[Updated Forecast] Tropical Wave 43 Moves West, Showers & Isolated Thunderstorms Affect T&T

Key Messages:
— A weak tropical wave has moved across T&T, producing isolated showers and thunderstorms through Thursday morning.
— Air quality is forecast to be reduced through Friday as Saharan Dust follows Tropical Wave 43.
— Highly isolated areas of street or flash flooding are possible through the next three days, favoring Trinidad. Sustained winds are forecast to increase following the wave axis, with localized wind gusts in excess of 45 KM/H possible. Maximum temperatures are forecast to be hot.
Lightning may accompany thunderstorms. Funnel clouds and waterspouts are unlikely.
— There are no alerts, watches, or warnings in effect for Trinidad and Tobago from the Trinidad and Tobago Meteorological Service at this time.

The Forecast

Moisture ahead of Tropical Wave 43 moving across T&T (SSEC/CIMSS/UW-Madison)
Moisture ahead of Tropical Wave 43 moving across T&T (SSEC/CIMSS/UW-Madison)

Wednesday: After midnight, brisk, isolated showers and thunderstorms are forecast to move across Trinidad and Tobago, mainly across offshore areas. Partly to mostly cloudy skies are forecast through the day, interrupted by brisk showers and the brief, weak thunderstorm, with heavier rainfall favoring Trinidad. Conditions to become breezy and hazy by the late afternoon as Saharan Dust moves in, leading to a mostly settled night. Isolated showers and thunderstorms are possible mainly after midnight favoring eastern offshore areas.

Thursday: Early morning showers and thunderstorms are forecast to subside by daybreak. Mostly hot, hazy, breezy, and partly cloudy with brisk isolated showers moving across the country. There is a low to medium chance of thunderstorms favoring Trinidad during the late morning through the afternoon. A mostly settled and hazy evening and night are expected.

Friday: Mostly hot, hazy, breezy, and partly cloudy with brisk isolated showers moving across the country. There is a low chance of a thunderstorm favoring western coastal Trinidad during the afternoon. A mostly settled and hazy evening, with isolated showers possible near and after midnight.

Marine: Over the next 72 hours, seas are forecast to be moderate in open waters with waves up to 2.0 meters and less than 1.0 meters in sheltered areas. These higher-than-usual waves in sheltered areas are due to a combination of ongoing spring tides and subsiding long-period swells from Hurricane Larry.

Temperatures

Over the next 72 hours, while the minimum low is forecast to be between 23.0°C and 25.0°C for the country, the maximum high temperatures are forecast to be up to 34.0°C in Trinidad and 32.0°C in Tobago.

In urbanized areas like Port of Spain, Scarborough, San Fernando, and Chaguanas, the maximum high temperatures could exceed 34.0°C. The feels-like temperature, or heat index, is forecast to range between 35.0°C and 48.0°C through Friday.

This level of heat puts everyone at risk for heat illnesses; however, the risks are greatest for the elderly, young children, people with chronic illnesses such as breathing difficulties, heart conditions or psychiatric illnesses, people who work or who exercise in the heat, and the socially displaced.

Forecast Impacts

Forecast impacts due to Tropical Wave 43
Forecast impacts due to Tropical Wave 43

Tropical Wave 43 is not forecast to be a high-impact event. Over the next three days, the main hazards are forecast to be highly isolated heavy showers or thunderstorms triggering very localized street or flash flooding and gusty winds in excess of 45 KM/H. In thunderstorm activity, cloud-to-ground lightning is possible. Landslides, funnel clouds, and waterspouts are unlikely.

Winds

Sustained surface winds less than 25 KM/H are forecast through Wednesday afternoon. Winds are forecast to pick up by late Wednesday through the remainder of the week, with sustained winds up to 35 KM/H. 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

This is not forecast to be a widespread heavy rainfall event. Overall, higher rainfall totals are forecast to favor eastern areas of Trinidad and Tobago, with accumulations up to 50 millimeters. However, localized totals up to and in excess of 50 millimeters are possible in prolonged heavy showers or isolated thunderstorm activity across western coastal Trinidad.

  • Wednesday: Between 0-15 millimeters across the country, with isolated totals up to 20 millimeters favoring western coastal Trinidad.
  • Thursday: Between 0-15 millimeters across the country with isolated totals up to 20 millimeters favoring eastern Trinidad.
  • Friday: Less than 5 millimeters across the country with highly localized areas recieving up to 15 millimeters.

Highly localized street flooding or flash flooding is possible with low to medium chances. Riverine flooding is not expected.

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, particularly along the Northern Range but low rainfall totals are forecast to this is unlikely.

Tornadic Activity: Even with the potential for thunderstorms, funnel clouds, and waterspouts are unlikely. If funnel clouds touchdown or waterspouts encounter land, weak tornadoes can form.

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 showers and thunderstorms are forecast to occur through the forecast period.

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

Forecast Discussion

Infrared satellite imagery showing scattered showers and thunderstorms associated with tropical waves east of the Lesser Antilles. (Weathernerds)

Tropical Waves: At 00Z Thursday 9th September 2021, the axis of Tropical Wave 43 is along 64W, south of 15N, moving westward at 10-15 knots (18-27 KM/H) with highly isolated shower and thunderstorm activity. Tropical Wave 44 is along 43W, south of 16N, moving west at 15 knots (27 KM/H), forecast to move across the region on Saturday 11th September 2021. A new wave, Tropical Wave 45 has entered the Atlantic, at approximately 26W.

Over the next 12-18 hours, Tropical Wave 43 will be moving across the region, bringing increased instability, a marginal increase in atmospheric moisture, and coupled with a low-shear environment. Isolated, brief showers and thunderstorms are forecast through Wednesday afternoon.

By Wednesday evening, a modest surge of winds and Saharan Dust is forecast to begin moving across T&T as a surface to mid-level high-pressure ridge becomes dominant across the region, Additionally, wind shear is forecast to increase. At the very low levels of the atmosphere, moisture will be available for brief showers or weak thunderstorm development, but no significant rainfall is forecast through Friday.

Over the weekend, as Tropical Wave 44 nears on Saturday night, a high-shear environment will still be in place, limiting shower and thunderstorm strength and moisture will be lacking across T&T, with most of the deep tropical moisture moving north of the Windwards.

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