000 AXNT20 KNHC 202348 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 747 PM EDT Sun Aug 20 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... A tropical wave extends along 76W/77W moving W at 15-20 kt. The remnant circulation of Harvey continues to be analyzed as a 1006 mb low pressure along the wave axis near 14N77W with scattered to numerous showers and thunderstorms occuring from 15N- 21N between 74W-79W, and from 12N-16N between 77W-81W. This shower and thunderstorm activity has changed little in organization since earlier today. An Air Force Reserve Unit Hurricane Hunter aircraft investigating the remnants of Harvey found that the system still lacks a well-defined center of circulation, and so far there is no indication of winds to tropical storm force. Gradual development of this system is possible, and it could become a tropical cyclone once again while it moves west- northwestward across the northwestern Caribbean Sea, near the northern coast of Honduras, during the next day or two. The system is expected to reach Belize or the Yucatan Peninsula on Tuesday. Interests in northern Nicaragua, Honduras, Belize, and the Yucatan Peninsula should monitor the progress of this system. Regardless of development, the wave and associated low pressure (remnants of Harvey) will continue to impact the central Caribbean tonight and the western Caribbean Monday and Tuesday. The main concern will be heavy rainfall, with the potential of flash flooding and mudslides over parts of Nicaragua and Honduras. This system and associated shower and tstm activity will continue to affect Jamaica, the Cayman Islands, and parts of Cuba tonight and Monday, then reaching Belize and the Yucatan peninsula by late Monday. ...TROPICAL WAVES... A tropical wave is added to the 1800 UTC analysis/surface map and extends from 21N19W to 10N21W. The Hovmoller Diagram shows the westward propagation of the wave. In addition, this wave in a moist area based on TPW imagery and has a well pronounced 700 mb trough. Scattered moderate convection is noted where the wave meets the monsoon trough from 11N-13N between 19W-22W. A 1008 mb low pressure is analyzed ahead of the wave near 14N24W and it is forecast to move westward, in tandem with the wave, over the next 24-48 hours. Saharan dust is noted ahead of the wave axis and west of the Cabo Verde Islands. A tropical wave extends from 19N52W to 10N54W moving W at 15-20 kt. The wave shows up very well on the TPW animation and 700 mb streamline analysis. The northern portion of the wave has fractured and is analyzed as a surface trough extending from 25N48W to 20N50W. No significant deep convection is associated with the wave itself, however scattered moderate convection is occurring mainly east of the surface trough from 19N-24N between 46W and the trough axis. A tropical wave is reaching the Yucatan peninsula and Belize and extends from 19N87W across Honduras into the Eastern Pacific region to near 10N87W moving W at 15-20 kt. Subtle troughing is noted on 700 mb streamline analysis, but abundant moisture is observed on either side of the wave axis based on the TPW animation. The wave, combined with a diffluent pattern aloft, is generating scattered showers and thunderstorns over parts of the Yucatan peninsula, Belize and northern Guatemala, as well as over parts of Honduras, Nicaragua and El Salvador. ...ITCZ/MONSOON TROUGH... The monsoon trough extends from the African coast near 13N17W to 10N24W to 08N38W. Sattered moderate convection is from 11N-13N between 19W-22W, and within about 120 nm S of the monsoon trough between 33W-36W. ...DISCUSSION... GULF OF MEXICO... A large and well defined upper-level low centered over the eastern Gulf near 25N87W continues to generate scattered showers and thunderstorms, mainly over the SE Gulf and western Cuba, icluding also parts of the Florida peninsula. A surface trough, reflection of this upper-level low is analyzed over south Florida and the Florida Keys to western Cuba near 22N84W. The western half of the Gulf is under the influence of a weak ridge, anchored by a 1019 mb high pressure centered over the State of Alabama. Isolated showers and light to gentle anticyclonic winds prevail W of 90W. The upper-low will drift westward reaching the central Gulf on Monday. This system will continue to enhance the development of showers and tstms across the Gulf waters on Monday. Looking ahead, the remnant low of Harvey, currently moving across the Caribbean Sea is expected to reach Belize or the Yucatan Peninsula on Tuesday, and then move into the Bay of Campeche by the middle of the week, where redevelopment appears more likely. CARIBBEAN SEA... The primary area of concern across the Caribbean Sea is the low pressure (remnants of Harvey) that is generating scattered to numerous showers and thunderstorms over the central Caribbean. Please, see Special Features section for more details. A tropical wave is exiting the area, with axis along 87W. Please, see the Tropical Waves section for details. A trough of low pressure located across the Atlantic waters, north of Puerto Rico, combined with abundant tropical moisture supports the development of showers and strong thunderstorms across parts of Puerto Rico and Hispaniola this afternoon and evening. This trough and associated moisture will move away from Puerto Rico on Monday, but will continue to enhance the shower and tstm activity over Hispaniola. ...HISPANIOLA... Daytime heating, local sea breezes, and mountain upslope lifting will combine with available moisture to produce scattered showers and thunderstorms across the island mainly during the afternoon and evening hours. A trough of low pressure, currently located north of Puerto Rico will be north of Hispaniola on Monday, and will bring increased moisture, cloudiness, and precipitation to the island. ATLANTIC OCEAN... As previously mentioned, a trough of low pressure is north of Puerto Rico and extends from 26N67W to 20N68W. This system continues to produce disorganized showers and thunderstorms, with fresh to strong winds mainly on its northeast side based on scatterometer data. Environmental conditions are expected to be unfavorable for development of this system during the next day or two, but they could become slightly more conducive for development by midweek when the system is near the northwestern Bahamas or Florida. This feature is expected to move west-northwestward at 15-20 kt during the next few days. A pair of tropical waves are between the coast of Africa and the Lesser Antilles, and a another surface trough extends 25N48W to 20N50W. Please, see the Tropical Waves section for details. The remainder of the Atlantic is under the influence of a ridge, with a center of 1022 mb located SW of Bermuda near 31N68W. This high pressure center is forecast to remain nearly stationary over the next 24 hours. Another 1023 high pressure center is seen near 31N42.5W. For additional information please visit http://www.hurricanes.gov/marine $$ GR