000 AXNT20 KNHC 290004 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 804 PM EDT Sun May 28 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 2345 UTC. ...TROPICAL WAVES... A tropical wave came off the W coast of Africa earlier today. Its axis extends from 16N16W to 05N16W and is expected to move at 10 kt within the next 24 hours. Even though the wave is in a favorable wind shear environment, the CIRA LPW imgery show shallow moisture with large patches of dry air, which in part hinder convection at the time. A tropical wave is in the central Atlc with axis extending from 09N30W to 01S30W, moving W at 10-15 kt within the last 24 hours. Unfavorable wind shear is N of 05N, and dry air intrusion is seen on enhanced satelite imagery in the NW wave environment. However, CIRA LPW imagery show shallow moisture and large patches of dry air in the wave environment. Middle to upper level diffluece support scattered to isolated showers from 01N-06N between 25W- 35W. A tropical wave is in the W Atlc with axis extending from 15N51W to 05N52W, moving W at 20-25 kt within the last 24 hours. The wave is in an unfavorable wind shear environment and satellite enhanced imagery show Saharan dry air and dust in the wave environment, which in part inhibit convection at the time. A tropical wave is in the E Caribbean with axis extending from 17N62W to 10N63W, moving W at 20-25 kt within the last 24 hours. Cira LPW show mainly moderate low level moisture in the wave environment with small patches of dry air associated with the Saharan Air Layer. Even though the wave is in a region of unfavorable wind shear, upper level divergence support scattered heavy showers and tstms across the Lesser Antilles and the Virgin Islands. This showers will start affecting Puerto Rico tonight as the wave continues a westward track. ...ITCZ/MONSOON TROUGH... The monsoon trough is inland Africa. The ITCZ begins near 04N18W to 04N30W...then resumes W of a tropical wave near 04N32W and continues to 06N46W. For information about convection see the tropical waves section. ...DISCUSSION... GULF OF MEXICO... A weak surface ridge prevails in the eastern Gulf anchored by a 1017 mb high near 26N84W, which is forecast to stall through Monday evening. Scattered showers are off the Florida Panhandle coast N of 28N ahead of a cluster of heavy showers and tstms that is being supported by low level moisture being advected from the Caribbean by SE flow. This cluster of heavy showers is located S of Louisiana to 26N between 88W and 92W and is also being supported by upper level diffluence between a trough with base over the northern Gulf and a ridge that covers the remainder basin. GOES IFR show medium to high chances of dense fog in the NW basin, which is confirmed by surface observations. Low visibility is in that region...caution should be excercised by vessels. A thermal trough will is over the W Yucatan Peninsula, which will move west across the SW Gulf tonight and then will dissipate near 94W by late in the morning. A surge of fresh to locally strong winds will follow the trough. Little change in this weather pattern is expected through Tuesday. CARIBBEAN SEA... A tropical wave is in the E Caribbean supporting scattered heavy showers and tstms. See the tropical waves section for additional details. Shallow moisture along with a weak and broad upper level trough support scattered showers along Cuba and isolated showers over Jamaica and central Hispaniola. Heavy showers and tstms are in the SW basin S of 12N being supported by the EPAC monsoon trough that extends from Costa Rica to Panama to a low over NW Colombia. Strong dry air subsidence is elsewhere, which supports fair weather. Otherwise, high pressure over the central Atlantic extends a ridge SW across the northern Caribbean Sea, which will support fresh to strong easterly winds across the south-central Caribbean between 74W and 77W at night through Tuesday. Pulsing fresh to strong E to SE winds are also expected over the Gulf of Honduras through this period. Moderate trades are expected elsewhere. HISPANIOLA... A broad and weak upper level trough, middle level diffluent flow and shallow moisture in the vicinity of the Island support isolated showers and tstms mainly in the W Dominican Republic and Haiti. Scattered heavy showers are forecast Tuesday associated with the tropical wave currently over the eastern Caribbean. ATLANTIC OCEAN... Fair weather conditions are in the SW N Atlc with no significant surface features at the time. The remainder central and eastern Atlc is under the influence of a broad surface ridge anchored by a 1025 mb high near 29N44W, which is expected to move slightly SW to near 27N46W by Monday evening. A dissipating cold front extends from 30N20W to 26N30W to 28N40W with no associated convection. Otherwise, four tropical waves are passing over the tropical Atlc. Please refer to the Tropical Waves section for more details. For additional information please visit http://www.hurricanes.gov/marine $$ Ramos