Tropical Weather Discussion
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548 AXNT20 KNHC 162258 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 658 PM EDT Wed Aug 16 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 2215 UTC. ...SPECIAL FEATURES... Hurricane Gert is centered near 38.7N 62.4W at 16/2100 UTC or about 355 nm S of Halifax Nova Scotia and about 630 nm SW of Cape Race Newfoundland moving NE at 27 kt. Estimated minimum central pressure is 970 mb. Maximum sustained wind speed is 85 kt with gusts to 105 kt. Scattered to numerous moderate convection is from 37N-42N between 58W-65W. Widely scattered moderate convection is elsewhere from 35N-44N between 53W-66W. See latest NHC forecast/ advisory under AWIPS/WMO headers MIATCMAT3/WTNT23 KNHC for more details. A tropical wave extends from 14N37W to 24N37W moving W at 10-15 kt. A 1009 mb low is centered at the southern extent of the wave axis that coincides with maximum low to mid-level 700-800 mb relative vorticity. Scattered moderate convection is from 14N-16N between 38W-40W. A 1009 mb low is centered near 14N49W moving W at 10-15 kt. This low is also a focus of 850 mb relative vorticity on the southern periphery of a mid-level ridge anchored over the central Atlc to the N. Scattered moderate convection is from 12N-16N between 49W-54W. ...TROPICAL WAVES... A tropical wave extends from 09N18W to 21N14W moving W at 10-15 kt. The wave coincides with broad 700 mb troughing between 13W-27W that continues to emerge off the coast of West Africa this evening. A pair of surface lows...one a 1008 mb low centered near 17N18W and the other a 1010 mb low centered at the southern extent of the wave axis near 09N18W indicates the northern and southern vortices respectively and the broad nature of spin in the local environment surrounding the wave. Last evening...very strong and intense convection was occurring...however this evening only widely scattered moderate convection is noted from 06N-13N between 12W-22W. A tropical wave extends from 10N64W to 22N60W moving W at 20-25 kt. The wave coincides with 700 mb troughing between 59W-70W that continues to provide a favorable environment for scattered moderate convection from 13N-22N between 58W-68W. This area of convection also falls within the eastern periphery of an upper level low noted on water vapor imagery centered near 20N72W. A tropical wave extends from 10N84W to 21N83W moving W at 15-20 kt. The wave is noted on the southeastern periphery of a 700 mb ridge anchored over the Gulf of Mexico near 27N87W. Widely scattered moderate convection is from 09N-17N between 79W-87W. ...ITCZ/MONSOON TROUGH... The monsoon trough extends from the African coast near 11N15W to 08N21W to 11N30W. To the west...the monsoon trough and ITCZ is disrupted due to the tropical lows and tropical waves mentioned above. Otherwise...scattered moderate convection is from 06N-10N between 25W-31W...and from 06N-09N between 35W-50W. ...DISCUSSION... GULF OF MEXICO... Upper level divergent flow persists over the lower Mississippi River valley this evening between a broad upper level low centered in the western Gulf near 23N93W and an upper level anticyclone centered near 31N81W. Scattered showers and tstms are mainly occurring across inland portions of extreme eastern Texas...Louisiana...and Mississippi...with only a few isolated showers and tstms noted across the NW Gulf waters N of 26N W of 92W. This activity all lies on the northern side of a surface ridge extending east to west along 27N/28N and anchored by a 1020 mb high centered near 28N87W. Mostly light to gentle anticyclonic flow is E of 90W and gentle to moderate S-SE flow is W of 90W. The high is expected to persist across the NE Gulf waters through early Saturday. A surface trough will develop each evening across the Yucatan peninsula shifting W into the Bay of Campeche during the overnight hours. Locally higher winds can be expected in the vicinity of the trough axis. CARIBBEAN SEA... A tropical wave is analyzed across the western Caribbean this evening generating scattered showers and tstms across the Gulf of Honduras region and inland portions of Central America. Overall middle to upper level divergence is noted to the E of the wave axis over the SW Caribbean producing widely scattered showers and isolated tstms S of 13N between 72W-84W. Elsewhere...scattered showers and tstms have likely peaked in intensity across Cuba and continue moving offshore into the NW Caribbean waters. With the loss of daytime heating and instability...this activity will gradually decrease and then dissipate tonight. Farther east... another tropical wave is impacting the eastern Caribbean with scattered showers and tstms remaining E of 70W. Much of this activity is being enhanced by an upper level low centered N of Hispaniola near 20N72W. Otherwise...fresh to strong winds in the south-central waters and in the vicinity of the tropical wave in the eastern waters are expected through Thursday...with moderate to fresh trades elsewhere. ...HISPANIOLA... An upper level low is centered N of the island near 20N72W and is providing overall dry conditions this evening...however a tropical wave extends across the eastern Caribbean Sea and will move across the island through Friday. Scattered showers and tstms are expected to spread westward from the Mona Passage region tonight to the Windward Passage region by Thursday night into Friday. ATLANTIC OCEAN... Widely scattered showers and isolated tstms remain N of 27N between 65W and 77W associated with frontal troughing extending SW from Hurricane Gert centered N of the discussion area. Otherwise...the remainder of the basin generally N of 23N is under the influence of the Azores subtropical high which supports fair weather. A 1025 mb high is centered S of the Azores near 35N27W and a 1025 mb high is centered near 32N43W. For additional information please visit http://www.hurricanes.gov/marine $$ HUFFMAN

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