000 AGXX40 KNHC 261856 MIMATS Marine Weather Discussion NWS National Hurricane Center Miami FL 256 PM EDT Tue Sep 26 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 thermal trough will develop each evening in the NW Yucatan Peninsula, move W-NW across the SW Gulf during the overnight hours and dissipate in the SW Gulf waters by late each morning. Expect the trough to be accompanied by a surge of moderate to locally fresh winds that shift from NE to SE along with possible brief seas to 4 ft through early this morning. Weak high pressure will continue to support mainly gentle E-SE winds and 1-3 ft seas through Wednesday night. The flow increases slightly on Thursday in parts of the western Gulf where mainly moderate NE-E winds are expected along with seas of 3-4 ft. Gentle to moderate NE-E winds are expected elsewhere on Thursday along with seas of 2-3 ft. The first cold front of the autumn season is depicted by model guidance to move across the northern and western Gulf waters on Thursday, reach a position from northern Florida to the central and SW Gulf waters on Friday, then stall late Friday through Saturday night. Guidance indicates that this front will be rather shallow. The moderate NE-E winds expected in parts of the western Gulf on Thursday then will begin to expand N and S Friday through Saturday night as a result of the tightening of the gradient between the front and the high pressure that builds southward behind it. The latest guidance from both the GFS and ECMWF agree on this scenario. Seas of about 4-6 ft are expected behind the front mainly in zones GMZ017 and GMZ011. It is possible that the sea heights may be slightly higher if the high pressure that is behind the front becomes stronger. Elsewhere N of the front: the winds are expected to be mainly gentle NE-E with seas of 2-3 ft. Winds S and SE of the front are expected to be gentle to moderate SE-S in direction with seas of 2-3 ft. Isolated showers and thunderstorms may be possible with the front. ...CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... Trades increase across much of the eastern and central Caribbean as a central Atlantic Ocean ridge builds southwestward toward the eastern Caribbean Sea in the wake of a tropical wave that is currently along 71W/72W. A patch of fresh to strong E winds is S of 15N between 70W and 74W. Seas of 6-8 ft are with the fresh to strong winds. Seas elsewhere E of 70W are in the 4-6 ft range. Seas W of 70W are lower in the 1-3 ft range. Seas of 5-6 ft are in the tropical N Atlantic zones. The trades will expand westward in coverage toward much of the central Caribbean into late Wednesday morning before diminishing on Thursday. E-SE winds of 20-25 kt will continue to pulse across the Gulf of Honduras during the evening and nighttime hours through early Thursday. Seas are forecast to build to 6-7 ft during the period of strongest winds. The pressure gradient will continue to tighten some across the eastern and central Caribbean Sea, and will begin to tighten across the tropical N Atlantic waters later today as central Atlantic high pressure builds southwestward toward the tropical N Atlantic waters and NE Caribbean Sea in the wake of Hurricane Maria. A trough that is in the western Caribbean Sea along 83W will move slowly westward toward the Yucatan Peninsula through Thursday accompanied by scattered to numerous showers and thunderstorms with gusty winds and rough seas. Long period NE swell is expected to reach the waters E of the Leeward Islands late tonight and propagate across parts of the eastern tropical N Atlantic zones beginning on Wednesday, producing seas to 8 ft. The swell is forecast by wave model guidance to decay on Thursday allowing for these seas to subside to less than 8 ft. ...SW N ATLANTIC INCLUDING THE BAHAMAS... Hurricane Maria has moved to just N of the area near 33.6N 73.1W or 145 nm SE of Cape Hatteras North Carolina as of 2 PM EDT. It is moving N or 360 degrees at 6 kt, with maximum sustained winds of 65 kt with gusts to 80 kt. The pressure as of 2 PM EDT is 974 mb. This general motion with some decrease in forward speed is expected through tonight. The center of Maria will move well E of the southeast coast of the United States during the next couple of days. The 1516 UTC ASCAT pass shows that the wind speeds ranging from 20 kt to 33 kt cover the forecast waters from 29N northward between 70W and 78W. Altimeter data show sea heights of 12 feet or greater are to the N of 30N near 67W. Associated swell will continue to propagate across the forecast waters NE of the Bahamas through most of the forecast period, even with Maria pulling away from the basin more and more through tonight. Wave model guidance suggests that the swell will decay slowly through the end of the week while the bulk of the swell group shifts to the NE portion of the basin. Of note: Swells generated by Maria are affecting parts of the coast of the southeastern United States and Bermuda, and will be increasing along the Mid-Atlantic and southern New England coasts today. Swells also continue to affect Puerto Rico, the northern coast of Hispaniola, the Turks and Caicos Islands, and the Bahamas. It is likely that these swells may cause life- threatening surf and rip current conditions. A surface trough in the wake of Maria will extend from the N-central forecast waters SW to near the Central Bahamas through Wednesday night, then become diffuse Thursday as central Atlantic high pressure builds westward across the eastern part of the area. Scattered showers and thunderstorms are possible with the trough. On Friday, the ridge is forecast to extend E to W near 26N as a weak cold front approaches the SE United States coast, and far NW waters. Latest model signals suggest that the front will most likely wash out over or very near the far NW waters on Saturday as continental high pressure builds southward and strengthens across it. This will lead to a a gradual increase of NE winds over the NW waters on Saturday along with building seas. $$ .WARNINGS...Any changes impacting coastal NWS offices will be coordinated through AWIPS II Collaboration Chat, or by telephone: .GULF OF MEXICO... None. .CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... None. .SW N ATLANTIC INCLUDING THE BAHAMAS... None. $$ *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 MT. National Hurricane Center.