161 AXNT20 KNHC 172233 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0005 UTC Mon Dec 18 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 1800 UTC surface analysis and satellite imagery through 2230 UTC. ..SPECIAL FEATURES... Western Atlantic Storm Warning: A cold front extends south-southwestward from a 990 mb near 33N80W to central Cuba and into the Caribbean. A warm front extends from the low to near 22N67W. A tight pressure gradient between a ridge extending SW from strong high pressure of 1042 mb near 43N53W and the area of low pressure is supporting storm force winds over thewestern Atlantic waters. Seas in this area are in excess of 20 ft. A large area of 12 ft seas has been generated by this system, with seas greater than 12 ft over the waters N of 25N and W of 66W. The low will rapidly track further northeastward along the Atlantic coast tonight, with the area of storm and gale force winds shifting N of the area. The area of 12 ft seas will shift eastward, merging with another area of large swell generated from gales over the central Atlantic. Gulf of Mexico Gale Warning: The same system generating the storm force winds over the western Atlantic waters is also supporting gales over the NE Gulf of Mexico. Seas in this area are in the 10-13 ft range. The low will shift further from the area tonight, with winds and seas decreasing over the NE Gulf. Winds will diminish below gale force, and seas will subside below 12 ft, tonight. Central Atlantic Gale Warning: Strong high pressure will build over the north central Atlantic. This will tighten the pressure gradient between this area of high pressure and a surface trough, which will support gale force winds over the discussion waters N of 27N between 45W and 55W tonight. Seas will build over these waters, with seas greater than 12 ft spreading southward and westward, merging with the area of 12 ft seas generated from the storm force winds over the western Atlantic waters through the middle of the week. The area of high pressure will shift further from the area, loosening the pressure gradient across the central Atlantic waters diminishing winds below gale force Tue. Please read the latest NWS 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 on both Gale Warnings. ...MONSOON TROUGH/ITCZ... The monsoon trough enters the Atlantic near 08N13W, then extends westward to near 08N17W. The ITCZ continues westward from 08N17W to 08N24W to 03N35W to 05N44W. Scattered moderate convection is noted within 120 nm of the ITCZ/monsoon trough. ...GULF OF MEXICO... Please read the Special Features section above about an ongoing Gale Warning. A cold front extends from the Florida panhandle to the Yucatan Peninsula. Outside the Gale Warning area, fresh to strong NW to NNW winds and seas of 8 to 11 ft prevail E of 90W. Gentle to moderate winds are W of 90W. Seas of 8 to 10 ft are between 90W and 94W, with seas of 4-7 ft W of 94W. For the forecast, winds and seas will decrease through Mon. High pressure will then be in control of the weather pattern across the Gulf waters the remainder of the work- week. By mid-week, strengthening high pressure N of the region will bring fresh to strong NE winds across the eastern Gulf, including the Straits of Florida. ...CARIBBEAN SEA... A cold front extends from Cuba to NE Honduras. Fresh to strong winds prevail W of 81W. Moderate to fresh winds are E of 75W. Light to gentle winds are elsewhere. Seas are in the 6-8 ft range W of 83W, reaching 9 ft in the Yucatan channel. Seas of 3-6 ft are elsewhere. For the forecast, the cold front will reach from eastern Cuba to 10N80W Mon afternoon, and from Hispaniola near 20N70W to 10N79W Tue afternoon. Fresh to strong northerly winds and seas of 8 to 9 ft are expected in the wake of the front. Strong high pressure over the Atlantic will continue to produce fresh to locally strong winds over the NE Caribbean through tonight. ...ATLANTIC OCEAN... Please read the Special Features section for more on the Storm and Gale Warnings. A stationary front extends southwestward from a 1014 mb low near 31N38W to north of Puerto Rico, then continues as a warm front to a 990 mb storm center near 33N80W. A cold front extends from that low to central Cuba then into the NW Caribbean. Scattered moderate and isolated strong convection is N of 20N between 38W and 48W as well as over the Atlantic waters W of 66W. Outside of the warning areas, fresh to strong winds prevail N of 20N and W of 50W as well as N of 25N between 40W and 50W. Fresh to locally strong winds are found N of 20N and E of 25W. Gentle to moderate winds prevail elsewhere. Outside of the area of 12 ft seas, seas of 8-11 ft prevail N of 20N and W of 50W as well as N of 25N between 40W and 50W. Elsewhere, seas are in the 5-8 ft range. For the forecast W of 55W, the storm force winds are forecast to diminish to gale force by this evening. Behind the front, NW gales will also develop N of 27N early this evening. Scattered to numerous strong thunderstorms are ahead of the low and the cold front forecast to reach from 31N69W to eastern Cuba by Mon afternoon, and from 31N68W to the N coast of Hispaniola near 20N70W by Tue afternoon. Then, the front will then move slowly E into the middle of the week as high pressure builds behind it. Gales ahead of the front will persist through Mon night while gale behind the front are expected through late tonight. $$ AL