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AGXX40 KNHC 301757
MIMATS

MARINE WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
157 PM EDT WED JUL 30 2014

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.

12Z MODEL UPDATE...

LITTLE CHANGE WAS MADE TO THE FORECAST FROM OVERNIGHT...WITH THE EVOLUTION OF THE LOW PRESSURE SYSTEM NEAR 10N45W THE FORECAST PROBLEM OF THE DAY. THE EASTERLY SHEAR OVER THE SYSTEM IS EXPECTED TO DIMINISH SOMEWHAT OVER THE NEXT 24-48 HOURS...ALLOWING FOR SOME DEVELOPMENT OF THE SYSTEM. SOUTHERLY SHEAR SHOULD INCREASE ON THE SE SIDE OF A TUTT AS THE SYSTEM APPROACHES THE LEEWARDS. CONFIDENCE IS LOWERING IN THE FORECAST FOR A CLOSED LOW AS IT REACHES THE ISLANDS. THE PREVIOUS OFFICIAL GRIDS FOLLOWED THE 12Z ECMWF STRENGTH FORECAST OVER THE STRONGER GFS...BUT KEPT THE CENTER OF THE SYSTEM ON A MORE NLY TRACK INVOF THE NE CARIB. THE EARLIER DISCUSSION ABOUT FOLLOWING A MORE N OF W TRACK ALSO CONTINUES TO APPLY. THE 12Z GFS HAS TRENDED WEAKER AND FASTER AS THE SYSTEM BRUSHES THE NE CARIB AND PASSES N OF PUERTO RICO. LOOKING AHEAD...THE NEW GFS RUN THEN TRENDS FARTHER W...CARRYING THE SYSTEM NORTHWARD THROUGH THE BAHAMAS AND DISSIPATING IT BY WED. FOR NOW...STUCK WITH THE ECMWF SOLUTION WHICH CONTINUES TO BE FASTER THAN THE GFS CARRYING THE SYSTEM TOWARD THE NE CARIB WHICH IS IN BETTER AGREEMENT WITH THE CURRENT MOTION AND THE PREFERENCE FOR A WEAKER FORECAST.

THE ONLY OTHER SIGNIFICANT CHANGE TO THE FORECAST WAS TO LEAN MORE TOWARD AN MWW3/EC WAVE BLEND IN THE ATLC COMPARED TO THE PREVIOUS GRIDS WHICH WERE 2-3 FEET TOO HIGH WITH WAVE HEIGHTS IN NUMEROUS BUOY LOCATIONS ACROSS BOTH THE TROPICAL ATLC AND THE CENTRAL ATLC AT 12Z THIS MORNING.


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PREVIOUS DISCUSSION...


...GULF OF MEXICO... MODEL PREFERENCE: GFS

VERY WEAK RIDGE EXTENDS FROM 1018 MB HIGH ACROSS NW GULF...SE TO THE STRAITS OF FLORIDA...DUE TO FRONTAL BOUNDARY SINKING S ACROSS N CENTRAL COASTAL WATERS AND NE GULF ALONG 27N. RECENT ASCAT PASS DEPICTED N TO NW WINDS 10-15 KT N OF BOUNDARY ACROSS NE PORTIONS...AND W 10-15 TO THE S. A PRE FRONTAL TROUGH AHEAD OF FRONT BY ABOUT 2 DEGREES EXTENDS INTO SW FLORIDA. SUPPORTING UPPER TROUGH AXIS WILL SHIFT SLIGHTLY E THROUGH THU AND JUST OFFSHORE OF MID ATLC COAST BEFORE REDEVELOPING ALONG 85W THU NIGHT-FRI. FRONT AND TROUGH TO SINK SLOWLY S THROUGH WED BEFORE STALLING ALONG 26N INTO CENTRAL FLORIDA WITH TROUGH EXTENDING WWD FROM THE KEYS...WITH FEATURES THEN SHIFTING BACK TOWARD THE W AS UPPER TROUGH REALIGNS INTO SAT. MODELS IN GENERALLY AGREEMENT ON THIS SCENARIO. WINDS AND SEAS EXPECTED TO REMAIN LIGHT TO MODERATE WITH ONLY EVENING PULSE ALONG NW AND W COAST OF YUCATAN TO 20 KT THE EXCEPTION.


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

MODEL PREFERENCE: GFS-ECMWF CONSENSUS

THE ATLC RIDGE HAS BEGUN TO WEAKEN PAST 24 HOURS AND DIMINISHED WINDS ACROSS S CENTRAL PORTIONS OF CARIB...LIKELY ONLY TO 25 KT OFF CARIB JET REGION OFFSHORE OF COLOMBIA. RIDGE EXPECTED TO WEAKEN A BIT MORE NEXT 48 HOURS AS E COAST UPPER TROUGH AND ASSOCIATED FRONT NUDGES HIGH TO THE NE. DESPITE THIS...GFS STILL SHOWS WINDS OFF COLOMBIA PULSING TO 25 KT EACH NIGHT...BUT WITH MODEST AREA OF 8 AND 8-9 FT SEAS DEVELOPING EACH LATE NIGHT AND MORNING. BEYOND FRI...ALL INTERESTS ACROSS E AND NE CARIB SHOULD CONTINUE TO MONITOR TROPICAL LOW ACROSS CENTRAL ATLC ALONG ABOUT 43W THIS MORNING. GLOBAL MODELS IN GOOD AGREEMENT ON A WNW TRAJECTORY TOWARD THE NE CARIB NEXT 36-48 HOURS BEFORE TURNING A BIT MORE NW FRI-SAT-SUN. GFS CONTINUES THE SLOWEST AND MOST AGGRESSIVE MODEL...YET SYSTEM HAS YET TO INTENSIFY...AND MAY BE SUFFERING FROM ELONGATION OF MID LEVEL VORTICITY. THUS PREFER THE ECMWF SOLUTION...AND HAVE BLENDED STRONGLY INTO ATLC AND NE CARIB GRIDS. WEAKNESS BEING CARVED OUT BY TUTT LOW N OF PR IS ALTERING STEERING FLOW...AND EVEN A WEAK SYSTEM EXPECTED TO TAKE THIS NW TRACK. CONFIDENCE REMAINS MODERATE AT BEST ATTM.


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

MODEL PREFERENCE: ECMWF-GFS CONSENSUS

ATLC RIDGE CONTINUES TO SLOWLY WEAKEN AND REALIGN SW TO NE AS ERN U.S. UPPER TROUGH AND ASSOCIATED FRONTAL SYSTEM NUDGE THE ATLC HIGH NE. FRONTAL BOUNDARY CURRENTLY ACROSS FAR NW WATERS WITH PRE FRONTAL TROUGH JUST OFF E COAST OF FLORIDA...AND SW WINDS 15-20 KT STILL OCCURRING E OF TROUGH N OF 28N. FRONT TO DRIFT SE AND WEAKEN THROUGH EARLY THU THEN DRIFT BACK TOWARDS THE NW AND MERGE INTO ELONGATED TROFFING ACROSS THE PENINSULA THU-FRI. VIGOROUS UPPER LOW ACROSS THE NE ATLC TO SHIFT SW THEN W LATE IN WEAK AND WORK DOWN TO SFC IN FORM OF SFC LOW ACROSS CENTRAL ATLC...AND ALLOW SOME WEAK RIDGING TO RE-ESTABLISH ACROSS W PORTIONS THU-FRI-SAT...AHEAD OF TROPICAL LOW MOVING ACROSS OR JUST NE OF THE EXTREME NE CARIB. CURRENT LONG RANGE FORECASTS MOVE LOW TO THE NE-E OF BAHAMAS...RECURVING SOMEWHAT PARALLEL TO THE ISLANDS...WITH A STRONGER SYSTEM LIKELY TO RECURVE MORE STRONGLY. LOW TO MODERATE CONFIDENCE ATTM...AGAIN WITH GFS SLOWEST. GLOBAL DETERMINISTIC MODELS SHOW WEAKENING OF THIS LOW AFTER PASSING NE CARIB...AS TUTT LOW LIES IN WAITING AHEAD OF IT ACROSS THE SE BAHAMAS SAT-SUN. LOW EXPECTED TO REACH N HALF OF TROPICAL N ATLC WATERS FRI MORNING AND APPROACH LEEWARDS FRI NIGHT.

$$


.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/STRIPLING. NATIONAL HURRICANE CENTER.

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