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AGXX40 KNHC 181800
MIMATS

MARINE WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1137 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 FOR WINDS. TAFB NWPS BLENDED WITH PREVIOUS OFFICIAL FOR WAVES. HIGH CONFIDENCE.

SHOWERS AND THUNDERSTORMS ARE FOCUSING ALONG A TROUGH OVER THE NW GULF. THIS TROUGH IS FORECAST TO BE FORCED EASTWARD AS IT IS PICKED UP BY A DEEP LAYERED TROUGH ASSOCIATED WITH THE UPPER LOW CURRENTLY OVER COLORADO AND EXPECTED TO PHASE WITH A NORTHERN STREAM TROUGH AS IT PUSHES INTO THE MID MISSISSIPPI VALLEY MON. AS THE SURFACE TROUGH SHIFTS E...THE CONVECTIVE ACTIVITY IS EXPECTED TO FOCUS IN THE N CENTRAL GULF SUN AND THE NE GULF SUN NIGHT. THE LATEST GFS AND ECMWF ARE GENERALLY IN GOOD AGREEMENT WITH THIS SCENARIO...INCLUDING THE SURFACE COLD FRONT EXPECTED TO MOVE OFF THE TEXAS COAST MON MORNING AND WEAKEN AS IT MOVES E THROUGH THE N GULF. DIFFERENCES ARISE BY TUE NIGHT WHEN THE GFS ALLOWS MORE SOUTHERN STREAM ENERGY TO PASS FROM AN UPPER LOW OVER THE U.S. W COAST THROUGH THE SOUTHERN PLAINS AND INTO THE SE U.S. COMPARED TO THE ECMWF. THE GFS SHOWS MORE PRECIPITATION IN THE GULF AS A RESULT...BUT THE WINDS AND SEAS GENERALLY REMAIN BELOW ADVISORY CRITERIA THROUGH THE END OF THE PERIOD THU 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 EARLY SUN MORNING...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.




...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 NIGHT THEN THE ECMWF WAS BLENDED WITH THE PREVIOUS FORECAST. 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...THEN THE 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 STRONGER RIDGING OVER THE SW N ATLC. THE GFS THEN BECOMES A SLOW OUTLIER CARRYING THE NEXT FRONT OFF THE U.S. MID ATLC COAST THU...WITH THE ECMWF IN BETTER AGREEMENT WITH THE GEFS AND EC ENS MEANS. OVERALL...THIS MEANS 20-25 KT WINDS SHOULD HUG THE COAST OF COLOMBIA SLIGHTLY MORE THAN THE GFS IS SHOWING ON WED AND THU. A FRESH TO STRONG E-SE BREEZE IS EXPECTED OFFSHORE OF THE GULF OF HONDURAS EACH NIGHT...WITH SEAS BUILDING TO 8 FT. THE AREA SEEING A FRESH TO STRONG BREEZE SHOULD SHRINK AND SEAS SHOULD SUBSIDE ACCORDINGLY WED AND THU AS THE DRIVING RIDGING WEAKENS. 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 TONIGHT...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. AT 1200 UTC...BUOY 41044 WAS SHOWING SEAS TO 7 FT. THIS IN LINE WITH THE EC WAVE BUT 2 FT LOWER THAN THE MWW3.


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

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

THE LATEST GFS AND ECMWF MODELS ARE IN REASONABLE AGREEMENT UNTIL TUE NIGHT WHEN THE GFS BECOMES FASTER TO CARRY A FRONT OFF THE U.S. EAST COAST...WITH THE GFS THEN DEVELOPING A LOW OVER THE CENTRAL ATLC THAT DRAGS THE FRONT EASTWARD EVEN FASTER. THE GFS THEN BUILDS STRONGER RIDGING BEHIND THE FRONT THAN THE ECMWF. BY WED NIGHT...THE ECMWF ALONG WITH THE GEFS AND EC ENS MEANS CARRY ANOTHER FRONT OFF THE U.S. MID ATLC COAST WHILE THE GFS IS CONSIDERABLY SLOWER. THE ECMWF LINES UP BETTER WITH THE ENS MEANS AND THE MODEL CONSENSUS FROM WED ONWARD SO IT WAS USED TO ADJUST THE FORECAST. AT 1200...BUOYS 41046 AND 41049 REPORTED 7 FT AND 9 FT SEAS...RESPECTIVELY. THE 00Z EC WAVE MATCHED THESE OBSERVATIONS WHILE THE MWW3 AND NWPS WERE 2 FT LOWER BOTH OF THE BUOYS. WITH THE ECMWF PREFERRED FOR ADJUSTING THE WINDS...SEEMS TO MAKE SENSE TO USE THE EC WAVE TO ADJUST THE SEAS AS WELL. THE NWPS WAS RELIED ON MORE IN THE AREAS WHERE BATHYMETRY SIGNIFICANTLY IMPACTS THE FORECAST.



$$


.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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