000 AGXX40 KNHC 110801 MIMATS Marine Weather Discussion NWS National Hurricane Center Miami FL 401 AM EDT Fri Aug 11 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... Wind and sea conditions over the SW Gulf continue to subside in the wake of recent tropical cyclone Franklin. The SE swell that induced seas up to 8-9 ft over portions of the far western NW Gulf has abated allowing for seas there to lower to around 5-7 ft per latest buoy data. Elsewhere, latest buoy and scatterometer data indicate mainly gentle to moderate anticyclonic flow around a 1020 mb high center analyzed near 28N87.5W at 06Z. Moderate to fresh northeast to east winds are confined to the eastern Bay of Campeche where a tighter gradient exists there arising from the Yucatan Peninsula thermal trough that has moved to just offshore that peninsula. The buoys show seas in the range of 1-3 ft east of a line from southeast Louisiana to NW Cuba, and seas of 3-5 ft west of this same line except for higher seas of 5-7 ft as mentioned earlier over a portion of the far western section of the NW Gulf, and seas of 4-6 ft over the SW Gulf and Bay of Campeche. The high pressure center is forecast to drift southeastward through the weekend, then transition to a ridge roughly along 27N/28N early next week. The rather weak gradient associated with the ridge will allow for seas over the central and western sections of the basin will lower to 1-3 ft this weekend and change little into next week. A thermal trough will develop over the Yucatan Peninsula during the late afternoons and evenings, move slowly westward during the overnight hours, and dissipate over the SW Gulf by late each morning. A surge of fresh to locally strong winds with seas of 3-5 ft will accompany this trough. ...CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... The pressure gradient over the area will support fresh to locally strong nocturnal trades over the far south-central portions of the Caribbean south of about 13N to include portions of the coasts of Colombia and Venezuela and Gulf of Venezuela through late Sunday night. The gradient is forecast to tighten during Tuesday as the sub-tropical Atlantic ridge builds westward. This will allow for these winds to expand northward across the central Caribbean to near 17N. Seas produced by these winds are expected to be in the 8-10 ft range by Tuesday, with the highest of the seas near 12N76W. A tropical wave has recently entered the eastern portion of the central Caribbean. The wave is void of convection as it is under subsidence and related dry air aloft. It is moving westward at 10-15 kt. This wave will move across the rest of the central Caribbean through Saturday afternoon, and across the western Caribbean through Sunday night. Models generally suggest that northeast trades will increase across much of the Tropical N Atlantic forecast zones beginning late on Monday as the gradient tightens between an approaching central Atlantic tropical wave and the sub-tropical Atlantic ridge that builds westward. The trades are forecast to reach the strong range across these waters north of about 14N, and gradually expand westward to the Lesser Antilles on Tuesday, with wave model guidance indicating that associated seas will build to maximum values of 8-9 ft on Tuesday. ...SW N ATLANTIC INCLUDING THE BAHAMAS... An ill-defined surface is tilted northeast to southwest from near 25N61W to low pressure of 1015 mb at 22N63W and to just north of the Leeward Islands. Deep convection increased during the overnight hours within 150 nm of the low in the NE and SE quadrants. A tight gradient between the low and central Atlantic high pressure is bringing fresh to strong E to SE winds to within 120 nm of the low in the NE quadrant with seas of 6-8 ft. The trough and low is forecast to move northwest today, then in a more general northward motion over the weekend as it approaches the far north-central portion of the area. While there are still model differences regarding exact track and intensity of this system and as to whether it becomes a definitive low pressure feature, the overall depiction in the global model fields is for the trough or low to track around the western periphery of the sub- tropical Atlantic ridge through early next week staying to the east and northeast of the Bahamas. Unless it becomes a definitive low pressure system by itself, it appears based on the latest model guidance that the tight gradient of fresh to strong winds should remain to the northeast and east of the combined trough/low or weak low. These winds are expected to induce combined seas of around 8 or 9 ft, but may possibly be higher if the system where to strengthen under a forecasted marginally conducive atmospheric environment. Once the aforementioned feature departs the forecast waters late Sunday night or early on Monday, central Atlantic ridging will then build westward across the area through Tuesday night near 28N. The associated gradient is expected to allow for gentle to moderate east to southeast winds south of the ridge, and mainly gentle south to southwest winds north of the ridge. The exceptions will be between the SE Bahamas and Hispaniola where east winds there will pulse to strong in the late afternoons and evenings and over zone AMZ127 on Monday and Tuesday when winds increase to moderate to fresh. Fresh to strong northeast to east winds are expected across the approach to the Windward Passage early next week. Seas are forecast to be 4-5 ft south of the ridge and 3-4 ft north of the ridge. Seas are expected to build to 5-7 ft over zone AMZ127 early next week. $$ .WARNINGS...Any changes impacting coastal NWS offices will be coordinated through AWIPS II Collaboration Chat, or by telephone: .GULF OF MEXICO... None. .CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... None. .SW N ATLANTIC INCLUDING THE BAHAMAS... None. $$ *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.nhc.noaa.gov/marine $$ .Forecaster Aguirre. National Hurricane Center.