AGXX40 KNHC 251803

Marine Weather Discussion
NWS National Hurricane Center Miami FL
203 PM EDT Mon Sep 25 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.


A thermal trough will develop each evening over the NW Yucatan Peninsula, move W-NW across the SW Gulf during the overnight hours and dissipate over 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 brief seas to 4 ft through early Tuesday. Elsewhere, weak high pressure will continue to support mainly gentle E-SE winds and 1-3 ft seas through Wednesday night. The flow increase slightly on Thursday with gentle to moderate NE-E winds across most of the waters N of 22N with seas of 3-4 ft. Similar marine conditions are expected on Friday.

The first cold front of the autumn season is depicted by model guidance to move across the northern and western Gulf waters on Thursday, and reach a position from northern Florida to the central and SW Gulf waters on Friday. Currently, it appears that this front will be rather shallow as it is expected to be followed by mainly moderate NE winds and seas of 1-3 ft, except for higher seas of 3-5 ft over the far western Gulf waters.


The trades have begun to increase across the eastern Caribbean as a ridge reaches the NE Caribbean, and a tropical wave moves across the area. Recent scatterometer data provided observations of gentle to locally moderate winds across the basin W of about 70W, and a little tighter E of 70W with moderate to locally fresh E-SE winds, with the exception of fresh to locally strong winds S of 15N between 64W-70W where an altimeter pass indicated seas to 8 ft. Seas are rather low W of 70W where 1-3 ft seas are occurring, and 4-5 ft seas across the remainder of the waters E of 70W. Slightly higher seas of 5-6 ft are over the tropical N Atlantic zones. The trades will expand westward in coverage towards much of the central Caribbean into late Wednesday morning before diminishing on Thursday. Winds are also expected to increase to 20-25 kt across the Gulf of Honduras during the evening and night hours beginning with this evening 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 towards the tropical N Atlantic waters and NE Caribbean Sea in the wake of Hurricane Maria exiting the forecast waters of the SW N Atlantic.

Long period northerly swell is expected to reach the waters E of the Leeward Island on Tuesday, and E of the Windward Islands on Wednesday, with building seas to 7-8 ft. The swell will decay on Thursday allowing for these seas to lower below 8 ft.


Hurricane Maria continues to moves slowly northward and away from the forecast region. At 25/1500 UTC...Maria is located near 31.2N 72.9W or about 275 nm SSE of Cape Hatteras, North Carolina moving N or 360 degrees at 6 kt. This general motion with some decrease in forward speed is expected through Tuesday night. On the forecast track, the center of Maria will move well east of the southeast coast of the United States during the next day or so. Maximum sustained winds are 70 kt with gusts to 85 kt, with a minimum central pressure of 963 mb. A recent ASCAT pass E of Maria indicates that the 20-33 kt winds cover the forecast waters N of 26N E of 70W-71W. Both altimeter data and buoy observations reveal that seas 12 ft or greater are occurring to the N of 26N between 65W-78W. Buoy 41047 located at 27.5N71.5W showed subsiding seas from 21 ft to 12 ft during the past 12-15 hours. Although Maria is soon on its way out of the basin, the main issue will be the associated swell that will continue to propagate across the forecast waters NE of the Bahamas through most of the forecast period. Wave model guidance suggests that the swell will slowly decay through the end of the week while the bulk of the swell group shifts to the NE portion of the basin. The seas of 8 ft along the entrances to the Bahamas passages will subside to less than 8 ft on Tuesday.

Of note, Swells generated by Maria are affecting portions 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. These swells are likely to cause life-threatening surf and rip current conditions. Otherwise, in the wake of Maria a surface trough 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 portion 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.


.WARNINGS...Any changes impacting coastal NWS offices will be coordinated through AWIPS II Collaboration Chat, or by telephone:



.AMZ113...ATLANTIC FROM 27N TO 31N BETWEEN 70W AND 77W... Hurricane Warning today. Tropical Storm Warning tonight into Tue.
.AMZ115...ATLANTIC FROM 27N TO 31N BETWEEN 65W AND 70W... Tropical Storm Warning today.


*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 GR. National Hurricane Center.