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Tropical Weather Discussion...updated

Tropical Weather Discussion...Updated NWS National Hurricane Center Miami FL 522 PM EDT Mon Jul 16 2018 Updated Tropical Waves section 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 2100 UTC. ...SPECIAL FEATURES... SW Caribbean Sea gale warning: The synoptic pattern set-up with strong high pressure situated over the central Atlantic interacting with broad low pressure over the SW Caribbean Seas and over northern S America will allow for the ongoing strong to near gale force NE to E strong winds near the coast of Colombia from 11N to 13N between 74W and 76W to again reach minimal gale force Tue night and Wed night over the same area along with seas in the range of about 9-13 ft. Please read the High Seas Forecast, under the AWIPS/WMO headers HSFAT2/FZNT02 KNHC, for more details. ...TROPICAL WAVES...Updated An eastern Atlantic tropical wave axis stretches from near 23N38W to 15N40W and to 05N42W, moving westward at 15-20 kt. The wave is depicted on GOES-16 RGB imagery as having a rather broad inverted-V shape envelope of broken to overcast of mainly stratocumulus clouds covering over an area from 09N-23N between 30W-50W. Scattered moderate convection is behind the wave along and within 60 nm either side of the ITCZ between 35W-40W. Scattered showers and isolated thunderstorms are ahead of the wave from 06N-09N between the wave and 44W. The GOES-16 RGB images along with visible images of the far eastern Atlantic are depicting yet another massive plume of Saharan dry air and associated dust following in behind the wave from 09N-27N east of 36W to well inland Africa, where even more intense Saharan dust is being captured by the GOES-16 imagery behind and around another tropical wave. Visibilities within these areas of dust are expected to be sharply reduced. An eastern Caribbean Sea tropical wave is tilted NE to SW with its axis reaching from Puerto Rico to just inland the coast of Venezuela at 11N69W, moving westward at about 20 kt. This wave continues to be impinged upon by Saharan dust as observed in GOES-16 satellite imagery. Scattered showers and isolated thunderstorms moving quickly west-northwestward are seen north of 15N between 67W-72W, while isolated showers also moving quickly west-northwestward are seen north of 13N and east of 74W to vicinity of the Leeward Island and northern Windward Islands. This wave will move across the rest of the eastern Caribbean Sea through by early Tue, then across the central Caribbean Sea through Wed night and the western Caribbean Seas Thu through Fri before moving inland Central America and the Yucatan Peninsula Fri night. The Saharan dust in its wake will filter across the eastern Caribbean and much of the central Caribbean through Wed. A western Caribbean Sea tropical wave has its axis along 84W, moving westward at 10-15 kt. Scattered moderate isolated strong convection is occurring within 180 nm east of the axis over the southwestern Caribbean from just east of northern Panama, north to 12N. Scattered showers and thunderstorms are seen over much of the southern and central sections of Nicaragua. This wave will move west of the area and into the eastern Pacific late Tue. ...MONSOON TROUGH/ITCZ... The monsoon trough extends from the coast of southern Guinea Africa to 07N17W and to 08N26W, where latest scatterometer data indicate that it transitions to the ITCZ and continues to 08N33W to 06N41W and to near 05N51W. Aside from the convection near the eastern Atlantic tropical wave, scattered moderate convection is within 60 nm north of the ITCZ between 44W-51W. Similar activity is to the NW of the ITCZ from 05N-07N between 51W-57W. ...DISCUSSION... GULF OF MEXICO... A 1019 mb high centered over the central gulf waters near 26N91W, and is the main feature that is influencing the synoptic pattern across the basin. Its associated gradient is allowing for generally light to moderate anticyclonic flow to exist over the gulf waters. Current NWS mosaic radar displays show scattered to numerous showers and thunderstorms rapidly increasing over the far northern gulf north of 28N between 86W-90W. This activity is expected to remain active through at least the next couple of days as upper-level disturbances move from E to W around the eastern periphery of an upper-level anticyclone centered over western Texas. Isolated showers and thunderstorms moving westward are present over much of the eastern gulf waters as well as over the eastern half of the central gulf. This activity should continue through tonight and into Tue. Expect high pressure to prevail across the northern waters through Thu. A surface trough will move westward off the Yucatan Peninsula each evening through Thu, enhancing nocturnal winds over the eastern section of the SW Gulf. CARIBBEAN SEA... Please read the Special Features section for details about pulsing gale force winds near the coast of Colombia. Aside from the tropical waves mentioned above, an upper level low is noted on water vapor imagery just to the south of the Yucatan Channel. A rather dry and stable environment is only for isolated showers moving quickly with the trade wind flow to occur across much of the basin. Mainly fresh E winds will continue over the central Caribbean Sea through Thu, with the exception of strong NE-E winds in the SW and S central sections of the Caribbean outside the near gale to minimal gale force wind area described above. ATLANTIC OCEAN... A weak surface trough extends from near 32N78W southwestward to just east of NE Florida. Scattered showers and isolated thunderstorms are seen north of 28N between 72W and 79W. Another surface trough extends from near 32N60W to 29N67W and northwestward to near 32N76W. Scattered moderate isolated strong convection is along and within 90-120 nm SE of this trough between 60W-64W while isolated showers and thunderstorms are along and within 60 nm SE of the trough between 64W-75W. This trough will slowly weaken through Tue as the supporting upper trough lifts to the NE away from it. High pressure will build in the wake of the trough. A large area of Saharan Air Layer (SAL) dust that is currently over the central Atlantic from 08N-24N and between 45W-60W will continue to translate westward through the rest of the week. A weaker area of dust is visible from the SE Bahamas to 60W and from 09N-27N, also translating in westward motion. For additional information please visit