000 AXNT20 KNHC 150600 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 200 AM EDT Sat Apr 15 2017 Tropical Weather Discussion for North America, Central America Gulf of Mexico, Caribbean Sea, northern sections of South America, and Atlantic Ocean to the African coast from the Equator to 32N. The following information is based on satellite imagery, weather observations, radar and meteorological analysis. Based on 0000 UTC surface analysis and satellite imagery through 0545 UTC. ...SPECIAL FEATURE... Low pressure over the southwest north Atlantic near 23N66W will dissipate Saturday night as it moves northeast. The remnants of this low will then merge with a frontal system over the central Atlantic. Strong high pressure building behind the cold front will tighten the gradient, thus supporting gale force winds of 35 kt N of 30N between 52W and 56W Saturday night...increasing to 40 kt on Sunday. Please refer to the high seas forecast under AWIPS/WMO headers MIAHSFAT2/FZNT02 KNHC for more details. ...ITCZ/MONSOON TROUGH... The Monsoon Trough extends across the western Africa coast near 07N12W to 05N15W. The Intertropical Convergence Zone continues from 05N15W to 02N30W to 0N50W. Scattered moderate convection and isolated tstms are within 240 nm either side of the ITCZ. ...DISCUSSION... ...THE GULF OF MEXICO... Broad surface high pressure anchored by a 1029 mb high over NW Atlc waters continue to extend a ridge axis SW across the Florida peninsula and Gulf of Mexico. This is supporting moderate to fresh easterly-southeasterly flow across the basin according to latest surface and scatterometer data. Water vapor imagery show middle to upper level dry air across the western basin where a short-wave trough is noted. Diffluent flow east of the short-wave trough aloft along with shallow moisture being advected from the Caribbean support scattered showers and isolated tstms over the NE Gulf. Showers are also occurring in the Yucatan peninsula where a thermal trough extends from 22N88W to 16N92W. No major changes expected through Sunday. CARIBBEAN SEA... The pressure gradient between strong high pressure over the west Atlantic and low pressure over northern Colombia continue to support fresh to strong winds from 10N to 12N between 74W and 77W. This synoptic pattern is expected to continue over the weekend. Water Vapor and CIRA LPW imagery show very stable conditions over the western Caribbean while SW winds advects moisture from South America to the eastern basin. Moisture is also being advected from the tropical Atlc waters to the NE Caribbean by SE flow associated with an area of low pressure in the SW Atlc waters. All this moisture along with middle level troughing in the region may induce the development of showers mainly over the NE basin...including Puerto Rico, the Virgin Islands and the Leeward Islands. Shower activity for this region and Hispaniola may increase Sunday as the tail of a cold front pass to the N of the Islands. ...HISPANIOLA... Low and upper level dry air across the region support fair weather conditions tonight. However, the remnants of an area of low pressure over the SW Atlc will merge with a cold front. The tail of this front will pass just north of the Island Sat through Sun supporting the development of showers. ATLANTIC OCEAN... Low pressure of 1012 mb resides near 22N66W with a surface trough that extends from the low to 20N70W. This area of low pressure is being supported by a broad middle to upper level trough. The low is forecast to dissipate by Saturday night as it moves E-NE. The remnants of the low will then merge with a cold front N of the area and gale force winds are expected to develop due to strong high pressure building behind the front. See the special features section for further details. Otherwise, a cold front over NE Atlc waters enters the discussion area from 30N26W to 21N34W with scattered to isolated showers within 90 nm either side of the boundary. For additional information please visit http://www.hurricanes.gov/marine $$ Ramos