000 AXNT20 KNHC 111756 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Mon Sep 11 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 1200 UTC surface analysis and satellite imagery through 1750 UTC. ...SPECIAL FEATURES... Major Hurricane Lee is centered near 23.5N 63.5W at 11/1500 UTC or 320 nm N of the Northern Leeward Islands, moving to the northwest at 7 kt. Estimated minimum central pressure is 948 mb. Maximum sustained wind speed is 105 kt with gusts to 130 kt. Recent satellite imagery and aircraft data have indicated concentric eyewalls, with ongoing eyewall replacement cycles. Numerous moderate to scattered strong convection is forming the northern lobe of an inner eyewall within 45 nm in the northern semicircle of Lee. Scattered moderate convection is evident within 90 nm in the southeast semicircle of the hurricane, and clusters of thunderstorms between 150 to 180 nm in the northern semicircle. As The wave field continues to expand from Lee as it makes its turn northward. Seas in excess of 12 ft reach as far as 330 nm in the northern semicircle, and 270 nm in the southern semicircle. Surrounding seas associated with Lee will bring dangerous surf and life-threatening rip currents to portions of the northern Leeward Islands, the Virgin Islands, Puerto Rico, Hispaniola, the Turks and Caicos Islands, the Bahamas, Bermuda, and most of the U.S East Coast through much of the week. Please consult products from your local weather office. Tropical Storm Margot is centered near 26.1N 40.0W at 11/1500 UTC or 1080 nm NW of the Cabo Verde Islands, moving to the north at 9 kt. Estimated minimum central pressure is 993 mb. Maximum sustained wind speed is 60 kt with gusts to 75 kt. Scattered moderate to isolated strong convection is evident within 90 nm of the center of Margot, and seas in excess of 12 ft are noted within 180 nm of the center. Margot may strengthen slightly as it continues to move northward over the next couple of days. 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 NHC Forecast/Advisory and Public Advisory on Lee and Margot at www.hurricanes.gov for more details. ...TROPICAL WAVES... A far eastern Atlantic tropical wave is along 22W, to the south of 19N, and moving west around 5 to 10 kt. Scattered moderate isolated strong convection is from 08N to 13N between 22W and 27W. Environmental conditions appear conducive for gradual development of this system during the latter part of this week, and a tropical depression could form by next weekend as it moves westward to west-northwestward over the central tropical Atlantic. There is a low chance of tropical cyclone formation during the next two days and a medium chance from 3 to 7 days. An eastern Atlantic tropical wave is analyzed along 31W, south of 16N, moving westward around 5 to 10 kt. A 1014 mb low pressure center (Invest AL97) is near 13N 31W. Scattered moderate isolated strong convection is noted from 12N to 13N between 32W and 34W. This system is forecast to merge with the aforementioned tropical wave to the east in a couple of days. As a result, there is a low chance of tropical cyclone formation during the next 7 days. ...MONSOON TROUGH/ITCZ... A monsoon trough enters the Atlantic near over the coast of Senegal near 15N17W then reaches southwestward through the low (Invest AL97) near 13N31W to 14N35W. The ITCZ reaches from 11N53W to 10N61W. Convection is described above in the tropical wave sections. ...GULF OF MEXICO... A surface trough reaches from off the mouth of the Mississippi River in the north-central Gulf to off Tampico, Mexico in the west-central Gulf. Farther east, a weak ridge extends from the western Atlantic into the northeastern Gulf. This pattern is supporting only light to gentle breezes and slight seas across the basin. No significant shower or thunderstorm activity is evident. For the forecast, the weak ridge will dominate the Gulf waters throughout the forecast period supporting light to gentle winds. Scattered thunderstorms can be expected across the western Yucatan and eastern Bay of Campeche each late afternoon and evening. ...CARIBBEAN SEA... Please read the Special Features section about large swell generated by Major Hurricane Lee impacting the northeast Caribbean islands. Divergent flow aloft is assisting a few clusters of thunderstorms over the western Caribbean, south of the Isle of Youth, over parts of the Gulf of Honduras, and just east of Providencia Island. The subtropical ridge that is normally present north of the basin is being disrupted in part by Hurricane Lee. This pattern is supporting gentle to moderate breezes. Swell from Lee is penetrating the Mona and Anegada Passages, with combined seas of 6 to 8 ft in the passages, with plumes of 4 to 6 ft swell south of the passages over the northeast Caribbean. Combined seas are 2 to 4 ft elsewhere. For the forecast, moderate to fresh trade winds will continue in the central and eastern basin through this evening before Lee in the Atlantic disrupts the pressure pattern. The large easterly swell across the adjacent Atlantic will gradually become NE and then N today through Thu, and move through the Caribbean Passages and into the Caribbean waters between the Leeward Islands and the Mona Passage. Seas across these Caribbean Passages and waters will diminish significantly Thu night through Fri. ...ATLANTIC OCEAN... Please see the Special Features section for information about Hurricane Lee and Tropical Storm Margot. Outside of the weather described above associated with the tropical waves and tropical cyclones, no significant convection is noted across the basin. Weak low pressure near 14.5N47.5W is producing a small cluster of scattered moderate convection. A recent scatterometer satellite pass indicated a compact but weak swirl in the wind field near 14N48W, with only 5 to 10 kt winds near it. It is in an area of almost calm breezes over the western tropical Atlantic. The scatterometer passes also revealed a band of moderate E to SE winds over the eastern Atlantic from the coast of Western Sahara toward T.S. Margot, south of 1020 mb high pressure centered near 30N26W. Gentle breezes are noted elsewhere across the Atlantic outside of the areas near Lee and Margot, with combined seas of 4 to 6 ft in mixed swell. For the forecast west of 55W, Lee is expected to maintain a slow NW motion and strengthen modestly through Tue, then begin a gradual turn toward the N on Wed.Lee will move to 23.9N 64.4W this evening, 24.4N 65.5W Tue morning, 24.9N 66.5W Tue evening, 25.7N 67.2W Wed morning, 27.0N 67.7W Wed evening, and 28.8N 68.0W Thu morning. Lee will change little in intensity as it moves N of the area early Fri. Large E to SE swell dominating the waters east of 76W early this morning will continue to propagate westward across the Atlc, reaching the NW Bahamas and 78W late this afternoon or evening, and the Florida coasts Tue afternoon. Large swell from Lee will dominate regional waters Tue night through Fri. $$ Christensen