000 AXNT20 KNHC 181800 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 100 PM EST Mon Dec 18 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 1200 UTC surface analysis and satellite imagery through 1715 UTC. ...SPECIAL FEATURES... ...Gale Warning in the Caribbean Sea... Please read the latest NHC High Seas Forecast under AWIPS/WMO headers MIAHSFAT2/FZNT02 KNHC for more details. The gale-force wind conditions will start. They will last for periods of 12 hours or so, and then the wind speeds will slow down to less than gale-force. Pulsing nocturnal NE-to-E winds to gale-force are expected again from tonight into the midday hours of tomorrow Tuesday. The gale- force conditions are expected from 11N to 13N between 74W and 77W, off the coast of Colombia. Expect sea heights to range from 10 feet to 15 feet. ...ITCZ/MONSOON TROUGH... The monsoon trough passes through the coastal sections of Sierra Leone near 07N12W, to 05N21W. The ITCZ continues from 05N21W to 04N33W and 04N43W. Precipitation: widely scattered moderate to isolated strong within 120 nm to 180 nm on either side of 11N33W 07N35W 05N46W. Isolated moderate also from 07N southward from 30W eastward. An upper level trough is along 25N34W 18N37W 15N42W 11N48W 09N54W 07N58W. Broken-to-overcast multilayered clouds and other possible rainshowers are to the SE of the line from 24N16W to 24N30W 13N40W, and 07N57W. A surface trough is along 44W/45W from the Equator to 08N. Precipitation: isolated moderate from 10N southward between 40W and 50W. ...DISCUSSION... ...THE GULF OF MEXICO... A surface trough extends from the SW corner of Louisiana to the coast of the Deep South of Texas, to the coast of Mexico near 23N98W. Low clouds, and possible rain and fog, within 120 nm of the coast from 90W westward. A surface ridge extends from 29N75W in the Atlantic Ocean, across central Florida, to 25N91W in the central Gulf of Mexico. ...CURRENT CONDITIONS AND WEATHER, FOR THE OFFSHORE OIL PLATFORM SITES, THAT ARE IN THE AREA WHOSE BOUNDARIES ARE FROM 27N NORTHWARD AND FROM 88W WESTWARD... IFR/MVFR conditions, mist and haze, at the platforms. CURRENT CONDITIONS AND WEATHER, FOR THE COASTAL PLAINS OF THE U.S.A., FROM THE DEEP SOUTH OF TEXAS TO FLORIDA... TEXAS: LIFR/MVFR, light rain, and mist in the coastal plains and inland areas. LOUISIANA: IFR/MVFR, with smaller areas of LIFR, light rain and fog, from Hammond and Baton Rouge southward. MISSISSIPPI: LIFR/IFR, with rain and mist, from Natchez-to- Hattiesburg southward. ALABAMA: IFR/LIFR,and light rain and mist, from Evergreen-to-Dothan southward. FLORIDA: IFR/MVFR, with smaller areas of LIFR, and drizzle/mist. LIFR from the Pensacola metropolitan area to Marianna. MVFR/IFR from Cross City to Tallahassee. ...THE CARIBBEAN SEA... A middle level anticyclonic circulation center is near SE Cuba. An upper level ridge extends from Puerto Rico to Hispaniola to the Cayman Islands, and beyond NW Cuba. Comparatively drier air in subsidence, also spans the entire Caribbean Sea. Rainshowers are possible in areas of broken low level clouds, to the south of the line from 20N64W to 17N74W, to SE Cuba. Please refer to the SPECIAL FEATURES section for more details about the gale-force winds for the coast of Colombia during the next two days. 24-hour rainfall totals in inches, for the period that ended at 18/1200 UTC, according to the PAN AMERICAN TEMPERATURE AND PRECIPITATION TABLES...MIATPTPAN/SXCA01 KNHC...are: 0.65 in Curacao, 0.12 in Guadeloupe, 0.04 in St. Thomas in the Virgin Islands and in Trinidad, and 0.01 in San Juan in Puerto Rico. ...HISPANIOLA... Upper level NW wind flow is moving across Hispaniola. NE-to-E wind flow from 400 mb to 800 mb also is present across the island. SURFACE OBSERVATIONS...HAITI, in Port-au-Prince: VFR. in the DOMINICAN REPUBLIC: Puerto Plata: MVFR. ceiling 1800 feet. Santiago: VFR, for the most recent observation. earlier rainshowers. VFR at the rest of observation sites. The GFS MODEL forecast for 250 mb shows that Hispaniola will be to the east of a ridge. Expect N-to-NW wind flow during the next 48 hours. The GFS MODEL forecast for 500 mb shows that NE wind flow will move across the area during the next 2 days. An anticyclonic circulation center will move from the waters that are between the Bahamas and Cuba, toward NW Cuba. The GFS MODEL forecast for 700 mb shows that NE wind flow will move across the area. An anticyclonic circulation center will be off the coast of SE Florida, in the Straits of Florida. ...THE ATLANTIC OCEAN... A deep layer trough in the central Atlantic is supporting a cold front that passes through 32N42W to 26N50W and 22N62W. The cold front is dissipating from 22N62W to 21N72W in the SE Bahamas. Isolated moderate within 180 nm on either side of the line that passes through 32N37W to 28N40W and 24N44W. Rainshowers are possible from 25N northward between 40W and 60W, and within 60 nm to 120 nm on either side of the line 22N60W 22N70W 25N74W 30N73W. A 1026 mb high pressure center is near 30N68W. Surface anticyclonic wind flow covers the Atlantic Ocean to the NW of the 32N42W 21N72W cold front. A surface ridge passes through 32N25W to 28N31W and to 25N44W. For additional information please visit http://www.hurricanes.gov/marine $$ MT