000 AXNT20 KNHC 190000 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 800 PM EDT Thu May 18 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 1800 UTC surface analysis and satellite imagery through 2315 UTC. ...SPECIAL FEATURES... The persistent upper-level trough located over the NW Caribbean the past few days has begun to fracture with the southern portion of the trough beginning to fill and drift westward. The upper level flow over Hispaniola is gradually becoming more zonal which has partially resulted in an abatement of deep convection over the island this evening. The large area of deep convection noted earlier across the central Caribbean has propagated southward toward the extreme southern Caribbean. Additional convection was developing near western Jamaica. The associated surface trough and a tropical wave have moved well west of the area with the surface trough over western Cuba/Florida straits and the tropical wave along 80W. The 1200 UTC Kingston rawinsonde still indicated deep layered moisture with precipitable water values of 2.27". Some drying between 800 and 500 mb was noted on the 1200 UTC Santo Domingo rawinsonde suggesting some dry air was advecting into Hispaniola/Haiti. Per NWP model guidance and recent trends, the heavy rainfall threat appears to be shifting to Jamaica and the NW Caribbean over the next 24 hours or so. Please monitor advisories and bulletins from local meteorology offices, emergency management services, and other governmental agencies. Please refer to the METEO-FRANCE High Seas Forecast, listed on the website: WWW.METEOFRANCE.COM/PREVISIONS-METEO-MARINE/BULLETIN/ GRANDLARGE/METAREA2. Gale-force winds are forecast for the areas of AGADIR and CANARIAS. These conditions will dissipate during the next 24 hours. ...TROPICAL WAVES... Tropical wave axis extends from 11N44W to 01N45W, moving west at 15-20 KT. Moisture within the wave environment has decreased some over the last six hours as noted in TPW imagery. Scattered showers are observed from 04N-08N between 47W-50W. A tropical wave is moving across central Venezuela with axis from 11N65W to 01N65W, moving westward at 10 knots. No significant convection is related to this wave at this time. A tropical axis extends from 15N80W across central America into the EPAC near 05N81W, moving west at 10 kt. Abundant moisture prevails in the wave's environment, as noted in TPW imagery. Scattered moderate convection is observed within this wave affecting the south-central Caribbean from 13N-18N between 73W-79W. ...ITCZ/MONSOON TROUGH... The Monsoon Trough extends from 18N16W to 09N27W. The ITCZ extends from 05N33W to 01S47W. Scattered moderate to strong convection was noted from 04N-09N between 17W-21W. Scattered moderate covection was noted within 180-240 NM of the coast of Liberia. ...DISCUSSION... GULF OF MEXICO... Upper-level westerly flow covers the Gulf of Mexico with water vapor imagery depicting deep layered subsidence over the southeastern half of the Gulf. A band of upper level moisture swept across the far NW Gulf. Satellite derived winds indiacted the axis of the subtropical jet along the Texas coast. At the surface, a ridge extends along 29N/30N anchored across the western Atlantic near 33N64W. Lower pressures prevail across Mexico and the far west Gulf waters. The resulting pressure gradient is supporting moderate to fresh SE winds across the northern half of the basin. Light to gentle winds prevail elsewhere. Little change is expected during the next 24 hours. CARIBBEAN SEA... A tropical wave is moving across the south-central portion of the basin along 80W. Please refer to the SPECIAL FEATURES section above for details. A deep-layered trough extends its axis across the western Caribbean and western Atlantic and was in the process of fracturing. A surface trough was analyzed from 22N80W to 19N82W. Some diffluence prevailed to the east of the trough over the southern Caribbean with waning support for scattered showers and thunderstorms within 90 NM of 12N77W. Despite the fact that the convection has moved south of the island of Jamaica, Cuba and Hispaniola, re-development could occur tonight and Friday mainly over Jamaica and Cuba. Please monitor advisories and bulletins from local meteorology offices and other governmental agencies. 1500 UTC ASCAT passes depicted fresh to locally strong trades over the central portion fo the basin between 70W-77W with subnormal trades over the far western portion of the basin. The surfrace trough and tropical wave should move further west with stronger trades spreading westward in their wake. ...HISPANIOLA... Upper-level flow has become more zonal across the island with a break in the heavy rainfall from the past few days. As noted above, mid-level drying was noted on the 1200 UTC Santo Domingo rawindsonde from 800-500 mb. NWP model guidance and the recent trend of mid-level srying suggests the threat of heavy rainfall should lessen over the next 24 to 48 hours. Please monitor advisories and bulletins from local meteorology offices, emergency management services, and other governmental agencies. ...ATLANTIC OCEAN... A Gale Warning is in effect for the far east Atlantic waters. Please refer to the SPECIAL FEATURES section above for details. A 1025 mb surface high is centered near 33N64W. Its associated ridge extends across the western Atlantic W of 50W. Another surface ridge extends across the remainder of the basin, anchored by a 1030 mb high centered near 41N23W. For additional information please visit http://www.hurricanes.gov/marine $$ Cobb