000 AXNT20 KNHC 192332 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 632 PM EST Tue Dec 19 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 1800 UTC surface analysis and satellite imagery through 2315 UTC. ...SPECIAL FEATURES... ...Gale Warning in the Caribbean Sea... Pulsing nocturnal easterly winds to gale-force are expected again near the coast of Colombia during the overnight tonight and early morning hours on Wednesday, particularly from 11N to 13N between 74W and 76W. Expect sea heights to range from 10 to 14 ft within the area of gale force winds, with a larger area of 8-11 ft seas extending into the west-central Caribbean. Wind will diminish below gale-force by Wednesday morning. Thereafter, strong to near-gale force winds will persist in the area each night this week. Please read the latest NHC High Seas Forecast under AWIPS/WMO headers MIAHSFAT2/FZNT02 KNHC for more details. ...ITCZ/MONSOON TROUGH... The monsoon trough enters the Atlantic Ocean through Sierra Leone and continues to 04N28W. The ITCZ extends from 04N28W to northeast Brazil near 02N51W. Scattered moderate isolated strong convection is noted from 2N-4N between 6W-11W. Similar convection is near 3.5N14.5W. Scattered moderate convection is within about 30 nm on either side of the trough between 19W-23W, and within 60 nm N of the ITCZ between 35W-38W. ...DISCUSSION... ...GULF OF MEXICO... A ridge dominates the Gulf, anchored by a 1023 mb high centered over the Florida Big Bend. Scatterometer and surface data depict gentle to moderate anticyclonic flow across the basin, with seas generally below 5 ft. Patchy dense fog will occur again tonight into the early morning hours along the Gulf coast from the western Florida Panhandle all the way westward to across most of the coast of Texas. The visibility is expected to drop below one mile. Moist air, in a southerly wind flow, will move across the cooler sea surface to generate this dense fog over the bays and nearshore coastal waters. Dense fog advisories are in effect. The high pressure will move eastward over the next 24 hours. A weak cold front will reach the coast of Texas Wed, and stall across the northern Gulf by Thursday, then move north as a warm front late Thursday. A stronger cold front will reach the NW Gulf on Friday, move SE and reach from the western Florida Panhandle to the SW Gulf near Veracruz, Mexico by late Saturday. Fresh southerly return flow is expected across the western Gulf ahead of the front. Fresh to strong northerly winds and building seas will follow the front. ...CARIBBEAN SEA... Please refer to the Special Features section for details about the gale warning near the coast of Colombia. The most recent scatterometer data indicated fresh to strong winds across the basin roughly between 70W and 83W. An altimeter pass indicated seas of up to 14 ft over the southwest Caribbean in association with the strong to minimal gale force winds. Fresh to strong NE to E winds are expected in the lee of Cuba and across the Windward Passage through Wed night. Patches of low-level moisture embedded in the trade wind flow are moving across the area producing isolated to scattered passing showers. Broad mid to upper-level anticyclonic wind flow and strong subsidence dominates the entire Caribbean Sea producing generally dry conditions. However, the trade winds will continue to carry isolated to scattered showers. ...HISPANIOLA... As previously mentioned, broad mid to upper-level anticyclonic wind flow and strong subsidence dominates the entire Caribbean Sea supporting mostly stable conditions. However, low-topped trade wind showers will continue to affect Hispaniola from time to time tonight and Wednesday. ...ATLANTIC OCEAN... A deep layer trough in the eastern Atlantic is supporting a stationary frontal boundary that extends from 31N39W to 21N60W. This front will dissipate over the next 24 hours. Mainly low- level clouds with isolated showers are along the front. A ridge is noted in the wake on the front, with a 1023 mb high pressure center located just E of the NW Bahamas near 26N75W. East of the stationary front, the Azores high dominates the remainder of the eastern Atlantic. A second cold front is approaching from the north, and now crosses Bermuda to near 30.5N80W. The high pressure over the western Atlantic is forecast to dissipate as the the second cold front reaches from 31N58W to the NW Bahamas by Wednesday morning, then the front will stall and begin to dissipate. Another cold front will reach the waters E of northern Florida by Thursday morning and extend from 31N58W to 27N65W to along 27N to near the NW Bahamas. Moisture associated with this front may reach south Florida on Friday. For additional information please visit http://www.hurricanes.gov/marine $$ GR