000 AXNT20 KNHC 081012 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 612 AM EDT Sat Jul 8 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 0945 UTC. ...TROPICAL WAVES... A tropical wave is over the far eastern Atlantic with axis extending from 16N22W to 12N24W to 05N25W, moving westward around 10 kt. The wave is in a region of favorable to neutral wind shear. Atmospheric moisture continues to increase along and to the east of the wave. The Meteosat 9 imagery along with depicts an extensive area of African Saharan dry air and dust to its west. Convection remains limited to across the far southern extent of the wave axis where it intersects the monsoon trough axis and south of the trough axis. It consists of the scattered moderate to strong type intensity within 180 nm west of the axis from 05N-07N. Scattered moderate convection is within 180 nm east of the axis from 05N- 08N. A tropical wave, remnants of Tropical Depression Four, is over the central Atlantic with its axis extending from near 22N54W to 19N54W to 13N55W. It is moving west-northwest around 18 kt. The atmospheric environment surrounding the wave is very moist as observed on the Total Precipitable Water (TPW) loop series. Also, the CIRA moisture analysis reveals the presence of deep layer moisture over and near the wave. Deep convection is pulsing along the wave axis. This convection is observed as a large cluster of the scattered moderate type intensity from 17N-19N between 54W- 56W. Scattered moderate convection is ahead of the wave within 30 nm of 20N58W. An Ascat pass from 0110Z last night nicely depicted a northeast to southeast wind shift across the wave axis, with fresh to strong east to southeast winds east of the axis from 17N- 20N between the wave and 50W. The wave is forecast to pass to the northeast of the Leeward Islands by Sunday evening attendant with possible brief gusty winds and squalls over portions of the northeast Caribbean. It is then forecast to approach the SE Bahamas on Monday. A tropical wave is over the Caribbean Sea with axis extending from 19N69W to 15N70W to inland Venezuela near 10N70W, moving westward around 18 kt. The wave is entering an upper level environment of neutral to unfavorable wind shear. The latest water vapor imagery shows subsidence and and associated dry air over and around the wave environment. Isolated showers and thunderstorms moving quickly to the west are seen east of the wave, and also to the west of the wave north of 16N and westward to just east of Jamaica. A tropical wave is over the Bay of Campeche and over southeastern Mexico with axis extending from near 24N92W to inland Mexico at 18N94W. It is moving westward near 16 kt. The wave is embedded in a very moist and unstable atmospheric environment. Clusters of scattered moderate to strong convection are south of 22N and west of the wave to along and just inland the coast of Mexico. Scattered moderate convection is within 60 nm east of the wave south of 20N. The wave is forecast to move across the remainder of the SW Gulf through early this evening, then move inland Mexico tonight. ...ITCZ/MONSOON TROUGH... The Monsoon Trough axis extends from 16N17W to 09N23W to 05N35W. The Intertropical Convergence Zone extends from 05N35W to 03N13W to 03N43W to 04N52W. Aside from the convection related to the tropical wave over the far eastern Atlantic. Scattered moderate to strong convection is along and within 120 nm south of the axis between 28W-32W, and within 60 nm north of the axis between 35W- 36W. Scattered moderate convection is within 60 nm north of the axis between 30W-34W, between 38W-40W and within 60 nm south of the axis between 43W-46W. A surface trough is just north of the ITCZ along a position from 07N41W to 03N42W. Scattered moderate convection is within 90 nm west of the trough from 03N-05N. Scattered moderate to strong convection in clusters are along and just offshore the coast of Africa from 07N-11N. This activity extends inland as swell for 60 nm, and is in advance of the next tropical wave forecast to approach the coast in the near future. ...DISCUSSION... GULF OF MEXICO... A tropical wave is over the Bay of Campeche and extends southward to southeastern Mexico. See above for details on its associated convection. A 1019 mb high is centered over the eastern Gulf near 27N84W. It is producing light to gentle anticyclonic winds across the eastern part of the Gulf north of 26N. Water vapor imagery indicates that a small upper level low is near 25N84W, and is trending to shift southward. Ample present moisture and instability to its east and southeast is bringing scattered showers and isolated thunderstorms to the SE Gulf waters. Isolated showers and thunderstorms are occurring to its northeast and east. Scattered showers and isolated thunderstorms are also over the western Gulf north of the deep convection associated with the tropical wave. This activity is noted from 21N-28N and west of 90W. CARIBBEAN SEA... A tropical wave axis is near 70W. See above for details. Scattered moderate convection earlier along and near the coast of Cuba is dissipating. Isolated showers and thunderstorms are seen north of 18N between 77W-82W. Scattered moderate to isolated strong convection is over the SW Caribbean south of 14N and west of 79W. This activity will persist through the weekend. In the upper levels, anticyclonic flow covers the western half of the sea, while a small upper low is situated over the central part of the Caribbean. Southerly upper flow is present east of the upper low. This is transporting upper debris cloudiness from deep convection over Venezuela northward to portions of the eastern half of the Caribbean. Isolated showers and thunderstorms are developing over some sections of the eastern Caribbean in very moist easterly trade wind flow. Additional showers and thunderstorms are expected to develop through the weekend. The analyzed pressure gradient supports 10-15 kt trades across the Caribbean, except for stronger winds in the 20-25 kt range along the coast of Colombia. These conditions will continue into early next week. ...HISPANIOLA... Scattered showers and thunderstorms moving west-northwestward over the eastern section of Hispaniola have increased in coverage due to the approach of the tropical wave as discussed above. This activity is expected to continue to affect most of eastern Hispaniola, and some areas of the central section of the island through the weekend. Scattered showers and thunderstorms over the southwestern portion of Haiti are mainly the result of a small upper level low between Haiti and Jamaica acting on very moist and unstable tropical air present through the region. This activity is expected to continue through today, with a good chance it may expand eastward as added moisture from the aforementioned tropical wave approaches. ATLANTIC OCEAN... The remnants of Tropical Depression Four, now a tropical wave, is over the central tropical Atlantic and a tropical wave is over the far eastern tropical Atlantic. See above for details on these features. Otherwise, strong high pressure of 1030 mb is centered north of the discussion area at 35N37W moving northwest. It extends a ridge southwestward to 32N50W and to central Florida. The ridge will change little through Sunday, then begin to lift back to the north on Monday. Water vapor imagery shows an elongated upper low (TUTT) centered near 29N55W lifting northward. A large upper anticyclone is near 29N70W. Scattered showers and thunderstorms are southeast and south of the upper low from 22N- 25N between 52W-57W. Isolated showers and thunderstorms are noted from 25N-29N between 51W-53W. Scattered showers and isolated thunderstorms moving northwestward in very moist southeast flow along the southwest periphery of the ridge axis are over the western part of the area south of 28N and west of about 75W. An extensive area of African Saharan dust is situated over the eastern and central Atlantic E of 53W, and is gradually migrating westward. For additional information please visit http://www.hurricanes.gov/marine $$ Aguirre