000 AXNT20 KNHC 311741 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 141 PM EDT Wed Jul 31 2019 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...TROPICAL WAVES... An Atlantic Ocean tropical wave is along 31W from 04N-18N, moving W around 15 kt. Scattered moderate convection is noted close to where the wave intersects the monsoon trough, from 06N-10N between 33W-36W, in an area where a recent scatterometer pass indicated a small scale low pressure area may be forming along the monsoon trough, part of a much broader gyre along the monsoon trough between 25W and 40W. Looking ahead, upper- level winds are forecast to gradually become more conducive for further development as the wave moves westward, and a tropical depression could form over the weekend several hundred miles east of the Lesser Antilles. An Atlantic Ocean tropical wave is along 48W/49W from 04N-25N, moving W around 15 kt, and is very well defined on low level precipitable water imagery. Recent scatterometer satellite passes from around 13 UTC depicted the wave very well at the surface as well. Despite abundant low level moisture, the wave is moving through an area of fairly dry mid and upper levels, and no significant convection is noted with this wave. A Caribbean tropical wave extending from central Colombia through western Haiti is moving west at 10 kt. A small area of showers and thunderstorms is noted between Jamaica and western Cuba just west of the wave axis, but otherwise no significant convection is observed near the wave over the Caribbean. An earlier scatterometer satellite pass showed a surge of moderate to fresh trade winds in the wake of the tropical wave south of Hispaniola, responsible for a line of clouds reaching from Jamaica to Costa Rica on morning visible satellite imagery. ...MONSOON TROUGH/ITCZ... The monsoon trough extends from the coast of Senegal near 14N16W to 10N35W to 11N45W to 10N50W. The ITCZ continues from 10N50W to the coast of Suriname near 05N55W. Scattered moderate convection is evident at the mouth of the Gambia River off Senegal and Gambia, and from 06N-10N between 33W-36W. GULF OF MEXICO... The main weather maker in the Gulf of Mexico currently is a broad upper low pressure centered near 27N88W. Divergence aloft on the southeast side of this upper cyclone is supporting clusters of showers and thunderstorms over the southeast Gulf, Florida Keys and parts of South Florida. Divergence aloft between the upper low and a large upper anticyclone over New Mexico is enhancing showers and thunderstorms off the coast of Texas as well. A few showers and thunderstorms are also active over the warm Loop Current in the central Gulf. Despite the thunderstorms, buoy and scatterometer passes indicated overall winds remain light to gentle. Buoys and altimeter passes show seas mainly 2 ft or less. Looking ahead, weak high pressure ridging will remain over the northern Gulf through the next few days providing for generally a gentle to moderate wind flow and relatively low seas across the area. CARIBBEAN SEA... See the Tropical Waves section above for information on the tropical wave over Caribbean Sea between Colombia and Haiti. Judging from surface based observations, buoys, scatterometer and the way the low level cloud motion is on visible satellite imagery, moderate E to SE winds dominate the eastern Caribbean east of 70W. This is in an area where a tropical wave had been entering, but the surface data and regional sounding data indicate this feature may have lost a clear definition. However, low level troughing is evident from the USVI and Puerto Rico into the Atlantic, related to a sharp upper trough north of the area. Numerous showers and thunderstorms remain active in this area extending westward into Hispaniola, related to the divergence aloft south of the upper trough axis. The pattern is fairly dry over the eastern Caribbean, and no trade wind showers are noted on regional mosaic radar imagery there. Satellite based lightning data shows a few thunderstorms active over the southwest Caribbean between Panama and Nicaragua, mainly due to trade wind convergence associated with the approaching tropical wave. Seas are 2 to 3 ft in the northwest Caribbean, 5 to 7 ft in the south central Caribbean where trade winds are strong behind the tropical wave, and 3 to 5 ft elsewhere. For the forecast, the tropical wave over between Colombia and Haiti will reach the far western Caribbean by early Sat. Another tropical wave will move across the tropical Atlantic waters through Fri enter into eastern Caribbean by late Sat, then reach thecentral Caribbean Sun and Sun night. Scattered showers and thunderstorms will be associated with these waves. In the wake of these waves, trade winds will increase to strong speeds over the south central Caribbean waters. ATLANTIC OCEAN... West of 50W, a string of upper lows interconnected by sharp upper troughs reaches from 31N50W southwestward through the Turks and Caicos and into central Cuba. Divergence aloft south of this axis is supporting clusters of showers and thunderstorms mainly south of 24N and west of 55W, with the heaviest activity over the Old Bahama Channel, where the northern extent of a tropical wave is present. A few thunderstorms are active over the Gulf Stream Current off northeast Florida. Recent scatterometer also shows fresh trad winds south of 24N with light to gentle breezes farther north into the subtropical ridge. Seas are 4 to 6 ft south of 24N and 2 to 4 ft north of 24N. Looking ahead, the northern part of the tropical wave is moving through the southeastern Bahamas will continue to move west- northwestward across the central Bahamas through Thu, then northwestward across the NW Bahamas Thu night and to southern and central Florida Fri through through Sat night. Scattered to numerous showers and thunderstorms, some with strong gusty winds and heavy rainfall, will impact the waters between Florida, the Bahamas and Cuba through Sat night. Otherwise, moderate breezes will generally prevail across the area. Farther east, a few thunderstorms are noted are noted north of 25N between 45W and 50W, related to the upper low west of the area. farther south into the tropics, scatterometer satellite passes showed fresh trade winds following the well- defined tropical wave along 48W/49W. A concurrent altimeter pass indicated 5 to 6 ft seas in the area of fresh trade winds in the deep tropics as far east as 35W. Fresh trade winds are also noted over the tropical east Atlantic, north of the broad gyre along the monsoon trough where it intersects the tropical wave along 31N. Seas east of 35W are 5 to 7 ft throughout the eastern Atlantic east of 35W. Another tropical wave may be starting to emerge into the eastern Atlantic off Africa. Looking ahead, much will depend on the development over the eastern Atlantic, particularly with the wave along 31W. Please see the Tropical Weather Outlook on hurricanes.gov for more information regarding these developments. For additional information please visit http://www.hurricanes.gov/marine $$ Christensen