000 AGXX40 KNHC 250747 MIMATS Marine Weather Discussion NWS National Hurricane Center Miami FL 347 AM EDT Sat Mar 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 ...GULF OF MEXICO... Strong high pressure extending from the Mid-Atlantic U.S. coast southwestward over the northern waters will slide eastward through Sunday as a cold front approaches the far northwest gulf. The tight gradient currently inducing fresh to strong southerly winds over the northwest and north-central waters will relax today allowing for these winds to diminish to mainly moderate winds through the tonight, and moderate to locally fresh winds Sunday through early next week. Seas of 7-9 ft in the northwest gulf will subside to around 4-7 ft today. The front will stall along the Texas coast this afternoon. The 0226Z Ascat pass revealed a swath of strong east winds over the southeast gulf waters south of 25N and east of 86W, including the Straits of Florida. Seas associated with these winds are in the 6-8 ft range. These winds are forecast to diminish to 15-20 kt this afternoon, with seas lowering to 4-6 ft. Deep layer moisture associated with the upper trough currently moving over eastern Texas, and that supports the cold front that will approach the far northwest gulf this weekend, is streaming eastward across portions of the north-central and northeast gulf. This moisture and upper level energy with the trough is expected to bring scattered shower and thunderstorm activity over those portions of the gulf through Sunday morning. Some of this activity may contain brief gusty winds. A thermal trough will move off the Yucatan and over the eastern Bay of Campeche each night the next several nights. Fresh to strong winds will be possible with the trough each night, then mainly fresh winds thereafter. ...CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... The fresh to strong northeast to east winds across the northwest and north-central Caribbean waters have diminished to mainly moderate to locally fresh winds per the 0226Z Ascat pass and recent buoy observations there. These winds are forecast to remain in the moderate range through Tuesday, then become east to southeast moderate to locally strong winds on Wednesday. A narrow swath of north to northeast strong winds is noted in the Ascat pass just south of the eastern part of Hispaniola from 18.5N to 17N and between 69.5W and 71W. A weaker than normal pressure pattern will persist over the central and eastern Caribbean the next several days, as low pressure begins to develop north of Hispaniola and slowly tracks north to northeast. This pressure pattern will result in mainly gentle to moderate trades over the Caribbean. A new set of large northerly swell with seas of 8-10 ft has just recently started to propagate across the northwest portion of zone AMZ127. This swell is forecast to reach into zone AMZ027 by late tonight, however the swell will be decaying at that time with seas down to 8 ft, and to less than 8 ft by late on Sunday afternoon. A very well pronounced upper trough in water vapor imagery stretches from the southeastern Bahamas to Jamaica, and continues further southwest to Costa Rica. Divergence aloft associated with a northeast to southwest oriented jet stream branch east of the trough in combination with a moist and unstable atmospheric environment in place over much of the eastern Caribbean is triggering off scattered showers and isolated thunderstorms east of about 71W. This pattern will change little through early next week. Expect pockets of heavy rain with some of the showers and thunderstorms to affect the waters around Puerto Rico, the northern Leeward Islands, and eastern Hispaniola. ...SW N ATLANTIC INCLUDING THE BAHAMAS... The stationary front earlier analyzed 24N has weakened, and as of 06Z is analyzed as a dissipating boundary east of 68W, and as a shear line west of 68W. Strong high pressure is present north of the front and shear line. The main marine issues over the next few days will be related to the near future development of surface low pressure, and the impacts to the winds and combined seas due to the tight pressure gradient between it and the strong high pressure. Global models have been consistently suggesting that low pressure will form over the far southeast waters in the general area of just north of the Mona Passage and the eastern part of the Dominican Republic. As a matter of fact, latest satellite imagery and surface observations from "MDPC" on the eastern tip of the Dominican Republic indicate that weak low pressure may forming near 19N68W along a surface trough situated to the southeast of the aforementioned stationary front, and southeast of an upper low located just north of eastern Cuba. The ensuing result of the tight gradient is observed as strong to near gale northeast to east winds over a large swath of area east of the Bahamas from near 22N to 29N as depicted in the latest Ascat data. Seas with these winds are in the range of 10-15 ft. Model guidance all point to the low attaining momentum through the next 24 to 36 hours as it drifts from just north of Hispaniola to our northeastern waters. The strong to near gale force winds are forecast to increase to gale force within a portion of the aforementioned swath this afternoon. This swath of winds will gradually shift translate over the eastern portion of the basin through Monday with northeast to east winds of 30-40 kt gale force. These winds will then shift northeast of zone AMZ115 early on Tuesday, with strong to near gale force north to northeast winds lingering in the northeast portion of that zone, with large seas of 10-15 ft. These winds then shift east of that zone Tuesday night as the low accelerates eastward leaving fresh to strong northerly winds in the far northeast portion. Relatively weak high pressure is forecast to move south to over the western half of the basin on Tuesday. The associated gradient will bring light to gentle anticyclonic flow over the western portion through Wednesday, while the central section of the basin will see moderate northerly flow, and the eastern half north of 22N will be under moderate to fresh northerly flow except in the northeast portion as mentioned above for Tuesday night. On Wednesday, the northeast portion will see winds diminishing to the moderate range. Northerly winds will be lighter south of 22N Tuesday through Wednesday, with gentle to moderate flow northwest to north flow expected there. Aside from the 10-15 ft seas in the northeast portion of zone AMZ115 on Tuesday as stated earlier, north to northeast swell will be slow in decaying over the eastern half of the basin Tuesday through Wednesday, with seas of 8-12 ft. $$ .WARNINGS...Any changes impacting coastal NWS offices will be coordinated through AWIPS II Collaboration Chat, or by telephone: .GULF OF MEXICO... None. .CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... None. .SW N ATLANTIC INCLUDING THE BAHAMAS... .AMZ113...ATLANTIC FROM 27N TO 31N BETWEEN 70W AND 77W... Gale Warning Sun. GALE CONDITIONS POSSIBLE Sun night. .AMZ115...ATLANTIC FROM 27N TO 31N BETWEEN 65W AND 70W... Gale Warning Sun. GALE CONDITIONS POSSIBLE Sun night into Mon night. .AMZ119...ATLANTIC FROM 22N TO 27N E OF BAHAMAS TO 70W... Gale Warning Sun. GALE CONDITIONS POSSIBLE Sun night. .AMZ121...ATLANTIC FROM 22N TO 27N BETWEEN 65W AND 70W... Gale Warning today through Sun. GALE CONDITIONS POSSIBLE Sun night. $$ *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.