000 AXNT20 KNHC 170427 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0605 UTC Wed Nov 17 2021 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 0000 UTC surface analysis and satellite imagery through 0415 UTC. ...MONSOON TROUGH/ITCZ... The monsoon trough remains mainly inland over Africa, reaching the Atlantic through the coast of Guinea near 12N16W to 09N19W. The ITCZ extends from 09N19W to 09N30W, then resumes west of a surface trough from 05N36W to 04N45W. The surface trough extends from 10N31W to 03N35W. Scattered moderate and isolated strong convection is noted from 01N to 13N and between 21W and 41W. GULF OF MEXICO... The influence of a 1026 mb high pressure system located between the Outer Banks and Bermuda extends into the Gulf of Mexico. A dry continental airmass continues to dominate the region, maintaining tranquil weather conditions. Fresh E-NE winds are present in the SE Gulf waters, including the Florida Straits, and in the NW Gulf, especially within 100 nm of southern Texas. Seas of 4-6 ft are occurring in the SE Gulf, including the Florida Straits, and NW Gulf. Moderate or weaker winds and 1-3 ft seas prevail elsewhere. For the forecast, strengthening high pressure has moved E into the Atlantic, leaving fresh E winds over the SE Gulf and Florida Straights into Thu. A cold front will move through the Gulf Thu night and Fri. Fresh to strong northerly winds and building seas will follow the front. Scattered showers and isolated thunderstorms are expected ahead of this front. CARIBBEAN SEA... A surface trough extends from central Cuba to just west of Swan Island near 18N85W. Another surface trough extends across the Gulf of Honduras from the Yucatan peninsula to E Honduras. Plenty tropical moisture associated with these boundaries and divergence aloft results in a large area of showers and isolated thunderstorms, mainly W of 80W and N of 14N. A few showers are also noted in the SW Caribbean Sea between SE Nicaragua and N Panama, likely enhanced by the eastern portion of the Pacific monsoon trough that enters the Caribbean near SE Costa Rica. Dry air dominates the rest of the basin, allowing for tranquil weather conditions. The pressure gradient between the 1026 mb high pressure system in the W Atlantic and lower pressures over South America allows fresh to strong trades to prevail across the south-central Caribbean Sea, with the strongest winds occurring off NW Colombia. A recent scatterometer satellite pass also detected a small area of near- gale trades within 90 nm of the Guajira peninsula of Colombia. Fresh trades are also noted in the north-central and NE Caribbean and N of 19N in the NW Caribbean. Seas of 6-9 ft are prevalent in the central, SW and E Caribbean Sea, with the highest seas occurring off NW Colombia. Seas of 3-6 ft are present elsewhere. For the forecast, a remnant stationary front has devolved into a trough that stretches from central Cuba to E of Belize. This trough will dissipate later tonight, and high pressure will strengthen and build south through the basin. Combined with lower pressure over South America, the pressure gradient will increase, thus winds will increase, to strong over portions of the central Carribbean and passages off the Greater Antilles through Thu. A cold front is forecast to approach the Yucatan Channel Fri. ATLANTIC OCEAN... A cold front enters the tropical Atlantic near 31N57W and extends to 27N67W, where it transitions into a dissipating stationary front that continues to the central Bahamas, where it becomes a surface trough that continues into the NW Caribbean Sea. Only a few showers are observed near the trough axis. A recent scatterometer satellite pass show fresh to strong NE winds within 200 nm to the north of the frontal boundary and trough axis, with the highest winds occurring S of 26N and W of 76W. A weak surface trough extends from 29N58W to 22N60W and no deep convection is present near the trough axis. Farther east, a 1013 mb low pressure is near 28N33W. A weakening surface trough associated with the low pressure extends from 30N30W to 26N28W to 20N41W. Scattered moderate convection is noted N of 26N and between 25W and 31W. The latest scatterometer satellite data indicate that fresh to strong cyclonic winds are present N of 26N and between 25W and 42W. Another surface trough extends from 15N46W to 09N49W and a few showers are seen on satellite imagery within 200 nm of the trough axis. The rest of the basin enjoys fairly tranquil weather conditions. Satellite-derived wind data depict fresh to strong NE winds off Western Sahara, mainly from 25N to 29N and E of 17W. Moderate or weaker winds prevail elsewhere in the basin. Seas of 4-8 ft are found W of 60W, while 6-10 ft seas are prevalent elsewhere in the tropical Atlantic. Peak seas of 10 ft are noted well NW and SW of the Cabo Verde Islands, near 26N38W and 11N32W, respectively. The Cumbre Vieja volcano, on the island of La Palma in the Canary Islands, has been erupting since 19 September 2021. Marine and aviation interests should monitor this ongoing situation by reading the Volcanic Ash Advisory issued by Meteo-France, at http://vaac.meteo.fr/volcanoes/la-palma/. For the forecast, the aforementioned cold front will continue to move east, and the stationary front will dissipate through Wed as high pressure builds over the western Atlantic. This will lead to increasing E winds and building seas S of about 28N Wed night through Thu night. Looking ahead, a cold front will move offshore NE Florida Thu night, then stall from Bermuda to central Cuba over the weekend. This front will be followed by fresh to strong northeast to east winds and building seas north and northeast of the Bahamas. $$ DELGADO