000 AXNT20 KNHC 111751 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 151 PM EDT Tue Jul 11 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 1200 UTC surface analysis and satellite imagery through 1715 UTC. A tropical wave is analyzed over the far eastern Atlantic along 21N from 05N to 13N. Deep layer moisture is associated with the tropical wave south of 11N, with Saharan dust prevaling north and ahead of the wave. A cluster of moderate to isolated strong convection is noted ahead of the wave axis from 07N to 10N between 21W and 24W. The tropical wave previously located along 34W/35W is relocated farther west along 37W based on visible satellite imagery and the TPW animation. This tropical wave remains well defined in satellite derived wind fields. Scattered showers are near the wave axis between 35W and 40W. A tropical wave is analyzed along 56W/57W on the 1200 UTC analysis/surface map based also on visible satellite imagery, that shows some inverted-V pattern in the cloud field, and the TPW product where a sharp inverted trough is noted. This wave coincides with a broad trough previously located along 55W. A patch of moisture with embedded showers is related to this wave forecast to reach the Lesser Antilles late today. A tropical wave is over the central Caribbean Sea and extends from eastern Cuba to the coast of Colombia near 10.5N75W. No significant convection is noted with it. ...ITCZ/MONSOON TROUGH... The monsoon trough passes through Senegal near 14N16W to 10N19W to 09N35W. The ITCZ extends from 08N38W to 09N60W. Scattered moderate convection is observed within about 150 nm N of ITCZ axis between 49W and 55W. A small cluster of moderate to isolated strong convection is from 09N to 11N between 17W and 18.5W. ...DISCUSSION... ...THE GULF OF MEXICO... A ridge continues to dominate the Gulf waters producing mainly gentle winds and slight seas. The ridge will persist through Thursday. A trough is over the NE Gulf and extends from 27N85W to 23N86W. Scattered showers and thunderstorms are over the NE Gulf associated with this trough forecast to dissipate by tonight. Similar convective activity is noted over the western Gulf, and mainly from 21N to 24N west of 95W, including also the mexican coastline. A diffluent pattern aloft ahead of an upper-level low centered over NE Mexico is helping to induce this activity. As usual, a thermal trough will develop over the Yucatan Peninsula during the late afternoons, move NW during the overnight hours dissipating over the SW Gulf by late each morning. A surge of moderate to locally fresh winds will be associated with this thermal trough. Looking ahead, a surface trough, associated with the remnants of T.D Four, currently located along 68W, will move across south Florida on Thursday, and across the E Gulf Thursday night into Friday, reaching the central Gulf later on Friday. This trough is expected to increase the likelihood of showers with embedded thunderstorms. ...THE CARIBBEAN SEA... A recent scatterometer pass provided observations of fresh to strong winds over the south-central Caribbean ahead of and in the wake of a passing tropical wave. The area of strong trade winds is shrinking slightly however as high pressure north of the region weakens. A large area of showers and thunderstorms is over the SW Caribbean, and covers the region South of 14N west of 80W, and south of 13N between a tropical wave with axis along 75W and 80W. This convective activity is likely associated with a weak low pressure system located along the monsoon trough near 10N79W. In addition, a very well defined diffluent pattern aloft supports this strong convective activity. An upper-level low persists near the Cayman Islands and continues to enhance some shower activity over eastern Cuba and the Cayman Islands. This upper-level low is forecast to persist on Wednesday while weakening. Looking ahead, a stronger tropical wave is forecast to approach the Windward Islands late Thursday and enter the eastern Caribbean early on Friday. ...HISPANIOLA... Available moisture will combined with the local effects to produce scattered showers and isolated and thunderstorms during the afternoon and early evening hours. The upper-level low located west of the area, that was enhancing convection across the island is forecast to weaken on Wednesday, then dissipate over the next 24 hours. ...THE ATLANTIC OCEAN... A 1014 mb low pressure, remnants of T.D. Four is situated near 23N68.5W. Scattered showers and thunderstorms area near the low center, with another area of cloudiness with embedded showers and thunderstorms to the SE of the low center. This low is forecast to approach the SE Bahamas by early Wednesday morning. So far, the GFS Computer Model suggests that a trough associated with the remnants of T.D. Four will move across the Bahamas through Wednesday night, reaching south Florida on Thursday. A surface trough extends from 24N45W to 19N46W. Scattered showers are near the northern end of the trough axis. Another surface trough is along 73W from 26N to 30N. Isolated showers and thunderstorms are near the trough axis. Farther east, an upper-level low is centered near 28N58W, supporting scattered showers and thunderstorms from 26N to 29N between 57W and 61W. The Bermuda-Azores high extends a ridge across the remainder of the forecast region. An extensive area of African Saharan dust is reaching 45W based on the Saharan Air Layer Tracking Product from CIMSS. 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