Updated @7.12 pm
An unfavourable upper level environment has led to a significant reduction(from 20 mp/h to now 5-10 mp/h) in forward speed of the tropical wave which is presently located a few hundred miles east of the island chain.
However, moisture ahead of the wave produced occasional moderate showers across some Grenadine islands today under cloudy skies, whereas heavier showers and thunderstorms mainly affected Grenada.
Nevertheless, showers are still likely in pockets over the next 24 hours due to low-level instability. Currently, additional rainfall activity is confined closer to and behind the wave’s axis and models suggest the islands could be affected by these conditions as early as late Friday into Saturday.
Gentle to moderate(15-25km/h) east north easterly trades would cross the islands with gusts near showers. A shift to south easterly should occur by Thursday late afternoon. An increase in speed(near 35km/h) is likely on Saturday.
Seas are currently slight to moderate in open water with swells peaking to 1.0m on western coasts and ranging between 1.8m – 2.0m on eastern coasts. There is no significant haze intrusion within this forecast period.
Updated @7.24 am -June 23 2021
At the Argyle International Airport 5.6mm of rainfall was recorded overnight. Model guidance is indicating the possibility of 20mm of rainfall accumulation across the mainland, and approximately 50mm of rainfall across the Grenadines by tonight.
The wave continues to move slowly across the island chain and during the course of the day, an upper level trough will add to this instability. While the chance of showers remains high with the possibility of isolated thunderstorms, and gusty winds for the remainder of the week across the mainland, the Grenadine Islands will be mostly impacted.
Residents and motorists in areas prone to flooding and landslides and near rivers and streams should exercise caution.
Winds will blow generally from the east north east (ENE) at 20km/h-35km/h, becoming easterly on Thursday and decreasing in speed to 15km/h-25km/h. A south easterly flow is anticipated around Thursday night into Friday.
Seas will remain slight to moderate in open waters with swells peaking at 1.0m on the western coasts, and ranging between 1.5m-2.0m on the eastern coasts. In addition, there will be no significant haze intrusion today.
Updated @ 9.16 pm June 22
In the Atlantic, there’s a disorganized tropical disturbance several hundred miles east of the Caribbean Islands.
The National Hurricane Center is giving it a slight chance of developing into at least a tropical depression over the next couple of days.
Right now, it’s mostly just a blob of tropical moisture.
It appears to have a short window of time to pull itself together, if it’s going to happen.
Once the system reaches the islands late Thursday or on Friday, the upper-level winds are forecast to become hostile to development, so that should be it.
In general, the environment ahead of the system does not appear supportive for development, so most likely it will pass through the Caribbean as simply a moisture surge.
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Moisture ahead of a tropical wave, located more than 500 miles east of the Windward Islands could result in increased cloudiness across St. Vincent and the Grenadines (SVG) this afternoon.
Light rain, pockets of moderate showers and isolated thunderstorms are possible across SVG tonight.
The tropical wave could linger near the island chain during Wednesday and Thursday, with upper-level features supporting moderate/heavy showers and thunderstorm activity…Be alert in areas prone to flash-flooding, or near rivers and streams.
Showers and thunderstorms associated with this tropical wave/disturbance have increased overnight and there’s a low (30%) chance for additional development over the next couple of days. However, upper-level winds could become less favourable by Thursday…The St Vincent and the Grenadines Meteorological Services will continue to monitor this tropical wave/disturbance and issue the necessary updates/advisories.
Satellite Image Caribbean Wether Online