000 AXNT20 KNHC 170555 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0605 UTC Thu Aug 17 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 0000 UTC surface analysis and satellite imagery through 0535 UTC. ...SPECIAL FEATURES... Invest 99L: A 1009 mb low pressure is located near 12N39W, or about 760 nm west-southwest of the Cabo Verde Islands. Scattered moderate and isolated strong convection is noted from 05N to 15N and between 35W and 53W. Environmental conditions appear conducive for gradual development of this system, and a tropical depression could form during the next several days while it moves west- northwestward at 10 to 15 mph across the central tropical Atlantic. This system has a medium chance of tropical development in 48 hours. Please refer to the latest NHC Tropical Weather Outlook at www.hurricanes.gov for more details. ...TROPICAL WAVES... An eastern Atlantic tropical wave has its axis along 25W, south of 19N, moving westward at 10 kt. This disturbance (Invest 98L) is producing a large area of disorganized showers and thunderstorms near and to the southwest of the Cabo Verde Islands. Further development of this low is possible while it moves toward the west-northwest or northwest at around 10 mph across the eastern tropical Atlantic, and a tropical depression could form over the weekend before environmental conditions become unfavorable for development early next week. This system has a low chance of tropical development in 48 hours. A central Atlantic tropical wave has its axis along 43W, south of 20N, moving westward at 10-15 kt. Please see the Special Features section for information of convection near this tropical wave. An eastern Caribbean tropical wave has its axis along 65W, south of 20N, moving westward at 10-15 kt. Scattered moderate convection is noted near the northern portion of the wave. ...MONSOON TROUGH/ITCZ... The monsoon trough enters the Atlantic through the coast of Mauritania near 20N16W and continues southwestward to 13N27W to a 1009 mb low pressure near 12N39W and to 12N51W. The ITCZ extends from 12N51W to 12N60W. See Tropical Waves section for details on convection. GULF OF MEXICO... The Gulf of Mexico is in the western periphery of an expansive subtropical ridge positioned between Bermuda and the Azores. Scattered showers and isolated thunderstorms are affecting the eastern Bay of Campeche, associated with convection that fired up over the Yucatan peninsula earlier today. A few showers and isolated thunderstorms are also noted in the eastern Gulf of Mexico due to favorable upper level dynamics. No deep convection is observed in the rest of the basin. The weak pressure gradient allows for moderate or weaker winds and 1-3 ft across the entire Gulf of Mexico. For the forecast, a surface trough will continue to support isolated thunderstorms across the N-central and NE Gulf tonight and tomorrow. A surface ridge over the central Gulf will support mostly gentle to moderate winds and slight seas across the basin through the weekend. Looking ahead, a broad area of low pressure could form in the central or W Gulf by the beginning of next week. CARIBBEAN SEA... Isolated showers and thunderstorms are present in the SW Caribbean Sea and east of the Yucatan peninsula. Similar convection is seen in the Gulf of Gonave. Otherwise, no deep convection is noted in the remainder of the basin. The pressure gradient between the subtropical ridge in the central Atlantic and lower pressures in NW Colombia support fresh to strong easterly trade winds in the central Caribbean. A recent scatterometer satellite pass indicate that the strongest winds are occurring within 75 nm of northern Colombia. Seas of 4-8 ft are found in the central Caribbean. Moderate to fresh easterly winds are evident in the eastern Caribbean, Windward Passage and Gulf of Honduras, along with seas of 3-5 ft. Elsewhere, slight to gentle winds and slight seas prevail. For the forecast, fresh to locally strong tradewinds will prevail across the central Caribbean through tonight. The pressure gradient between the Bermuda High and the Colombian Low will loosen by tomorrow morning, resulting in a slight decrease in winds over the area for the next few days. Gentle to moderate tradewinds will prevail elsewhere. ATLANTIC OCEAN... An expansive subtropical ridge dominates the tropical Atlantic, extending from the far NE Atlantic to offshore Florida. Scattered moderate to isolated strong convection is seen west of 73W and north of 25N due divergence aloft associated with a upper level trough over the SE United States. A recent scatterometer satellite pass show fresh to strong southerly winds in the areas with the strongest convection. Seas in the waters described are 3-5 ft. The pressure gradient between the 1025 mb subtropical ridge and lower pressures in the deep tropics support fresh to locally strong easterly winds south of 27N and between Africa and the Bahamas. Wave heights in these waters are 5-9 ft, with the highest seas occurring within 120 nm of 22N32W and 20N55W. Elsewhere, moderate or weaker winds and moderate seas are prevalent. For the forecast W of 55W, fresh to locally strong trade winds will pulse off Hispaniola each evening through the next several days. Fresh tradewinds will develop south of 25N starting Thu and diminishing again on Sat. A cold front will approach the NW waters then stall, but fresh SW winds ahead of the cold front can be expected Thu and Fri in the NW waters. Gentle to moderate winds will prevail elsewhere. $$ DELGADO