Tropical Weather Discussion
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000 AXNT20 KNHC 191033 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 633 AM EDT Sat Aug 19 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 0600 UTC surface analysis and satellite imagery through 1030 UTC. ...SPECIAL FEATURES... Tropical Storm Harvey is located near 13.8N 65.9W at 19/0900 UTC, or about 243 nm south of St. Croix, moving west at 18 kt. Estimated minimum central pressure is 1005 mb. Maximum sustained wind speed is 35 kt with gusts to 45 kt. The low-level center of Harvey remains near the eastern edge of a strong convective area that covers the area from 10N-17N between 65W-71W. Harvey will continue moving through the eastern and central through the day. Interests in the Caribbean Sea and the adjacent land areas of eastern Central American and northern South America should monitor the progress of Harvey. Locally heavy rains could occur tonight over portions of the Windward Islands and the offshore islands of northern Venezuela. Locally heavy rains could also occur over Aruba, Bonaire, and Curacao today. See the latest NHC Intermediate Public Advisory under AWIPS/WMO headers MIATCPAT4/WTNT34 KNHC, and the full Forecast/Advisory under AWIPS/WMO headers MIATCMAT4/WTNT24 KNHC for more details. ...TROPICAL WAVES... A tropical wave is in the east Atlantic with axis extending from 20N39W to a 1010 mb low pressure located near 13N40W to 10N40W. Satellite imagery indicates a large cyclonic circulation in the cloud field, but convection is limited in association with this low. Saharan dust surrounds the wave/low. This system coincides with a well defined 700 mb trough, and a high amplitude northward bulge of moisture is noted on the TPW imagery. Environmental conditions appear somewhat conducive for gradual development over the next few days while the system moves west-northwestward to northwestward at about 15-20 kt, but upper-level winds are forecast to become unfavorable by the middle of next week. This system has a low change of becoming a tropical cyclone within the next 48 hours. A tropical wave extends across the central Atlantic with axis from 22N57W to 11N57W, moving west at 10-15 kt. The wave shows up very well on the TPW animation and 700 mb streamline analysis. At this time, scattered showers are noted across the northern portion of the wave mainly north of 18N between 53W-59W. Environmental conditions are expected to be only marginally conducive for development during the next few days. This system has a low change of becoming a tropical cyclone within the next 48 hours. A tropical wave extends from the northern Bahamas, across central Cuba and west of Jamaica, then to the southwest Caribbean, moving west at 10-15 kt. An area of moderate convection is along the wave`s axis from 22N-28N between 74W-80W. The wave shows up very well on the TPW animation and 700 mb streamline analysis. Moisture associated with this wave will continue spreading over the northern Bahamas and central Cuba this morning, and across south Florida and western Cuba in the afternoon and evening, increasing the likelihood of showers and thunderstorms. There is a potential of locally heavy rain and localized flooding with this activity. ...ITCZ/MONSOON TROUGH... The monsoon trough extends from the African coast near 15N17W to the low/wave near 14N40W. No significant convection is observed at this time. ...DISCUSSION... GULF OF MEXICO... A weak surface ridge continues to dominate the Gulf waters, anchored by a 1017 mb high centered near 28N88W. Mainly light to gentle anticyclonic winds are prevailing across the basin. A surface trough is analyzed from 30N84W to 28N86W. Scatterometer and surface data indicate the wind shift associated with this trough. A thermal trough will develop during the evening hours over the Yucatan Peninsula before pushing offshore into the SW Gulf each night. A surge of fresh winds will accompany this trough. Little change in this weather pattern is expected through early next week. In the upper levels, a large and well-defined upper-level low is spinning over the Straits of Florida inducing some shower activity over the southeastern Gulf and the Florida Peninsula. The upper-low will drift westward across the eastern Gulf during the weekend. CARIBBEAN SEA... A tropical wave is over eastern Cuba along 79W. Please, see the Tropical Waves section above for details. Tropical Storm Harvey will continue moving through the eastern and central Caribbean through the day. Please, see the Special Features section for more details. An upper-level low spinning over the waters just north of western Cuba supports scattered showers across the northwest Caribbean waters and the Yucatan Channel. Scattered showers and thunderstorms are noted over the southwest Caribbean mainly south of 10N associated with the eastern extent of the Pacific`s monsoon trough combined with a diffluent pattern aloft. ...HISPANIOLA... Daytime heating, local sea breezes and mountain upslope lifting will combined with available moisture will produce scattered showers and thunderstorms across the island mainly during the afternoon and evening hours through the weekend. ATLANTIC OCEAN... A pair of tropical waves are moving westward across the tropical Atlantic while the northern portion of another tropical wave is affecting the northern Bahamas. Please, see the Special Features and Tropical Wave sections above for details. The remainder of the Atlantic is under the influence of a surface ridge, with a center of 1026 mb located near 39N22W. A belt of fresh to locally strong easterly winds is noted per scatterometer data roughly between 17N-23N due to the pressure gradient between the ridge and the tropical waves and associated areas of low pressure between the coast of Africa and the Lesser Antilles. Fresh to strong northerly winds are also noted between the coast of Africa and the Madeira/Canary Islands. These winds are the result of the pressure gradient between the Atlantic ridge and lower pressures over west Africa. For additional information please visit http://www.hurricanes.gov/marine $$ ERA

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