000 AXNT20 KNHC 251753 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Sun Jul 25 2021 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 1730 UTC. ...SPECIAL FEATURES... A 1011 mb low is centered near 29N78.5W. Earlier scatterometer satellite data showed a broad and well defined cyclonic circulation, with peak winds to 30 kt within 60 nm across the SE semicircle. Disorganized shower and thunderstorm activity continues mainly to the east and southeast of the center. Environmental conditions are expected to be marginally conducive for development, and a tropical depression could still form later today or early Monday while the system drifts westward toward the east coast of Florida. Interests in Florida should continue to monitor the progress of this system. This system has a medium chance of development within 48 hours. Please read the latest Tropical Weather Outlook at hurricanes.gov for more information. Heavy rainfall is expected to continue in Southern Central America, particularly in Panama, Costa Rica and Southern Nicaragua. High moisture content, persistent monsoon flow, and favorable conditions aloft will continue to support scattered to numerous strong convection capable of producing torrential rain through Monday. Heavy rainfall in these areas could cause significant flooding and mudslides. ...TROPICAL WAVES... An Atlantic tropical wave is near 22W/23W from 20N southward, moving westward at 10 kt. Scattered moderate convection is note from 06N to 08N between 22W and 24W. An Atlantic tropical wave 57W south of 12N moving west at 15-20 kt. There is reasonable evidence of this wave in Hovmoller diagrams going back several days. Recent satellite- derived wind data from the lower levels of the atmosphere hints the wave is restricted to the deep tropics. Scattered moderate convection is evident from 07N to 11N between 50W and 58W. A Caribbean Sea tropical wave is along 72W from central Hispaniola to northwest Venezuela, moving W at 10 kt. The tropical wave is moving west of an upper level low centered off northern Haiti. Dry, subsident air in the northerly flow on the west side of this upper low is inhibiting any major convection near the tropical wave. A Caribbean Sea tropical wave is near 81W from 22N southward, moving W at 10 to 15 kt. Convection associated with this wave is confined to near the monsoon trough, S of 12N and is described below. ...MONSOON TROUGH/ITCZ... The monsoon trough enters the Atlantic Ocean along the coast of Senegal near 13N17W to 11N18W to 08N35W. The ITCZ continues from 08N35W to 08N52W. No significant convection is evident along these features at this time. ...GULF OF MEXICO... A surface trough extends from southwest Florida near Flamingo to 1012 mb low pressure near 25N85W to off southeast Louisiana near 29N90W. Farther west, 1018 mb high pressure is centered near 26N94W. A few showers are likely ongoing off Louisiana near the trough, and farther south over the central Gulf along the loop current. Light to gentle winds and slight seas prevail across the Gulf. For the forecast, showers and maybe a few thunderstorms will continue south of the trough today. The high pressure will meander and weaken through Mon as a low pressure currently located about 140 nm east of Daytona Beach, Florida, drifts westward toward the east coast of Florida. ...CARIBBEAN SEA... Refer to the Tropical Waves section above for more information on convection across the Caribbean Basin. Overall, a relatively benign pattern continues across the Caribbean today. There are scattered showers and thunderstorms over the far southwest Caribbean, south of 12N, from western Colombia to Costa Rica, to include the coast of Panama, posing a risk of flooding. A few showers and thunderstorms are starting to develop over the higher terrain of central Hispaniola, enhanced by an upper low centered the Turks/Caicos. But no significant showers or thunderstorms are noted elsewhere. Light breezes and slight seas are noted over the northwest Caribbean, and gentle to moderate trade winds with 2 to 4 ft seas elsewhere. The trade wind flow is lighter than usual, related in part to a relatively weaker subtropical ridge north of the area. For the forecast, the current pattern will continue, with diminished tradewinds across the basin through Wed. Look for scattered showers and tstms across the eastern Caribbean and tropical Atlantic waters today associated with another tropical wave. ATLANTIC OCEAN... See the Special Features section for more information on the low east of Florida and the Tropical Waves section for information on the wave off the African coast. Clusters of showers and thunderstorms are noted over the Atlantic north of Puerto Rico and east of the Bahamas, specifically from 20N to 25N between 62W and 68W. This activity is tied to upper level divergence between an upper low over the Turks/Caicos Islands and an upper trough in the northwest flow aloft farther to the northeast over the central Atlantic. A weak surface trough is analyzed in this area of convection, from 22N68W to 29N62W. Another trough is analyzed farther east, from 22N to 28N between 45W and 50W. The troughs are south of a 1029 mb high pressure near 38N37W. Recent scatterometer satellite passes indicated fresh E winds near western trough. This is evidence of a broader area of fresh winds from 18N to 25N between 55W and 70W between the trough and the ridge, with seas estimated to be 5 to 7 ft. Similarly fresh winds and 5 to 7 ft seas are likely between the eastern trough and the ridge, from 25N to 30N between 35W and 50W. Aside from fresh to strong winds near the Cape Verde Islands and off Morocco, this pattern is support generally moderate trade winds and 4 to 6 ft seas across the basin. $$ Christensen