000 AXNT20 KNHC 151812 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Fri Dec 15 2023 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 31N. The following information is based on satellite imagery, weather observations, radar and meteorological analysis. Based on 1200 UTC surface analysis and satellite imagery through 1700 UTC. ...SPECIAL FEATURES... Central Atlantic Residual Large Swell: The 1006 mb low located near 29.5N42W has weakened enough to allow winds in its vicinity to drop below gale force earlier this morning. However, residual large swell will maintain seas of 12 to 16 ft north of 25N between 36W and 31W through early this evening. Afterward, seas will subside below 12 ft by early Saturday morning. Please read the latest High Seas Forecast issued by the National Hurricane Center at https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for more detail. Western Atlantic and Florida Offshore Waters Gale Warning and Significant Swell: A cold front curves west-southwestward from the north-central Atlantic across 31N51W to 25N69W, then continues westward as a stationary front through the central Bahamas and Florida Straits. Widely scattered to scattered moderate convection is seen near and up to 200 nm north of this boundary. Coincided with a strong 1037 mb high pressure over South Carolina, tight gradient between these two features are maintaining near-gale to gale- force ENE winds from the southeast Florida offshore waters eastward across northwest Bahamas to near 74W. Combined with large NE swell, seas of 12 to 18 ft are persisting from 23N to 29N between 65W and the Florida east coast, except the waters within the Bahamas. A low pressure is forecast to form in the central Gulf of Mexico tonight and then track northeastward across central Florida into the western Atlantic on Saturday. This system will prolong near-gale to gale southerly winds from the southeast Florida and northwest Bahamas offshore waters northward to beyond 31N through Sunday afternoon. It will also sustain the 12 to 19 ft seas across the western Atlantic through Monday morning. Gulf of Mexico Gale Warning: The western end of a stationary front runs westward from the Florida Straits to the central Gulf. Combined with a strong 1037 mb high over South Carolina, tight gradient is causing near-gale to gale-force easterly winds and 12 to 16 ft seas across the eastern and north-central Gulf. These conditions will last through Saturday morning, then mainly concentrating at the northeastern Gulf Saturday afternoon and night. On both Gale Warnings, please read the latest High Seas and Offshore Waters Forecasts issued by the National Hurricane Center at https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and https://www.nhc.noaa.gov/marine/offshores.php for more details. ...MONSOON TROUGH/ITCZ... The monsoon trough remains across the Africa continent. An ITCZ extends westward from the southern Liberia coast across 06N30W to 03N49W. Scattered moderate convection is evident up to 150 nm south, and 80 nm north of the ITCZ. ...GULF OF MEXICO... Please read the SPECIAL FEATURES section about the ongoing Gale Warning. The western end of a stationary front runs westward from the Florida Straits to the central Gulf. Scattered showers and isolated thunderstorms are occurring near the front and northward to the Gulf States coasts. A surface trough extends northwestward from the central Bay of Campeche to near Corpus Christi, Texas. Widely scattered showers and isolated thunderstorms are found over the western Gulf. Outside the areas in the Gale Warning, fresh to strong easterly winds and 10 to 12 ft seas are present at the eastern and central Gulf. Gentle to moderate with locally fresh NNW to ENE winds and seas of 5 to 8 ft prevail for the western Gulf. For the forecast, strong high pressure building across the eastern United States will support strong winds over the northern and eastern Gulf today, with easterly gales offshore Florida through this afternoon. Low pressure will form in the southwestern Gulf tonight, then move northeastward Sat and inland across central and northern Florida Sat night. This will produce additional gales in the northeastern Gulf beginning tonight. Thunderstorms in association with this low will provide additional marine hazards Sat. A cold front will trail from the low, exiting the Gulf by Sun morning. Strong north winds will spill into the western Gulf Sat and Sat night behind the front. High pressure will then settle in over the area through early next week allowing for marine conditions to improve. Expect widespread showers and thunderstorms over most of the central and eastern Gulf through early Sun. ...CARIBBEAN SEA... A relatively fair trade-wind regime continues across the entire basin. Convergent trades are causing widely scattered showers over the northern half of the basin. Moderate to fresh with locally strong NE to E winds and 7 to 9 ft seas are present at the north- central and northwestern basin. Moderate to fresh NE to ENE winds and seas at 6 to 8 ft are noted at the southwestern basin north of eastern Panama and northwest Colombia. Gentle to moderate NE to E winds and seas of 3 to 6 ft prevail for the rest of the basin. For the forecast, strong high pressure north of the region across the eastern U.S. will support fresh to strong trade winds across most of the basin north of 15N into tonight, before the high pressure shifts eastward and weakens, causing winds to gradually diminish through late Sat. A cold front will move through the Yucatan Channel and into the northwestern basin Sat night into Sun, and reach from the Windward Passage to Costa Rica Mon night. Fresh to strong NW to N winds will follow this front. ...ATLANTIC OCEAN... Please read the SPECIAL FEATURES section at the beginning about the ongoing Gale Warning and Significant Swells. A cold front curves south-southwestward from the north-central Atlantic across 31N39W to 21N40W. A surface trough runs southward from a 1006 mb low with part of an occluded front near 29N42W to 21N44W. Scattered moderate convection is noted north of 24N between 35W and the cold front. Enhanced by an upper-level trough running southeastward from 31N40W to 15N30W, convergent trades are triggering similar convection from 13N to 24N between 22W and 35W. Refer to the Monsoon Trough/ITCZ section for additional convection in the Atlantic Basin. Besides the areas mentioned in the Special Features section at the beginning, fresh to strong NE to ENE winds and 8 to 12 ft seas exist north of 20N between 60W and the Florida coast/Bahamas. Fresh to strong southerly winds are present at the central Atlantic north of 22N between 36W and the cold front. For the eastern Atlantic, gentle to moderate with locally fresh NE to SE trades and 5 to 8 ft seas in moderate northeasterly swell are seen north of 08N between the Africa coast and 35W, including the Canary and Cabo Verde Islands. For the tropical western Atlantic, gentle with locally moderate ENE to ESE winds and 6 to 8 ft seas are evident from 05N to 20N between 35W and the Lesser Antilles. Light to gentle winds and 6 to 8 ft seas in mixed moderate swell prevail elsewhere in the Atlantic Basin. For the forecast, the cold front across the western Atlantic will sink southward before becoming fully stationary along 23N by Sat. The pressure gradient between the strong high pressure building north of the area and the front will result in near gale to gale force NE to E winds and high seas over the waters west of 70W and north of 24N into this afternoon. The front will then gradually dissipate Sat night through Sun, in advance of a Gulf of Mexico low pressure that will move northeastward across Florida Sat night. This low will move through the northwest Atlantic waters Sun into Sun night, when a large area of southerly gales will exist east of the low. Thunderstorms in association with this low will provide additional marine hazards this weekend. $$ Chan