000 AXNT20 KNHC 300002 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 801 PM EDT Thu Jun 29 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... Please refer to the METEO-FRANCE High Seas Forecast, that is listed on the website: WWW.METEOFRANCE.COM/PREVISIONS-METEO- MARINE/BULLETIN/GRANDLARGE/METAREA2. Gale-force winds are being forecast for the areas: AGADIR and TARFAYA and for CANARIAS LATE. The OUTLOOK, for the 24 hours that follows the forecast that is valid until 01/0000 UTC, consists of: N or NE gale or severe gale in AGADIR and TARFAYA, and N or NE near gale or gale in CANARIAS. Threat of near gale east of MADEIRA. ...TROPICAL WAVES... A far eastern Atlantic tropical wave has its axis along 21W from 02N to 20N, moving westward at 10-15 kt. This wave remains embedded within an envelope of southwesterly monsoonal moisture that observed in latest satellite imagery to be present just offshore the coast of Africa. Scattered moderate to isolated strong convection is within 60 nm east of the axis from 09N to 12N. Scattered moderate convection is within 300 nm west of the axis from 04N to 10N. A surface trough is along 28W/29W from 18N to 25N. This trough is part of the energy of the northern vorticity center that is accompanying the above tropical wave. No significant deep convection is noted with this feature. A central Atlantic tropical wave has its axis along 45W/46W from 02N to 16N, moving westward at about 15 knots. A large plume of Saharan African dust is observed to the north and northeast of this wave. This appears to be suppressing deep convection from developing along and near the wave axis for the time being. Only isolated showers and thunderstorms are within 150 nm either side of the wave axis from 08N to 12N. This wave is forecast to enter the eastern Caribbean on Saturday. A strong tropical wave is moving through the eastern Caribbean Sea, and has its axis along a position from near 19.5N66W to 15N67W to inland Venezuela near 10N68W. It is moving westward at about 16 knots. This wave maintains a good track history going back several days, and continues to mark the leading edge of an extensive area of unsettled weather consisting of scattered showers and thunderstorms, some of which of capable of producing gusty winds This activity is confined to north of 13N east of the wave axis to across the Windward Islands and portions of Puerto Rico. Scattered showers and isolated thunderstorms are noted ahead of the wave to near 73W and south of 15N. The wave will move across the remainder of the central Caribbean through Friday night, and across the western Caribbean on Saturday and Saturday night. The earlier western Caribbean tropical wave that was along 89W/90W continues to move inland, and is discussed in the the eastern Pacific Tropical Weather Discussion. ...ITCZ/MONSOON TROUGH... The Monsoon Trough axis extends from inland Africa to the far eastern Atlantic near 12N22W. The Intertropical Convergence Zone then extends from 12N22W to 11N33W to just east of the tropical wave along 45W/46W. It resumes from just west of the same wave to 08N51W to 09N59W. Scattered moderate convection is within 120 nm north of the axis between 51W and 55W. Similar activity is south of the ITCZ axis within 30 nm of line from 08N30W to 07N34W. ...DISCUSSION... ...THE GULF OF MEXICO... A mid to upper-level trough stretches from northern Louisiana southwest to along the Texas coast and to NE Mexico. An upper level anticyclonic circulation is centered over the eastern Gulf near 26N85W. The associated anticyclonic flow covers just about the entire basin, except over the far western portion south of 27N where the flow is west to northwest south of the base of the mid-upper trough. The area of deep moisture that affected the NW and north-central Gulf the past few days has lifted northward and inland the SE U.S. The western periphery of the Atlantic high pressure ridge is the main feature across the area controlling the wind regime throughout keeping mainly moderate to fresh southeast to south winds throughout, except for lighter winds in the NE Gulf through Saturday. Presently, only isolated showers and thunderstorms are noted over some portions of the Gulf. Scattered showers and thunderstorms are increasing over the interior of the Florida peninsula, with some of this activity moving westward over Gulf waters adjacent to SW Florida. ...THE CARIBBEAN SEA... An upper-level trough extends from 24N73W in the Atlantic Ocean to across Hispaniola and south to 15N73W. With the exception of convective activity associated with the eastern Caribbean tropical wave as described above, the other scattered shower and thunderstorm activity is that which is confined to the far SW Caribbean just north of the eastern extension of the Pacific monsoon trough that extends across Costa Rica. Otherwise over the remainder of the central and western portions of the Caribbean, isolated showers and thunderstorms are noted there. The scattered showers and thunderstorms over the eastern Caribbean behind the strong tropical wave described above will spread westward to the central Caribbean Friday night through Saturday night. In the wake of the moisture, Saharan African dust may move across portions of the eastern Caribbean on Saturday. ...HISPANIOLA... Upper-level cyclonic wind flow is moving across the area. An upper level trough extends from 24N73W in the Atlantic Ocean, across Hispaniola and to 15N73W. Subsidence aloft and resultant dry air over the vicinity of the trough has spread southward to cover Hispaniola, the Windward Passage and eastern Cuba. This is limiting the coverage of shower and thunderstorm activity across and near Hispaniola. Latest satellite imagery shows only a few clusters of scattered showers and thunderstorms over the interior of northern Haiti and over the far western section of the Dominican Republic early this evening. Model guidance suggests that upper cyclonic flow will continue for the next 24 hours or so. Moisture associated with the strong eastern Caribbean tropical wave is moving across the Mona Passage, and is approaching the southeast portion of Hispaniola. As the tropical wave nears the island tonight and into Friday, expect for this moisture to bring increasing shower and thunderstorm activity to most sections of the island into late on Friday. Gusty winds can be expected with some of the shower and thunderstorms. ...THE ATLANTIC OCEAN... An upper-level cyclonic circulation is located near 32N37W, and is lifting northward. A trough extends from the cyclonic center to 20N40W and to near 10N48W. Only isolated showers moving westward are possible north of 25N and between 36W and 46W. An upper-level cyclonic circulation center is near 28N52W, with a trough extending from it to near 20N55W and southwest to across Hispaniola. A small upper-level cyclonic circulation is evident over the far northwest portion of the area at 32N75W, with a narrow trough stretching southeastward to just east of the central Bahamas. The eastern periphery of an eastern Gulf of Mexico upper level anticyclone is pressing eastward into the far western portion of the basin. Strong northwest winds within this eastern periphery of the anticyclone have set up over the waters north of the NW Bahamas, and also north of 27N between 73W-78W. Debris upper cloudiness from strong convection over northern and central Florida is spilling southward across much of the far western portion of the basin north of 25N. West to northwest upper level winds to the east of the narrow upper trough are advecting some of this cloudiness eastward to near 55W and north of 28N. The tail- end of a central Atlantic cold front reaches southwestward to near 31N71W, where it becomes a dissipating stationary front to just east of NE Florida. The aforementioned debris high clouds cover this frontal boundary, however, scattered showers and isolated thunderstorms are possible along and within 120 nm south of the boundary between 71W and 74W. Multilayer clouds are spreading northward from the northeast Caribbean Sea to near 24N and between 55W-66W due to southwest winds aloft found to the east of the previously mentioned upper- level trough. Scattered showers and thunderstorms are occurring under these clouds, and are moving in a general northward direction. This activity is expected to continue into Friday. Elsewhere, surface high pressure covers the basin with the associated ridge axis extending from 32N49W and westward to just east of the cold portion near 31N71W. Another high pressure ridge extends east to west to the north of 32N and west of 70W. Anticyclonic wind flow is present north of 20N between Africa and the Bahamas. Only isolated showers and thunderstorms are observed elsewhere to the west of 54W. Last visible satellite imagery and satellite airmass animation depict a large area of Saharan African dust gradually spreading westward over the eastern Atlantic Ocean, and over portions of the central Atlantic Ocean, especially to the north of the tropical wave along 45W/46W. Some of this dust is likely to spread over the Atlantic waters just north of the NE Caribbean on Saturday. For additional information please visit http://www.hurricanes.gov/marine $$ Aguirre