000 AXNT20 KNHC 222201 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0005 UTC Sun Nov 22 2020 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 2200 UTC. ...TROPICAL WAVES... A tropical wave extends from near Grand Cayman Island to western Panama, moving westward at 10 to 15 kt. The wave combined with a middle level inverted trough is producing scattered moderate convection over the western Caribbean, mainly off Nicaragua and in the Gulf of Honduras. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the coast of Guinea near 11N15W to 09N20W. The ITCZ continues from 09N20W to 03N50W. A few showers are observed from 08N-10N between 23W-25W, and from 05N- 07N between 40W-43W. GULF OF MEXICO... A weak surface ridge extends north of the Gulf from the 1023 mb high pressure over north Georgia to the Lower Mississippi Valley. The high pressure is weakening ahead of a cold front approaching the area from the northwest. A surface trough extends off the western coast of the Yucatan peninsula, reaching into the northwest Gulf. This pattern is supporting gentle to moderate NE to E winds across the Gulf currently. Seas are 2 to 4 ft except for a tongue of 4 to 6 ft seas reaching from the Yucatan Channel into the central Gulf due to southerly swell moving northward from the northwest Caribbean Sea. No significant shower or thunderstorm activity is noted at this time across the Gulf of Mexico. For the forecast, the cold front will reach the northern Gulf tonight into Mon and quickly dissipate. High pressure will follow the front. Fresh southerly return flow will set up over the western Gulf Mon night through Tue night ahead of the next cold front forecast to reach the northern Gulf late on Wed, then stall and lift northward Thu. Looking ahead, a third and stronger cold front is expected to move across the Gulf waters during the upcoming weekend. CARIBBEAN SEA... Divergence aloft on the southeast side of a broad mid to upper level trough north of the area is interacting with the tropical wave moving into the western Caribbean to support scattered showers and thunderstorms over much of the western Caribbean and south of Haiti. Scatterometer satellite data from 15 UTC and recent buoy observations indicate mostly gentle trade wind flow across the basin, except for moderate trade winds over the eastern Caribbean, due to the influence of the subtropical ridge to the north. These moderate trade winds are supporting 5 to 7 ft seas over the eastern Caribbean. Larger seas, of 7 to 9 ft, are impacting the Atlantic waters east of the Leeward and Windward Islands, and possibly the adjacent Atlantic passages. Lingering SE swell is supporting 4 to 6 ft combined seas in the northwest Caribbean. Seas are 3 to 5 ft elsewhere. For the forecast, fresh easterly winds and seas in the 8-9 ft range will continue to impact the waters east of the Lesser Antilles through Mon night. Building high pressure north of the area will bring an increase in winds and seas across the south- central Caribbean Tue through Thu. Fresh to strong NE winds are expected across the Windward passage Tue night through Thu night. ATLANTIC OCEAN... East of 65W, a mid to upper level low centered near 27N70W is supporting a surface trough reaching from the Turks and Caicos Islands to near 30N66W. The surface trough is well defined in buoy observations and earlier scatterometer satellite data. Moderate to fresh SE winds and a few showers are possible within 300 nm east of the trough axis. Seas reach 6 to 8 ft in this area as well with a component of NE swell. Moderate NE to E winds are noted west of the trough axis, with 5 to 7 ft seas in open waters. For the forecast, there is a slight chance that the surface trough could briefly develop into a subtropical storm while it moves northeastward during the next day or two before it merges with a cold front on Tue. The front will move into the NW waters on Mon and progress through the area through the middle of week while gradually weakening. Farther east, recent scatterometer data showed a pair of troughs east of 40W and south of the Azores, with 15 to 20 kt winds between each trough and ridging farther norther. The ridging is supporting generally moderate trade winds elsewhere. $$ Christensen