000
AGXX40 KNHC 200754
MIMATS

MARINE WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
254 AM EST FRI DEC 20 2013

MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN
SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND
64W...AND THE SW N ATLANTIC INCLUDING THE BAHAMAS.

...GULF OF MEXICO...

MODEL PREFERENCE: PREVIOUS/OFFICIAL FORECAST BLENDED WITH LATEST
GFS AND ECMWF. PREVIOUS FORECAST AND MWW3 BLEND USED FOR WAVE
PARAMETERS. MEDIUM-HIGH CONFIDENCE.

THE 0308 UTC ASCAT PASS AND SEVERAL SHIP OBSERVATIONS SHOWED WINDS
AND SEAS HIGHER THAN THE MODEL GUIDANCE IN THE SE GULF.
ADJUSTMENTS WERE MADE TO THE SHORT TERM BASED ON THESE
OBSERVATIONS. OTHERWISE...THE PRESSURE GRADIENT BETWEEN THE
BERMUDA HIGH AND TROUGHING OVER THE GREAT PLAINS IS INDUCING
MODERATE TO FRESH S-SE RETURN FLOW ACROSS THE GULF OF
MEXICO...WITH SEAS RUNNING MAINLY 4-6 FT. WINDS WILL INCREASE TO
FRESH TO STRONG AHEAD OF THE FRONT FRI NIGHT THROUGH SAT BUILDING
SEAS TO 6-9 FT. THAT FRONT WILL MOVE INTO THE NW GULF SAT
NIGHT...BRIEFLY STALLING OUT FROM S CENTRAL LOUISIANA TO NE MEXICO
SAT NIGHT INTO SUN MORNING. CONFIDENCE IN THE GFS FORECAST WANES AS
A REINFORCING SURGE OF NORTHERLY WINDS AND COLD AIR ARRIVES IN THE
NW PORTION LATE SUN INTO MON. THE GFS IS SLOWER THAN THE ECMWF BRINGING
IN THE REINFORCING TROUGH ALOFT...BUT THESE MODELS AGREE ON FRESH
TO STRONG WINDS ACROSS THE MAJORITY OF THE GULF BEHIND THE FRONT
AND GALE FORCE WINDS POSSIBLE IN GMZ023 MON. THE ECMWF IS 6-12
HOURS FASTER WITH THE ONSET OF GALES IN THE SW GULF THAN THE GFS
WHICH WAITS TILL LATE MON. 03Z SREF 34 KT PROBABILITIES ARE OVER
70 PERCENT BY THE END OF ITS RUN AT 18Z MON. THE 06Z GEFS ONLY
SHOWS AROUND A 30 PERCENT CHANCE OF GALES...BUT SPREADS THE CHANCE
OF GALE FORCE WINDS NORTHWARD INTO ZONE GMZ017. CONFIDENCE IS LOW
ON THE TIMING OF THE REINFORCING SURGE. FOR NOW...BLENDED THE GFS
AND ECMWF WITH THE PREVIOUS OFFICIAL FORECAST WHICH RESULTED IN
GALES ONLY IN ZONE GMZ023 MON AFTERNOON AND EVENING. 


...CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN
55W AND 65W...

MODEL PREFERENCE: PREVIOUS/OFFICIAL FORECAST BLENDED WITH LATEST
GFS THROUGH MON THEN A BLEND OF GFS AND ECMWF MON AND TUE.
NWPS/MWW3 BLEND USED FOR WAVE PARAMETERS. HIGH CONFIDENCE.

A GALE WARNING HAS BEEN ISSUED FOR THE COAST OF COLOMBIA LATE
TONIGHT INTO SATURDAY MORNING. THE 00Z GFS EXPLICITLY SHOWS GALE
FORCE WINDS. IT IS GENERALLY THE MOST RELIABLE GLOBAL MODEL FOR
THE STRONG WINDS OFF COLOMBIA. THE ECMWF AND UKMET...WHICH
GENERALLY RUN LOW UNDER SUCH A PATTERN...BOTH SHOW AN AREA OF 30
KT WINDS HERE EARLY SAT. OTHERWISE...HIGH PRESSURE N OF THE AREA
WILL MAINTAIN FRESH TO STRONG TRADE WINDS ACROSS THE
CARIBBEAN...EXCEPT MODERATE TO FRESH IN THE NW CARIBBEAN WHERE THE
PRESSURE GRADIENT WILL BE SLIGHTLY WEAKER. TRADE WINDS WILL
DIMINISH SIGNIFICANTLY LATE MON INTO TUE AS THE PRESSURE GRADIENT
N OF THE AREA WEAKENS DUE TO COLD FRONTAL INTRUSION. THE GFS IS
SLOWER WITH THIS FRONT THAN THE ECMWF...AS NOTED IN THE GULF OF
MEXICO SECTION. A BLEND OF THEIR SOLUTIONS IS PREFERRED AS THE
FRONT MOVES INTO THE AREA.

IN THE TROPICAL N ATLC...FRESH TO LOCALLY STRONG TRADE WINDS WILL
PREVAIL THROUGH THE WEEKEND...DIMINISHING OVER THE SOUTHERN WATERS
SUN INTO MON. SEAS WILL BE 8-12 FT IN PRIMARILY NE SWELL.

...SW N ATLANTIC W OF 65W INCLUDING THE BAHAMAS...

PREVIOUS/OFFICIAL FORECAST BLENDED WITH LATEST GFS AND ECMWF
INCLUDED FOR COLD FRONT MOVING INTO NW WATERS MON/TUE. NWPS/MWW3
BLEND USED FOR WAVE PARAMETERS. HIGH CONFIDENCE.

THE BERMUDA HIGH IS DRIVING THE EASTERLY FLOW ACROSS THE
AREA...WITH A BELT OF FRESH NE WINDS NEAR A WEAKENING LOW LEVEL
BOUNDARY ALONG 27N AS WELL AS FRESH TRADE WINDS S OF 22N. LOOK FOR
THIS BOUNDARY AND THE WINDS NEAR IT TO DIMINISH TODAY. TRADE WINDS
TO THE S WILL DIMINISH MON AFTERNOON AS THE NEXT COLD FRONT
APPROACHES FROM THE W. THAT FRONT WILL ENTER THE NW WATERS LATE
MON...STRETCHING FROM 31N75W TO PALM BEACH FLORIDA TUE MORNING.

$$

.WARNINGS...ANY CHANGES IMPACTING COASTAL NWS OFFICES WILL BE
COORDINATED THROUGH AWIPS 12 PLANET CHAT OR BY TELEPHONE:

.GULF OF MEXICO...
GMZ011...NONE.
GMZ013...NONE.
GMZ015...NONE.
GMZ017...NONE.
GMZ019...NONE.
GMZ021...NONE.
GMZ023...GALE CONDITIONS POSSIBLE MON. 
GMZ025...NONE.

.CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN
55W AND 64W...
AMZ011...NONE.
AMZ013...NONE.
AMZ015...NONE.
AMZ017...NONE.
AMZ019...NONE.
AMZ021...NONE.
AMZ023...NONE.
AMZ025...NONE.
AMZ027...NONE.
AMZ029...NONE.
AMZ031...GALE WARNING TONIGHT INTO SAT. 
AMZ033...NONE.
AMZ035...NONE.
AMZ037...NONE.
AMZ039...NONE.

.SW N ATLANTIC INCLUDING THE BAHAMAS...
AMZ111...NONE.
AMZ113...NONE.
AMZ115...NONE.
AMZ117...NONE.
AMZ119...NONE.
AMZ121...NONE.
AMZ123...NONE.
AMZ125...NONE.
AMZ127...NONE.

*FOR DETAILED ZONE DESCRIPTIONS PLEASE VISIT:
HTTP://WWW.NHC.NOAA.GOV/ABOUTTAFBPROD.SHTML#OWF

NOTE: GRIDDED MARINE FORECASTS ARE AVAILABLE IN THE
NATIONAL DIGITAL FORECAST DATABASE (NDFD) AT:
HTTP://WWW.NHC.NOAA.GOV/MARINE/GRIDS.PHP

FOR ADDITIONAL INFORMATION PLEASE VISIT:
HTTP://WWW.HURRICANES.GOV/MARINE

$$
.FORECASTER SCHAUER. NATIONAL HURRICANE CENTER.