000 AXNT20 KNHC 181002 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 602 AM EDT TUE OCT 18 2016 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 1000 UTC. ...SPECIAL FEATURES... A middle to upper level trough is noted on water vapor imagery over the W Atlc, with a broad base reaching the southern Bahamas. The troughing aloft is supporting a 1005 mb low near 22N70W and a large area of scattered heavy showers and isolated tstms from 17N to 27N between 60W and 70W. The low is expected to slowly intensify as upper-level winds become more conducive, and a subtropical or tropical cyclone could form during the next day or two as the low moves northward or north-northwestward. There is a medium chance on this disturbance becoming a tropical cyclone during the next two days. ...TROPICAL WAVES... Tropical wave is in the eastern Atlantic extending from 07N to 15N with axis near 28W, expected to move W at 5-10 kt over the next 24 hours. The wave is in a region of unfavorable deep layer wind shear and CIRA LPW imagery from surface to 850 mb show pockets of dry air in the wave environment. Shallow moisture and divergent wind flow aloft support scattered showers from 08N to 13N between 25W and 29W. ...ITCZ/MONSOON TROUGH... The Monsoon Trough extends from the African coast near 12N16W to 06N22W to 04N41W. Aside from the convection associated with the tropical wave, widely scattered moderate convection is from 0N to 06N between 15W and 44W. ...DISCUSSION... GULF OF MEXICO... A broad surface ridge anchored by a 1018 mb high over Atlantic waters near 35N68W extends SW across the SE CONUS and into the Gulf where it provides gentle to moderate E to SE flow, except over the E Bay of Campeche where winds are from the NE. A surface trough extends from 27N89W to N of the Yucatan Peninsula near 22N89W with possible isolated showers within 60 nm either side of its axis. Middle to upper level ridging and strong dry air subsidence support stable and fair weather conditions. Gentle to moderate anticyclonic winds are expected to persist today, increasing slightly tonight into Wednesday. The next cold front is expected to emerge off the Texas and Louisiana coasts by Thursday night into early Friday. CARIBBEAN SEA... A broad and elongated middle level trough extends across the W Atlantic W of 60W and into the W Caribbean to a base over Panama coastal waters. This middle level feature along with abundant moisture in the region and favorable deep layer wind shear support scattered showers within 90 nm of the Central America coast as well as S of 18N between 68W and 82W. The extension of this trough to the upper levels with a base across the southern Bahamas and upper ridging across the E Caribbean generate diffluent flow just N of Hispaniola and Puerto Rico, thus supporting scattered to isolated showers in both islands and adjacent waters. Generally low pressure is across the basin at the surface with gentle to moderate S to SE winds in the E half of the Caribbean and light NE flow elsewhere W of 80W. Global models are suggesting cyclogenesis to occur N of Hispaniola and Puerto Rico today, which is already resulting in a disruption of the usual trade wind flow across the eastern Caribbean. As a low center organizes today through Wednesday and lifts generally northward, lingering weak surface troughing will extend across the Greater Antilles into the SW Caribbean through Saturday. ...HISPANIOLA... An upper trough over the W Atlantic waters with a base reaching the southern Bahamas and an upper ridge between 50W and 65W generate diffluent flow to the NNE of Hispaniola, thus supporting isolated showers in the across the island. The island is expected to remain within an area of weak surface troughing through Wednesday as cyclogenesis occurs across the SW North Atlc waters overnight through Wednesday. Showers are expected to increase tonight and continue through the middle of the week. ATLANTIC OCEAN... A middle to upper level trough is noted on water vapor imagery over the W Atlc, with a relatively broad base reaching the southern Bahamas. The troughing aloft is supporting a 1005 mb low near 22N70W and a large area of scattered heavy showers and isolated tstms from 17N to 27N between 60W and 70W. The low pressure is forecast to shift ENE this morning, then attempt to become better organized later today as it begins to lift northward. Strong easterly winds are expected to occur within 240 nm across northern portions of this low and a shearline that extends from 20N52W to 22N63W to the low center. See special features for further details. Farther east, the central Atlc is under the influence of a stationary front extending from the circulation associated with Tropical Storm Nicole well to the N of the discussion area. The front extends from 30N38W SW to 23N44W to 20N53W. Surface ridging is elsewhere in the eastern Atlantic. For additional information please visit http://www.hurricanes.gov/marine $$ RAMOS