000 AGXX40 KNHC 130800 RRA MIMATS Marine Weather Discussion NWS National Hurricane Center Miami FL 300 AM EST TUE DEC 13 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. 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 28N83W. 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 0238Z 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 western gulf north of about 21N and west of 90W. Seas of 3-5 ft in a mixed east and southeast swell are confined to the far southern portion of the eastern gulf in the entrance of the Yucatan channel. Models are in very good agreement that the high pressure across the gulf will weaken through Wednesday. 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 on Wednesday. The forecast continues on track with the next cold front to move into the northern gulf late this afternoon or evening, reach from northern Florida southwest to 26N90W, and to near Brownsville by Wednesday evening, and to the Straits of Florida Thursday afternoon. Northerly flow in the mostly moderate range will follow in behind the front. Some pockets of winds in the fresh range are expected mainly over the western gulf. 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 feet, except for higher seas of 6-8 ft in the western gulf on Saturday. ...CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... MODEL PREFERENCE: Global model consensus. High confidence. The 0234 Ascat pass showed fresh to strong northeast winds between 68W and 79W and also from 12N to 17N between 70W and 79W. The Ascat pass again noted strong northeast to east winds over the Gulf of Venezuela, and within 90 nm of the coast of Colombia. Seas are in the 8-10 ft range over the central Caribbean, except for 10-11 ft seas within 90 nm of the coast of Colombia. 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 western Caribbean south of 20N and west of 79W. 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 some on Saturday. ...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. A surface trough extends from near 31N75W southwest to near 29N79W. The 0238Z Ascat pass showed strong south to southwest winds east of the trough to near 73W. A small patch of fresh east winds is between the southeast Bahamas and Haiti. Buoys observations reveal seas are in the 8-10 ft range east of the Bahamas, and 5-7 ft elsewhere except for lower seas of 1-3 ft within and west of the Bahama island chain. The trough will weaken as reaches the eastern portion zone AMZ113 this afternoon. Scattered showers and thunderstorms with possible gusty winds ahead of the trough will shift to zone AMZ115 on tonight and Wednesday as this activity is being sustained by a an upper level trough located over the northwest waters. A cold front currently analyzed just northwest of the area will drop southward and become stationary just north of the forecast waters this morning, then move north in the afternoon as a warm front as low pressure forms along the North Carolina coast. This low is forecast to track northeastward through tonight pushing a trailing cold front southeastward across the far northern waters Wednesday and Wednesday night, then across zones AMZ111, AMZ113 and AMZ115 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 the northern waters Thursday night into Friday. This flow then veers around to the northeast to east on Friday and into Saturday at which time the wind west of the Bahamas veer around to the east to southeast. 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 or 12 ft are expected behind the front. $$ .WARNINGS...Any changes impacting coastal NWS offices will be coordinated through AWIPS II Collaboration Chat, or by telephone: .GULF OF MEXICO... None. .CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... None. .SW N ATLANTIC INCLUDING THE BAHAMAS... None. $$ *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.hurricanes.gov/marine $$ .Forecaster Aguirre. National Hurricane Center.