000 AXNT20 KNHC 080557 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 157 AM EDT Tue May 8 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 0530 UTC. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the coastal sections of Sierra Leone near 09N13W to 04N15W. The ITCZ continues from 04N15W to 01N37W to 03S45W along the coast of Brazil. Scattered moderate convection is noted from 01N to 03N between 13W and 18W, and from 01N to 03N between 35W and 50W. ...DISCUSSION GULF OF MEXICO... A very broad mid-latitude trough continues to move across the southeastern U.S. The main impact of the trough is north of the region, limiting mid/upper support for a stalling and dying frontal boundary reaching from South Florida to the south central Gulf. 1020 mb high pressure is centered over the northwest Gulf behind the front, maintaining generally gentle to light winds and slight seas. Moderate to fresh northerly winds are noted over the far eastern Gulf between the high pressure and lower pressure off the Georgia coast, supporting 2 to 4 ft seas. No significant shower activity is observed. The high pressure will shift east toward the northeast Gulf through Fri, then into the Atlantic Sat. This will maintain moderate NE to E winds and 2 to 4 ft seas across the eastern Gulf through the period. High daily temperatures over the Yucatan peninsula will set up a weak thermal trough each evening, which will move over the eastern Bay of Campeche during the morning then dissipate during the afternoon each day beginning Wed. CARIBBEAN SEA... A sharp elongated trough reaches from central Cuba to the southwest Caribbean near 15N80W. Riding over the central Atlantic is supporting moderate to fresh E to SE winds across the basin east of the trough axis. Buoy observations and altimeter satellite data show 5 to 7 ft west of the trough. Generally gentle to light northerly winds are noted across the Caribbean. Moderate to fresh trade winds are noted across the tropical north Atlantic waters west of 55W, south of the main ridge. Seas are reaching 8 ft, but this includes a component of decaying NE to E swell. Regional radar mosaics indicate a few warm topped showers south of the central Cuba near the trough, supported by a broad mid/upper level trough south of the Caymans. A few fast moving trade wind showers are observed moving off the Atlantic into the Leeward and Windward Islands. Otherwise, no significant weather is noted. The trough is expected to drift westward and weaken through mid week, but will remain the focus for showers and a few thunderstorms through late Tue as the supporting mid/upper trough lifts northeast and dampens out. Trade wind flow will increase over the south central Caribbean by Fri night as ridging builds north of the region. Little change otherwise in the forecast. ATLANTIC OCEAN... A cold front reaches from weak 1013 mb low pressure centered north of the area, approximately 180 nm southeast of Charleston, SC, ahead of a positively tilted mid/upper trough reaching from the southern Appalachians to the lower Mississippi Valley. Scattered moderate to isolated strong convection is active from 180 to 240 nm east of the frontal boundary. The front is making very slow progress eastward as most of the supporting dynamics aloft are lifting northward. Fresh to strong southerly winds persist ahead of the front north of 27N between 70W and 75W, between the low pressure off the Carolinas and the main subtropical ridge centered farther east over the central Atlantic. Buoy observations and an altimeter satellite pass from 01 UTC indicated 5 to 7 ft seas in open waters. Higher seas and stronger gusts are possible near the aforementioned stronger thunderstorms ahead of the front. The winds ahead of the front will diminish to gentle to moderate by Wed as the low pressure lifts north. High pressure ridging extending east to west along 31N Fri through Sat night will generate gentle to moderate E to SE winds over the forecast waters, except that fresh to locally strong winds will pulse between the southeast Bahamas and the coast of Hispaniola. Farther east, a large mid/upper trough reaches from the Azores to near 18N50W. Despite upper support on the east side of the mid/upper trough, no significant moisture is noted north of the ITCZ as deep layer moisture remains limited. A front over the eastern Atlantic is keeping the subtropical ridge fairly weak east of 40W, and latest scatterometer satellite passes indicated generally moderate trade wind flow as well, except for the fresh trades west of 55W which is south of 1031 mb high pressure centered near 35N45W. Concurrent altimeter passes indicate seas are generally 5 to 7 ft over central and eastern portions of the tropical and subtropical North Atlantic. For additional information please visit http://www.hurricanes.gov/marine $$ Christensen