Alert archive / Louisiana / Mesoscale Discussions in 2004

Mesoscale Discussion 2575

December 25, 200430 parishes in Louisiana; Hancock County, Mississippi; 4 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Dec 25, 2004, 12:33 AM CST for 30 parishes in Louisiana; Hancock County, Mississippi; 4 counties in Texas. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: Dec 25, 2004, 12:33 AM CST (06:33 UTC)
Expired: Dec 25, 2004, 6:30 AM CST
In force: 6 hr
Issued by: the Storm Prediction Center

All 35 counties

Acadia Parish, LA, Allen Parish, LA, Ascension Parish, LA, Assumption Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, East Baton Rouge Parish, LA, Evangeline Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Davis Parish, LA, Jefferson Parish, LA, Lafayette Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Pointe Coupee Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, Saint Tammany Parish, LA, St. Mary Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Vermilion Parish, LA, West Baton Rouge Parish, LA, Hancock County, MS, Chambers County, TX, Hardin County, TX, Jefferson County, TX, Orange County, TX

The radar

The Lake Charles radar (KLCH), 96 km from the middle of the area, began a volume at 06:35 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, 6.6 hours before the alert went out and 95 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: 1832 m above ground
0-6 km bulk shear: 56 kt
0-1 km storm-relative helicity: 35 m²/s²
0-3 km storm-relative helicity: 144 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.

903 
ACUS11 KWNS 250634
SWOMCD
SPC MCD 250633 
MSZ000-LAZ000-TXZ000-251230-

MESOSCALE DISCUSSION 2575
NWS STORM PREDICTION CENTER NORMAN OK
1233 AM CST SAT DEC 25 2004

AREAS AFFECTED...ERN UPPER COASTAL PLAIN OF SE TX/SRN LA

CONCERNING...WINTER MIXED PRECIPITATION 

VALID 250633Z - 251230Z

...POTENTIAL FOR SNOW/SLEET DEVELOPING ACROSS PORTIONS OF SRN LA
BEFORE 12Z...

LATEST SFC ANALYSIS SHOWS FREEZING LINE EXTENDS FROM OCH/JAS/ARA/HSA
AS OF 06Z. RECENT RADAR IMAGERY SHOWS PRECIPITATION IS OCCURRING
ALOFT...WITH PRECIPITATION BEING REPORTED AT THE SFC AS FAR EAST AS
NEW ORLEANS. WITH UPSTREAM VORT MAX QUICKLY APPROACHING THE
AREA...IT WILL NOT TAKE MUCH TIME BEFORE LOW LEVELS BECOME
SATURATED. CONVECTIVE CELLS ARE PRECIPITATING INTO THE LOWER
LAYERS...VIA A SEEDER/FEEDER TYPE PROCESS AND EFFECTIVELY
COOLING/MOISTENING THE LAYER. CURRENT DEWPOINTS ARE LOW...GENERALLY
IN THE LOWER 20S WITH WETBULB ZERO TEMPERATURES BELOW FREEZING AS
WELL. 

00Z ETA IS ALREADY TOO SLOW IN DEVELOPING THE WAA PRECIPITATION
FIELD...GIVEN CURRENT RADAR/SATELLITE OBSERVATIONS. THERMODYNAMIC
PROFILES YIELD MAINLY SNOW WITH POSSIBLY SOME SLEET OR FREEZING RAIN
MIXING IN. HOWEVER THE COMBINATION OF STRONG MID LEVEL FRONTOGENESIS
AND STRONG DYNAMICAL FORCING SHOULD COOL THE COLUMN SUFFICIENTLY TO
SUPPORT ALL FROZEN PRECIPITATION.

..TAYLOR.. 12/25/2004

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

...NOTICE...
SPC WINTER WEATHER MESOSCALE DISCUSSIONS WILL BE ISSUED ON A 
SCHEDULED BASIS...FOUR TIMES A DAY...BETWEEN 00-01 UTC...
06-07 UTC...12-13 UTC...AND 18-19 UTC AS SIGNIFICANT SHORT
RANGE WINTER WEATHER EVENTS UNFOLD.  THIS SCHEDULE WILL BE
USED FROM DECEMBER 1 THROUGH FEBRUARY 28.

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

29469462 29939495 30679418 30839338 30819179 30739068
30498969 30198901 29338950 29209050 29649275 29789320

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Dec 25, 6:52 AM CST	Mesoscale Discussion	SPC	Ascension, Assumption, East Baton Rouge, Iberia, Iberville, Jefferson and 16 more	5 hr
Dec 24, 6:35 PM CST	Mesoscale Discussion	SPC	Aransas, Bee, Brooks, Cameron, Duval, Goliad and 13 more	6 hr
Dec 24, 11:51 PM CST	Mesoscale Discussion	SPC	Aransas, Bee, Brazoria, Brooks, Calhoun, Cameron and 17 more	5 hr

Nearby

Mesoscale Discussions in Louisiana, 2004 Mesoscale Discussions in Texas, 2004 Mesoscale Discussions in Mississippi, 2004 Every mesoscale discussion in 2004

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.