665 AXNT20 KNHC 270551 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 151 AM EDT Mon Aug 27 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 far eastern Atlantic tropical is just west of the African coast with its axis along 18W/19W from 04N to 20N, moving westward at 10-15 kt. The wave is embedded within the broad monsoonal trough region of W Africa. Moisture and convection within this region of the far eastern Atlantic has increased during the past few days as observed on GOES-16 imagery. The latest satellite imagery shows scattered moderate to strong convection just east of the wave axis to along and just inland the coast of Africa from 07N to 12N. This activity is holding together as it moves away from the African coast. Similar convection is west of the wave axis along and within 120 nm south of the monsoon trough between the wave and 23W. A central Atlantic tropical wave has its axis along 48/49W from 03N to 20N, moving westward at 15 to 20 kt. This wave is surrounded by a rather stable and dry environment. Only isolated weak showers and thunderstorms are seen within 150 nm west and within 120 nm east of the wave from 08N to 14N. A western Caribbean Sea tropical wave has its axis along 79W south of 20N, moving westward at 10-15 kt. This wave is moving into an area of pre-existing upper level cyclonic wind flow. The northern portion of the wave is helping to trigger off scattered moderate convection within 120 nm west of the wave axis from 18N to 20N. This activity is being further enhanced by an upper-low over east-central Cuba. Isolated showers are possible within 120 nm on either side of the wave. ...MONSOON TROUGH/ITCZ... The monsoon trough axis passes through the coastal sections of Guinea-Bissau near 12N17W to 10N24W to 10N34W and to 09N445. No ITCZ was discernible. Aside from convective activity associated with the far eastern Atlantic tropical wave, scattered moderate isolated strong convection is within 240 nm south of the trough axis between 23W and 27W. Scattered moderate convection is within 180 nm south and 600 nm north of the trough axis between 34W and 41W. ...DISCUSSION... GULF OF MEXICO... An upper-level trough extends from northeastern Florida to 29N83W, and continues as a shear axis to an upper-level low at 24N93W. At the surface, a westward moving trough extends from 2991W to 23N92W. Upper-level cyclonic wind flow covers nearly the entire Gulf of Mexico east of 94W eastward. A second upper-level low is noted at the coast of Mexico near 20N97W. With these features in play along with a very moist and unstable atmosphere in place, scattered shower and thunderstorm activity will continue over much of the basin through the next couple of days. A surface trough will develop during the evening hours in the Yucatan Peninsula, before pushing offshore into the SW corner of the Gulf of Mexico each night. This trough, in combination with Sunday's daytime heating acting on ample instability in place, triggered off scattered moderate isolated strong convection over much of the Yucatan Peninsula. Over the past few hours this activity has diminish some as it pushes off the west coast of the Yucatan and to the eastern Bay of Campeche. Scattered showers and isolated showers remain over sections of the Yucatan Peninsula. A surge of moderate to fresh NE to E winds will accompany this trough. A weak surface ridge will remain over the rest of basin, with its associated gradient supporting a gentle to moderate wind flow regime. CARIBBEAN SEA... An upper-level trough extends from a small upper-level low near 22N63W west-southwestward to Hispaniola, and continues to another upper-level low over east-central Cuba. A trough extends from this low southward to just south of Jamaica and to northwestern Colombia. Plenty of atmospheric instability over the western half of the Caribbean for these features to work with is bringing scattered moderate convection in clusters over the waters just south of Cuba to 19N between 81W and 85W. Isolated moderate convection is seen elsewhere north of 13N west of 77W. Instability from the upper-level low over Cuba earlier resulted in scattered to numerous showers and thunderstorms over much of the central and eastern sections of that island. This activity has decreased during the past few hours, but is expected to quickly re-develop today as daytime gets underway. The activity will gradually shift from east to west as the upper low pulls further away to the west. The eastern segment of the eastern Pacific monsoon trough stretches eastward into the far southwestern Caribbean to the northwestern coast of Colombia. Scattered showers and thunderstorms are south of 13N and west of 75W. Fresh to strong winds, and building seas to 10 feet, will continue in the south central Caribbean Sea through Wed. A tropical wave will approach the waters east of the Lesser Antilles on Tue accompanied by fresh easterly winds and wave heights expected to max out around 8 ft. The wave will enter the eastern Caribbean early on Wed, increasing the likelihood of scattered showers and isolated thunderstorms over much of the Lesser Antilles. ATLANTIC OCEAN... Several small surface and upper-level feature are evident across this area of the discussion domain. The tail-end of an upper-level trough extends from within 180 nm offshore the southeastern United States southwestward to NE Florida. An upper-level low moving westward is near 28N71W, with and inverted trough stretching southwestward to 25N74W and to an upper-level low over east-central Cuba. Another inverted trough extends from the upper low northeastward to north of the area at 32N70W. At the surface, a trough with good track history, is analyzed from near 29N75W to the central Bahamas and to just north of the coast of Cuba at 22N78W. Latest satellite imagery shows scattered showers and thunderstorms moving westward over much of the central Bahamas west through the Straits of Florida and to southern Florida. The surface trough is forecast to move across the area through Mon. Gentle to moderate winds will be associated with this trough. A small upper-level moving steadily westward is seen in water vapor imagery to be near 22N63W, with a trough extending westward to Hispaniola and to an upper-level low over east-central Cuba. This upper low is showing a surface signature identifies as a trough from 27N64W to near 22N66W. Scattered moderate convection is noted within 180 nm west of the trough from 24N to 27N. Isolated showers and thunderstorms are elsewhere to the west of 60W. An upper-level trough stretches from an upper-level low also located well north of the area at 35N39W southwestward through 32N45W to 27.5N50W and to the upper-level low that is near 22N63W. A pair of surface troughs are analyzed from near 32N43W to 29N50W, and from near 32N50W to 29N56W to 31N51W. Scattered moderate convection is within 75 nm southeast of the first trough. Isolated showers and weak thunderstorms are along and within 30 to 60 nm of the the second trough. Isolated showers are elsewhere to the north of 24N between 45W and 60W. Outside the above described features, surface high pressure is present across the Atlantic, with the strongest high pressure found north of 28N and east of 50W. Water vapor imagery and the Total Precipitable Water (TPW) animation reveal that atmospheric moisture is increasing over much of the basin east of 52W. East winds will pulse to fresh to strong at night just north of Hispaniola through Tue. A weak surface ridge will remain over the remainder of these waters, with its associated gradient supporting gentle to moderate east to southeast winds west of about 50W. For additional information please visit http://www.hurricanes.gov/marine $$ Aguirre