Forecast: Cloudy Skies & Periodic Showers Across T&T This Weekend

Increasing low-level moisture through the weekend is forecast to fuel scattered showers and cloudy skies across Trinidad and Tobago. Here is what you need to know:

— Partly cloudy to cloudy skies are forecast through the weekend, with heavier showers expected on Saturday by the afternoon across Trinidad. Overall heavier rainfall is forecast to remain mainly across and offshore southern and eastern areas of T&T due to persisting strong westerly wind shear. There is a low chance of a thunderstorm on Saturday, favoring western coastal Trinidad, eastern coastal, and eastern offshore areas.
— The main hazards include wind gusts up to 45 KM/H, mainly on Sunday, with brief heavy rainfall resulting in street flooding on Saturday.
Lightning will accompany thunderstorms. Funnel clouds and waterspouts are possible on Saturday but unlikely on Sunday and Monday due to elevated low-level winds. Landslides remain unlikely due to dry soils.
— At this time, there are no alerts, watches, or warnings in effect for Trinidad and Tobago from the Trinidad and Tobago Meteorological Service.

The Forecast

Moisture approaching Trinidad and Tobago. (SSEC/CIMSS/UW-Madison)
Moisture approaching Trinidad and Tobago. (SSEC/CIMSS/UW-Madison)

Heavier showers, thunderstorms, and overall higher rainfall accumulations are forecast to remain south and east of the county through the forecast period.

Friday night: Mostly clear skies initially with brisk showers and partly cloudy skies towards the early morning.

Saturday: After a mostly sunny start to the day, increasingly cloudy skies with scattered showers and periods of rain are forecast. Gusty winds are possible, accompanying rainfall activity. There is a low chance of isolated thunderstorms and a medium chance of heavy showers during the afternoon favoring western and eastern coastal Trinidad and eastern offshore areas. Variably cloudy skies with brief showers are forecast to continue into the night.

Sunday: Breezy with partly to mostly cloudy skies, interrupted by intervals of showers favoring Trinidad forecast through the day. One or two of these showers may become heavy from late morning through the afternoon. A mostly settled, partly cloudy night is expected.

Monday: Mostly sunny and breezy conditions are forecast across Trinidad and Tobago, with brisk showers possible during the afternoon.

Pockets of cloudiness east of Trinidad and Tobago on Friday evening. (Weathernerds.org)

Marine: Seas are forecast to be normal for this time of year. In open waters, waves are forecast to be up to 2.0 meters. Seas are forecast to be below 1.0 meter in sheltered areas.

Temperatures

Through the forecast period, the minimum low in Trinidad and Tobago is forecast to be between 22.0°C and 24.0°C.

Maximum highs across the country are forecast to be generally up to 30.0°C in Trinidad and Tobago. However, with increased cloud cover, maximum highs are forecast to be relatively cooler, particularly on Saturday.

In urbanized areas like Port of Spain, Scarborough, San Fernando, and Chaguanas, the maximum high temperatures could exceed 31.0°C.

Forecast Impacts

Forecast impacts and confidence for the approaching trough system.

The main hazards include brief heavy rainfall, street flooding, gusty winds, and lightning will accompany thunderstorms.

Rainfall & Flooding

Through the forecast period, wind shear is forecast to remain unfavorable for persisting heavy rainfall. Still, favorable lower-level conditions are forecast to produce shallow pockets of deep convection that may produce heavy to violent rainfall rates and thunderstorm activity, mainly on Saturday.

Over the next 48 hours across Trinidad, widespread totals up to 15 millimeters are forecast, with isolated totals up to 35 millimeters across Trinidad’s western and eastern coastal areas, with generally 5-15 millimeters across Tobago. In highly isolated areas, mainly across eastern and southern coastal Trinidad, totals of up to 50 millimeters are possible.

  • Saturday: Less than 5 millimeters of rainfall across the country, trending wetter across western and eastern coastal areas of Trinidad. Isolated rainfall totals up to 20 millimeters are possible, and higher in isolated heavy showers or thunderstorms.
  • Sunday: Less than 5 millimeters of rainfall across the country, trending wetter across western and eastern coastal areas of Trinidad as well as southern Trinidad. Isolated rainfall totals up to 20 millimeters are possible, and higher in isolated heavy showers or thunderstorms.
  • Monday: Less than 5 millimeters of rainfall across the country.

Putting the rainfall forecast into context, rainfall rates in excess of 50 millimeters per hour or areas that receive in excess of 25 millimeters within an hour tend to trigger street flooding across the country or flash flooding in northern Trinidad. For riverine flooding to occur, a large area of the country (not just in highly localized areas of western coastal Trinidad) would have to record upwards of 75 millimeters within 24 hours, and rainfall would have to fall across major rivers’ catchment areas.

Street flooding remains the main hazard, with flash flooding possible. Riverine flooding is not expected.

Gusty Winds

On Saturday, low-level winds are forecast to be light but increase on Sunday and Monday with peak sustained winds between 20 to 30 KM/H. In heavy to violent shower and thunderstorm activity, gusts up to and in excess of 45 KM/H are possible.

With wind gusts in excess of 45 KM/H, whole trees are expected to be in motion, and there may be some inconvenience when walking against the wind gusts. Light outdoor objects may topple or become airborne such as garbage cans, potted plants, loose galvanize or construction material, and other outdoor furniture. Tents may jump. Older/weaker trees may fall, bringing down utility poles and lines.

Other Adverse Weather Impacts

Lightning: Lightning is possible in thunderstorm activity. Lightning can cause power outages, voltage dips, damage to life and property, particularly during cloud-to-ground lightning strikes.

Landslides: Landslides are not expected due to drier soils in elevated areas.

Severe Thunderstorms: With light low-level winds and the low possibility of thunderstorms, there is the chance for funnel clouds and waterspouts, mainly along eastern and western coastal areas.

Why I May Not/Will Not See 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.

Scattered rainfall is forecast on Saturday, becoming more isolated to scattered on Sunday and Monday.

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

Forecast Discussion

Moisture being advected northwestward across the Windward Islands due to the influence of a merging, powerful low-pressure weakening the high-pressure influence across the region. (NASA/RAMMB/CIRA)
Moisture being advected northwestward across the Windward Islands due to the influence of a merging, powerful low-pressure weakening the high-pressure influence across the region. (NASA/RAMMB/CIRA)

Tropical Waves: There are no tropical waves in the Atlantic Basin.

A dominant ridge pattern has held across the region this week. However, with an induced trough resulting from a powerful low-pressure system developing in the northwestern Atlantic Ocean, the ridge will temporarily weaken, allowing for southeasterly winds with moisture being advected across the region.

This moisture will provide fuel for brief showers across Trinidad, Tobago, and the Southern Windward Islands, becoming heavy at times on Saturday. Moisture will quickly move to the west on Sunday and Monday as the high-pressure system regains strength across the Lesser Antilles, allowing for breezier conditions.

As showers or thunderstorms move across T&T, convection may weaken, with cloudiness associated with showers or thunderstorms that develop across western Trinidad or Tobago moving eastward. Mainly, the surface to mid-levels of the atmosphere will remain favorable for showers, lesser so for thunderstorms, to develop, but strong wind shear remains present across the country. This wind shear will also keep heavier rainfall south and east of the country.

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