000 AXNT20 KNHC 112346 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0005 UTC Fri Nov 12 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 1800 UTC surface analysis and satellite imagery through 2315 UTC. ...MONSOON TROUGH/ITCZ... A monsoon trough exits the African coast near the Guinea-Sierra Leone border at 09N13W through a 1011 mb low near 08N18W to another 1011 mb low near 06N26W and to 07N28W, where latest scatterometer data indicates that it transitions to the ITCZ to 08N39W to 08N46W and to just north of Suriname. Numerous moderate to isolated strong convection is noted within 180 nm south of the trough and lows between 16W-29W, and within 180 nm south of the ITCZ between 32W-36W. Scattered moderate convection is within 120 nm north of the trough and low near 08N18W between 17W-25W, and within 60 nm north of the ITCZ between 28W-32W. Similar convection is noted from 08N to 14N east of 17W to inland western Africa. ...GULF OF MEXICO... An outflow boundary extends from just offshore southeastern Louisiana as of 21Z to near 26N95W. A cold front has moved into the NW Gulf, and as of 21Z it is analyzed from south-central Louisiana to inland southern Texas near Corpus Christi. Satellite imagery shows a few showers and thunderstorms along and just south of the outflow boundary between 92W-95W. Scattered showers and isolated thunderstorms are noted over the southeastern Gulf waters and Straits of Florida, where a very moist and unstable air mass is present. Latest ASCAT data indicates fresh to locally strong winds associated to the shower and thunderstorm activity over the NW Gulf. Recent altimeter data passes reveal seas of 3-4 ft throughout, except for slightly higher seas near the shower and thunderstorms over the NW Gulf. Otherwise, relatively weak high pressure across the area is supporting light to gentle winds over the basin. For the forecast, the cold front that is presently over the NW Gulf will move southward then stall and dissipate across the Yucatan Channel through Sat. A reinforcing front will follow closely behind the first front, entering the northern Gulf area Fri night, then move southeast of the Gulf through Sun. Looking ahead, high pressure building across the northern Gulf Sun, will strengthen into Mon, supporting fresh winds over the southeast and south-central Gulf. The high pressure will shift east of the region Tue. ...CARIBBEAN SEA... A surface trough is coupling with divergent winds aloft to trigger scattered showers and thunderstorms across the western half of the basin, including the waters near western Cuba. The western end of a shear line continues to produce similar conditions over the northern coast of central Cuba. Recent satellite scatterometer and altimeter data passes depict moderate to fresh easterly trades and seas of 5-6 ft over the south- central section of the sea and 4-5 ft over the northwestern section of the sea. Northeast to east gentle to moderate trades, with seas at 2-4 ft prevail over the remainder of the basin. For the forecast, a cold front will stall over the Yucatan Channel Sat, then dissipate. A slight stronger front will move into the NW Gulf Sun then stall from eastern Cuba to the Gulf of Honduras. Looking ahead, this second front will shift eastward into the Windward Passage through Mon as reinforcing high pressure builds north of the area behind a third front moving through the W Atlantic. This pattern will support fresh northeast winds across parts of the northwestern Caribbean Mon through Tue. ...ATLANTIC OCEAN... A weakening cold front curves southwestward from the north- central Atlantic across 31N44W to near 24N58W, then continues westward as a shear line across the southeastern Bahamas to the northern coast of central Cuba. Scattered showers and thunderstorms are within 180 nm east of front north of 29N. Ample moisture that is ahead of an upper trough is observed over the western part of the area. The upper-level moisture is advancing eastward around an upper ridge that is also situated over the western half of the area. Numerous showers and thunderstorms are quickly expanding in coverage south of 30N and west of 70W. Farther east, an upper-level trough located near 24N20W is generating scattered showers along the Guinea-Bissau/Senegal/Mauritania coast and adjacent waters. Refer to the Monsoon Trough/ITCZ section of additional convection in the basin. North to east-northeast gentle to moderate winds and locally fresh winds and seas of 7-10 ft are present near and N of the cold front/shear line, between 46W and the Florida coast/Bahamas. Moderate to fresh northeast trades and seas of 5-7 ft are found near the Canary Islands from 23N to 28N between the NW African coast and 21W. A 1018 mb high over the central Atlantic near 26N47W is promoting light to gentle winds and seas of 4 5 ft north of 20N between 21W-46W. Gentle to moderate north- northeast and east- northeast trades, with seas of 4-5 ft are present from 08N to 20N between the African coast and Lesser Antilles. Gentle to moderate with locally fresh E to SE trades and seas of 4-6 ft prevail for the remainder of the basin. For the forecast west of 65W, high pressure between Bermuda and NE Florida will shift east today ahead of a cold front that will move off the northeastern Florida coast by early Fri. The front will stall and weaken from roughly 31N72W to central Cuba by early Sat. Afterwards, a second front will move off the northeast Florida coast later on Sat, then merge with the first front before stalling from roughly Bermuda to central Cuba Sun. Looking ahead, a third and stronger front will move off the northeast Florida coast late Sun night, eventually overtaking the aforementioned stalled front, and then reach from 27N65W to the Windward Passage by late Mon and Tue. The Cumbre Vieja volcano, on the island of La Palma in the Canary Islands, has been erupting since 19 September 2021. Medium ash concentration is in the western vicinity of the volcano. Marine and aviation interests should monitor this ongoing situation by reading the latest Volcanic Ash Advisory issued by Meteo-France at website http://vaac.meteo.fr/volcanoes /la-palma/. $$ Aguirre