[Updated] Tropical Waves, ITCZ Forecast To Bring Days of Heavy Rainfall To T&T

Key Messages:
Weather: Over the next 5 days (and likely through next week), periods of showers and thunderstorms associated with the ITCZ and tropical waves will affect T&T, with partly to mostly cloudy periods.
Rainfall: Through Monday, between 1 to 3 inches (25 to 75 millimeters) are possible across Trinidad and Tobago with isolated totals between 4 to 6 inches (100 to 150 millimeters) mainly across eastern and southern areas of Trinidad. Note the highest rainfall totals will remain east of T&T. There is an elevated threat of street flooding and flash flooding beginning Thursday evening. Chances of riverine flooding will begin to increase, particularly by Saturday, across eastern areas of Trinidad initially.
Seas & Tides: While no abnormal tides are ongoing, strong wilds will contribute to moderate to rough seas into next week, with long-period swells affecting T&T.
Winds: A surge in trade winds will move across the region from Friday, with breezy conditions forecast over the weekend. Gusty winds in excess of 60 KM/H possible, particularly on Saturday into Sunday. Winds of this strength will produce wind damage including downed trees, utility poles, and roof damage. Localized power outages possible.
Other Impacts: Landslides possible in elevated areas. Funnel clouds are possible.

Trinidad and Tobago is under no alerts, watches, or warnings from the Trinidad and Tobago Meteorological Service at this time.

The Forecast

Thursday: Isolated showers and the odd thunderstorm are possible, with partly to mostly cloudy skies. After midday, a few isolated showers and the odd thunderstorm may develop across Trinidad’s western and northern areas but remain brisk. By the late afternoon, showers and thunderstorms are forecast to arrive from the east, moving across both islands, with increasing cloudiness. Conditions will settle by night, with a resurgence in activity after midnight

Friday: Showers and thunderstorms are forecast mainly during the early morning hours, nearing sunrise across T&T with mostly cloudy skies throughout the day. While the odd, brisk thunderstorm with brief showery intervals are possible during the late morning through the afternoon, conditions will generally be variably cloudy and breezy. Activity to return by early Saturday morning.

Saturday: Showers and thunderstorms are forecast across both islands during the early morning hours through daybreak. A mostly breezy and cloudy day is forecast with periods of showers and thunderstorms throughout the day, continuing into the night. Severe thunderstorms are possible (violent rainfall, frequent lightning, possible funnel clouds, and even hail!) Light to moderate rain also possible between heavier activity. This is forecast to be the wettest day during the initial 4-day period. Chances of flooding high!

Sunday: Cloudy and breezy conditions are forecast to be interrupted by brisk periods of showers and thunderstorms, with light to moderate rain between heavier activity.

Note that this wet pattern will continue through next week as the ITCZ remains in place across T&T.

The Forecast Discussion

On Thursday, a surface to mid-level high-pressure ridge remains in place across T&T and the Windwards. Increasing moisture will begin to move across the area as Tropical Wave 58 nears and moves across the region overnight into Friday, interacting with the ITCZ. A marginally favorable upper-level environment will be in place, enhancing showers and thunderstorms, though wind shear will be moderate to strong from the northwest. Winds will increase into Friday.

As Tropical Wave 58 moves away, lingering surface to low-level instability remains in place across T&T on Friday, with abundant moisture. The ITCZ will be present across T&T, with activity peaking after midnight through the sunrise, then again in the afternoon. Activity will be enhanced by an increasingly favorable upper-level environment, through wind shear will be moderate to strong. Also, a surface to low-level jet will be moving in across the region, associated with a surge in trade winds.

Tropical Wave 59 will be nearing T&T, interacting with the ITCZ on Saturday into Sunday. Abundant moisture will be present across the islands, with a low-level jet in place associated with a surge in trade winds. Highly favorable upper-level conditions due to an upper-level trough will provide enhancement of showers and thunderstorms.

Temperatures

With increased cloud cover across both islands, much-needed heat relief is forecast for the next four days, though during the late mornings, particularly on Thursday, temperatures will be elevated.

The maximum high for Trinidad is forecast to be near 34.0°C on Thursday, and higher in urbanized areas but Friday through the weekend, up to 32.0°C but generally remaining much cooler when persisting cloudiness, showers and thunderstorms occur, in the upper twenties.

In Tobago, the maximum high is forecast to be near 32.0°C on Thursday and up to 31.0°C through the weekend.

Forecast Impacts

Hazards associated with Tropical Wave 58, Tropical Wave 59 and the ITCZ over the next four days.
Hazards associated with Tropical Wave 58, Tropical Wave 59, and the ITCZ over the next four days.

For Trinidad and Tobago, the main hazards will be gusty winds up to and in excess of 60 KM/H, particularly Friday through Saturday, and flooding. Street and flash flooding will be likely on Friday and Saturday, with riverine flooding possible by Sunday (dependent on where overall heavier rainfall totals fall.

While thunderstorm activity is forecast to be brief, due to strong low-level winds, frequent lightning will still be possible as upper-level enhancement may trigger locally severe thunderstorm activity, particularly on Saturday afternoon. This means violent rainfall, gusty winds in downburst-like fashion, up to and in excess of 60 KM/H., frequent lightning, funnel cloud activity, and even hail! With rainfall through the weekend, landslides are also possible in elevated areas, particularly Saturday into Sunday..

Winds

Gusty winds associated with a surge in trade winds over the next five days, as Tropical Wave 58 and Tropical Wave 59 move across T&T.
Gusty winds associated with a surge in trade winds over the next five days, as Tropical Wave 58 and Tropical Wave 59 move across T&T.

Sustained surface winds elevated, beginning on Friday, between 20 KM/H and 40 KM/H at times. In thunderstorm and shower activity, gusts up to and in excess of 60 KM/H are possible.

With wind gusts in excess of 60 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.

For unsecured roofs, and weaker structures, wind damage will be likely.

Rainfall

Through Monday, between 1 to 3 inches (25 to 75 millimeters) are possible across Trinidad and Tobago with isolated totals between 5 to 6 inches (125 to 150 millimeters) across eastern and southern areas of Trinidad. There is an elevated threat of street flooding and flash flooding beginning Thursday evening. Chances of riverine flooding will begin to increase, particularly by Saturday, across eastern areas of Trinidad initially.

Thursday: Generally less than 10 millimeters across both islands. Across Eastern and Southern parts of Trinidad, between 10 to 20 millimeters are possible. In heavier showers and thunderstorms where violent rainfall occurs, isolated totals up to and in excess of 25 millimeters possible.

Friday: Generally less than 15 millimeters across both islands. Across Eastern and Southern parts of Trinidad, between 15 to 25 millimeters are possible. In heavier showers and thunderstorms where violent rainfall occurs, isolated totals up to and in excess of 25 millimeters possible.

Saturday: Generally less than 20 millimeters across both islands. Across Eastern and Southern parts of Trinidad, up to 30 millimeters are possible. In heavier showers and thunderstorms where violent rainfall occurs, isolated totals up to and in excess of 25 to 50 millimeters possible.

Sunday: Generally less than 20 millimeters across both islands. Across Eastern and Southern parts of Trinidad, up to 30 millimeters are possible. In heavier showers and thunderstorms where violent rainfall occurs, isolated totals up to and in excess of 25 millimeters possible.

Other Impacts

Landslides possible in elevated areas, particularly Saturday through Sunday.

Strong low-level winds will create unfavorable conditions for funnel clouds and tornadoes, but particularly on Thursday and Saturday, this activity is possible.

Frequent 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.

Seas will become moderate to rough over the next four days.

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 beginning Thursday night, becoming widespread at times on Friday through Sunday.

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

Facebook Comments