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AGXX40 KNHC 180534
MIMATS

MARINE WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
134 AM EDT SAT APR 18 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 BLENDED WITH PREVIOUS OFFICIAL WHICH WAS A GFS/ECMWF BLEND. TAFB NWPS USED FOR WAVE PARAMETERS. MEDIUM-HIGH CONFIDENCE.

LOW LEVEL SOUTHERLY RETURN FLOW AND DIFFLUENT UPPER FLOW AHEAD OF A SERIES OF UPPER TROUGHS MOVING E FROM THE SOUTHERN PLAINS THROUGH THE LOWER MISSISSIPPI VALLEY WILL MAINTAIN THE POTENTIAL FOR SCT SHOWERS/ISOLATED TS ACROSS THE NW AND N-CENTRAL GULF WATERS. CURRENTLY THE HEAVIEST CONVECTION HAS SHIFTED INLAND TX AND LA ALONG A QUASI-STATIONARY FRONT. EMBEDDED AREAS OF 3-5 NM VSBY IN PATCHY FOG HAS DEVELOPED AGAIN OVER THE NW WATERS...AND THIS WILL BE DENOTED IN THE WEATHER GRIDS FOR THIS MORNING. AN E TO W SURFACE RIDGE ACROSS THE NORTHERN GULF WILL CONTINUE TO SLOW THE EASTWARD ADVANCE OF THE FRONT TODAY. HOWEVER...SOME GUIDANCE STILL FAVORS THE FRONT BRIEFLY DRIFTING OFF THE TX COAST TODAY BEFORE DRIFTING BACK INLAND. THE RIDGE WILL RETRACT E LATE SUN AS THE FRONT TRANSITIONS BACK TO A COLD FRONT AND MOVES E ACROSS THE N-CENTRAL GULF EARLY MON...AND ACROSS THE THE NE GULF WATERS ON MON NIGHT. THE GFS IS STILL THE MOST AGGRESSIVE MODEL WITH THE POST-FRONTAL FLOW. MODELING BLENDING USED TO TONE DOWN THE GFS RESULTS IN 10-15 KT NE-E WINDS NOW EXPECTED ACROSS THE NW WATERS ON TUE. EXPECT THE LOCALIZED EVENING THERMAL ENHANCEMENT ALONG THE NW COAST OF THE YUCATAN PENINSULA TO BE IN THE 20-25 KT RANGE THIS EVENING...THEN ONLY A 15-20 KT EVENTS 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 WHICH WAS A GFS/ECMWF BLEND AFTER TUE. TAFB NWPS USED FOR WAVE PARAMETERS. MEDIUM-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 SUN NIGHT...THEN THE AFFECTED AREA SHOULD SHRINK TO WITHIN 90 NM OF THE COAST EACH NIGHT THROUGH TUE NIGHT. A GFS/ECMWF BLEND OF GUIDANCE HINTS AT THE AFFECTED AREA EXPANDING OUTWARD TO 180 NM AGAIN ON WED NIGHT. E- SE TRADES WILL INCREASE TO 20-25 KT ACROSS THE GULF OF HONDURAS EACH NIGHT WITH SEAS BUILDING TO 9 FT...NOTING THAT THE AFFECTED AREA WILL EXPAND N TO ALONG 18.5N TONIGHT...SUN AND MON NIGHTS. THEN THE AFFECTED AREA SHOULD SHRINK A LITTLE AS THE ATLC RIDGING WEAKENS. MODERATE TO FRESH TRADES EXPECTED ELSEWHERE. N SWELL WILL PROPAGATE SW THROUGH THE TROPICAL ATLC WATERS E OF LEEWARDS BEGINNING TONIGHT...INCREASING THE COMBINED SEAS TO 8 FT AND REACHING THE EASTERN CARIBBEAN PASSAGES ON SUN. THESE CONDITIONS WILL SPREAD S ACROSS THE TROPICAL WATERS E OF THE WINDWARDS ON SUN REACHING THE NE COAST OF S AMERICA ON MON...THEN GRADUALLY SUBSIDE FROM THE N WITH SEAS LESS THAN 8 FT ACROSS THE TROPICAL WATERS BY TUE EVENING.


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

MODEL PREFERENCE: LATEST GFS BLENDED WITH PREVIOUS OFFICIAL WHICH WAS A GFS/ECMWF BLEND. TAFB NWPS USED FOR WAVE PARAMETERS WITH MANUAL ADJUSTMENTS ACROSS WATERS N OF 27N E OF 60W. MEDIUM- HIGH CONFIDENCE.

A STATIONARY FRONT IS TRANSFORMING INTO A WARM FRONT FROM 28N55W INTO A 1013 MB LOW PRES NEAR 32N77W...WITH A WEAK STATIONARY FRONT EXTENDING S FROM THE LOW ACROSS CENTRAL FL. E-SE 15-20 KT FLOW CURRENTLY OBSERVED N OF THE DEVELOPING WARM FRONT WILL GRADUALLY CLOCK TO THE S TODAY BEHIND THE WARM FRONT WHILE T HE SURFACE LOW LIFTS NE AND DRAGS THE SECOND STATIONARY FRONT E AS A DEVELOPING COLD FRONT ACROSS THE WATERS N OF THE BAHAMAS...BUT ONLY ACCOMPANIED BY A SW-W-NW 10 KT WIND SHIFT. THE COLD FRONT WILL REACH FROM BERMUDA TO THE NW BAHAMAS THIS EVENING...THEN STALL E-W ALONG ABOUT 26N ON SUN AND GRADUALLY WASH OUT THROUGH TUE. SOUTHERLY FLOW WILL INCREASE TO 15-20 KT OVER THE NW WATERS ON SUN NIGHT AND MON AHEAD OF A SECOND WEAK COLD FRONT MOVING E OFF THE SE GA/NE FL COASTS ON MON NIGHT. THIS SECOND COLD FRONT WILL REACH FROM 31N62W TO THE NW BAHAMAS LATE TUE NIGHT...THEN STALL ALONG 26N ON WED. N SWELLS PROPAGATING S ACROSS THE DISCUSSION WATERS BETWEEN 66-55W RESULT IN COMBINED SEAS OF 7-10 FT WHICH WILL SUBSIDE BELOW 8 FT BY LATE SUN. ANOTHER ROUND OF N SWELLS WILL ARRIVE ACROSS THE WATERS N OF 29N E OF 65W ON LATE MON GRADUALLY BUILDING SEAS TO 7-11 FT ACROSS THE WATERS BETWEEN 65-55W LATE TUE. THIS SECOND ROUND OF N SWELLS WILL SUBSIDE BELOW 8 FT BY EARLY THU.

$$


.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 NELSON. NATIONAL HURRICANE CENTER.

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