000 AXNT20 KNHC 150940 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 540 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 0600 UTC surface analysis and satellite imagery through 0930 UTC. ...SPECIAL FEATURE... Low pressure over the southwest north Atlantic near 22N66W will dissipate tonight as it moves northeast. The remnants of this low will then merge with a newly formed center of low pressure near 28N57W, which will be dragged by a cold front racing towards 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 05N10W to 02N15W. The Intertropical Convergence Zone continues from 02N15W to 01N30W to 0N50W. Scattered moderate convection and isolated tstms are within 120 nm either side of the ITCZ and S of the Monsoon Trough. ...DISCUSSION... ...THE GULF OF MEXICO... Broad surface high pressure anchored by a 1030 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 and a short-wave trough over the north-central gulf. Diffluent flow east of the short-wave trough aloft along with shallow moisture being advected from the SW N Atlc support isolated showers over the NE basin. Showers are also occurring off the western Yucatan peninsula where a thermal trough extends from 22N89W to 18N91W. No major changes expected through Monday morning. CARIBBEAN SEA... The pressure gradient between strong high pressure over the west Atlantic and lower 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 continue to show very stable conditions over the western Caribbean while SW winds aloft 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 across 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 late today and Sunday as the tail of a cold front pass to the N of the Islands. ...HISPANIOLA... Low and upper level dry air across the area continue to support fair weather this morning. However, the remnants of an area of low pressure over the SW Atlc will merge with a cold front, which tail will pass just north of the Island Sat through Sun supporting the development of showers. ATLANTIC OCEAN... The 1012 mb center of low pressure near 22N66W continues to weaken this morning while a new center of low pressure developed NE of it near 28N57W. The former low will dissipate tonight as it moves E-NE to merge with the new area of low pressure. These areas of low pressure are being supported by a broad middle to upper level trough, which also supports a cold front that extends from 30N61W to 28N65W. The cold front is forecast to merge with the area of low pressure tonight and gale force winds will develop as strong high pressure builds behind the front. See the special features section for further details. Otherwise, a cold front continues to weaken over NE Atlc waters from 30N25W to 22N32W with isolated showers within 90 nm either side of the boundary. For additional information please visit http://www.hurricanes.gov/marine $$ Ramos