000 AXNT20 KNHC 262359 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 805 PM EDT Mon Jun 26 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. ...TROPICAL WAVES... A tropical wave axis is along 26W from 01N to 11N, moving westward at 15 kt. The wave is embedded within a rather moist environment, however Saharan dry air and dust is intruding some around the northern segment of the wave s surface ridging noses south just to the west of the wave. Only widely scattered moderate to isolated moderate convection is present within 120 nm either side of the axis from 07N to 10N. This activity appears to be on the decreasing trend. A broad tropical wave with axis is along 46W from 01N to 11N, moving westward at 10-15 kt. The wave is in a region of favorable wind shear. It is also within a moderate moist environment and under an area of diffluent flow aloft that is located between an upper anticyclone near 15N51W and mid/upper ridging to the southeast of the wave. In addition 700 mb streamline analysis also supports a wave signal near that of the surface position. Scattered moderate isolated strong convection is seen within 180 nm east of the axis from 06N-08N, within 180 nm west of the axis from 10N-11N and within 60 nm west of the wave from 07N-08N. A tropical wave is over the central Caribbean axis along 69W/70W south of 19N to inland Venezuela near 08N69W, moving westward at 15-20 kt. The wave is in a region of unfavorable wind shear and in a limited moist environment. Deep convection that develops near and along the wave axis is observed to have a short duration due to the moderate to strong westerly winds aloft. Scattered moderate isolated strong convection is seen within 30 nm of a line from 17N71W to 17.5N74W. Scattered showers and isolated weak thunderstorms are elsewhere within 120 nm west of the axis from 14N-17N. Isolated showers are within 60 nm east of the wave axis. A tropical wave is over the western Caribbean with axis along 86W south of 21N to the northwest section of Costa Rica, moving westward at about 15 kt. The southern portion of the wave is very near the eastern Pacific monsoon trough that extends across the SW Caribbean Sea. The wave marks the leading edge of deep tropical moisture that trails the wave east to near 78W. Clusters of scattered moderate isolated strong convection are located within this area of deep moisture south of 17N to inland northern Honduras between the wave axis and 83W, and also south of 16N between 77W and the coast of central America. The activity south of 16N between 77W and the coast of central America is mainly associated with the monsoon trough. This wave is forecast to move inland early on Tuesday. ...MONSOON TROUGH/ITCZ... The Monsoon Trough axis extends from the coast of Africa near 15N17W southwest to near 05.5N25W. The Intertropical Convergence Zone axis then begins just to the west of the tropical wave along 26W near 05N28W, and continues to 06N37W to 05N45W. 05N52W. Scattered moderate isolated strong is within 180 nm south and 60 nm north of the axis between 41W-43W. ...DISCUSSION... GULF OF MEXICO... A broad upper level trough extends from over the eastern United States seaboard southwest to the extreme northeast portion of the Gulf, then becomes a narrow trough south to near 24N85W. This feature supports a stationary front that is analyzed from just offshore NE Florida southwest to Cross City and to 29N86W, and northwest from there to inland southeastern Louisiana. Widely scattered showers and isolated thunderstorms are noted along, and within 60 nm south of the boundary west of 88W. Isolated showers are elsewhere within 30 nm of the boundary. The boundary is forecast to gradually become diffuse through Tuesday afternoon, with the remnants possibly lifting back north as a warm front. The portion of the front along the Florida coast may sag some to the south through Tuesday as high pressure to its north builds in from the northwest. Upper level anticyclonic wind flow covers the rest of the Gulf of Mexico, especially from the area of the upper level trough, southwestward to over SW portion of the area. A pair of surface troughs are analyzed over the SW and far western portions of the Gulf. One surface trough extends from just east of southern Texas to 21N96W and southeast to near 18N94W. Scattered showers and isolated thunderstorms are noted within 90 nm east of the trough south of 23N, while isolated showers are within 60 nm to its west south of 23N. The second surface trough extends along 93W from 20N-26N. Scattered moderate isolated strong convection is within 120 nm east of this trough from 22N-24N, and also within 60 nm west of the trough from 21N-23N. A weak pressure pattern is present elsewhere. CARIBBEAN SEA... The main features in the basin are two tropical waves already discussed in the waves section above. Aside from the shower and thunderstorm activity associated with them as described above, latest scatterometer data depicts fresh to strong winds in the vicinity of the waves south of about 17N. These winds are expected to increase to near gale across the Gulf of Venezuela on Tuesday night. Otherwise, scattered showers and thunderstorms are developing over the Windward Passage and just north of Jamaica. Isolated showers in streamer fashion are observed over the eastern Caribbean, and over portion of the northwest Caribbean north of the shower and thunderstorm activity associated with the tropical wave along 86W. A broad tropical wave currently over the central tropical Atlantic is expected to enter the eastern Caribbean Sea on Tuesday night, and reach the central Caribbean late on Wednesday. This wave will be accompanied by scattered showers and thunderstorms, some of which may contain gusty winds. ...HISPANIOLA... Upper level moderate to strong southwest to west winds continue to advect deep level moisture over Hispaniola and surrounding waters as the northern portion of a tropical wave moves across the far eastern part of the island this evening. With these factors in play and in addition to the presence of ample instability as well, expect scattered showers and thunderstorms to be on the increase over much of the island through the next day or so. ATLANTIC OCEAN... Surface high pressure covers the basin, with the parent 1025 mb anticyclonic center located just north of the area at 33N47W. A broad upper trough along the United Stated eastern seaboard supports a stationary front that extends from a 1016 mb low pressure center near 32N79W southwest to inland NE Florida. A short-wave trough riding along the southern periphery of the upper trough in combination with the surface boundary is activating increasing clusters of scattered moderate isolated strong convection over the far northwest portion of the basin to inland NE Florida. This activity is expected to continue quite active through late Tuesday as the surface boundary begins to drift southward, and upper level dynamics provide further support to maintain it active. A large upper level cyclonic circulation is situated over the central Atlantic 28N57W, and is slowly moving northwestward. Isolated showers and thunderstorms are noted north of 24N between 52W-63W. Similar activity is to its west within 30 nm of a line from 28N66W to 32N69W. Another upper level cyclonic is moving south-southwest over the eastern portion of the basin near 28N26W. Isolated showers and thunderstorms are possible within 120 nm of the southeast quadrant of the low. Otherwise, isolated showers and thunderstorms are evident elsewhere west of about 50W. They are moving in a general westward motion. Stable and rather stable atmospheric conditions are present to the east of 50W under stronger high pressure. For additional information please visit http://www.hurricanes.gov/marine $$ Aguirre