021 AXNT20 KNHC 150004 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 804 PM EDT Tue Aug 14 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 1800 UTC surface analysis and satellite imagery through 2330 UTC. ...SPECIAL FEATURE... A low pressure center is near 37N47W, and it is interacting with a strong upper level trough. Rainshowers with thunder are in the eastern and southern sections of its circulation. It is possible that this feature may acquire some subtropical characteristics during the next day or so. The low pressure center is expected to move northeastward, across an area of colder waters, and it will merge with a frontal boundary that will be in the northern Atlantic Ocean. The potential for this feature to become a subtropical cyclone during the next 48 hours is medium. ...TROPICAL WAVES... An Atlantic Ocean tropical wave is along 31W/32W, from 22N southward. 15 kt. Rainshowers are possible within 360 nm of the wave to the east, and within 180 nm of the wave to the west. An Atlantic Ocean tropical wave is along 53W/54W, from 20N southward. Isolated moderate rainshowers are within 420 nm of the wave to the east, and within 360 nm of the wave to the west. A Caribbean Sea tropical wave is along 71W/72W from 21N southward. Areas of upper level cyclonic wind flow are nearby. It is possible that any precipitation may be more related to the areas of upper level cyclonic wind flow. A Caribbean Sea tropical wave is along 83W/84W, from 23N southward. The wave is moving through a pre-existing area of upper level cyclonic wind flow. It is possible that any precipitation may be more related to the upper level cyclonic wind flow. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the coastal sections of Guinea near 11N15W, to 10N17W, to 12N24W, to 09N40W. The ITCZ continues from 09N40W to 08N47W, to 06N54W near the coast of French Guiana. Widely scattered moderate to isolated strong rainshowers cover the Atlantic Ocean from 03N to 13N between 34W and 60W. ...DISCUSSION... GULF OF MEXICO... An upper level cyclonic circulation is over southern Mexico near 18N100W. Isolated showers are over the area. Upper level cyclonic wind flow covers the Gulf of Mexico south of 24N and west of 90W. A broad upper level anticyclonic circulation centered near 28N94W spans the rest of the area. Widely scattered moderate rain showers are over the NE Gulf from 26N to 31N between 82W and 87W. On the surface a surface trough is over the NE Gulf from 31N86W to 28N90W. Another surface trough is over the Bay of Campeche from 20N95W to 17N94W. Scattered showers are within 90 nm of the trough axis. A nocturnal trough will develop during the evening hours in the Yucatan Peninsula, before pushing offshore into the SW Gulf of Mexico each night. A surge of fresh to occasionally strong NE to E winds will accompany this trough. The trough will become weaker on Thursday, allowing the winds to subside. A surface ridge near the northern coast of the Gulf of Mexico will support light to moderate E to SE winds across the remainder of the basin through Sunday night. CARIBBEAN SEA... An upper level cyclonic circulation is along the coast of N Cuba near 23N78W. Upper level diffluence is over Hispaniola enhancing convection. Another upper level cyclonic circulation is over the NW Caribbean near 19N85W. Upper level diffluence is over Honduras and Nicaragua enhancing convection. The monsoon trough is along 09N between 73W and 85W. Scattered moderate to isolated strong convection is S of 12N between 74W and 84W, to include N Colombia, Panama, and Costa Rica. A ridge extending across the western Atlantic will maintain fresh to locally strong winds over the south-central Caribbean, including the Gulf of Venezuela through Sun night. Moderate to fresh trades are expected elsewhere, except for the NW Caribbean, where winds will be gentle to moderate. ATLANTIC OCEAN... An upper level trough is off the coast of N Florida. Scattered showers are over the W Atlantic N of the N Bahamas and W of 77W. A large upper level anticyclonic circulation is centered over the W Atlantic near 33N59W. Upper level diffluence E of the center is enhancing convection near 29N50W. A ridge N of the forecast waters will support fresh to strong winds along the N coast of Hispaniola and the approaches to the Windward Passage during the evening and overnight hours through Sun night. Otherwise, gentle to moderate anticyclonic flow will continue N of 23N, while moderate easterly winds will generally prevail S of 23N. For additional information please visit http://www.hurricanes.gov/marine $$ mrf/mt