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Forecast: Back-to-Back Tropical Waves To Affect T&T

June 21, 2024
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Three tropical waves, interacting with the Intertropical Convergence Zone, are forecast to affect Trinidad and Tobago over the next five days. On Monday through Tuesday next week, a trade wind surge accompanying a tropical wave will bring gusty winds to the region.

What you need to know

— Rainfall: Over the next five days, overall rainfall accumulations across the country are forecast to range from 25 to 75 millimeters. Across the southern and eastern halves of Trinidad and Tobago, as well as along isolated areas of western coastal Trinidad, localized totals exceeding 125 millimeters are possible.
— Saharan Dust: A significant surge of Saharan Dust is forecast overnight Friday through Saturday morning and on Monday afternoon through the night.
— Hazards: Over the next five days, the main hazards will be localized street/flash flooding in heavy showers/thunderstorms, which may be accompanied by gusty winds up to 50 KM/H, as well as lightning in thunderstorm activity.
— Marine: Seas are forecast to be moderate over the next five days, with waves in open waters generally up to 1.5 meters, and occasionally up to 2.5 meters from Monday afternoon. In sheltered areas, waves are forecast to be up to 1.0 meter and choppy in showers/rain and thunderstorms, and between 1.0 and 1.5 meters on Monday into Tuesday.

Latest Alert

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

Friday Night

Friday Night
3 10 0 1
Partly cloudy and increasingly hazy, with isolated showers and the odd thunderstorm favoring eastern and southern areas of Trinidad, as well as eastern Tobago.
Partly cloudy and increasingly hazy, with isolated showers and the odd thunderstorm favoring eastern and southern areas of Trinidad, as well as eastern Tobago.
3/10
Thunderstorm Chances
Low

Saturday

Saturday
6 10 0 1
Initially partly cloudy, hazy and misty/foggy in low-lying areas, becoming increasingly cloudy. Isolated thunderstorms and showers possible from the late morning through the afternoon, favoring the western half of Trinidad initially, then across the remainder of Trinidad during the afternoon. Unsettled conditions to continue into the night, with rain/showers/isolated thunderstorms favoring southern and eastern areas, spreading northwestward as the night progresses.
Initially partly cloudy, hazy and misty/foggy in low-lying areas, becoming increasingly cloudy. Isolated thunderstorms and showers possible from the late morning through the afternoon, favoring the western half of Trinidad initially, then across the remainder of Trinidad during the afternoon. Unsettled conditions to continue into the night, with rain/showers/isolated thunderstorms favoring southern and eastern areas, spreading northwestward as the night progresses.
6/10
Thunderstorm Chances
Medium – High

Sunday

Sunday
5 10 0 1
Early morning showers and thunderstorms are forecast to interrupt a variably cloudy and hazy night, leading to a partly to mostly cloudy day. Isolated late morning through afternoon showers and thunderstorms favoring Tobago and the northern half of Trinidad initially, spreading across the islands through the afternoon. A partly cloudy night, with a resurgence of showers nearing midnight.
Early morning showers and thunderstorms are forecast to interrupt a variably cloudy and hazy night, leading to a partly to mostly cloudy day. Isolated late morning through afternoon showers and thunderstorms favoring Tobago and the northern half of Trinidad initially, spreading across the islands through the afternoon. A partly cloudy night, with a resurgence of showers nearing midnight.
5/10
Thunderstorm Chances
Medium

Monday

Monday
6 10 0 1
Scattered early morning showers and thunderstorms set to interrupt cloudy skies, becoming mostly settled after daybreak and increasingly hazy. Isolated showers and thunderstorms are forecast to interrupt hazy skies across both islands from midday through the early afternoon. A variably cloudy and hazy afternoon, evening and night, barring the odd shower favoring Tobago and eastern Trinidad. Increasingly breezy/windy overnight.
Scattered early morning showers and thunderstorms set to interrupt cloudy skies, becoming mostly settled after daybreak and increasingly hazy. Isolated showers and thunderstorms are forecast to interrupt hazy skies across both islands from midday through the early afternoon. A variably cloudy and hazy afternoon, evening and night, barring the odd shower favoring Tobago and eastern Trinidad. Increasingly breezy/windy overnight.
6/10
Thunderstorm Chances
Medium – High

Tuesday

Tuesday
7 10 0 1
Early morning showers, rain, and thunderstorms across both islands continuing through the early afternoon. A variably cloudy and breezy evening.
Early morning showers, rain, and thunderstorms across both islands continuing through the early afternoon. A variably cloudy and breezy evening.
7/10
Thunderstorm Chances
High

Wednesday

Wednesday
3 10 0 1
A few overnight showers and isolated thunderstorms, favoring southern and eastern areas as well as Tobago, giving way to a breezy, warm and hazy day. A few isolated showers are possible along western coastal Trinidad during the afternoon, and eastern areas during the night.
A few overnight showers and isolated thunderstorms, favoring southern and eastern areas as well as Tobago, giving way to a breezy, warm and hazy day. A few isolated showers are possible along western coastal Trinidad during the afternoon, and eastern areas during the night.
3/10
Thunderstorm Chances
Low

Marine Forecast

Temperatures

Saturday

Low: 25-27°C

High: 31-33°C

Sunday

Low: 24-26°C

High: 30-32°C

Monday

Low: 24-26°C

High: 31-33°C

Tuesday

Low: 23-25°C

High: 29-31°C

Wednesday

Low: 25-27°C

High: 32-34°C

Forecast Impacts

Flooding

Flooding
6 10 0 1
Over the next five days, overall rainfall accumulations across the country are forecast to range from 25 to 75 millimeters. Across the southern and eastern halves of Trinidad and Tobago, as well as along isolated areas of western coastal Trinidad, localized totals exceeding 125 millimeters are possible. The chances of street/flash flooding are medium to high. It should be noted that due to dry soil conditions, riverine flooding is not expected.
Over the next five days, overall rainfall accumulations across the country are forecast to range from 25 to 75 millimeters. Across the southern and eastern halves of Trinidad and Tobago, as well as along isolated areas of western coastal Trinidad, localized totals exceeding 125 millimeters are possible. The chances of street/flash flooding are medium to high. It should be noted that due to dry soil conditions, riverine flooding is not expected.
6/10
Likelihood
Medium – High

Forecast Rainfall Totals

  • Saturday: Across the country, between 5 and 10 millimeters are forecast, with totals up to 15 millimeters, favoring eastern and southern areas. In isolated thunderstorm activity, rainfall totals exceeding 25 millimeters are possible.
  • Sunday: Across the country, between 5 and 10 millimeters are forecast, with totals up to 15 millimeters, favoring eastern and northern areas. In isolated thunderstorm activity, rainfall totals exceeding 25 millimeters are possible.
  • Monday: Across the country, between 5 and 15 millimeters are forecast, with totals up to 35 millimeters, favoring eastern and southern halves of Trinidad, as well as Tobago. In isolated thunderstorm activity, rainfall totals exceeding 25 millimeters are likely.
  • Tuesday: Across the country, between 5 and 15 millimeters are forecast, with totals up to 35 millimeters, favoring eastern and southern halves of Trinidad, as well as Tobago. In isolated thunderstorm activity, rainfall totals exceeding 25 millimeters are likely.
  • Wednesday: Across the country, less than 5 millimeters are forecast, with isolated totals up to 10 millimeters, favoring eastern areas.

Understanding Rainfall Accumulations

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
5 10 0 1
From Sunday through Tuesday, due to a fairly saturated atmosphere, strong low- to mid-level winds, and ample instability across the atmosphere, there is the potential for an isolated strong thunderstorm, with the main hazards being heavy to violent rainfall rates through the 3-day period, but damaging wind gusts mainly Monday and Tuesday.
From Sunday through Tuesday, due to a fairly saturated atmosphere, strong low- to mid-level winds, and ample instability across the atmosphere, there is the potential for an isolated strong thunderstorm, with the main hazards being heavy to violent rainfall rates through the 3-day period, but damaging wind gusts mainly Monday and Tuesday.
5/10
Likelihood
Medium
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
Throughout the forecast period, maximum sustained winds are forecast to range between 15 and 30 KM/H, gusting to 40 KM/H outside of shower/thunderstorm activity. On Monday and Tuesday, and in the vicinity or during showers/thunderstorms, sustained winds up to 45 KM/H are possible with gusts exceeding 50 KM/H are possible.
Throughout the forecast period, maximum sustained winds are forecast to range between 15 and 30 KM/H, gusting to 40 KM/H outside of shower/thunderstorm activity. On Monday and Tuesday, and in the vicinity or during showers/thunderstorms, sustained winds up to 45 KM/H are possible with gusts exceeding 50 KM/H are possible.
4/10
Likelihood
Low – Medium

With winds gusting to 50 KM/H and occasionally above, whole trees can be in motion, with larger trees and weaker branches falling. Light outdoor objects can topple or become airborne, such as garbage cans, loose galvanize, construction material, and outdoor furniture. Tents may also jump.

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.

Throughout the forecast period, isolated to scattered rainfall is forecast.

Forecast Discussion

A series of tropical waves interacting with the Intertropical Convergence Zone are forecast to affect Trinidad and Tobago over the next five days. However, the limiting factors will be the ever-present Saharan Dust, which will provide a drier low-level atmosphere at times and moderate wind shear at times.

On Friday night into Saturday morning, a significant surge of Saharan Dust is forecast to move across T&T while Tropical Wave 12 nears the country. By Saturday night, the axis of the wave is forecast to move across T&T with an increasingly moist and unstable low and upper-level environment. Saharan Dust is forecast to keep the mid-levels relatively dry.

Trailing convergence on Sunday, associated with the Intertropical Convergence Zone, after Tropical Wave 12 is forecast to move across T&T, producing cloudiness, showers and thunderstorms.

By Sunday night into Monday morning, Tropical Wave 13 is forecast to move across T&T with a generally moist and unstable atmosphere, with cloudiness, showers and thunderstorms once more. However, as this wave pulls away, the mid-levels are forecast to become dry as a brief but moderate to high-concentration surge of Saharan Dust moves in. Still, ample instability and upper/low-level moisture and favorable upper-level divergence will support shower and thunderstorm activity.

Monday night into Tuesday, Tropical Wave 14 is forecast to move across Trinidad and Tobago, which is moving across the Atlantic accompanied by a surge in trade winds. As a result, low-level winds are forecast to increase as high as 35 knots, which will translate to the surface in heavy showers and thunderstorms through mid-afternoon on Tuesday. Note that as a result of this trade wind surge, damaging, gusty winds are possible, favoring Tobago, between Monday night and Tuesday.

On Wednesday, a ridge pattern returns with a surge of Saharan Dust moving into T&T as the ITCZ shifts south.

While localized, short-lived flooding is possible in isolated heavy showers/thunderstorms, flooding across the country has been sparse due to very dry soils. As a result, riverine flood chances remain low to non-existent at this time.

Note that as an extended forecast goes further into the future, it is normal for the certainty to be reduced relative to the extended period.

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