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Forecast: Tropical Waves To Bring Scattered Showers, Thunderstorms

June 3, 2023
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Tropical waves are forecast to bring increased rainfall to Trinidad and Tobago. However, persisting and widespread rainfall is not expected.

What you need to know

— Rainfall: Over the next five days, rainfall accumulations will vary between 15 and 35 millimeters across both islands. Across eastern and southern areas of Trinidad, eastern Tobago, and western coastal Trinidad, totals may near 50 millimeters. In highly isolated areas, totals could exceed 75 millimeters over the five-day period in the above-mentioned areas. The heaviest rainfall days are expected on Saturday and Tuesday into Wednesday due to the passages of successive tropical waves, improving wind shear and deep, tropical moisture.
— Saharan Dust: A surge of Saharan Dust is forecast to return to the area from Saturday night. Dust levels are set to increase from Saturday night.
— Hazards: The main hazards, particularly on Saturday, will be street/flash flooding and gusty winds. Though overall winds are forecast to remain near calm or light, in heavy showers or thunderstorms, wind gusts may exceed 45 KM/H. Daily through the next five days, localized street/flash flooding is possible, with the potential for landslides in elevated areas.
— Marine: Seas are forecast to be slight to moderate in open waters, with waves up to 1.5 meters and below 0.5 in sheltered areas. Seas may become locally choppy or rough in heavy showers or thunderstorms.

Latest Alerts

2 minute read

Adverse Weather Alert Discontinued For T&T

The Trinidad and Tobago Meteorological Service (TTMS) has discontinued the Adverse Weather Alert for Trinidad and Tobago. — What has happened: Fast-moving showers and thunderstorms affected…
October 25, 2024

Trinidad and Tobago is NOT under any tropical storm or hurricane threat, watch, or warning at this time.

The Forecast

Saturday

Saturday
7 10 0 1
Variably cloudy conditions after midnight with periods of rain and isolated showers during the early morning favoring Tobago and eastern Trinidad. With partly cloudy start, sunshine is possible across the western half of Trinidad after sunrise. Scattered showers and isolated thunderstorms are forecast to develop during the mid to late morning through the early afternoon, favoring Tobago and offshore eastern Trinidad initially, gradually moving north to northwestward across the country. While rainfall is forecast to decrease across the country as the day progresses, isolated strong thunderstorms are possible during the late morning through afternoon. A mostly settled and hazy night. Street/flash flooding, gusty winds possible in heavier showers/thunderstorms.
Variably cloudy conditions after midnight with periods of rain and isolated showers during the early morning favoring Tobago and eastern Trinidad. With partly cloudy start, sunshine is possible across the western half of Trinidad after sunrise. Scattered showers and isolated thunderstorms are forecast to develop during the mid to late morning through the early afternoon, favoring Tobago and offshore eastern Trinidad initially, gradually moving north to northwestward across the country. While rainfall is forecast to decrease across the country as the day progresses, isolated strong thunderstorms are possible during the late morning through afternoon. A mostly settled and hazy night. Street/flash flooding, gusty winds possible in heavier showers/thunderstorms.
7/10
Thunderstorm Chances
High

Sunday

Sunday
3 10 0 1
Mostly sunny, hazy day with isolated late morning showers and isolated afternoon thunderstorms favoring Trinidad. A mostly settled and hazy night.
Mostly sunny, hazy day with isolated late morning showers and isolated afternoon thunderstorms favoring Trinidad. A mostly settled and hazy night.
3/10
Thunderstorm Chances
Low

Monday

Monday
4 10 0 1
Early morning showers and isolated thunderstorms to give way to a partly cloudy and hazy day, additional showers possible across both islands during the late morning into the early afternoon. Increasingly cloudy, but mostly settled conditions are forecast by nightfall.
Early morning showers and isolated thunderstorms to give way to a partly cloudy and hazy day, additional showers possible across both islands during the late morning into the early afternoon. Increasingly cloudy, but mostly settled conditions are forecast by nightfall.
4/10
Thunderstorm Chances
Low – Medium

Tuesday

Tuesday
6 10 0 1
Partly to mostly cloudy skies, with isolated showers and isolated thunderstorms affecting both islands during the early morning and continuing through the day, with overall heavier activity remaining offshore eastern Trinidad. Conditions to gradually settle by the evening with showers/thunderstorms returning mainly after midnight. Street/flash flooding, gusty winds possible in heavier showers/thunderstorms.
Partly to mostly cloudy skies, with isolated showers and isolated thunderstorms affecting both islands during the early morning and continuing through the day, with overall heavier activity remaining offshore eastern Trinidad. Conditions to gradually settle by the evening with showers/thunderstorms returning mainly after midnight. Street/flash flooding, gusty winds possible in heavier showers/thunderstorms.
6/10
Thunderstorm Chances
Medium – High

Wednesday

Wednesday
6 10 0 1
Partly to mostly cloudy with scattered early morning showers and thunderstorms, continuing through midday, favoring southern and eastern areas of Trinidad initially, gradually moving west. Conditions to settle by the early afternoon, barring the odd shower. A mostly settled and hazy night. Street/flash flooding possible. Gusty winds likely.
Partly to mostly cloudy with scattered early morning showers and thunderstorms, continuing through midday, favoring southern and eastern areas of Trinidad initially, gradually moving west. Conditions to settle by the early afternoon, barring the odd shower. A mostly settled and hazy night. Street/flash flooding possible. Gusty winds likely.
6/10
Thunderstorm Chances
Medium – High

Marine Forecast

Temperatures

Generally, over the next five days, maximum highs and minimum lows are forecast to be near average.

Saturday through Wednesday

Low: 24-26°C

High: 28-33°C

Maximum high temperatures are forecast to range between 28°C to 33°C, trending cooler on Saturday and Wednesday and higher across urbanized areas of Trinidad, where in built-up areas, maximum high temperatures could exceed 33°C. Overall hotter days are forecast on Sunday and Monday. Minimum lows are forecast to remain mild, ranging between 24°C and 26°C in Trinidad and Tobago, trending cooler in interior areas. The heat index will generally be near 34°C on Saturday and Wednesday and reach up to 40°C on other days.

Forecast Impacts

Flooding

Flooding
7 10 0 1
Over the next five days, rainfall accumulations will vary between 15 and 35 millimeters across both islands. Across eastern and southern areas of Trinidad, eastern Tobago and western coastal Trinidad, totals may near 50 millimeters. In highly isolated areas, totals could exceed 75 millimeters over the five-day period in the above-mentioned areas. The heaviest rainfall days are expected on Saturday and Tuesday into Wednesday due to the passages of successive tropical waves, improving wind shear and deep, tropical moisture.
Over the next five days, rainfall accumulations will vary between 15 and 35 millimeters across both islands. Across eastern and southern areas of Trinidad, eastern Tobago and western coastal Trinidad, totals may near 50 millimeters. In highly isolated areas, totals could exceed 75 millimeters over the five-day period in the above-mentioned areas. The heaviest rainfall days are expected on Saturday and Tuesday into Wednesday due to the passages of successive tropical waves, improving wind shear and deep, tropical moisture.
7/10
Likelihood
High

Forecast Rainfall Totals

  • Saturday: Between 5 and 15 millimeters of rainfall across the country, trending higher across eastern and southern Trinidad, eastern Tobago, and western coastal Trinidad, where in localized areas, totals may near 25 millimeters. In areas where thunderstorms occur, isolated totals could exceed 25 millimeters.
  • Sunday: Between 0 and 5 millimeters across both islands. In isolated areas where heavier afternoon showers or the odd thunderstorm occur, favoring western coastal areas, rainfall accumulations are forecast to exceed 5 mllimeters.
  • Monday: Between 0 and 5 millimeters across Trinidad, with totals trending higher across the southern, eastern, and western coastal Trinidad, ranging between 10 and 25 millimeters. For Tobago, rainfall totals are forecast to range between 5 and 15 millimeters.
  • Tuesday: Between 5 and 15 millimeters of rainfall across both islands, with totals nearing 25 millimeters across the southern and eastern halves of Trinidad, as well as localized areas of western Trinidad where thunderstorms occur. In isolated areas, totals may exceed 25 millimeters.
  • Wednesday: Between 0 and 10 millimeters of rainfall across both islands, with totals nearing 20 millimeters across Trinidad, particularly in the east, south, and western coastal areas. In isolated heavy showers and thunderstorms, totals may exceed 20 millimeters.

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.

Strong Thunderstorms

Strong Thunderstorms
3 10 0 1
On Saturday, moderate to strong instability is forecast to be present, particularly during the early morning through afternoon hours across T&T, with a very moist atmosphere. As a result, there is a low chance of thunderstorms becoming strong. Shear is forecast to be at low levels, but generally low-level convergence and upper-level divergence will not be very favorable. The best chances for stronger thunderstorms exist on Saturday. See forecast discussion for more information.
On Saturday, moderate to strong instability is forecast to be present, particularly during the early morning through afternoon hours across T&T, with a very moist atmosphere. As a result, there is a low chance of thunderstorms becoming strong. Shear is forecast to be at low levels, but generally low-level convergence and upper-level divergence will not be very favorable. The best chances for stronger thunderstorms exist on Saturday. See forecast discussion for more information.
3/10
Likelihood
Low
What is a strong or severe thunderstorm?

Given how rare these types of thunderstorms are in our region – we classify a severe or strong thunderstorm as one that produces any of the following:

  • Damaging wind gusts exceeding 55 KM/H;
  • Frequent lightning (more than 30 cloud-to-ground strikes within a 10-minute period);
  • Hail (of any size);
  • Rainfall of more than 50 millimeters or more within an hour or exceeding 75 millimeters or more within three hours;
  • The sighting of a funnel cloud or touchdown of a waterspout/tornado associated with the thunderstorm.

Gusty Winds

Gusty Winds
4 10 0 1
Over the next five days, sustained winds are forecast to be light to gentle, generally remaining below 25 KM/H and gusts up to 40 KM/H possible. In heavy showers or thunderstorms, with higher gusts possible exceeding 45 KM/H, particularly on Saturday and Wednesday.
Over the next five days, sustained winds are forecast to be light to gentle, generally remaining below 25 KM/H and gusts up to 40 KM/H possible. In heavy showers or thunderstorms, with higher gusts possible exceeding 45 KM/H, particularly on Saturday and Wednesday.
4/10
Likelihood
Low – Medium

Possible impacts include localized wind damage to trees, power lines, and small structures.

Other Hazards

Saharan Dust Forecast

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.

On Saturday and Tuesday into Wednesday, isolated to scattered rainfall is forecast, with isolated rainfall forecast on Sunday and Monday.

Forecast Discussion

Tropical Update

A lingering plume of moisture at the surface to mid-levels with moderate to high instability is forecast to move across Trinidad and Tobago through the early afternoon on Saturday as Tropical Wave 07 moves across Trinidad and Tobago. Marginally favorable low and upper-level conditions are forecast to support isolated strong convection through Saturday afternoon.

At the lower levels of the atmosphere, the Lesser Antilles will be on the periphery of an Atlantic high-pressure system anchored northeast of the Leewards, producing some surface to mid-level confluence, particularly on Saturday, which will support rainfall and cloudiness.

In addition, winds are also forecast to be southerly to southeasterly, with winds veering at the lower levels of the atmosphere. This wind profile, combined with T&T’s topography and localized climatic effects, could result in heavier showers/thunderstorms along hilly and western areas of both islands, including the south-facing slopes of the Northern Range.

However, by the evening, conditions are forecast to greatly improve across Trinidad and Tobago as an Atlantic high-pressure system regains dominance across the region. However, this same high-pressure system has provided a conveyor belt of Saharan Dust to be transported directly from the west coast of Africa to T&T, albeit at slower-than-typical speeds. Dust models show a moderate to high concentration surge of Saharan Dust arriving by late Saturday.

By Sunday, although moderate to high levels of TPW are still forecast to be present, the Atlantic high-pressure system is forecast to regain dominance at all levels of the atmosphere, leading to more stable weather. However, with trade winds remaining light, localized climatic effects (sea-breeze convergence, daytime heating, and orographic convergence) will result in the usual Wet Season late morning through afternoon showers along coastal and hilly areas.

In the past, numerical weather prediction models do not accurately take into consideration the role of Saharan Dust in limiting showers and thunderstorms from forming. However, this surge of dust is being reflected in the lack of significant rainfall on Sunday into Monday, even with ample moisture present.

Regardless, there will still be fuel for showers and thunderstorms to form and sufficient moisture for cloudiness at all levels of at atmosphere. This is due to very moist conditions persisting, with total precipitable water (TPW – a measure of atmospheric moisture) above 2.0 inches (50mm) through the 5-day forecast period. Wind shear over the next five days will be on the decrease but still be at moderate levels through Sunday. As a result, stronger convection (showers and thunderstorms) are forecast to remain offshore eastern Trinidad and Tobago, with generally eastern and southern areas of both islands receiving the highest rainfall accumulations.

Come late Monday through Wednesday, moisture and instability are set to increase yet again as Tropical Wave 09, currently in the central Atlantic Ocean, is forecast to near the southern Windward islands, including Trinidad and Tobago.

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