000 AGXX40 KNHC 151923 MIMATS Marine Weather Discussion NWS National Hurricane Center Miami FL 223 PM EST THU DEC 15 2016 Marine Weather Discussion for the Gulf of Mexico, Caribbean Sea, and Tropical North Atlantic from 07N to 19N between 55W and 64W and the Southwest North Atlantic including the Bahamas ...GULF OF MEXICO... MODEL PREFERENCE: Global model consensus. The 18Z surface analysis consists of a cold front that passes through 31N70W in the Atlantic Ocean, across south Florida near 26N80W, to the central Gulf of Mexico, to 24N96W. The front becomes stationary and it continues from 24N96W to 23N99W inland in Mexico, and then northwestward toward the Texas Big Bend. This front is forecast to become stationary and dissipate through Friday. Mostly moderate northerly flow with some pockets of fresh flow will follow in behind the front during the rest of the day today. The high pressure in the wake of this front will shift eastward quickly through Friday night. The winds will respond by veering around to an east to southeast direction in the central and eastern gulf, and to more of a southerly direction in the western sections where they increase to the fresh to locally strong category on Saturday. Seas behind the front are expected to build to the range of 3-5 ft, except for higher seas of around 6-8 ft in the western gulf on Saturday. The strong return flow in the western gulf will occur in advance of the cold front to approach the area. The global models depict this cold front as a rather strong one, that will be followed by a large area of strong high pressure. This high pressure will usher arctic air into the gulf of Mexico behind this next front. The cold front is forecast to reach the NW Gulf of Mexico waters during the early morning hours of Sunday. Gale-force winds are forecast to develop behind this cold front, in cold arctic northerly flow mixing down to the surface as the front moves across the western gulf zones on Sunday and Sunday night. The front is forecast to move quickly and to reach from the Fl panhandle to the southwest gulf on Sunday night, and become stationary from north/central Fl to the Bay of Campeche by late on Monday. Will highlight possible gale conditions for Sunday in zone GMZ017, and for zone GMZ023 for Sunday night and Monday. It may be necessary to include zone GMZ011 for frequent gusts to gale force early on Sunday with the next forecast. The sea heights are expected to build to around 12 ft with these conditions in the far western part of zone GMZ017, and to 13-15 ft in the far southwest part of zone GMZ023 on Monday. Wavewatch and NWPS guidance suggests that these seas will be slow in subsiding late on Monday. ...CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... MODEL PREFERENCE: Global model consensus. The latest scatterometer data show moderate/moderate-to-fresh winds from 70W eastward, fresh-to-strong from 10N to 14N between 74W and 78W off the coast of Colombia. Moderate/moderate-to-fresh winds cover the rest of the area that is from the coastal waters of the Greater Antilles southward between 74W and 80W. Gentle-to- moderate winds are around SE Cuba, and in the Windward Passage. The comparatively highest sea heights correspond to the area of the comparatively fastest wind speeds, off the coast of Colombia, from 9 feet to 11 feet. The tight pressure gradient that is producing the fresh to strong trades will slacken, allowing for coverage of the fresh to strong winds to decrease some. The Atlantic high pressure is forecast to continue to slide eastward through tonight. These wind speeds will decrease more on Friday. This trend will be short-lived as strong high pressure will re-establish itself across the western part of the SW Atlantic beginning late Friday afternoon and evening, and through early next week. The associated tight pressure gradient is expected to initiate a widespread increase of the northeast-to- east trades in the Caribbean Sea to the east of 81W, and in the tropical north Atlantic Ocean zones. Wavewatch guidance, including the wavewatch ensemble guidance, was suggesting that related seas will build to around 11 ft with the trades affecting the Caribbean Sea, and to a higher maximum of 12 or 13 ft in the eastern section of tropical north Atlantic zones AMZ127 and AMZ027. ...SW N ATLANTIC INCLUDING THE BAHAMAS... MODEL PREFERENCE: Global model consensus. High pressure in the far eastern waters is sliding eastward. Moderate-to-fresh cyclonic wind flow is around a cold front. Earlier sea heights were in the 4-6 ft range to the east of the Bahamas. Higher sea heights of 6-8 ft were to the southeast of a line from 26N65W to near 20N71W. Significantly lower seas of 0-2 ft were around the western parts of the Bahama island chain. Forecast is on track with current trend of the high pressure continuing to slide eastward through late tonight in response to a slowly-moving cold front that moved into the far northwestern waters yesterday evening, and as of 15/1800 utc, was passing through 31N70W in the Atlantic Ocean, to south Florida near 26N80W. The forward motion of the front is forecast to be increase this afternoon as a large area of Canadian high pressure builds southeastward, to the north of the front. The front will move across the northern and central waters today and tonight, and reach the southern waters on Friday where it will become stationary from 25N65W to the Straits of Fl by Friday evening. The large area of high pressure in its wake will encompass the entire basin. The associated tight pressure gradient between the high and the front will induce fresh to strong northerly flow over much of the northern and central waters beginning this afternoon, and into Friday. The northerly wind flow will become northeast-to- east on Friday and into Saturday, at which time the winds that are to the west of the Bahamas will veer around and be east-to- southeast, as the aforementioned high shifts eastward. A swath of strong northeast-to-east winds and seas in the 8-10 ft range are expected from 24N to 26N between 71W and the Bahamas Friday through Saturday afternoon, and then become confined to the far southern waters east of 75W Saturday evening through Monday. Similar winds are expected through the Windward Passage and adjacent waters. The front is forecast to be preceded by fresh to strong southerly winds, and seas in the 8-10 ft range. Seas of up to 11 ft are expected behind the front Friday night in zone AMZ115, and from 8 to 10 ft in zones AMZ111 and AMZ113. Seas subside in zones AMZ113 and AMZ115 on Monday, but will be slow in subsiding in the waters east of the Bahamas south of 26N where wavewatch and TAFB NWPS guidance indicate seas in the 8-11 ft range there. $$ .WARNINGS...Any changes impacting coastal NWS offices will be coordinated through AWIPS II Collaboration Chat, or by telephone: .GULF OF MEXICO... .GMZ017...W CENTRAL GULF FROM 22N TO 26N W OF 94W... GALE CONDITIONS POSSIBLE Sun. .GMZ023...SW GULF S OF 22N W OF 94W... GALE CONDITIONS POSSIBLE Sun night into Mon. .CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... None. .SW N ATLANTIC INCLUDING THE BAHAMAS... None. $$ *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.nhc.noaa.gov/marine $$ .Forecaster MT. National Hurricane Center.