060 AXNT20 KNHC 200528 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0605 UTC Sun Aug 20 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 0500 UTC. ...SPECIAL FEATURES... Tropical Depression Six is centered near 17.2N 51.5W at 20/0300 UTC or 660 nm E of the Northern Leeward Islands, moving W at 12 kt. Estimated minimum central pressure is 1006 mb. Maximum sustained wind speed is 30 kt with gusts to 40 kt. The low level center is completely exposed due to strong westerly shear impacting the system and keeping the thunderstorm activity 60 to 90 nm east of the center. The depression will continue west through Monday, then turn more to the west-northwest. T.D. Six has likely already peaked, and will likely become post- tropical remnant low in 36 hours and dissipate by 48 hours if not sooner. 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 Depression Six NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov for more details. Gale Warning (AL98): 1006 mb low pressure is centered near 18N37W. A recent scatterometer satellite pass indicate winds were approaching gale force within 60 nm on the north side of the low pressure, and a gale warning is in effect accordingly. Seas are expected to be as high as 11 ft in the area of strong winds. Scattered moderate to isolated strong convection is evident within 120 nm of the low mainly to the northeast of the center. Environmental conditions appear generally favorable for further development, and a short-lived tropical depression is likely to form within the next day or so while it moves west-northwestward or northwestward at about 5 to 10 kt across the eastern tropical Atlantic. This disturbance has a high chance of formation through 48 hours. By early next week, upper-level winds over the system are forecast to increase, and further development is not expected. Near the Windward Islands (AL90): Shower and thunderstorm activity continues in association with an area of low pressure near the Windward Islands. Some additional development of this system is likely and a tropical depression could form by early next week while this system moves westward to west-northwestward at 10 to 15 mph over the eastern and central Caribbean Sea. Regardless of development, heavy rainfall is possible over portions of the Windward Islands during the next couple of days. Interests in the eastern and central Caribbean should monitor the progress of this system. This disturbance has a medium chance of formation through 48 hours. Please refer to the latest NHC Tropical Weather Outlook at www.hurricanes.gov for more details. ...TROPICAL WAVES... A new tropical wave extends from 07N to 20N along 20W, moving west at 10 to 15 kt. Scattered moderate isolated strong convection is from 13N to 15N between 16W and 18W. Some slow development is possible while it moves generally west-northwestward across the tropical eastern Atlantic during the next several days. An Atlantic tropical wave is co-located with AL98 along 37W, from 08N to 22N, and moving westward at 10 to 15 kt. Scattered moderate to isolated strong convection is evident from 18N to 21N between 35W and 37W. A tropical wave is moving west at 10 to 15 kt across the Lesser Antilles along 62W, associated with a 1007 mb low centered near 13N62W. Scattered showers and a few thunderstorms are evident from 12N to 14N between 62W and 63W. A western Caribbean tropical wave is evident along 83W south of 22N, moving west at 10 to 15 kt. No significant convection is noted with this tropical wave. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the coast of Senegal to the low pressure near 18N37W then westward to T.D. Six near 17N52W. The Intertropical Convergence Zone is evident from 14N55W to 16N60W. Other than the convection already discussed in the Special Features and Tropical Wave sections, no additional significant convection is noted. GULF OF MEXICO... A trough is moving across the Florida peninsula, on the northern end of the tropical wave moving across the western Caribbean. This is supporting clusters of showers and a few thunderstorms across the Lower Florida Keys and Cay Sal area of the Straits of Florida, with isolated showers across South Florida. Weak 1015 mb high pressure is evident over the northwest Gulf. Moderate winds are likely over the Straits of Florida and the west coast of the Yucatan peninsula, but otherwise this pattern is supporting light to gentle breezes and slight seas across the basin. For the forecast, the trough located over the Florida peninsula is expected to move into the Gulf of Mexico through the early part of the week, where a broad area of low pressure is expected to form. Some slow development of this system is possible thereafter, and a tropical depression could form as it moves westward and approaches the western Gulf of Mexico coastline by the middle of next week. This system has a low chance of development in 48 hours and a medium chance in the next 7 days. CARIBBEAN SEA... A recent scatterometer satellite pass along with land-based observations indicated fresh to strong winds across the Leeward Islands and adjacent Caribbean and Atlantic waters, associated with the low pressure and tropical wave moving through that area. Seas are likely reaching 7 to 9 ft. Farther west, the pressure gradient between the subtropical Atlantic ridge and lower pressure over Colombia and Panama is supporting fresh to strong E to NE winds in the south-central Caribbean off the coast of Colombia, where seas are currently 4 to 6 ft. Elsewhere in the basin, trades are mainly moderate with seas of 3-6 ft. Scattered showers and tstorms are noted near Jamaica and in the lee of E Cuba. For the forecast, the main forecast issue will be the development of AL90 in the eastern and central Caribbean as described above in the Special Features sections. Regardless of development, heavy rainfall is possible over portions of the Windward Islands during the next couple of days, along strong winds and moderate to rough seas. ATLANTIC OCEAN... The subtropical ridge dominates the tropical Atlantic. The pressure gradient between the ridge and all of our disturbances to the south is driving a band of fresh to locally strong trades across the basin from 18N to 25N. North of 25N, trades are mainly moderate. Farther south, winds are gentle to moderate from various directions. Seas are 4-7 ft across the basin. For the forecast west of 55W, Tropical Depression Six is near 17.2N 51.5W at 11 PM EDT, and is moving west at 12 kt. Maximum sustained winds are 30 kt with gusts to 40 kt, and the minimum central pressure is 1006 mb. T.D. Six will move to 17.5N 53.3W Sun morning, 17.8N 55.5W Sun evening, become a remnant low and move to 18.3N 57.5W Mon morning, and dissipate Mon evening. Strong winds and rough seas are expected with this system as it tracks east of the Lesser Antilles. Additionally, fresh to strong tradewinds will pulse off Hispaniola and the Windward Passage each evening into early next week. Fresh tradewinds south of 25N will persist through the weekend. $$ Christensen