Dry air dominates the central Atlantic to the Lesser Antilles. A few showers and isolated thunderstorms are around Leewards, Trinidad and Guyana.
A trade wind surge will bring a few showers and slight chance of thunderstorms and gusty winds in the early week. A large tropical wave in the eastern Atlantic has broad spin as seen on satellite scans(2nd image).
Models keep it mostly weak as a tropical wave/low pressure but a few especially of the ECENS members(and fewer of the GEFS) were showing weak development as it approaches the Leewards late week to weekend. Best bet is that it will bring a surge of moisture with showers and isolated thunderstorms in the Lesser Antilles from late week.
The NHC marked a tropical wave, still over coastal West Africa, with 20%… but it too will likely stay weak, move WNW.
25th Anniversary of Tropical Storm Debby(Sep 10, 1994). The storm formed from a large tropical wave that moved off the coast of Africa on September 4. By September 6, satellite images indicated a vigorous tropical wave with intense convection about midway between Africa and the Lesser Antilles.
Convection weakened next day but redeveloped on September 8 after shear dropped. Post-analysis(months later) indicated that it reached tropical depression status on September 9 at 8am, about 185 mi (300 km) east of Barbados; however, it was not operationally classified as Tropical Depression until almost 24 hours later when near Barbados.
At 11pm whilst aircraft flying into the system reported strong flight level winds a tropical storm warning was issued for St. Lucia, Barbados, SVG, Dominica. Martinique officials opted for no watch/warning. Martinique was soon reporting much stronger winds than the 40mph NHC indicated in advisory with winds 50-70mph at different stations including some gusts on hills close to 100mph. Heavy rains with up to 3-4 inches per hour at times fell in a few hours causing widespread flooding and mudslides on St. Lucia.
St. Lucia Met Services had issued flash flood warnings earlier in the day before the NHC called to advise tropical storm warnings be issued that night. Without a cyclone warning, there was less awareness of adverse weather. The severity of the flash flood threat expected was also emphasized by the HTS forecaster Mary Polius on TV. It was unfortunate that the NHC had not upgraded the system earlier due to insufficient evidence supporting formation of a tropical cyclone. Criteria for Tropical depression/storm formation is not considered met until defined circulation, thunderstorms lasting at least 6-12 hours, etc.
