Tropical Wave 60 & 61 Forecast To Bring Heavy Rainfall To T&T

Key Messages:
Weather: Over the next 5 days (and likely through next week), brisk showers and thunderstorms associated with two tropical waves (Tropical Wave 60 and Tropical Wave 61) will affect T&T, with partly to mostly cloudy skies and periods of light to moderate rain.
Rainfall: Through Monday, between 1 to 3 inches (25 to 75 millimeters) are possible across Trinidad and Tobago with isolated totals between 4 to 5 inches (100 to 125 millimeters) mainly across eastern areas of Trinidad and across Tobago. Heavier rainfall mainly forecast to occur on Friday and Saturday. 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, generally remaining low, 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 on Thursday, with moderate seas and long-period swells affecting T&T through the weekend into next week.
Winds: A surge in trade winds will move across the region from Wednesday night through Thursday night, with breezy conditions forecast over the weekend. Gusty winds up to and in excess of 60 KM/H possible. 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. Though unlikely due to strong low-level winds, brief funnel cloud and even tornado development are possible, favoring western areas of Trinidad.

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

The Forecast

Remainder of Wednesday: Across Trinidad, through the afternoon, isolated showers and thunderstorms are possible across the Western and northern halves of the island. Then, partly cloudy conditions are forecast to be interrupted by brisk showers and possible thunderstorms from the east through the night. Across Tobago, mostly cloudy skies with brisk periods of showers and isolated thunderstorms through the afternoon and into the night.

Thursday: Partly cloudy skies with breezy conditions across T&T will be interrupted by brisk showers across both islands. Brief, isolated thunderstorms are possible across Trinidad during the late morning through the afternoon. Conditions will gradually deteriorate by the late-night, with light to moderate rain and the odd thunderstorm mainly affecting Tobago and moving across Trinidad closer to midnight.

Friday: Periods of rain with brisk heavy showers and thunderstorms are forecast across both islands after midnight, with showers and thunderstorms are forecast to become scattered to widespread across Trinidad and Tobago by daybreak through the late afternoon. While activity will persist through the night, rainfall will favor eastern areas of Trinidad and Tobago into Saturday, remaining brisk elsewhere.

Saturday: Showers and thunderstorms are forecast during the early morning hours (from 3:00 AM) through daybreak, with heavier activity remaining east of Trinidad, mainly affecting Tobago and our eastern coastal areas. From daybreak through the afternoon, activity forecast to spread across Trinidad, becoming scattered with intervals of heavy showers and thunderstorm activity. Light to moderate rain also possible between heavier activity. Conditions are forecast to settle into the night gradually. This is forecast to be the wettest day during the 5-day period. Chances of street/flash flooding high!

Sunday & Monday: Showers and isolated thunderstorms are possible after midnight through sunrise but remaining in our coastal waters, with brief activity moving onshore. By the late morning (11:00 AM), showers and thunderstorms are forecast to develop across much of Trinidad, lesser so Tobago, but remain brisk. Brief showers may persist into the late afternoon, settling into night. A resurgence of activity, mainly in our coastal waters, are forecast by the late-night into Monday.

The Forecast Discussion

On Wednesday into Thursday, the axis of Tropical Wave 60 will be moving across T&T, though stronger showers and thunderstorms are forecast to remain to our north and east. Low-level winds are forecast to increase following this wave’s passage on Thursday, with winds peaking near 50 KM/H and gusts up to and in excess of 60 KM/H possible.

On Friday into Saturday, the axis of Tropical Wave 61 will be moving across our area. Favorable low-level convergence and upper-level divergence will be in place across T&T, particularly on Saturday, allowing for stronger showers and thunderstorms – meaning higher chances for heavy rainfall.

On Sunday into Monday, lingering moisture and a favorable atmospheric setup will allow for showers and thunderstorms to persist across T&T, though wind shear will increase across the region.

Through Monday, a mid to upper-level trough will be favorably positioned across the Lesser Antilles, enhancing convection (showers and thunderstorms) across and in the vicinity of T&T.

However, by Friday through the weekend, wind shear will be weakening across the Windwards, between 0 to 20 knots, still mainly from the west, allowing showers and thunderstorms to gain intensity but keeping stronger activity to T&T’s east. Strong low-level winds will keep the activity moving briskly to the west to northwest.

Temperatures

With increased cloud cover across both islands, the heat will be on the lower side through the weekend, though during the late mornings, particularly on Thursday, temperatures will be elevated.

The maximum high for Trinidad is forecast to be near 33.0°C on Thursday, and higher in urbanized areas but Friday through the weekend, up to 31.0°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 30.0°C through the weekend.

Forecast Impacts

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 on Thursday, 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. This means violent rainfall, gusty winds in a downburst-like fashion, up to and in excess of 60 KM/H, and frequent lightning. With rainfall through the weekend, landslides are also possible in elevated areas, particularly Saturday into Sunday.

Though unlikely due to strong low-level winds, brief funnel cloud and even tornado development are possible, favoring western areas of Trinidad.

Winds

Sustained surface winds are forecast to be elevated, beginning on Thursday between 20 KM/H and 50 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 4 to 5 inches (100 to 125 millimeters) across eastern areas of Trinidad.

Heavier rainfall mainly forecast to occur on Friday and Saturday. 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, generally remaining low, particularly by Saturday, across eastern areas of Trinidad initially.

Thursday: Generally less than 5 millimeters across the western half of Trinidad. Across the eastern half of Trinidad and across Tobago, 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: Between 10 and 15 millimeters of rainfall is across both islands. Across the eastern half of Trinidad and across Tobago, 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: Between 10 and 15 millimeters of rainfall is across both islands. Across the eastern half of Trinidad and across Tobago, between 15 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.

Sunday and Monday: Generally less than 20 millimeters across both islands. In heavier showers and thunderstorms where violent rainfall occurs, isolated totals up to and in excess of 25 millimeters possible.

Note that some models, namely the GFS, is trending wetter through the forecast period, particularly on Friday and Monday. This rainfall forecast will be updated over the next 5 days if other models show similar trends.

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 on days with sunny mornings, funnel clouds are 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 be moderate to rough over the next five days, mainly rough on Thursday.

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?

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