000 AGXX40 KNHC 140801 MIMATS Marine Weather Discussion NWS National Hurricane Center Miami FL 300 AM EST WED DEC 14 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. High confidence, except average confidence western gulf zones Sunday and Sunday night. The 06Z surface analysis shows the western periphery of Atlantic high pressure extending westward to eastern gulf waters where a 1020 mb high center is analyzed at 26N86W. As a result, the general flow pattern is anticyclonic across the forecast waters. Latest buoy observations reveal gentle to moderate southerly flow throughout, except for light and variable winds near the high center. An Ascat pass from 0356Z last night depicted similar observations. The observations from the buoys along with recent altimeter data show seas in the 2-3 ft range, except for slightly higher seas of 3-4 ft in the northwest gulf zone GMZ011. Seas of 3-5 ft in a southeast swell are confined to the far southern portion of the eastern gulf in the entrance of the Yucatan channel. Enhanced IR satellite imagery shows patches of mostly dense fog with sharply reduced visibilities according to surface observations and simulated GOES-R low stratus/fog IFR probabilities along and just offshore the coastal plains of the northwest and north/central gulf, and along some portions of the w central Florida coast. The fog is forecast to linger through part of the morning before it dissipates. Models are in very good agreement that the high pressure across the gulf will weaken through tonight. This will relax the gradient further allowing for seas to be in the range of 1-3 ft. The seas of 3-5 ft in the entrance to the Yucatan channel are forecast to lower to 2-3 ft tonight. The aforementioned cold front will drop southeast across the northwest and central waters this morning, and quickly reach a position from northeast southwest to 26N90W, and to near southern Texas/northeast Mexico border by early this evening, and to the far southeast gulf and Straits of Florida Thursday. Mostly moderate northerly flow with some pockets of fresh flow will follow in behind the front through Thursday. The high pressure in the wake of this front will quickly shift eastward through Friday night. The winds will respond by veering around to an east to southeast direction over the central and eastern gulf, and to more of southerly direction in the western portion where they increase to the strong range on Saturday. Seas behind the front are expected to build to the range of 3-4 ft, except for higher seas of 6-8 ft in the western gulf on Saturday. The strong return flow in the western gulf will be in anticipation of the next cold front to approach the area. Models are suggesting, although there are some difference in timing. UKMET and GFS are similar with timing of front moving through eastern Texas and approaching the northwest gulf late Saturday night, while the ECMWF is a bit faster in taking the front to just offshore the Texas and southwest Louisiana coasts at that time. Will favor a blend of models for now for the long term periods of the forecast. Model ensemble and probabilities indicate possibe gale conditions in northerly flow behind the front as it moves across the western gulf zones Sunday and Sunday night. Will highlight possible gale conditions for Sunday in the far western portion of zones GMZ017 and in the far southwest portion of GMZ023 on Sunday night. Seas are expected to build to around 12 ft with these conditions, but mat be higher if the gale winds are stronger and longer in duration. ...CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... MODEL PREFERENCE: Global model consensus. High confidence. The 0214Z Ascat pass showed fresh to strong northeast winds between 68W and 79W and also from 11N to 13N between 70W and 76W. Seas are in the 8-9 ft range within the area of fresh to strong northeast winds. Both buoy and Ascat data show moderate to fresh northeast to east winds elsewhere, with seas in the 5-7 ft range, except for 4-5 ft west of 82W and 5-6 ft seas in the windward passage. Latest Satellite imagery is revealing scattered showers and isolated thunderstorms over the northwest Caribbean north of 15N west of 85W, and south of 20N and west of 80W. This activity is within a large area of deep tropical moisture advecting northwestward around the western periphery of broad upper level high pressure anchored near 16N73W. This activity should gradually diminish through this evening. As Atlantic high pressure slides eastward through Wednesday, the tight pressure gradient producing the fresh to strong trades will slacken allowing for these winds to diminish to mostly fresh trades over the central Caribbean, with the exception of strong northeast to east trades in the far southern part of the central Caribbean including near the coast of Colombia. By Friday, the trades over the central Caribbean diminish further to the fresh category, however northeast winds increase to the fresh category over much of the western Caribbean. On Saturday, a large and strong area of high pressure is forecast to surge eastward across the western Atlantic. This will result in a tightening of the pressure gradient once again ushering in another increase of the trades to the strong category across much of the central Caribbean zones, and also through the windward passage and vicinity waters. Seas will build to around 10 ft with these trades, but stay below 8 ft in the windward passage on Saturday. Strong northeast to east trades across the Atlantic zones AMZ127, AMZ027 and the northern half of zone AMZ037 as seen in the 0054Z Ascat pass from last night will diminish to fresh trades on Wednesday, and remain with little change through Friday night before increasing some on Saturday. Seas of 8-10 ft with these trades are forecast to subside to 6-8 ft on Wednesday and to 5-7 ft on Thursday, with little change through Friday night then build to 10 ft Saturday night, and continue at that maximum into Sunday. ...SW N ATLANTIC INCLUDING THE BAHAMAS... MODEL PREFERENCE: Global model consensus. High confidence. Strong high pressure present east of the Bahamas continues to shift eastward. The 0214Z Ascat pass showed strong south to southwest winds east of the trough to near 73W. Buoy observations reveal seas are in the 7-9 ft range east of the Bahamas, and 4-6 ft elsewhere except for lower seas of 1-3 ft within and west of the Bahama island chain. The high pressure will shift eastward through late tonight in response to a frontal boundary currently north of the area near 33N that will push southward across the far northern waters through tonight as the attendant low pressure just offshore the South Carolina quickly tracks northeastward. The front will sweep across the northeast part of the forecast waters Thursday and zone AMZ115 Thursday night. The southern segment of the front will be weaker as it passes across zones AMZ111, AMZ119 and AMZ121 Thursday through Friday. The front will then move east of 65W late on Friday. The front will be followed by a large and strong area of high pressure that 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 Thursday night into Friday. This flow then will veer around to the northeast to east on Friday and into Saturday at which time the winds west of the Bahamas veer around to the east to southeast, with strong southeast winds are expected northwest of the Bahamas. These winds lift north of the basin on Sunday. The front is forecast to be preceded by fresh to strong southerly winds, and seas possibly up to 8 ft. Seas of up to 11 ft are expected behind the front Friday night in zine AMZ115, and around 9 or 10 ft in zones AMZ111 and AMZ113. $$ .WARNINGS...Any changes impacting coastal NWS offices will be coordinated through AWIPS II Collaboration Chat, or by telephone: .GULF OF MEXICO... .GMZ017...W CENTRAL GULF FROM 22N TO 26N W OF 94W... GALE CONDITIONS POSSIBLE W OF 96W Sunday. .GMZ023...SW GULF S OF 22N W OF 94W... GALE CONDITIONS POSSIBLE W OF 95W Sunday night. .CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... None. .SW N ATLANTIC INCLUDING THE BAHAMAS... None. $$ *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.hurricanes.gov/marine $$ .Forecaster Aguirre. National Hurricane Center.