000 AXNT20 KNHC 210603 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 203 AM EDT SUN AUG 21 2016 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. ...SPECIAL FEATURES... Tropical Storm Fiona is centered near 21.7N 50.1W at 21/0300 UTC or about 717 nm east-northeast of the Leeward Islands, moving northwest at 13 kt. Estimated minimum central pressure is 1004 mb. Maximum sustained wind speed is 45 kt with gusts to 55 kt. A cluster of heavy showers is from 20N-23N between 47W-50W. Please see the latest NHC Intermediate Public Advisory under AWIPS/WMO headers MIATCPAT1/WTNT31 KNHC and the full Forecast/Advisory under the AWIPS/WMO headers MIATCPAT1/WTNT21 KNHC for more details. Tropical wave is just off the west coast of Africa extending from 06N-19N with axis near 16W. There is a 1011 mb low near 12N16W associated with the wave, which is expected to move at 10-15 kt within the next 24 hours. The wave is within a moderate moist environment and it is in a region of favorable to neutral deep layer wind shear that favors scattered heavy showers and isolated tstms from 06N-15N E of 21W. Environmental conditions appear conducive for gradual development, and a tropical depression is likely to form in a few days while the system moves westward and then northwestward over the eastern tropical Atlantic Ocean. ...TROPICAL WAVES... Tropical wave is in the central Atlantic extending from 05N-18N with axis near 39W, moving W at 15-20 kt within the last 24 hours. There is a 1009 mb low near 12N39W associated with the wave. Intrusion of Saharan dry air and dust to the wave environment continue to limit the convection to scattered showers from 05N-17N between 35W and 49W. Any development of this system during the next couple of days should be slow to occur due to its large size and proximity to dry air. Environmental conditions are forecast to be more conducive for development beyond a couple of days, and a tropical depression could form by the middle of next week while the system moves westward and then west-northwestward across the tropical Atlantic Ocean, through the eastern Caribbean Sea, and then near the Greater Antilles. Tropical wave in the central Caribbean extends from 09N-19N with axis near 71W, moving W at 10 kt within the last 24 hours. Even though the wave is in a region of favorable to neutral deep layer wind shear, strong dry air subsidence from aloft inhibits convection at the time. Tropical wave across the Yucatan Peninsula and northern Central America extends from 09N-22N with axis near 88W, moving W at 20 kt within the last 24 hours. CIRA LPW imagery from surface to 850 mb show mainly dry air in the wave environment. However, satellite derived data indicate the wave is in a region of mainly unfavorable deep layer wind shear. These two factors combined support the lack of convection in the NW Caribbean and Yucatan Peninsula. ...ITCZ/MONSOON TROUGH... The Monsoon Trough extends across Africa into the east Tropical Atlantic near 12N17W to 10N30W through the 1009 mb low near 12N39W to 08N48W. The ITCZ begins near 08N48W to the coast of Venezuela near 08N61W. For convection information, see the tropical waves section. ...DISCUSSION... GULF OF MEXICO... Weak surface ridging dominates across the Gulf waters N of 22N, being anchored by a 1016 mb high near 26N84W. The ridge continue to provide gentle variable flow across the east basin and E-SE gentle to moderate flow elsewhere. A tropical wave is moving across the Yucatan Peninsula supporting cloudiness and providing NE moderate to fresh wind across the eastern Bay of Campeche. Dry air subsidence and unfavorable deep layer wind shear support fair weather elsewhere. Mostly gentle to moderate E-SE winds are expected through late Sunday. Fresh to strong winds are forecast to develop over the Bay of Campeche Monday before sunrise. CARIBBEAN SEA... Water vapor imagery continue to show very dry and stable air across the Caribbean, thus supporting fair weather basin-wide. The exception are isolated heavy showers and tstms within 90 nm off the coasts Costa Rica and Panama associated with the proximity of the east Pacific monsoon trough. Two tropical waves remain the main features across the basin, the westernmost wave moving across Central America and the second one moving across the central basin. For more details about the waves see the tropical waves section. The tropical wave in the central Caribbean has amplified the area of fresh to strong trades to S of 18N between 68W and 80W. These winds are forecast to prevail through near Tuesday sunrise. ...HISPANIOLA... A tropical wave is moving across the central Caribbean, however very dry air subsiding from aloft is supporting fair weather conditions across the entire Island. These favorable weather conditions are forecast to prevail through Monday near sunrise. ATLANTIC OCEAN... The primary concern in the Atlantic waters S of 30N continue to be Tropical Storm Fiona. Please see the Special Features section above for more details. The remainder of the basin is dominated by a surface ridge anchored by a 1022 mb high near 29N35W. For additional information please visit http://www.hurricanes.gov/marine $$ RAMOS