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AGXX40 KNHC 280621
MIMATS

MARINE WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
221 AM EDT TUE APR 28 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.

MODEL PREFERENCE: 12Z ECMWF BLENDED WITH PREVIOUS OFFICIAL. TAFB NWPS AND EC WAVE BLENDED WITH PREVIOUS OFFICIAL SEAS. MEDIUM CONFIDENCE.

THE 00Z GFS CONTINUES TO HAVE SOME GRID-SCALE FEEDBACK ALONG THE N CENTRAL AND NE GULF COAST. THE MASS FIELDS DO APPEAR TO BE CORRUPTED INTO THE FORECAST BECAUSE OF THIS...WITH THE GFS DEVELOPING A SURFACE LOW IN THE NE GULF TODAY THAT DISPLACES THE LOWEST PRES AWAY FROM THE DEEP LAYER TROUGHING TO THE N AND DELAYS THE AMPLIFICATION OF THAT SURFACE LOW OVER THE NORTHEASTERN GULF COAST. THIS CAUSES THE GFS TO BE SLOWER TO BUILD HIGH PRES BEHIND THE FRONT. THE GFS GOES ON TO HANG MORE TROUGHING OVER THE EASTERN GULF THU IN THE WAKE OF THE FRONT IN RESPONSE TO A STRONG UPPER LEVEL SYSTEM IT CARRIES THROUGH THE NE GULF. IT IS AN OUTLIER SOLUTION WITH THIS FEATURE. THE ECMWF HAS BEEN MORE CONSISTENT WITH ITS FORECAST. IT WAS USED TO ADJUST THE OFFICIAL FORECAST AND ITS WAVE MODEL WAS ALSO ADDED TO THE MIX FOR SEAS IN ADDITION TO THE TAFB NWPS.

NESDIS/SAB SMOKE PRODUCTS INDICATE FIRES MAINLY FROM AGRICULTURAL BURNING CONTINUE TO SUPPLYING SMOKE AND HAZE PRIMARILY TO THE SW AND S CENTRAL GULF...WITH THE HIGHEST CONCENTRATION OF SMOKE CURRENTLY FOUND S OF 23N W OF 87W. WINDS IN THE WESTERN GULF ARE SHIFTING NORTHERLY BEHIND THE COLD FRONT. THIS WILL CLEAR OUT THE WESTERN GULF...WITH SMOKE LIKELY TO TRACK EASTWARD AHEAD OF THE FRONT BEFORE IT MOVES SE OF THE GULF WED NIGHT.


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

MODEL PREFERENCE: 12Z ECMWF BLENDED WITH PREVIOUS OFFICIAL THROUGH WED THEN THE 00Z GFS ADDED TO THE BLEND. TAFB NWPS FOR SEAS. MEDIUM CONFIDENCE.

A FRESH TO STRONG SE BREEZE IS PULSING FOR THE LAST TIME THIS MORNING IN THE GULF OF HONDURAS. THE 0248Z ASCAT-A PASS CAPTURED THESE CONDITIONS DEVELOPING N OF EASTERN HONDURAS. THE ECMWF IS REASONABLY WELL INITIALIZED HERE AND IS THE PREFERRED SOLUTION WITH THE COLD FRONT APPROACHING FROM THE GULF OF MEXICO WHICH WILL REDUCE THE PRES GRADIENT OVER THE AREA AND DIMINISH THE WINDS LATER TODAY. BOTH THE GFS AND 12Z ECMWF AGREE ON CARRYING THE FRONT INTO THE YUCATAN CHANNEL WED AFTERNOON. DIFFERENCES IN THE STRENGTH OF THE RIDGING N OF THE AREA BETWEEN THESE SOLUTIONS PROMPTS THE CHANGE IN MODEL PREFERENCE TOWARD A BLEND BY WED NIGHT. AS LOW PRES BUILDS OVER THE SW N ATLC...THE SUBTROPICAL HIGH WILL SHIFT EASTWARD AND THE PRES GRADIENT WILL WEAKEN IN THE SW CARIB. LOOK FOR THE GRADIENT TO BUILD OVER THE S CENTRAL AND SE CARIB MON THROUGH THU BETWEEN THE SUBTROPICAL RIDGE AND LOWER PRES IN THE WESTERN CARIB ASSOCIATED WITH THE COLD FRONT. A GROWING AREA OF FRESH TO STRONG TRADES IS EXPECTED MON NIGHT THROUGH THU NIGHT PRIMARILY OFF THE N CENTRAL AND NW COAST OF VENEZUELA. THE ECMWF CARRIES THE SYSTEM IN THE SW N ATLC ON A MORE NLY TRACK THAN THE GFS...ALLOWING FOR MORE RIDGING TO DEVELOP BETWEEN THE SYSTEM AND THE N COAST OF S AMERICA. A BLEND OF THE GFS AND 12Z ECMWF IS PREFERRED WITH THE PATTERN TO THE N BY WED NIGHT...SO IT WAS ALSO ADOPTED HERE. SEE THE SECTION BELOW FOR DETAILS. THE TAFB NWPS LOOKED REASONABLE TO BLEND WITH THE PREVIOUS SEAS FORECAST.


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

MODEL PREFERENCE: 12Z ECMWF BLENDED WITH PREVIOUS OFFICIAL THROUGH WED THEN THE 00Z GFS ADDED TO THE BLEND. EC WAVE AND TAFB NWPS FOR SEAS THROUGH WED THEN MWW3 ADDED TO BLEND. MEDIUM CONFIDENCE THROUGH WED WITH LOW CONFIDENCE THEREAFTER.

AS MENTIONED IN THE GULF OF MEXICO SECTION...CONFIDENCE IS LOW IN THE FEEDBACK-RIDDLED 00Z GFS FORECAST TODAY. THIS FEEDBACK HAS IMPACTED THE MASS FIELDS AND LIKELY SENDS THE MAIN LOW PRES SYSTEM TOO FAR S AS IT TRAVERSES FLORIDA AND MOVES INTO THE SW N ATLC. HOWEVER...THE ECMWF APPEARS TO BE AN OUTLIER WITH THE LOW CENTER FROM WED NIGHT ONWARD. ALOFT...THE ECMWF CARRIES A MORE NEGATIVELY TILTED TROUGH OVER THE GREAT LAKES/OH VLY REGION. AS THE LOW PRES SYSTEM MOVES OFFSHORE...IT ENCOUNTERS DEEPER TROUGHING COMPARED TO THE OTHER MODELS WHICH CAUSES IT TO BE DEEPER AND MORE WESTERLY AT THE SURFACE AS THE LOW DEVELOPS. THE GEFS AND EC ENS MEANS SUPPORT A COMPROMISE BETWEEN THESE SOLUTIONS WITH THE STRENGTH AND PATH OF THE LOW. A BLEND OF THE GFS AND 12Z ECMWF WAS USED TO ADJUST THE FORECAST FROM WED NIGHT ONWARD AS A RESULT. THE TAFB NWPS AND EC WAVE WERE BLENDED WITH THE OFFICIAL FORECAST EARLY IN THE PERIOD...WITH THE MWW3 ADDED TO THE MIX WED NIGHT ONWARD WHEN THE GFS WAS ADDED TO THE WIND BLEND.

$$


.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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