393 AXNT20 KNHC 250558 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 158 AM EDT Wed Jul 25 2018 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 32N. The following information is based on satellite imagery, weather observations, radar and meteorological analysis. Based on 0000 UTC surface analysis and satellite imagery through 0545 UTC. ...TROPICAL WAVES... A tropical wave is over the far eastern Atlantic just to the west of the Cape Verde Islands with its axis along 30W extending from 06N-20N, moving westward at 15-20 kt. A large area of Saharan dry air and dust is hindering convective activity from developing at the time. A tropical wave is over the central Atlantic with axis along 42W from 04N-15N, moving westward at 15-20 kt. A large area of Saharan dry air and dust is hindering convective activity from developing at the time. A tropical wave is SE of the Lesser Antilles with its along 57W from 05N-16N, moving westward at 15 kt. A large area of Saharan dry air and dust is hindering convective activity from developing at the time. A tropical wave is over the central Caribbean with axis along 78W from E Cuba to inland Panama, moving westward at 15-20 kt. Shallow moisture in the northern wave environment along with a region of middle to upper level diffluence ahead of the wave is supporting isolated showers off the coast of SW Cuba and W coast of Jamaica. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends from the coast of Africa near 13.5N16.5W to 10.5N30W and ends just to the east of the tropical wave with axis along 42W. The ITCZ extends from 07.5N44W to the coast of South America near 06N56W. Scattered moderate convection is seen within 60 nm north of the monsoon trough between 31W-37W. ...DISCUSSION... GULF OF MEXICO... A deep layer trough extends from southern Georgia through the central Gulf of Mexico as seen in water vapor imagery. This upper feature supports a dissipating stationary front that extends from a 1011 mb low pressure over SE Georgia to 29N85W to 27N89W. A pre-frontal trough extends from Tampa Bay SW to 25N85W to 23N90W. Diffluence aloft ahead of this boundary is sustaining convection, moving southeastward over the waters from 24N-27N between 81W-95W. The front will vanish later this morning, leaving a surface trough over the E Gulf. With upper diffluence and shallow moisture remaining in place, convection is expected to continue over the east-southeast Gulf through Thu morning. The Atlc subtropical ridge will then extend an axis SW across the eastern Gulf. Surface ridging is forecast to continue through the weekend, thus providing light to gentle variable flow across the basin. Elsewhere, a surface trough will move off the Yucatan Peninsula into the Bay of Campeche each evening, accompanied by fresh nocturnal winds. Scattered to isolated showers are possible in the Bay of Campeche with the surface trough. CARIBBEAN SEA... A tropical wave is in the central Caribbean with axis along 78W. For further details see tropical waves section. Scattered moderate convection and isolated tstms are off the coast of Colombia associated with a 1011 mb low near 09N73W. Isolated showers are located over waters S of Puerto Rico and Hispaniola between 65W and 75W. This convection is being sustained by a small region of shallow moisture and diffluence aloft. Relatively dry and stable conditions persist elsewhere. The 1011 mb low over Colombia is expected to move westward over SW Caribbean waters today, bringing showers and tstms to Panama, Costa Rica and southern Nicaragua as well as adjacent waters. This shower activity in this region will continue through the weekend being enhanced by the EPAC monsoon trough and a tropical wave that will move into SW Caribbean waters Friday night. With forecasted diffluence aloft and shallow moisture present in the north-central Caribbean, scattered showers are expected through the weekend as well. Otherwise, the Atlc subtropical ridge will continue to extend an axis S-SW into the NE Caribbean, thus supporting fresh to strong winds in the south-central basin through Fri. Elsewhere, stable conditions with light to moderate winds are expected. ATLANTIC OCEAN... Three tropical waves are moving across the basin, however all lacking convection due in part to the presence of the dry air of the Saharan Air Layer. Refer to the tropical waves section above for more details. Isolated showers are across the central and northern Bahamas extending N of 30N and to 75W being supported by diffluent flow aloft. Farther east, a middle to upper level low supports an area of scattered showers and tstms from 24N-29N between 55W-62W. Otherwise, the Atlc subtropical ridge dominates the remainder basin being anchored by a 1032 mb high centered near 37N54.5W. With ample moisture and diffluence aloft associated with an upper level feature, scattered moderate to isolated strong convection is expected north of the Bahamas through the weekend. The aforementioned 1032 mb subtropical high along with low pressure over the southeast U.S. will produce moderate to fresh southerly winds across the waters north of 25N and west of 70W including Florida coastal waters through today. Moderate to fresh winds are also expected south of 22N, including approaches to the Windward Passage. Ridging will dominate the area through the end of the week providing stable and dry conditions in the central Atlantic. For additional information please visit http://www.hurricanes.gov/marine $$ Sangster/Ramos