Marine Interpretation Message
Issued by NWS

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000
AGXX40 KNHC 171801
MIMATS

MARINE WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
201 PM EDT FRI APR 17 2015

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: LATEST GFS/ECMWF BLENDED WITH PREVIOUS OFFICIAL
FOR WINDS. TAFB NWPS/MWW3 BLENDED WITH PREVIOUS OFFICIAL FOR
WAVES. MEDIUM-HIGH CONFIDENCE.

AS OF 1700 UTC...THE FOG IS LIFTING IN THE NW GULF WITH NEARLY
ALL STATIONS DROPPING FOG IN THEIR OBSERVATIONS. SCATTERED SHOWERS
AND THUNDERSTORMS ARE EXPECTED TO REMAIN IN THE NORTHERN GULF
OVERNIGHT BEFORE FOCUSING OFF THE TEXAS COAST SAT AND REACHING
THE N CENTRAL GULF SUN AND NE GULF SUN NIGHT IN ASSOCIATION WITH
THE REMAINS OF THE UPPER LOW CURRENTLY OVER THE NM/CO BORDER
EXPECTED TO PHASE WITH A NORTHERN STREAM TROUGH AS IT PUSHES INTO
THE MID MISSISSIPPI VALLEY MON. THE 12Z GFS AND 00Z ECMWF ARE
GENERALLY IN GOOD AGREEMENT WITH THE UPPER LOW TRACK AND INTENSITY
BUT THE GFS IS STRONGER WITH SHORTWAVE ENERGY SE OF THE LOW SUN
AND MON OVER THE SERN U.S. THE GFS APPEARS TO BE A STRONGER
OUTLIER COMPARED TO THE MODEL CONSENSUS SO BLENDING THE ECMWF WITH
ITS SOLUTION HOPEFULLY DAMPENS OUT ANY DISCREPANCIES. WINDS AND
SEAS WILL GENERALLY REMAIN BELOW ADVISORY CRITERIA THROUGH THE END
OF THE PERIOD WED NIGHT WITH THE EXCEPTION OF LOCALIZED EVENING
THERMAL ENHANCEMENT ALONG THE NW COAST OF THE YUCATAN PENINSULA.
WINDS HERE ARE EXPECTED REACH THE 20-25 KT RANGE THROUGH SAT
EVENING...AND THEN ONLY 15-20 KT EVENTS EXPECTED EACH EVENING
THROUGH THE REMAINDER OF THE PERIOD. THESE E-SE PULSES WILL
PROPAGATE W ACROSS THE E BAY OF CAMPECHE DURING THE MORNING
DAYLIGHT HOURS WITH THE TROUGH...LOSING IDENTITY OVER THE CENTRAL
BAY OF CAMPECHE BY THE EARLY AFTERNOONS.


...CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN
55W AND 64W...

MODEL PREFERENCE: LATEST GFS BLENDED WITH PREVIOUS OFFICIAL FOR
WINDS THROUGH TUE THEN ECMWF ADDED TO BLEND. TAFB NWPS BLENDED
WITH PREVIOUS OFFICIAL FOR WAVES...WITH THE EC WAVE ALSO ADDED IN
THE TROPICAL N ATLC. HIGH CONFIDENCE.

ATLC RIDGING N OF THE AREA...COMBINED WITH LOW PRES OVER NW
COLOMBIA...WILL SUPPORT 20-25 KT NE WINDS WITHIN 180 NM OF THE
NW COAST OF COLOMBIA TONIGHT AND SAT NIGHT...THEN THE AFFECTED
AREA SHOULD SHRINK TO WITHIN 90 NM OF THE COAST EACH NIGHT THROUGH
TUE NIGHT. BY WED...THE GFS AND ECMWF DIFFER OVER THE SW N
ATLC...WITH THE GFS SHOWING A RIDGE AND STRONGER WINDS OFF
COLOMBIA AND THE ECMWF SHOWING A TROUGH. CONFIDENCE IS LOW IN THE
DETAILS BY THIS POINT IN THE FORECAST...SO A BLEND OF THE GFS AND
ECMWF WAS BLENDED FURTHER WITH THE OFFICIAL FORECAST WHICH
ALLOWED FOR A SLIGHT EXPANSION OF THE 20-25 KT WINDS OFF COLOMBIA.
A FRESH TO STRONG E-SE BREEZE IS EXPECTED OFFSHORE OF THE GULF OF
HONDURAS EACH NIGHT THROUGH MON NIGHT...WITH SEAS BUILDING TO 8-9
FT. AS THE RIDGING TO THE N WEAKENS TUE AND WED...THE AREA SEEING
A FRESH TO STRONG BREEZE SHOULD SHRINK AND SEAS SHOULD SUBSIDE
ACCORDINGLY. ELSEWHERE...MODERATE TO FRESH TRADES ARE EXPECTED.
NE SWELL WILL PROPAGATING SW THROUGH THE TROPICAL ATLC WATERS E OF
LEEWARDS INCREASING THE COMBINED SEAS AROUND 8 FT ON SAT
NIGHT...WITH THESE CONDITIONS SPREADING S ACROSS THE TROPICAL
WATERS E OF THE WINDWARDS ON SUN. THIS TIMING IS SLIGHTLY FASTER
THAN THAT SEEN IN THE NWPS AND MWW3...ADJUSTING FOR THE EC WAVE
WHICH GENERALLY PERFORMS BETTER WITH LONG-PERIOD SWELL MOVING INTO
THE REGION.

 ...SW N ATLANTIC INCLUDING THE BAHAMAS...

MODEL PREFERENCE: LATEST GFS/ECMWF BLENDED WITH PREVIOUS OFFICIAL
FOR WINDS. TAFB NWPS/EC WAVE BLENDED WITH PREVIOUS OFFICIAL FOR
WAVES. MEDIUM-HIGH CONFIDENCE.

AT 1200 UTC A COLD FRONT WAS ANALYZED FROM 31N40W TO 28N47W TO
27N58W THEN STATIONARY THROUGH 28N70W TO 31N74W. A 1327 UTC
ALTIMETER PASS SHOWED SEAS TO 11 FT N OF THE FRONT ALONG 66W AND
BUOY 41049 NEAR 27.5N62.9W SAW SEAS IN THE 10-11 FT RANGE FROM
1200 UTC TO 1700 UTC. THESE CONDITONS BEST MATCH THE EC WAVE. THE
1400 UTC ASCAT PASS SHOWED A FRESH TO STRONG E-NE BREEZE STILL
PERSISTED N OF THE FRONT BETWEEN 54W AND 60W. NEITHER THE 00Z
ECMWF NOR THE 12Z GFS SHOWED 25 KT WINDS HERE AT 12Z THIS MORNING.
WINDS WERE BUMPED UP HERE SLIGHTLY INITIALLY BUT A BLEND OF THE
GFS AND ECMWF WAS USED OVERALL FOR THE WIND FORECAST. THESE MODELS
ARE IN REASONABLE AGREEMENT UNTIL TUE WHEN THE GFS BECOMES FASTER
TO CARRY A FRONT OFF THE U.S. EAST COAST...WITH THE GFS APPEARING
TO HAVE SOME CONVECTIVE FEEDBACK PROBLEMS BY TUE NIGHT NEAR 39N63W
WHICH CAUSE IT TO DRAG THE FRONT EASTWARD TOO QUICKLY. THE GFS AND
ECMWF DIFFER SIGNIFICANTLY BY WED AFTERNOON WHEN THE GFS PLACES A
HIGH ALONG 31N74W WHILE THE ECMWF CARRIES A SECONDARY COLD FRONT
THROUGH THE AREA. THE EC ENS MEAN SUPPORTS THE OPERATIONAL RUN
WHILE THE GEFS IS SLOWER WITH THE FRONT AND THE HIGH BEHIND IT
THAN THE GFS...MORE LIKE THE ECMWF. BLENDING IN THE ECMWF FORECAST
ALSO SUPPLIED MORE CONFIDENCE TO USING THE EC WAVE IN THE BLEND
FOR ADJUSTING THE WAVE FIELD.

$$

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

.GULF OF MEXICO...
     NONE.

.CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN
55W AND 64W...
     NONE.

.SW N ATLANTIC INCLUDING THE BAHAMAS...
     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.HURRICANE WARNINGS.GOV/MARINE

$$

.FORECASTER SCHAUER. NATIONAL HURRICANE CENTER.



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