Caribbean: A few Light to moderate showers is around the Leewards. Scattered Light to heavy showers is affecting NE Trinidad with more to the east, some over and east of St Vincent and Grenadines, near south St Lucia, and a few near Barbados and Grenada.
The ITCZ is active over these islands with an upper low/trough active near Leewards. The Upper trough is starting to exert influence on the ITCZ and induce a low to mid-level trough to the east of the Lesser Antilles.
Expect Light to, at times, moderate to heavy showers in the southern Windwards and Trinidad today. As the upper trough continues to deepen its influence, a low-level trough will bring some more showers late Fri night to Sat.
A surface trough is embedded within the ITCZ moist flow behind 91L and has been moving across the Windwards, T&T down to NE Venezuela today. There is also a broken extension of the surface trough north across the northeast Leewards to the north of the Leewards underneath the upper-level trough.
Scattered moderate to heavy showers, periods of rain and thunderstorms are from St. Lucia, Barbados, St. Vincent, Grenadines, Grenada, Trinidad and Tobago. The ITCZ extends to the east/SE of Windwards and is expected to keep bringing scattered showers, sometimes moderate to heavy, with isolated thunderstorms across those islands through Friday, although with less frequency than today.
Later Friday to Saturday, 1 or 2 new surface troughs will form under the influence of the digging upper-level trough over the Leewards, bringing increasing chances for showers and isolated thunderstorms. The upper trough will help keep ITCZ moist flow across the south Windwards and Trinidad and Tobago, extending the period of occasional showers, intermittently moderate to heavy, and chance of thunderstorms.
Earlier, there were also Scattered heavy showers and continuous rain, which impacted east Trinidad and parts of Tobago this morning. Trinidad and Tobago are under orange river alerts, and schools are closed. There are also intermittent moderate to heavy showers and times of rain impacting St Lucia, St Vincent and the Grenadines. ITCZ moist flow behind 91L will be enhanced by an upper-level trough into Friday. Expect some more periods of rainfall today, gradually becoming less frequent tonight to Friday.
91L is producing very heavy rainfall, with the main core now looking well organized over the northern coast of Venezuela and ita Caribbean Sea islands. Heavy showers are also impacting the ABC islands and will be worse later today and tonight as the main core passes.