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Marine Weather Discussion



000
AGXX40 KNHC 261800
MIMATS

MARINE WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT TUE JUL 26 2016

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: FOR WINDS USED BLEND OF 12Z GFS WITH PREVIOUS
OFFICIAL. FOR WAVEHEIGHTS USED BLEND OF 12Z MWW3 AND TAFB NWPS
OUTPUT WITH PREVIOUS OFFICIAL FORECAST. HIGH CONFIDENCE.

A MID TO UPPER LEVEL LOW NEAR 30N91W ALONG WITH AMPLE DEEP
MOISTURE PRESENT ACROSS THE AREA IS PROVIDING INSTABILITY LEADING
TO THE EXISTENCE OF SCATTERED SHOWERS AND ISOLATED TSTMS OVER MUCH
OF THE CENTRAL AND ERN GULF PORTIONS. IN ADDITION...A SURFACE
TROUGH EXTENDS FROM NEAR 30N88W NW TO A 1013 MB LOW OVER SE
LOUISIANA TO THE NW GULF NEAR 28N96W. WEAK HIGH PRES RIDGING IS
PRESENT OVER N FLORIDA.

LATEST BUOY OBSERVATIONS AND RECENT ASCAT DATA INDICATE THAT THE
PRES GRADIENT OVER THE AREA IS SUPPORTING GENERALLY GENTLE TO
MODERATE WINDS THROUGHOUT WITH WINDS NOTED IN A CYCLONIC FASHION
OVER THE N CENTRAL WATERS BETWEEN 86W-92W. THE BUOY OBSERVATIONS
ALONG WITH RECENT ALTIMETER PASSES SHOW RELATIVELY LOW SEAS OF 1-2
FT RANGE... EXCEPT FOR HIGHER SEAS IN THE 3-5 FT RANGE S OF 25N
BETWEEN 89W- 97W AND FROM 25N-29N BETWEEN 84W-91W.

THE MID TO UPPER LEVEL LOW IS FORECAST TO WEAKEN AS IT CONTINUES
WESTWARD TO NW GULF TONIGHT. GLOBAL MODELS ARE IN GOOD AGREEMENT
THAT THE ATLC RIDGE WILL EXTEND WESTWARD ACROSS THE REMAINDER OF
THE GULF TODAY THROUGH SAT NIGHT. OTHERWISE...THE TYPICAL CLIMO
THERMAL TROUGH IN THE YUCATAN PENINSULA WILL PUSH OFFSHORE INTO
THE SW GULF EACH NIGHT THROUGH THE PERIOD ATTENDANT BY A BRIEF
PERIOD OF FRESH N TO NE WINDS AND A SLIGHT INCREASE OF SEAS.

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

MODEL PREFERENCE: FOR WINDS USED BLEND OF 12Z GFS WITH PREVIOUS
OFFICIAL. FOR WAVEHEIGHTS USED BLEND OF 12Z MWW3 AND TAFB NWPS
OUTPUT WITH PREVIOUS OFFICIAL FORECAST. HIGH CONFIDENCE.

THE PRES GRADIENT BETWEEN HIGH PRES ACROSS THE CNTRL ATLC AND
LOWER PRES IN THE NRN PORTIONS OF S AMERICA...AND ALSO IN THE SW
CARIBBEAN WHERE THE ERN PORTION OF THE E PACIFIC MONSOON TROUGH
IS LOCATED IS MAINTAINING FRESH TO STRONG ELY WINDS ACROSS THE S
CNTRL CARIBBEAN. THE GRADIENT PRODUCING THESE WINDS WILL TIGHTEN
FURTHER TONIGHT...AND CONTINUE TO DO SO THROUGH THU. THIS WILL
ALLOW FOR THESE WINDS TO EXPAND IN COVERAGE N TO JUST S OF
HISPANIOLA...AND EWD TO NEAR 69W BY THU WITH RESULTANT SEAS
BUILDING TO 10 FT. AS THE GRADIENT RELAXES ON FRI...THE WINDS
WILL RESPOND BY DECREASING IN BOTH COVERAGE AND IN SPEEDS.
HOWEVER...THE SEAS TO 10 FT WILL BE SLOW IN SUBSIDING IN THE
CNTRL CARIBBEAN ON FRI.

A TROPICAL WAVE MOVING RAPIDLY WWD UNDER THE ATLC RIDGE CROSSED
THE LESSER ANTILLES ON MON EVENING...AND IS ANALYZED OVER THE ERN
CARIBBEAN AS OF 12Z. SCATTERED SHOWERS AND TSTMS ARE OCCURRING
ALONG AND NEAR THE NRN PORTION OF THE WAVE OVER PUERTO RICO AND
EASTERN HISPANIOLA. THE WAVE WILL MOVE ACROSS THE REMAINDER OF
THE ERN CARIBBEAN TONIGHT...THEN ACROSS THE CNTRL CARIBBEAN WED
AND WED NIGHT...AND THE WRN CARIBBEAN THU AND THU NIGHT BEFORE
MOVING INLAND CENTRAL AMERICA. ANOTHER TROPICAL WAVE WILL REACH
THE TROPICAL N ATLC LATE FRI NIGHT...AND THE ERN CARIBBEAN SAT AND
SAT NIGHT. MODELS SUGGEST THAT THIS WAVE WILL BE ACCOMPANIED BY A
WELL PRONOUNCED NE TO SE WIND SHIFT ALONG A WITH A POCKET OF TIGHT
PRES GRADIENT AND BUILDING SEAS ALONG ITS NRN SEGMENT.

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

MODEL PREFERENCE: FOR WINDS USED BLEND OF 12Z GFS WITH PREVIOUS
OFFICIAL. FOR WAVEHEIGHTS USED BLEND OF 12Z MWW3 AND TAFB NWPS
OUTPUT WITH PREVIOUS OFFICIAL FORECAST. HIGH CONFIDENCE...EXCEPT
AVERAGE CONFIDENCE SE PORTION SAT AND SAT NIGHT.

A RIDGE AXIS EXTENDING FROM A 1021 MB HIGH NEAR 27N67W WNW TO NE
FL IS THE MAIN FEATURE OVER THE BASIN. ISOLATED SHOWERS AND TSTMS
ARE NOTED FROM 22N-25N BETWEEN 76W-79W AT THIS TIME.

THE 12Z ANALYSIS REVEALS A RATHER WEAK PRES GRADIENT THROUGHOUT
WITH LIGHT TO GENTLE E-SE WINDS ACROSS MUCH OF THE BASIN...EXCEPT
FOR THE NE PORTION WHERE WINDS ARE LIGHT AND VARIABLE MAINLY W-NW
IN DIRECTION AND FROM THE SE BAHAMAS TO THE COAST OF HISPANIOLA
WHERE E WINDS ARE IN THE MODERATE TO FRESH RANGE. BOTH BUOY AND
ALTIMETER DATA SHOW SEAS IN THE RANGE OF 3- 5 FT E OF THE
BAHAMAS...EXCEPT FOR SEAS OF 2-3 FT N OF 25N AND ALSO N OF THE
BAHAMAS W OF 77W. SEAS IN THE LOWER RANGE OF 1-2 ARE SW OF THE
BAHAMAS...AND 1-2 FT N OF 27N W OF 70W. A SMALL POCKET OF SEAS IN
THE 5-6 FT RANGE ARE NOTED BETWEEN THE SE BAHAMAS AND HISPANIOLA.

THE RIDGE IS FORECAST TO CHANGE LITTLE THROUGH THU NIGHT...THEN
WILL BE REPLACED BY STRONGER CNTRL ATLC RIDGING THAT BUILDS
WESTWARD NEAR 29N FRI THROUGH SAT NIGHT. MODELS SUGGEST THAT
TIGHTENING OF THE PRES GRADIENT IS LIKELY TO OCCUR IN THE SE
PORTION OF THE BASIN BEGINNING LATE ON SAT AS THE NRN PORTION OF
A TROPICAL WAVE MOVES THROUGH THAT AREA. WINDS THERE WILL
RESPOND IN A NE TO SE FASHION WILL INCREASING IN SPEEDS WITH
RELATED SEAS POSSIBLY BUILDING TO AROUND 7 OR 8 FT. OTHERWISE...
THE FLOW PATTERN S OF THE RIDGE WILL BECOME E-SE WITH WINDS IN
THE GENTLE TO MODERATE RANGE...EXCEPT FOR THE STRONGER PULSING E
WINDS TO THE STRONG CATEGORY BETWEEN THE BAHAMAS AND HISPANIOLA.
WITH THESE WINDS SEAS ARE EXPECTED TO BUILD TO 7 FT...WITH
WAVEWATCH GUIDANCE AND NWPS OUTPUT SHOWING SEAS BUILDING TO 8 FT
WED NIGHT AND AGAIN ON SAT NIGHT.

$$

.WARNINGS...ANY CHANGES IMPACTING COASTAL NWS OFFICES WILL BE
COORDINATED THROUGH AWIPS II COLLABORATION 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:
WWW.NHC.NOAA.GOV/ABOUTTAFBPROD.SHTML#OWF

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

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

$$

.FORECASTER FORMOSA. NATIONAL HURRICANE CENTER.