000 AXNT20 KNHC 221749 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 149 PM EDT Fri Jun 22 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 1200 UTC surface analysis and satellite imagery through 1715 UTC. ...TROPICAL WAVES... A tropical wave is emerging off the west coast of Africa and will likely be added to the 1800 UTC surface map. The Hovmoller Diagram indicates the westward propagation of the wave. A large cluster of moderate to isolated strong convection is noted from 6N-10N between 11W-15W in association with this system. The axis of a tropical wave extends from 16N32W to 04N34W. African dust surrounds the wave limiting convection. A patch of low level moisture is near the northern end of the wave's axis. A tropical wave is along 50W from 6N-18N, moving W at 20 kt. A cluster of moderate to isolated strong convection is seen near the southern end of the wave's axis from 06N-08N between 50W and 52W. This wave will pass west of 55W early on Sat, and move across the Windward Islands by Sat night. The axis of a tropical wave extends from 18N65W to the coast of Venezuela near 10N66W, moving W at 10-15 knots. The wave is generating scattered moderate convection across the basin, mainly E of 67W, including the Lesser Antilles, where showers and locally heavy rain have been reported. Upper diffluent ahead of an upper-level trough that now crosses Hispaniola is helping to induce this convective activity. Moisture related to this wave will spread out over Puerto Rico and the UK/US Virgin Islands today, reaching Dominican Republic tonight into Sat, increasing the likelihood of showers with embedded tstms. A recent scatterometer pass clearly indicates the wind shift associated with the wave's axis. A tropical wave extends from the westernmost tip of Jamaica to eastern Panama near 09N79W. Lingering moisture from this tropical wave will continue to support scattered showers and isolated thunderstorms across Jamaica and regional waters today. Scattered showers and isolated tstms are observed between Haiti and Jamaica while some shower activity is near the wave's axis from 15N-18N. Abundant tropical moisture will persist over the NW Caribbean and central America through at least early Sat. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the coastal sections of Guinea near 10N14W to 06N26W. The ITCZ continues from 06N26W to 04N40W to the coast of Guyana near 07N58.5W. Outside of the convection associated with the tropical waves, scattered moderate convection is within about 90 nm N of the ITCZ W of 52W. Isolated moderate convection is from 07N-09N between 38W-47W. ...DISCUSSION... GULF OF MEXICO... A weak ridge dominates the Gulf waters, producing gentle to moderate winds with seas of 3-5 ft over the western Gulf, and seas of 3 ft or less across the eastern Gulf. Weak ridging will persist from the southeast Gulf to the coast of Texas through early next week. SE return flow will increase slightly over the western Gulf between the ridge and weak low pressure over northern Mexico starting Sat night. A surface trough will develop in the Yucatan Peninsula each afternoon, then move westward across the SW Gulf during the overnight hours, accompanied by fresh to occasionally strong east to southeast winds. CARIBBEAN SEA... A tropical wave is moving across the western Caribbean. Another tropical wave is over the eastern Caribbean. Please, see Tropical Waves section for more details. Expect increasing showers and isolated thunderstorms in association with the passage of these tropical waves. Trade winds over the south central Caribbean will strengthen and expand in areal coverage across the basin through early next week as high pressure builds across the central Atlantic. Winds could reach near gale force along the coast of Colombia by Sat night. ATLANTIC OCEAN... An upper-level trough extends from a cyclonic circulation centered near 22N69W across Hispaniola and the waters between eastern Cuba and Jamaica. The low continues to generates scattered showers and tstms mainly over the waters from 23N to 26N between 68W and 72W. Lightning density indicates frequent lightning with some of the observed convection. High pressure of 1029 mb centered near 34N37W extends a ridge westward across the forecast area. Fresh trades are noted along the southern periphery of the ridge. This high pressure will slowly shift westward through Sat night, then remain nearly stationary near 30N55W through Tue night. The tightening pressure gradient that results over the central Atlantic will support fresh to strong trade winds and seas of 8-9 ft E of the Lesser Antilles to about 45W by early Sat morning. These marine conditions will persist on Sun with seas building up to 10 ft. Fresh to strong winds are also expected off Hispaniola at night. The Saharan Air Layer (SAL) from CIMSS and visible satellite imagery confirm the presence of African dust between the west coast of Africa and the Lesser Antilles, more concentrated E of 50W. For additional information please visit http://www.hurricanes.gov/marine $$ GR