000 AXNT20 KNHC 272113 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0005 UTC Thu Sep 28 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 2000 UTC. ...SPECIAL FEATURES... Tropical Storm Philippe is centered near 17.7N 54.0W at 27/2100 UTC or 520 nm E of the Northern Leeward Islands, moving WNW at 4 kt. Estimated minimum central pressure is 998 mb. Maximum sustained wind speed is 45 kt with gusts to 55 kt. Peak seas are currently around 23 ft. Numerous moderate isolated strong convection is noted within 390 nm in the NE semicircle and 75 nm in the SW semicircle. Philippe is moving toward the west- northwest and west-northwestward motion is expected over the next few days. Little change in strength is forecast during the next day or two, with slow weakening forecast this weekend. Philippe is forecast to produce 2 to 4 inches of rain across the northern Leeward Islands, the Virgin Islands, and northern and eastern Puerto Rico Saturday through Monday. Elsewhere across Puerto Rico, 1 to 2 inches of rain is expected. Heavy rainfall from Philippe may produce isolated urban and small stream flooding impacts. 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 Philippe NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov for more details. Gale Warning Associated with Invest Area (AL91): A central Atlantic tropical wave is near 43.5W from 17N southward through a 1006 mb low (AL91) at 13.7N 44.2W, and moving west at around 15 kt. Numerous moderate isolated strong convection is noted from 07N to 18.5N between 40W and 50W. Seas are currently 8-12 ft. Environmental conditions are forecast to be conducive for development, and a tropical depression or storm is expected to form in the next day or so while the system moves west- northwestward across the central tropical Atlantic. The chance of development within the next 48 hours is high. Gale force winds are forecast to develop with this low pressure later tonight. 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 Tropical Weather Outlook at hurricanes.gov for more information. ...TROPICAL WAVES... Please refer to the SPECIAL FEATURES above for information on the tropical wave associated with AL91. A NW Caribbean Sea tropical wave is near 87W from 19N southward across Central America and into the East Pacific. It is moving west at around 10 kt. Aided by mid-level diffluent flow, scattered showers and thunderstorms are occurring W of 79W. ...MONSOON TROUGH/ITCZ... The monsoon trough enters the Atlantic along the Mauritania coast near 19N16W to 05N32W. Scattered moderate convection is noted within 300 nm NW of the monsoon trough. ...GULF OF MEXICO... A broad surface trough extends from the north-central Gulf to the central Bay of Campeche. Isolated convection is depicted in the central Gulf in association with this trough. Scattered moderate convection is depicted in the N-central and NE Gulf ahead of a frontal boundary. Another surface trough runs southwestward from Central Florida to across Marco Island, Florida to the Yucatan Channel. Scattered moderate convection is noted S of 26N and E of 88W. Moderate to fresh N-NE winds are N of the frontal boundary in the N-central and NE Gulf coastal waters. Winds are moderate or weaker elsewhere. Seas are mainly 1-3 ft across the basin, locally higher in and near any convection. For the forecast, gentle to moderate NE to E winds and slight seas will prevail across the basin through early Thu. Winds are forecast to increase over the northern Gulf the end of the week into the weekend as high pressure ridging strengthens over the southeastern United States. ...CARIBBEAN SEA... Refer to the Special Features section above for details on Tropical Storm Philippe. Refer to the Tropical Waves section for details on a tropical wave in the NW Caribbean Sea. An upper-level low over the eastern Caribbean Sea is producing scattered to numerous thunderstorms from 12N to 19N between 59W and 68W, including over the Lesser Antilles to Puerto Rico. Moderate to locally fresh trades and 4-6 ft seas prevail over the central Caribbean. Gentle to moderate trades and 3-5 ft seas prevail elsewhere. For the forecast, Philippe will move to 18.1N 55.1W Thu morning, 18.6N 56.5W Thu afternoon, 18.9N 57.7W Fri morning, 18.9N 58.8W Fri afternoon, 18.8N 60.0W Sat morning, and 18.7N 61.6W Sat afternoon. Philippe will weaken to a remnant low near 18.4N 64.0W Sun afternoon. Rough seas across the forecast zones east of the Leeward Islands generated by Tropical Storm Philippe will start to subside toward the end of the week. High pressure north of the area will support moderate to fresh trade winds across most of the eastern and central Caribbean through tonight. Winds across the Caribbean Sea will then diminish late this week into this weekend. ...ATLANTIC OCEAN... Refer to the Special Features section above for details on Tropical Storm Philippe and a Gale Warning related to Invest AL91. A stationary front extends from off the Carolinas to near Jacksonville, Florida. Convergent southeasterly winds to the east of the front and a surface trough over Central Florida are triggering scattered showers and isolated thunderstorms N of 26N and W of 74W. Fresh to strong winds are NW of the front across the SE Georgia and far N Florida coastal waters along with 4-7 ft seas. A surface trough is analyzed from 30N61W to 25N67W with some isolated showers and thunderstorms along and to the W of it. Otherwise, the Atlantic ridge associated with the Bermuda and Azores Highs is supporting moderate or weaker winds across the tropical Atlantic waters away from Philippe and AL91, except fresh to strong N of 18N within 180 nm of the coast of Africa due to a regionally tight pressure gradient. Seas are 3-5 ft W of 70W, and 4-7 ft elsewhere across the tropical Atlantic waters away from Philippe and AL91, except for 7-10 ft near the fresh to strong winds off Africa. For the forecast west of 55W, Philippe will move to 18.1N 55.1W Thu morning, 18.6N 56.5W Thu afternoon, 18.9N 57.7W Fri morning, 18.9N 58.8W Fri afternoon, 18.8N 60.0W Sat morning, and 18.7N 61.6W Sat afternoon. Philippe will weaken to a remnant low near 18.4N 64.0W Sun afternoon. Rough seas ahead of the storm are east of 60W, and will continue to spread east of 65W through the end of the week. Elsewhere, seas will build tonight and Thu north of the Bahamas and east of Florida in NE swell. $$ Lewitsky