000 AXNT20 KNHC 290557 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 157 AM EDT Sat Jul 29 2017 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 tropical wave came off the W African coast earlier today. The wave axis is not depicted in the latest surface analysis map, however latest satellite derived winds and imagery indicate its axis is approximately from 18N20W to 05N20W. The wave is in a region of low to moderate vertical wind shear and is being engulfed by Saharan dry air and dust. Abundant low level moisture along with middle to upper level diffluence support scattered moderate convection from 5.5N to 13N E of 30W. A tropical wave is in the central Atlc associated with a 1012 mb low near 11N39W. Its axis extends from 19N38W to the low to 06N39W and it has been moving W at 10 kt within the last 24 hours. The wave is in a region of weak vertical wind shear, however is being severely affected by Saharan dry air and dust intrusion to its environment, which is hindering convection. A tropical wave is in the central Atlc with axis extending from 22N51W to 16N52W to 08N52W, moving west at 20 kt within the last 24 hours. The wave is in a weak to moderate vertical wind shear environment, but continues to be severely affected by Saharan dry air and dust intrusion to its environment, which is inhibiting the development of convection. A tropical wave is in the E Caribbean with axis extending from 20N66W to 10N67W, moving W at 10 kt within the last 24 hours. Water vapor imagery depict dry subsident air over the wave also noticed in the CIRA LPW imagery. Besides dry air, strong vertical wind shear is in the E Caribbean, which is influencing to the lack of deep convection at this time. The wave will move through the central Caribbean on Saturday. A tropical wave is in the W Caribbean with axis extending from 19N81W to 08N81W, moving W at 15 kt within the last 24 hours. Scattered showers are within 90 nm off the coast of Costa Rica and northern Panama. Otherwise, strong vertical wind shear is in the W Caribbean, which is influencing the lack of deep convection elsewhere. The wave will move across inland over central America on Saturday. ...ITCZ/MONSOON TROUGH... The monsoon trough extends from 18N16W to 12N27W to 08N38W. The ITCZ extends from 08N42W to 08N58W. Aside from convection related to the tropical wave described above, scattered moderate isolated strong convection is from 05N to 11N between 33W and 37W. ...DISCUSSION... GULF OF MEXICO... A surface ridge prevails across the basin anchored by a 1014 mb high centered near 27N89W. Water vapor imagery and satellite derived winds indicate anticyclonic flow aloft covering most of the Gulf, which is centered in northern Texas. Deep layered subsidence accompany the flow over the Gulf west of 90W while upper level moisture prevails east of 90W. Scatterometer and surface observational data depict light to gentle winds across the basin. A fairly deep mid to upper level trough for mid-summer will push a cold front southward to the deep south by late Sat with an increase in showers and thunderstorms along the Gulf coast. The front itself will enter the northern Gulf on Sun with winds shifting to the north. Increasing SW to W winds will develop south of the front over the Gulf to 25N. CARIBBEAN SEA... Two tropical waves are moving across the basin. Refer to the section above for details on these features. Isolated heavy showers and tstms continue within 90 nm of the coast of SW Cuba being supported by a middle to upper-level low centered over the Island. Diffluent flow to the E of the low aloft support isolated showers over Haiti. Scatterometer data indicated fresh to strong trades over the south-central Caribbean with generally light winds over the western portion of the basin. Little change in the overall conditions is expected through the weekend. ...HISPANIOLA... Diffluent flow to the E of an upper-level low situated near central Cuba support isolated showers over Haiti early this morning. Moisture is expected to increase slightly Saturday as a tropical wave passes through the central Caribbean. Some pockets of dry air behind the wave will follow in behind the wave. ATLANTIC OCEAN... Three tropical waves are moving across the basin. Refer to the section above for details. Diffluent flow E of an upper level-low centered over Cuba continue to support scattered heavy showers and tstms in the Great Bahama Bank and southern adjacent waters of the central Bahamas. This activity is expected to lift northward on Saturday in response to a frontal boundary that will push off the southeastern United States and move to the northwest portion of the basin late Saturday through Sunday. The remainder of the basin is under the influence of a surface ridge anchored by a 1025 mb high centered near 30N38W. For additional information please visit http://www.hurricanes.gov/marine $$ Ramos