Two Surface To Low-Level Troughs Forecast To Increase Shower Chances This Week

The 2020 Dry Season continues with its forecast below-average rainfall materializing as little rainfall been recorded for April 2020 as of April 27th (2.6 mm at Piarco versus 28.6 mm at Crown Point). However, April is usually the transition month into the Wet Season, which has historically begun in May.

During this transition period, those April showers are forecast as two surface to low-level troughs will move across Trinidad and Tobago late Tuesday night into Wednesday and another on Friday.

Unfortunately, no significant rainfall accumulations are forecast as low-level winds continue to be brisk, keeping shower activity brief. In addition, mid to upper level conditions remain unfavorable for heavy shower development, but it is not impossible for one or two to form.

The trough on Friday has better chances of producing heavier showers, though activity will not be prolonged or widespread, with very low chances of thunderstorm activity.

GOES-East GEOCOLOR Satellite Animation showing an area of cloudiness approaching the region, forecast to bring increased showers to the area.
GOES-East GEOCOLOR Satellite Animation showing an area of cloudiness approaching the region, forecast to bring increased showers to the area.

Generally, after midnight tonight (Tuesday), increased low-level moisture will support cloudiness and showers across both islands, favoring Eastern areas. This activity will continue into Wednesday with generally light to moderate showers. Gusty winds are possible in moderate to heavier showers.

There are no alerts, watches, or warnings in effect for Trinidad and Tobago as of 7:00 PM Tuesday 28th April 2020.

Note that heavy showers or thunderstorms will be short-lived due to forecast moderate to strong wind shear across the region, between 25-50 knots at times in some areas. This will impact the development of deep convection by tearing away the tops of the convection.

It is also important to note that this feature (surface to low-level trough) is not a tropical wave, nor will it bring the ITCZ across T&T – both of which are triggers for the onset of the 2020 Wet Season.

The Extended Weather Forecast

5-day weather forecast for Trinidad and Tobago

Wednesday: Partly to mostly cloudy skies are forecast, with intermittent showers, generally remaining light to moderate. Note that with partly to mostly cloudy skies, periods of sunshine are implied. There is the chance for heavy showers (rainfall rates greater than 7.6 millimeters/hour) or thunderstorms, mainly after midnight tonight through the afternoon. Conditions are forecast to settle by nightfall, with brisk isolated showers possible. The surface to low-level trough at this point is forecast to be moving through the region.

Thursday: Similar conditions to Tuesday are forecast, with isolated showers interrupting sunny to partly cloudy skies as the trough system moves through and away from the islands. A high-pressure system will rebuild in the trough’s wake, bringing mostly settled conditions by nightfall. Winds are forecast to substantially pick up across the region, with gusts up to 65 KM/H, agitating seas and bringing overall breezy conditions to the Eastern Caribbean.

Friday: Partly to mostly cloudy skies are forecast, with intermittent showers, generally remaining light to moderate. Note that with partly to mostly cloudy skies, periods of sunshine are implied. There is the chance for heavy showers (rainfall rates greater than 7.6 millimeters/hour) or thunderstorms, mainly after midnight tonight through the afternoon. Conditions are forecast to settle by nightfall, with brisk isolated showers possible. The surface to low-level trough at this point is forecast to be moving through the region. There is a low chance for thunderstorm activity, which has to potential to bring gusty winds up to 65 KM/H and street/flash flooding.

Saturday: The trough is forecast to move west away from the region, but lingering low-level moisture remains across Trinidad and Tobago. A surface to mid-level high pressure in the Atlantic continues to dominate conditions across the region. There is an increased chance for isolated showers and the low chance of thunderstorms are also possible across Western Trinidad and hilly areas due to localized climatic effects. Conditions are forecast to settle by nightfall, with a few brisk, isolated showers mainly after midnight. Gusty winds remain the main hazards, with gusts up to 65 KM/H

Sunday: Similar conditions to Saturday are forecast, with lower overall chances for showers and thunderstorms during the pre-dawn periods as well as the late morning through the afternoon.

Seas Forecast

Generally, through the next 7 days, moderate seas are forecast in open waters with waves between 1.5 to 2.0 meters in open waters during the first half of the forecast period and up to 2.5 meters during the weekend into next week.

In sheltered areas, below 1.0 meter during the first half but near 1.0 meter and choppy during the second half of the forecast period.

A marginal long-period swell event is forecast to affect the Northern coasts of Trinidad and Tobago, though the overall sea state will not be rough.

Sea state forecast through the next 7 days across Trinidad and Tobago
Sea state forecast through the next 7 days across Trinidad and Tobago

Winds: Maximum sustained surface winds between 30 KM/H and 45 KM/H with gusts up to 60 KM/H are likely, particularly after Thursday, with gusts, up to 65 KM/H possible, accompanying moderate to heavier showers across Trinidad and Tobago.

High Wind Event Precautions
High Wind Event Precautions

Rainfall: On days where a trough system is affecting T&T, daily rainfall totals are forecast to be between 5-15 millimeters, with isolated totals across Eastern Trinidad up to 20 millimeters.

There is a low chance of street flooding, particularly in flood-prone areas or areas with poor drainage and a very low chance of flash flooding in areas where heavy rainfall may occur.

Why I May Not/Will Not See Constant Rainfall?

A frequent complaint is the forecast is wrong because I didn’t experience any rainfall. Scattered showers mean that you, individually, may experience some showers intermittently throughout the day and there is a higher chance for this activity than isolated activity. Widespread showers mean that nearly all persons and areas may experience rainfall.

This week, isolated to scattered activity is forecast.

Forecast - Isolated, Scattered, Widespread - What do they mean?

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