Forecast: Hot Days With Showers & Thunderstorms Through The Week

What you need to know:
— A typical wet season pattern is forecast to hold this week with mostly hot and sunny days with light winds interrupted by late morning through afternoon thunderstorms daily across western and northern halves of Trinidad, lesser so Tobago.
— Tropical waves are forecast to enhance rainfall mainly on Tuesday and Thursday, with more scattered showers and isolated strong thunderstorms.
— Main impacts include locally heavy rainfall that may trigger street or flash flooding. Localized gusty winds in excess of 45 KM/H and lightning may accompany thunderstorms and heavy to violent showers causing power dips/outages, downed trees, and localized wind damage. Landslides, while possible, remain unlikely outside of heavy rainfall during the afternoon across the Northern Range. With light winds and the potential for isolated thunderstorms, funnel clouds, and waterspouts are possible, favoring the western half of Trinidad.
— There are no alerts, watches, or warnings for T&T from the Trinidad and Tobago Meteorological Service at this time. Trinidad and Tobago is not under a tropical storm watch or warning.

The Forecast

Moisture associated with Tropical Wave 39 and Tropical Depression 10, as well as the Intertropical Convergence Zone moving across and approaching T&T (SSEC/CIMSS/UW-Madison)

Monday: Mostly hot and sunny skies across both islands. Isolated showers and thunderstorms are possible from the late morning through the afternoon across Trinidad, gradually moving from the southeast to the northwest. Thunderstorms are possible across the country. Conditions are forecast to settle by the evening with a mostly fair night.

Tuesday: Early morning showers and thunderstorms, favoring offshore areas initially, then moving across eastern Trinidad and Tobago and subsiding by daybreak. Mostly hot and partly cloudy skies across both islands through the late morning, with conditions to become increasingly cloudy by midday, with isolated to scattered showers and thunderstorms across both islands, with heavier rainfall favoring Trinidad. Showers to subside by nightfall.

Wednesday: After isolated showers and thunderstorms during the early morning, mostly hot and sunny conditions are forecast. Isolated thunderstorms favoring Trinidad are possible through the afternoon favoring southern and western halves of the island. A mostly settled night is expected.

Thursday: Variably cloudy conditions with scattered showers and thunderstorms from the early morning through the afternoon across both islands. Conditions to settle by the evening.

Friday: Variably cloudy conditions with scattered showers and thunderstorms from the early morning through the afternoon across both islands. Conditions to settle by the evening.

Marine: Through Thursday, seas are forecast to be slight in open waters with waves up to 1.25 meters while in sheltered areas, near calm. Sea conditions on Friday into the weekend depend on how close a possible tropical cyclone gets to the Lesser Antilles, with a closer approach meaning moderate seas and long period swells. This forecast will be periodically updated throughout the week. Note seas may become locally choppy or rough in the vicinity and during heavy showers or thunderstorms.

Temperatures

Through the forecast period, the minimum low for Trinidad and Tobago is forecast to be between 23.0°C and 26.0°C. The maximum high for Trinidad and Tobago is forecast to be between 32.0°C and 35.0°C, with temperatures near that higher end of the range favoring Trinidad.

Higher temperatures are possible in urbanized areas like Port of Spain, Scarborough, San Fernando, and Chaguanas. Lower daytime temperatures are possible on days with increased cloud cover.

Forecast Impacts

Forecast impacts due to localized climatic effects and three tropical waves over the next 5 days.

Over the next five days, the main hazards include locally heavy rainfall that may trigger street or flash flooding. Localized gusty winds in excess of 45 KM/H and lightning may accompany thunderstorms and heavy to violent showers causing power dips/outages, downed trees, and localized wind damage. Landslides, while possible, remain unlikely outside of heavy rainfall during the afternoon across the Northern Range. With light winds and the potential for isolated thunderstorms, funnel clouds, and waterspouts are possible, favoring the western half of Trinidad.

Winds

Sustained surface winds up to 20 KM/H are forecast. In shower 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.

Rainfall

Overall higher rainfall is forecast to favor much of Trinidad, with accumulations between 25-75 millimeters. However, localized totals up to and in excess of 75 millimeters are possible in prolonged heavy showers or isolated thunderstorm activity.

  • Monday: Less than 5 millimeters of rainfall across the country, with isolated totals favoring localized areas of Trinidad, as well as eastern Tobago, up to 20 millimeters.
  • Tuesday: Between 5-20 millimeters of rainfall across Trinidad and Tobago, with highly isolated areas receiving up to 25 millimeters across the country.
  • Wednesday: Less than 5 millimeters of rainfall across the country, with isolated totals up to 15 millimeters, favoring western coastal Trinidad.
  • Thursday: Between 10-25 millimeters across the country. In heavy showers or thunderstorms across the country, totals may reach and exceed 25 millimeters.
  • Friday: Between 5-15 millimeters across the country. In isolated heavy showers or thunderstorms, totals may reach and exceed 25 millimeters.

As mentioned earlier, street flooding and flash flooding are likely with medium to high chances in heavy showers or thunderstorms and a very low chance of riverine flooding.

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 and fallen trees are possible through the forecast period, particularly in areas where heavy thunderstorms or persisting rains occur.

Tornadic Activity: With light easterly to southeasterly winds and the potential for strong thunderstorms, funnel clouds, and waterspouts are possible. If funnel clouds touchdown or waterspouts encounter land, weak tornadoes are possible.

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.

The scattered showers and thunderstorms are forecast to occur on Thursday into Friday, with isolated activity expected during the first half of the week.

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

Forecast Discussion

Tropical Weather Outlook from the National Hurricane Center, tracking Hurricane Ida, Post-Tropical Cyclone Julian, Tropical Depression 10 and anew area off the coast of Africa for tropical cyclone formation. (NHC)
Tropical Weather Outlook from the National Hurricane Center, tracking Hurricane Ida, Post-Tropical Cyclone Julian, Tropical Depression 10, and a new area off the coast of Africa for tropical cyclone formation. (NHC)

Tropical Waves: At 00Z Monday 30th August 2021, the axis of Tropical Wave 39 is along 61W moving across Trinidad and Tobago, south of 20N, moving westward at 10 knots (18 KM/H) with no significant shower or thunderstorm activity. The axis of Tropical Wave 40 is along 44W, south of 17N, moving westward at 10-15 knots (18-27 KM/H), forecast to move across the region on Tuesday. The axis of Tropical Wave 41 is along 29W, south of 19N, and moving west at 10-15 knots (18-27 KM/H), forecast to move across the region on Thursday into Friday.

Several low-pressure features, including Tropical Depression 10, now post-Tropical Cyclone Julian, and a frontal boundary in the north Atlantic has diminished the influence of the Atlantic high-pressure system across T&T. This has resulted in near calm to light winds across the region while high atmospheric moisture persists.

These light winds and high moisture will allow for the development of slow-moving, heavy afternoon showers triggered by daytime heating, sea breeze convergence, and orographic effects as light southeasterly winds move across the islands.

While this pattern is forecast to continue through the week, Tropical Waves 40 and 41 will enhance showers and thunderstorms on Tuesday and again Thursday into Friday respectively.

Through much of the week, light to no wind shear is forecast across T&T. This will result in any shower or thunderstorm that forms having ample moisture, little to no formation hindrances as well as slow movement due to light winds, potentially settling up conditions ripe for localized but severe street/flash flooding.

Infrared satellite imagery showing scattered showers and thunderstorms associated with the ITCZ, tropical waves and tropical cyclones. (Weathernerds)
Infrared satellite imagery showing scattered showers and thunderstorms associated with the ITCZ, tropical waves and tropical cyclones. (Weathernerds)
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