Forecast: More Tropical Waves & Saharan Dust To Affect T&T

The battle between Saharan Dust and tropical waves continues. High concentrations of Saharan Dust will remain present over the next five days as two tropical waves traverse Trinidad and Tobago. While strong wind shear and Saharan Dust may limit rainfall, gusty winds will still pose a threat.

The Forecast

Marine: Seas are forecast to be moderate, with waves generally up to 2.0 meters, during the forecast period in open waters. In sheltered areas, waves are forecast to be near 1 meter but occasionally choppy during heavy showers or thunderstorms. King tides are also forecast to begin over the weekend.

Temperatures

Through the forecast period, the minimum low in Trinidad and Tobago is forecast to be between 23.0°C and 26.0°C.

Maximum highs across the country are forecast to be generally up to 31.0°C in Trinidad and Tobago. In urbanized areas like Port of Spain, Scarborough, San Fernando, and Chaguanas, the maximum high temperatures could exceed 32.0°C.

Over the next five days, temperatures are forecast to be cooler overall due to increased cloud cover and anticipated rainfall.

Forecast Impacts

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.

While thunderstorms are forecast over the next five days, strong wind shear, Saharan Dust, and a generally unfavorable environment (outside of Friday night/Saturday morning) will limit strong thunderstorms from forming.

Still, frequent cloud-to-ground lightning will be likely, with heavy to violent rainfall rates in thunderstorms. Funnel cloud development is unlikely. If a funnel cloud touches down on a body of water, it becomes a waterspout, and if it touches down on land, it becomes a tornado.

Other Hazards

As rainfall continues through the weekend and into next week and soils become increasingly saturated, landslides are possible across elevated areas of Tobago, southern and northern Trinidad.

Saharan Dust will remain present across the region with a reinforcing surge on Sunday, reducing air quality and affecting visibility.

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.

Isolated to scattered rainfall is forecast into the weekend.

Forecast Discussion

Tropical Waves: Based on the Tropical Analysis and Forecast Branch’s 06Z surface analysis on June 8th, 2022:

• The sixth tropical wave for 2022 is along 55°W, south of 14°N, moving west at 20 knots (37 KM/H). This wave is forecast to move across Trinidad and Tobago by Wednesday evening. Scattered showers and isolated thunderstorms have been observed with this wave, mainly across inland South America.
• The seventh tropical wave for 2022 is along 43°W, south of 13°N, and moving west at 15 to 20 knots (27.8-37 KM/H). Scattered moderate convection has been observed with this wave, both ahead and following the wave axis. This wave is forecast to move across T&T overnight, June 10th, 2022, into Saturday, June 11th, 2022.

Surface to mid-level confluencing in conjunction with marginally favorable upper-level conditions continue to produce brisk rainfall, but the strongest showers and thunderstorms persist across inland South America. On Wednesday, Tropical Wave 06 will approach T&T and move across the islands by Wednesday night. This wave will bring a marginal increase in moisture and instability to T&T on Wednesday, fuelling isolated showers and even the odd thunderstorm, favoring Trinidad.

By Thursday, Saharan Dust will dry the low to mid-levels of the atmosphere out. However, an upper-level low remains anchored just northeast of the Lesser Antilles, with a trough extending southwestward from this low. This low/trough has enhanced showers and thunderstorms mainly east of T&T and allowed persistent upper-level clouds to move across the region from the southwest.

This upper-level system will gradually drift northwestward by Thursday, allowing for an increase in mid to upper-level moisture and generally more favorable upper-level conditions by Friday.

Tropical Wave 07 will be approaching and moving across the region during this period. With abundant moisture and instability and a favorable atmosphere, heavier showers and thunderstorms are possible on Friday into Saturday.

Strong westerly to southwesterly wind shear (up to 40 knots) will persist, keeping most of the heavy rainfall, showers, and thunderstorms south and east of the country.

Following the passage of this tropical wave on Saturday, a deep-layered high-pressure system is forecast to rebuild, with a gradual drying of the mid to low levels of the atmosphere. Still, we may continue to see a flow of upper-level clouds across the country from the southwest leading to a variably cloudy and hazy Sunday.

While rainfall is not forecast to be particularly severe, strong winds continue to prevail at low levels of the atmosphere, which can make their way down to the surface in heavy showers and thunderstorms. These winds remain a hazard through the weekend, with wind gusts in excess of 45 KM/H forecast, gusts in excess of 50 KM/H likely, and gusts in excess of 55 KM/H possible, mainly on Wednesday and then again Friday into Saturday.