853 AXNT20 KNHC 182143 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0005 UTC Thu Oct 19 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 2100 UTC. ...SPECIAL FEATURES... Newly formed Tropical Storm Tammy is centered near 13.0N 51.7W at 18/2100 UTC or 540 nm E of the Windward Islands, moving W at 20 kt. Estimated minimum central pressure is 1007 mb. Maximum sustained wind speed is 35 kt with gusts to 45 kt. Peak seas are currently around 15 ft. Numerous moderate isolated strong convection is noted from 06N to 15N between 44W and 54W, and extending from 13N to 15N between 33W and 44W. A westward motion at a slower forward speed is expected through Thursday. A turn toward the west-northwest is forecast by Thursday night, followed by a turn toward the northwest Friday night or Saturday. On the forecast track, the center of Tammy will move near or over the Leeward Islands Friday and Saturday. Gradual strengthening is forecast during the next couple of days. Swells generated by Tammy will begin affecting portions of the Lesser Antilles on Thursday. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office. Heavy rains from Tammy will begin to affect the northern Windward and Leeward Islands on Friday, spreading into the British and U.S. Virgin Islands and Puerto Rico over the weekend. This rainfall may produce isolated flash and urban flooding, along with isolated mudslides in areas of higher terrain. Please read the latest HIGH SEAS FORECAST issued by the National Hurricane Center at website - https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and the latest Tammy NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov for more details. ...MONSOON TROUGH/ITCZ... The monsoon trough reaches the Atlantic through the coast of Senegal 13N17W to 10N20W to 03N39W. The ITCZ extends from 03N39W to NE of the coast of Brazil near 02N49W. Numerous moderate isolated strong convection is noted within 270 nm either side of the monsoon trough between 19W and 30W, and from 02N to 07N between 32W and 38W. ...GULF OF MEXICO... A few related areas of high pressure across the SE United states with a ridge extending across the northern Gulf of Mexico coastal plain. Gentle to moderate anticyclonic flow is found across the basin waters N of 26N, with moderate to locally fresh easterly flow S of 26N. Seas are 1-3 ft across the NW half of the basin, and 3-5 ft across the SE half. Otherwise, a weak surface trough is analyzed in the western Bay of Campeche offshore Veracruz with little fanfare. For the forecast, high pressure will continue to dominate the Gulf waters through Thu night. Gentle to moderate anticyclonic winds will prevail through Thu night. A frontal system will bring fresh winds to the NE Gulf Fri and Fri night. Benign conditions will then return over the weekend as high pressure builds back in. ...CARIBBEAN SEA... Please see the SPECIAL FEATURES section above for more details on newly formed Tropical Storm Tammy. A stationary front extends from eastern Cuba to NE Honduras. Scattered moderate to strong convection is within 90 nm NW of the front, and S of the front to 11N between Jamaica and Nicaragua, as well as across the tip of eastern Cuba. Fresh to strong NE winds are noted S of 20N and west of the front per an earlier ASCAT scatterometer pass, along with seas of 4-7 ft. Fresh to strong trades are noted in the S-central Caribbean along with 4-6 ft seas. Mainly moderate trades and 3-5 ft seas prevail elsewhere SE of the front, except 1-3 ft in the SW Caribbean. For the forecast, Tammy will move to 13.1N 53.7W Thu morning, 13.5N 55.9W Thu afternoon, 14.1N 58.2W Fri morning, 15.0N 60.2W Fri afternoon, 15.9N 61.7W Sat morning, and 17.5N 62.7W Sat afternoon. Tammy will change little in intensity as it moves to near 21.4N 63.4W Sun afternoon. A stationary front extends from eastern Cuba to NE Honduras. The front should remain in place through tonight before dissipating on Thu. Fresh to locally strong NE winds and seas of 8 ft will persist over the northwest Caribbean W of the front through tonight as high pressure builds over the area. ...ATLANTIC OCEAN... Please see the SPECIAL FEATURES section above for more details on newly formed Tropical Storm Tammy. A stationary front remains draped across the western Atlantic from 31N63W to across the SE Bahamas to eastern Cuba. Scattered moderate to isolated strong convection is noted within 60-120 nm either side of the front. Winds across the same area of the convection W of the front are fresh to strong. Mainly moderate NE winds are elsewhere W of the front, along with 3-5 ft seas. A surface trough extends from 31N58W to N of the Mona Passage near 20N65W. Numerous moderate isolated strong convection is noted within 90-150 nm NW of the trough N of 22N. An upper-level low east of the Lesser Antilles is producing scattered to isolated strong convection from 15N to 24N between 52W and 61W. Fresh to locally strong easterly winds are within this convection, along with 7-10 ft seas. Farther east, 1021 mb high pressure is analyzed near 30N45W. Mainly light to gentle winds are under the ridge from 27N to 31N between the Canary Islands and 55W. Mainly moderate trades prevail elsewhere outside of the influence of Tammy. Seas are 5-7 ft across the remainder of the open waters, except 4-5 ft S of 20N and E of 30W, and within 240 nm NE of the coast of NE South America. For the forecast W of 55W, Tammy will move to 13.1N 53.7W Thu morning, 13.5N 55.9W Thu afternoon, 14.1N 58.2W Fri morning, 15.0N 60.2W Fri afternoon, 15.9N 61.7W Sat morning, and 17.5N 62.7W Sat afternoon. Tammy will change little in intensity as it moves to near 21.4N 63.4W Sun afternoon. A stationary front extends from 31N63W to eastern Cuba. The front will remain in place before dissipating Thu. High pressure will build over the area in the wake of the front. The next frontal system will move offshore the southeastern United States Fri night. Fresh to strong winds and rough seas are forecast north of 27N Fri night through Sat night with this system. $$ Lewitsky