Marine Interpretation Message
Issued by NWS

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000
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.

-----------------------------------------------------------------
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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