000 AXNT20 KNHC 292352 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 752 PM EDT Fri Sep 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... Tropical Storm Maria centered near 37.8N 57.4W at 2100 UTC has accelerated toward the east-northeast at 27 kt this afternoon. Minimum central pressure remains 988 mb. Maximum sustained winds are 50 kt with gusts to 60 kt. See the latest NHC Forecast/ Advisory under AWIPS/WMO headers MIATCMAT5/WTNT25 KNHC for more details. Tropical Storm Lee centered near 42.2N 46.0W at 2100 UTC is racing northeast at 31 kt. Estimated minimum central pressure is 996 mb. Maximum sustained winds are 55 kt with gusts to 75 kt. See the latest NHC Forecast/Advisory under AWIPS/WMO headers MIATCMAT4/WTNT24 KNHC for more details. A broad surface trough extending from western Cuba northeastward across south central Florida then eastward into the Atlantic is interacting with an upper-level low pressure system aligned north to south across the east-central Gulf of Mexico. The interaction is producing a large disorganized area of clouds and showers from the NW Caribbean across Cuba to south central Florida. A weak surface low may form from this system on either side of the Florida Peninsula this weekend as the surface trough drifts northward. Environmental conditions appear conducive for some development of the low during the next 2-3 days. Regardless, this system will produce areas of heavy rain from western Cuba northeastward across the Florida peninsula and adjacent waters during the next few days. This system has a moderate chance for tropical cyclone development in the next 48 hours. ...TROPICAL WAVES... A tropical wave in the E Atlantic along 32W-33w, moving west at 10-15 kt. Ample low level moisture accompanies this wave this evening as evident in TPW animations. An broad upper level trough is N of 14N to the NW of the wave axis an is currently enhancing showers and thunderstorms along the leading edge of the wave related moisture, from 13.5N to 15.5N between 32W and 36W. However the associated strong westerly wind shear being induced by the upper trough will begin to diminish convection across the northern part of the wave, and active convection will likely shift S of 12N and behind the wave axis later tonight and Saturday. A tropical wave is moving across the E Caribbean along about 64W-65W S of 19N and moving west at 10-15 kt. An upper level low center is developing just to the W of the wave, centered over the Mona Passage and far eastern Dominican Republic, and is interacting favorably with the wave to produce scattered moderate to strong thunderstorms across the east and northeast Caribbean extending NE into the Atlantic waters offshore of the Leeward Islands, or front 14N to 21N between 59W and 67W. The upper low will retrograde westward through early Sunday and remain in a favorable position to continue to induce and enhance active convection across the NE Caribbean Islands and adjacent Caribbean and Atlantic waters. ...ITCZ/MONSOON TROUGH... The monsoon trough extends from the coast of Africa near 09.5N14.5W to 09N23.5W to 06N36W. The ITCZ extends from 06N36W to 07.5N53W to 11N64W. A West African Squall Line is nearing the W coast of Africa from coastal Senegal to southern Liberia, ahead of an approaching tropical wave over Africa. Scattered moderate to strong convection is occurring behind the tropical wave along 32W-33W from 06N-12N between 20W-30W. ...DISCUSSION... GULF OF MEXICO... The tail end of a quasistationary front extends from the Florida Panhandle near 30N84W to 27.5N96W near the Texas coast, and has actually drifted slightly S during the afternoon hours across the NW Gulf. The front is becoming ill defined and is expected to dissipate during the next 24 hours. To the south, a stationary 1008 mb surface low is analyzed over the Bay of Campeche near 20.5N93.5W, embedded within an area of broad cyclonic turning across the entire Bay of Campeche extending southward into SE Mexico. Scattered moderate convection surrounding the low earlier today has shifted inland across Mexico. A sharp N to S aligned upper level low is centered over the NE Gulf near 28N86.5W and is producing subsidence across much of N central portions of the Gulf. Upper level diffluence SE of the center continues to enhance convection over SE Gulf as described above. CARIBBEAN SEA... Active convection will continue with the tropical wave across the E Caribbean as the upper low described above moves W and generally in tandem with the wave during the next 24-36 hours. The crux of wave related moisture is expected to shift NW across the NE Caribbean and into the Atlantic by late Saturday. Elongated low pressure also extends across the Yucatan Channel SW across the Gulf of Honduras, and is acting to force active convection across much of the NW Caribbean to Honduras. The upper level low across the NE Gulf extends weakly to the Yucatan Channel and is providing upper level divergence across the area that is acting to enhance and sustain the convection. The trough and associated convection is expected to drift slowly northwestward and across the Yucatan Peninsula through the weekend. Farther S, the eastern extent of the east Pacific monsoon trough extends into the SW Caribbean with isolated moderate convection over Panama and northern Colombia. Little change is expected through Sat. ...PUERTO RICO and U.S. Virgin Islands... Afternoon thunderstorms have moved NW and away from the NW coast of Puerto Rico from Arecibo to Aguadilla in the past few hour with gradual clearing expected there in the short term. The tropical wave moving across the Eastern Caribbean has begun to spread widely scattered moderate convection across the U.S. and British Virgin Islands and across NE portions of Puerto Rico this evening. Cells are currently moving WNW around 15 mph with SSW upper level wind shear weakening them eventually. Clusters of strong convection are seen across the open Caribbean SSE of St Croix where the best low level moisture currently resides. Global models forecast the moisture associated with the tropical wave to move WNW to NW overnight and Saturday and interact with the upper low to the west to produce scattered heavy showers and occasional thunderstorms. This weather will shift across all of the Virgin Islands and eastern Puerto Rico during the next several hours and may maximize in the early morning hours of Saturday. This majority of this moisture is forecast to shift NW of the islands Saturday afternoon. ...HISPANIOLA... Widely scattered evening showers and thunderstorms are seen in satellite photos across the interior mountains of the island, from north of Santo Domingo to interior NW Haiti, moving WNW near 15 mph. The upper low across the area is enhancing evening convection, and isolated areas of heavy rainfall should be expected during the few hours. Expect gradual clearing from east to west by around midnight before isolated showers and thunderstorms begin to move into E and NE portions of the island late tonight. ATLANTIC OCEAN... A broad plume of moisture is being pulled northward across the northern Bahamas and surrounding waters by a middle to upper- level low over the NE Gulf of Mexico, and supports scattered showers and isolated strong thunderstorms west of 75W. Elsewhere, surface ridging prevails across much of the remainder of the central and the eastern Atlantic, anchored by 1025 mb high pressure centered near 34N29W. For additional information please visit http://www.hurricanes.gov/marine $$ Stripling