000 AGXX40 KNHC 181949 MIMATS Marine Weather Discussion NWS National Hurricane Center Miami FL 249 PM EST Mon Dec 18 2017 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... A frontal trough extends from the far western Florida panhandle to inland southern Louisiana and southwest to just offshore the Texas coast and southward to near 21N97W. The western periphery of Atlantic high pressure extends westward into the eastern part of the gulf. Latest buoy and partial Ascat observations show gentle to moderate anticyclonic flow over the eastern and central waters, while gentle E-SE flow is over the far western portion of the gulf. The observations along with recent altimeter show seas in the range of 3-5 ft, except for lower seas of 1-2 ft in the far NE and NW sections of the gulf. The trough will move inland by this evening. The warm and moist southerly flow across the cooler shelf waters resulted in areas of dense fog over the coastal sections of the NW and N central gulf overnight last night into this morning, with patches of dense fog along the coast of the NE gulf. The fog will slowly dissipate through this afternoon before returning tonight into Tuesday morning. Scattered showers and isolated thunderstorms are moving quickly northeastward along and to the NW of trough. Mainly moderate to fresh SE winds and seas of 3-5 ft will prevail to the E of the surface trough as high pressure becomes established just E of the Florida peninsula tonight through Tuesday. The lower seas of 2-3 ft will continue over the NE and NW parts of the gulf through Tuesday night. A weak cold front is forecast to reach the NW Gulf Wednesday and become situated over the northern portion of the basin from W to E as a stationary front on Thursday. No significant increase in winds and seas are expected with this front. However, this front will be the focus for shower and isolated thunderstorms. The front will then lift northward as a warm front Friday morning. During this Wednesday through Thursday night time frame a ridge axis will extend from Atlantic high pressure across the southern Gulf supporting light winds and seas of 1-3 ft. In the mid to long range, forecast models are in good agreement on a strong cold front reaching the NW gulf by Friday afternoon accompanied by showers and thunderstorms and followed by strong NE winds. After Friday, there are differences in the models with respect to the speed of forward progress of the front across the gulf. Will await for more model runs to see if there is consensus with the frontal motion across the gulf for Friday night through Saturday night. ...CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... High pressure to the N of the basin will remain sufficiently strong to support a tight pressure gradient over the central Caribbean through Tuesday night, capable of producing nocturnal Gale force winds north of the NE coast of Colombia. Fresh to strong E to NE winds are expected elsewhere over the central Caribbean, including the Windward Passage through this time frame. The high pressure will weaken through Wednesday and will shift SE which will diminish winds by about 3-5 kt over the central Caribbean, likely keeping winds just below gale force N of NE Colombia Wednesday and Thursday nights. The stronger winds early this week will be supporting seas to 14 ft during the mornings through Tuesday morning, with a large area of 8-12 ft extending across the central and SW Caribbean during that time. Elsewhere over the Caribbean, mainly moderate to locally fresh E to NE can be expected the next several days with generally dry conditions. Late this week forecast models are indicating that the high pressure will re-intensify, with the resultant tight pres gradient likely to induce nocturnal gales within about 60 nm of the coast of Colombia once again beginning Friday night. ...SW N ATLANTIC INCLUDING THE BAHAMAS... A dissipating cold frontal boundary extends from near 22N65W to just SE of the Bahamas, while a 1023 mb high pressure is near 30N68W with a ridge extending west-southwestward to central Florida. Latest buoy, ship and scatterometer data generally show light to moderate NE-E winds S of 25N E of 75W, except for a swath of fresh NE winds from 20N-23N E of 68W. E-SE gentle to moderate winds are elsewhere, except for SW-W gentle to moderate winds over the the northern portion W of 68W and W-NW gentle to moderate winds elsewhere. Light anticyclonic winds are around the high center. The buoy and altimeter data show seas of 4-6 ft E of the Bahamas, and 2-4 ft W of the Bahamas. Seas of 5-7 ft are noted S of 23N between 67W and the SE Bahamas. Fog is likely to form over the coastal near offshore waters of the far NW portion tonight and persist into Tuesday morning. An area of high pressure building east-southeastward over the western portion of the basin will become centered just east of central Florida by this evening and through Tuesday night. The gradient associated with this synoptic pattern will support gentle winds and seas of 3-5 ft N of 26N, with moderate to fresh NE winds S of 26N, and seas of 5-7 ft outside of the Bahamas, with seas possibly to 8 ft near the entrance to the Windward Passage. The high will weaken and shift southeastward through Wednesday in response to low pressure that moves offshore the U.S. E coast on Wednesday night, becoming centered to the E of the Bahamas near 26N69W early on Thursday and to E of the area near 25N63W by early on Friday. This will allow for fairly benign marine conditions across the waters S of 31N and N of 23N during this time frame. The only exception will be the cold front that will trail from aforementioned low pressure impacting the waters to the N and NE of the Bahamas Wednesday night through Thursday night. This cold front will be preceded by fresh to strong SW winds along with seas expected to be about 8-10 ft. These conditions will be rather short-lived as the cold front will be quick in sweeping across those waters. Meanwhile, S of 23N, the gradient along the periphery of the high will support moderate to fresh NE-E winds Wednesday through Thursday night, except for mainly fresh NE winds at the entrance to the Windward Passage. On Friday, high pressure surging southward along the Atlantic seaboard will be replaced by stronger high pressure ridging that will build south-southwestward to encompass the entire basin by Saturday night. This high will control the wind regime throughout providing similar wind conditions as presently being observed. Winds may once again increase to fresh to strong through and near the Windward Passage Saturday night. $$ .WARNINGS...Any changes impacting coastal NWS offices will be coordinated through AWIPS II Collaboration Chat, or by telephone: .GULF OF MEXICO... None. .CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... .AMZ031...CARIBBEAN FROM 11N TO 15N BETWEEN 72W AND 80W INCLUDING COLOMBIA BASIN... Gale Warning within 60 nm of cost of Colombia tonight and Tuesday night. .SW N ATLANTIC INCLUDING THE BAHAMAS... None. $$ *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 Aguirre. National Hurricane Center.