000 AXNT20 KNHC 151812 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 212 PM EDT Thu Jun 15 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 1200 UTC surface analysis and satellite imagery through 1715 UTC. ...TROPICAL WAVES... A strong tropical wave has been added to the 1200 UTC surface map near the west coast of Africa based on visible satellite imagery and the Hovmoller Diagram, that shows very well the westward propagation of the wave. Its axis extends from 12N15W to 04N15W. A cluster of moderate to strong convection is along the wave axis from 06N to 09N between 13W and 17W. Scattered moderate to isolated strong convection is noted elsewhere from 03N to 10N between 12W and 19W. A tropical wave located several hundred miles south-southwest of the Cabo Verde Islands extends from 10N30W to a 1012 mb low pressure located near 06N30W to 02N30W. This wave is producing disorganized showers and thunderstorms, covering the area from 04N to 09N between 28W and 32W. Development, if any, of this system should be slow to occur during the next few days while the wave moves westward near 20 kt over the tropical Atlantic. The tropical wave situated along 39W on the 1200 UTC surface map is re-located farther east along 37W based on a recent ASCAT pass that indicates the wind shift associated with the wave axis. Now, the wave extends from 15N37W to 06N37W moving westward at around 10 kt. The wave remains embedded within an area of deep-layer moisture as depicted on the TPW product. The wave also coincides with an inverted trough at 700 mb. Satellite imagery shows a cluster of moderate to isolated strong convection with some cyclonic turning covering the area from 10N to 12.5N between 35W and 40W. this wave is forecast to cross 55W Saturday night, and move across the Windward Islands Sunday night. A tropical wave is over the eastern Caribbean and extends from Puerto Rico to the coast of central Venezuela. Convection is limited in association with this wave, that could enhance some shower and thunderstorm activity over Puerto Rico this afternoon and early evening. The wave is very well depicted in the moisture product and 700 streamline analysis. This wave is forecast to move across Hispaniola late today through Friday. Another tropical wave is drifting westward across the SW Caribbean with axis from 17N81W to the coast of western Panama. Scattered moderate convection is seen on either side of the wave axis covering the waters from 13N to 17N between 77W and 84W, and south of 12N west of 79W. This wave will reach central America tonight, and will be absorbed by the complex low pressure system forecast to develop over the northwestern Caribbean Sea and the Yucatan Peninsula this weekend. ...MONSOON TROUGH/ITCZ... The Monsoon Trough extends from the coast of west Africa near 10N14W to 07N20W to 07N28W. The ITCZ extends from 06N31W to 09N39W to 08N50W to 07N58W. Three tropical waves are embedded within the Monsoon trough/ITCZ. Most of the convective activity is associated with these tropical waves. ...DISCUSSION... GULF OF MEXICO... A ridge extends from the western Atlantic, across Florida into the Gulf of Mexico producing gentle to moderate E to SE winds across the area. A thermal trough, that normally develops during the evening hours over the Yucatan Peninsula and moves across the SW Gulf during the overnight and early morning hours, extends along 94W south of 22N. Water vapor imagery continues to reveal the presence of an upper-level low spinning over the SE Gulf, with a trough extending SW across the northern Yucatan Peninsula into the eastern Bay of Campeche. A few showers are associated with the upper-low. Upper diffluence on the east side of the low combined with a moist and humid SE flow at low levels, will continue to support the development of showers and thunderstorms over parts of south and central Florida, the Florida Keys and the SE Gulf. Abundant moisture is expected to persist over the SE Gulf and the Yucatan Peninsula through the weekend. This weather pattern will be associated with a complex area of low pressure forecast to form over the northwestern Caribbean Sea and the Yucatan Peninsula this weekend. Conditions appear to be favorable for gradual development of this system while it moves slowly northwestward toward the southern Gulf of Mexico by early next week. CARIBBEAN SEA... Two tropical waves are moving across the Caribbean Sea. Please see the tropical waves section for more details. These tropical waves will become absorbed in a broad area of low pressure forecast to form over the NW Caribbean during the upcoming weekend. Scatterometer data show moderate to fresh trades across the east and central Caribbean. Gentle to moderate winds are seen over the NW Caribbean. This wind pattern will continue through Saturday. Looking ahead, a broad area of low pressure is expected to form over the northwestern Caribbean Sea and adjacent land areas by the weekend. Experimental GOES-16 visible satellite imagery hints the presence of a low level circulation over eastern Honduras. This system will bring increasing winds and building seas across the central and western Caribbean during the upcoming weekend due to a tight pressure gradient between the developing low pressure and the Atlantic ridge. Plenty of moisture and very active weather is also expected with this low, likely affecting the western and central Caribbean Sea, Central America, and most of Cuba during the weekend. Locally heavy rain could occur over parts of Cuba, the Yucatan Peninsula and Central America. ...HISPANIOLA... A tropical wave, currently over Puerto Rico, will move across Hispaniola late today through Friday supporting scattered showers and tstms mainly in the afternoon and evening hours. ATLANTIC OCEAN... Three tropical waves are moving westward between the coast of Africa and the Lesser Antilles. Please refer to the Tropical Waves section above for details. A surface trough extends from 31N55W to 25N64W. This trough is a reflection of an upper-level low located near 29N58W, with a trough extending SW toward Puerto Rico. Scattered showers and thunderstorm are noted within about 180 nm SE of the trough axis. A weak low may develop along the trough axis on Friday. Otherwise, broad high pressure covers the Atlantic from the Azores to the Florida Peninsula. Moderate to locally fresh trades are around the southern periphery of the ridge between the Windward Islands and the coast of Africa. A surge of African dust continues to spread westward in the wake of the tropical wave located along 37W as noted in the Saharan Air Layer from CIMSS. For additional information please visit http://www.hurricanes.gov/marine $$ GR