000 AXNT20 KNHC 180958 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1205 UTC Fri Aug 18 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 0600 UTC surface analysis and satellite imagery through 0940 UTC. ...SPECIAL FEATURES... Eastern Tropical Atlantic (AL98): Showers and thunderstorms continue to show some signs of organization in association with a broad area of 1009 mb low pressure located a few hundred miles west of the Cabo Verde Islands near 16N31W. Environmental conditions appear generally favorable for additional development of this system, and a tropical depression is likely to form over the weekend while it moves toward the west- northwest or northwest at about 5 to 10 kt across the eastern tropical Atlantic. By early next week, upper- level winds over the system are forecast to increase, and further development is not expected. This system has a medium chance of tropical cyclone development within 48 hours. Central Tropical Atlantic (AL99): An elongated trough of 1009 mb low pressure located more than 1000 miles west-southwest of the Cabo Verde Islands near 13N42W is producing some disorganized showers and thunderstorms. Environmental conditions are only marginally conducive for further development of this system, but a tropical depression could still form during the next couple of days while it moves west- northwestward at 10 to 15 kt across the central tropical Atlantic. Thereafter, upper- level winds are forecast to become unfavorable for any further development. This system has a medium chance of tropical cyclone development within 48 hours. Please refer to the latest NHC Tropical Weather Outlook at www.hurricanes.gov for more details on both special features. ...TROPICAL WAVES... A tropical wave is along 31N through the low pressure mentioned in the Special Features section, moving west with the low pressure at 5 to 10 kt. Scattered moderate convection is evident from 90 to 180 nm in the northwest quadrant of the low, and from 09N to 12N between 32W and 35W. A western Atlantic tropical wave has its axis near 52W from 06N to 19N. It is moving westward near 15 kt. Scattered moderate and isolated strong convection is depicted from 10N to 13N between 50W and 55W. A Caribbean tropical wave has its axis near 75W, or from the western part of Haiti to just inland Colombia, moving west at 10 to 15 kt. No significant convection is evident at this time. ...MONSOON TROUGH/ITCZ... The monsoon trough axis enters the Atlantic near 19N16W to the low pressure mentioned in the Special Features section near 16N31N to the other low pressure mentioned in the Special Features section near 13N42W, then farther west to 11N55W. Scattered moderate to isolated strong convection is noted from 12N to 14N between 42W and 48W. GULF OF MEXICO... A weak pressure pattern extending across the basin is supporting light to gentle breezes and slight seas this morning, except for moderate winds off the western Yucatan peninsula. For the forecast, the surface ridge over the Gulf waters will support mostly gentle to moderate winds and slight seas across the basin through Sat night. Looking ahead, a surface trough is expected to move across the Gulf from east to west Sun through early next week. The trough could form into a broad area of low pressure in the central or W Gulf by the beginning of next week. Some slow development of this system is possible thereafter as it moves westward and approaches the western Gulf of Mexico coastline by the middle of next week. CARIBBEAN SEA... Fresh NE to E winds are converging over the northeast Caribbean and supporting scattered showers and a few thunderstorms over the region. Wave heights are 5 to 7 ft, although maybe near 8 ft in Atlantic passages due to easterly swell. Fresh winds are noted over the Gulf of Venezuela, off central Colombia, and the Gulf of Honduras, with 4 to 6 ft seas. Gentle to moderate trade winds and 3 to 5 ft seas are noted elsewhere. A few showers and thunderstorms are evident are noted over the Windward Passage and off western Cuba. For the forecast, moderate to fresh trade winds will prevail over the eastern and central Caribbean during the next few days. A strong tropical wave is likely to approach the E Caribbean this weekend and spread fresh to strong winds and building seas over the NE Caribbean Sat night into Tue. ATLANTIC OCEAN... Please refer to the SPECIAL FEATURES and the MONSOON TROUGH/ITCZ sections above for details on the two low pressure systems in the central and eastern Atlantic that could become tropical cyclones and convection in the tropical Atlantic. The subtropical ridge extends from 1024 mb high pressure northeast of Bermuda to the east-central Florida coast. This pattern is supporting moderate to fresh easterly flow south of 25N with 5 to 7 ft combined seas east of 50W and 6 to 9 ft combined seas over open waters west of 50W with a component of easterly swell. Gentle breezes are noted north of 25N, except moderate SW flow off the northeast coast of Florida. For the forecast west of 55W, fresh to locally strong tradewinds will pulse off Hispaniola each evening into early next week. Fresh tradewinds south of 25N will persist through Sat. A strong tropical wave could enhance winds and seas near the Leeward and Virgin Islands over the weekend, and north of Puerto Rico early next week. $$ Christensen