

The Lake Charles radar (KLCH), 111 km from the middle of the area, began a volume at 06:17 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 00:00Z, 6.3 hours before the alert went out and 110 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: 2250 J/kg
Mixed-layer CIN: 0 J/kg
Mixed-layer LCL: 575 m above ground
0-6 km bulk shear: 46 kt
0-1 km storm-relative helicity: 176 m²/s²
0-3 km storm-relative helicity: 254 m²/s²
Significant tornado parameter: 2.2
Supercell composite: 11.0

Open this sounding in Storm Lab

The text

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

837 
ACUS11 KWNS 180616
SWOMCD
SPC MCD 180616 
LAZ000-180715-

MESOSCALE DISCUSSION 2074
NWS STORM PREDICTION CENTER NORMAN OK
0116 AM CDT THU OCT 18 2012

AREAS AFFECTED...PORTIONS OF CNTRL AND SRN LA

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 180616Z - 180715Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...ISOLATED SEVERE STORMS CAPABLE OF LOCALLY DAMAGING WINDS
AND PERHAPS A BRIEF TORNADO WILL REMAIN POSSIBLE EARLY THIS MORNING.
CONVECTIVE TRENDS ARE BEING MONITORED FOR A POSSIBLE WW.

DISCUSSION...AS OF 0600Z...A PRE-FRONTAL BAND OF TSTMS EXTENDED FROM
TENSAS PARISH SWWD THROUGH RAPIDES AND VERNON PARISHES TO HARDIN
COUNTY TX.  SEMI-DISCRETE STORMS WITH MIDLEVEL ROTATION WERE
OBSERVED WITHIN THIS BAND WITH A STORM MOTION OF 310/20 KT. 
AMBIENT...INFLOW AIR MASS REMAINS WARM AND QUITE MOIST AND
MODIFICATION OF 00Z OBSERVED SOUNDINGS SUGGEST THAT MLCAPE REMAINS
IN THE 1000-1500 J/KG RANGE.  THIS COUPLED WITH AROUND 50 KT OF DEEP
WNWLY SHEAR SUGGESTS THAT STORMS MAY PERSIST FOR THE NEXT SEVERAL
HOURS.

WHILE AN ISOLATED TORNADO REMAINS POSSIBLE...THE TENDENCY FOR
LOW-LEVEL FLOW FIELDS TO GRADUALLY VEER AND DECELERATE WILL MITIGATE
THIS THREAT WITH TIME.  AS SUCH...DAMAGING WINDS WILL BE THE PRIMARY
HAZARD.

..MEAD.. 10/18/2012

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

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

LAT...LON   30519329 30839262 30909187 30899112 30489052 29929067
            29689151 29699255 30129346 30519329

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Oct 17, 7:01 PM CDT	Tornado Watch	SPC	Bienville, Bossier, Caddo, Caldwell, Catahoula, Claiborne and 20 more	8 hr
Oct 17, 9:28 PM CDT	Mesoscale Discussion	SPC	Bienville, Caldwell, Catahoula, Claiborne, Concordia, De Soto and 18 more	92 min
Oct 17, 11:49 PM CDT	Mesoscale Discussion	SPC	Caldwell, Catahoula, East Carroll, Franklin, Grant, LaSalle and 6 more	86 min
Oct 18, 2:40 AM CDT	Mesoscale Discussion	SPC	Ascension, East Baton Rouge, East Feliciana, Iberville, Livingston, Pointe Coupee and 8 more	65 min

Nearby

Mesoscale Discussions in Louisiana, 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.