000 AXNT20 KNHC 221039 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 639 AM EDT Tue May 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 0600 UTC surface analysis and satellite imagery through 1030 UTC. ...SPECIAL FEATURES... The southern end of a sharp upper trough over the northwest Caribbean is supporting a surface trough reaches from central Honduras to near Cozumel Island. Deep layer tropical moisture continues to stream northward on the eastern edge of the upper trough, where related upper divergence is supporting clusters of showers and thunderstorms from just north of San Andres Island to just south of Grand Cayman Island. While environmental conditions are expected to be unfavorable for development low pressure along the surface trough during the next couple of days, some gradual subtropical or tropical development is possible later this week while the system moves slowly northward into the central or eastern Gulf of Mexico. Regardless of development, locally heavy rainfall is possible across western Cuba and much of Florida during the next several days. For more information on the heavy rain threat, please see products issued by your local weather office. There is a very low chance for tropical storm formation within 48 hours. ...TROPICAL WAVES... A tropical wave is along 38W S of 10N, moving W at 10-15 kt. This wave is embedded in a sharp 700 mb trough. No significant convection is noted with this tropical wave. A weak tropical wave is over the eastern Caribbean Sea south of the Virgin Islands, moving W at 10-15 kt. No significant convection is noted with this tropical wave, and it will likely become diffuse through late today. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the coastal sections of Sierra Leone near 07N12W to 04N15W. The intertropical convergence zone continues from 04N15W to 04N27W to near the tropical wave along 38W, then continuing west to 00N50W near the coast of Brazil. From 00N to 05N between 15W and 35W. ...DISCUSSION GULF OF MEXICO... A sharp upper trough persists over the eastern Gulf this morning from the western Florida Panhandle to near the Yucatan Channel. An associated surface trough is analyzed directly beneath the near stationary trough. Divergent flow aloft is supporting a few showers and thunderstorms along 23N/24N east of 90W to the Straits of Florida. The trough interrupts a broad surface ridge reaching across the northern Gulf and Deep South states. Gentle to moderate E to SE winds are evident across the Gulf as noted in buoy observations and scatterometer satellite data. Buoys and altimeter satellite data show generally 2 to 4 ft seas. No other showers or thunderstorms are noted. The ridge over the northern Gulf coast will shift east through mid week ahead of a developing low pressure area expected to emerge off the coast of Yucatan Thu. The low pressure will continue to move northward into the north central Gulf through Sat, bringing fresh to strong winds and building seas to the eastern Gulf, then diminish Sun as the low moves north of the area. CARIBBEAN SEA... Please read the Special Features section for more details about the upper level trough and related surface weather features over the NW Caribbean Sea. Atlantic ridging north of the area is supporting moderate to fresh trade winds from the tropical north Atlantic west of 55W to the central Caribbean, except for fresh to strong winds funneling along the higher coastal terrain of northeast Colombia and northwest Venezuela. Trade wind convergence, possibly aided by the upper trough is supporting scattered convection from the central coast of Colombia to near 13N77W. Meanwhile a weak tropical wave over the far eastern Caribbean is starting to lose definition as it drifts west, and will likely dissipate. A line of showers and thunderstorms is active from near Guadeloupe to 18N55W, at the base of broad upper low centered north of the area. Buoy observations and altimeter data show5 to 7 ft seas in the northwest Caribbean, 6 to 8 ft seas over the central Caribbean, and 4 to 6 ft seas in the eastern Caribbean, and 5 to 7 ft seas elsewhere. The Atlantic ridge will maintain fresh to locally strong trades over the central Caribbean through Fri. Strong winds and seas to 9 ft will affect the NW coast of Colombia. Low pressure may form along the trough in the northwest Caribbean and near the Yucatan Peninsula through mid week, then move north into the Gulf of Mexico late Thu. Fresh to strong winds will develop between the trough and the Atlantic high pressure south of Cuba Fri, persisting through Sat. ATLANTIC OCEAN... A recent scatterometer satellite pass indicated fresh to strong trade winds pulsing off the north coast of Haiti. The stronger winds are due to localized overnight land breezes off the coast, and relatively tight gradient south of the subtropical ridge, reaching east to west along 30N. Otherwise, the ridge is supporting gentle to moderate SE winds north of 22N and moderate to fresh trade winds south of 22N. Seas are 4 to 6 ft in open waters. The ridge will shift eastward from mid to late week, as developing low pressure moves through the Gulf of Mexico west of the region. This change in the pattern will result in slightly stronger winds over the Cay Sal Bank area, and SE to S winds increasing over the northern Bahamas and off northeast Florida Sat. Winds and seas will diminish elsewhere due to a weakened and displaced Atlantic ridge. Farther east, a 1025 mb high is centered over the central Atlantic near 30N53W producing mostly fair weather, with moderate trade winds over tropical Atlantic. Recent altimeter satellite passes indicate seas to 8 ft over the deep tropics between 45W and 55W, likely in NE swell. This should diminish below 8 ft through late today. For additional information please visit http://www.hurricanes.gov/marine $$ Christensen