Wind Shear Forecast To Keep Heavy Rainfall East of T&T

Key Messages:
Weather: From late Sunday through Tuesday, isolated to scattered showers and thunderstorms with variably cloudy skies are forecast for Trinidad and Tobago, with heavier activity favoring eastern areas of both islands. This activity is associated with a deep-layered trough across the region, producing a favorable mid to upper-level environment, with an approaching tropical wave (Tropical Wave 65). A ridge will bring settled weather and Saharan Dust from late Wednesday into the weekend.
Rainfall: Through Wednesday, between 1 to 2 inches (25 to 50 millimeters) are forecast across Trinidad and Tobago with isolated totals up to and in excess of 3 inches (75 millimeters). Higher rainfall totals are expected across eastern areas of Trinidad and across Tobago. Note the highest rainfall totals will remain east of T&T. There is an elevated threat of street flooding and flash flooding. Chances of riverine flooding remain very low to low, mainly across eastern areas of Trinidad.
Seas & Tides: King tides are forecast to continue through Wednesday, which may hinder runoff during high tide periods. However, the overall sea state is forecast to remain slight to moderate.
Winds: Outside of heavy shower and thunderstorm activity, winds are forecast to be light to moderate, 10 KM/H to 25 KM/H. Across Trinidad, gusts up to and in excess of 55 KM/H are possible, and across Tobago, gusts up to and in excess of 60 KM/H are 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, particularly in Eastern areas of Trinidad and across Tobago.

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

The Forecast

Remainder of Sunday: Partly cloudy skies initially, with increasingly cloudy conditions nearing midnight. Isolated showers and thunderstorms are possible after 11:00 PM.

Monday: Stronger shower and thunderstorm activity is forecast to remain east of T&T. Few isolated showers are possible but not likely overnight. By daybreak, partly cloudy skies are forecast with the odd light to moderate shower. By the late morning (10:00 AM), showers and isolated thunderstorms are forecast, with mostly cloudy intervals through the afternoon. Heavy rainfall will still favor Eastern Trinidad. A break in activity will come by the late afternoon into the night, with brisk showers and light rain still possible. A resurgence of activity is possible near midnight.

Tuesday: Partly cloudy to cloudy skies throughout the day, with isolated showers and thunderstorms favoring the pre-dawn hours and again during the late morning through the afternoon. These conditions will settle initially by the evening, with a resurgence of showers and thunderstorms by late night.

Wednesday: Mostly sunny skies are forecast after a few early morning showers and the odd thunderstorms. By the late morning, isolated showers and one or two thunderstorms are possible across Trinidad, with heavier activity favoring western coastal areas. Activity is forecast to settle by the evening with partly to mostly cloudy skies. By nightfall, increasingly hazy skies are forecast with the brisk, isolated shower.

Thursday into the weekend: Mostly hazy and partly cloudy skies are forecast. Isolated showers are possible by the late morning through the afternoon, remaining fairly brisk. Heavier rainfall, if any occurs, to favor western coastal Trinidad and eastern areas of both islands.

The Forecast Discussion

Note that stronger activity associated with tropical waves tend to follow the wave axis, even with a surge is moisture ahead of the wave.
Note that stronger activity associated with tropical waves tend to follow the wave axis, even with a surge is moisture ahead of the wave.

The axis of Tropical Wave 64 is now well west of T&T, with the axis of Tropical Wave 65 along 48W, forecast to traverse the region on Tuesday into Wednesday. A deep-layered trough system is across the region presently, with the surface to low-level trough axis across the Lesser Antilles and the mid- to upper-level axis just east of the region.

Through Wednesday, abundant moisture will be present, mainly at the mid to low levels of the atmosphere. At the surface to low-levels, the trough is forecast to weaken Monday into Tuesday, with overall wind speeds picking up. The Windwards, including T&T, remain just on the fringe of the favorably positioned mid- to upper-level trough, providing upper-level divergence for shower and thunderstorm development mainly on Monday and Tuesday.

Wind shear will remain high through the week, from the northwest, gradually from the southwest by midweek, between 10-30 knots, at times up to 50 knots. Wind shear will keep stronger activity north and east of T&T and limit shower and thunderstorm development across much of Trinidad, contrary to most model predictions last few days. Any activity that has developed across the western half of Trinidad has been brief and mainly remained out in the Gulf of Paria.

By late Wednesday, a surface to low-level ridge is forecast to build across T&T and remain present through the weekend. Increased low-level winds with Saharan Dust concentrations and decreased moisture at low and mid-levels are forecast. However, surface to low-level confluence (winds slowing down and piling up, creating favorable convergence) with mid- to upper-level support may still trigger brisk, isolated showers and possible afternoon thunderstorms during the latter half of the week.

Temperatures

With increased cloud cover across both islands, the heat will be on the lower side through Tuesday, while from Wednesday onwards, high temperatures will be elevated.

The maximum high for Trinidad is forecast to be near 30.0°C on Monday and Tuesday, and higher in urbanized areas but generally remaining much cooler when persisting cloudiness, showers, and thunderstorms occur, in the upper twenties. From Wednesday onwards, up to 33.0°C, and higher in urbanized areas.

In Tobago, the maximum high is forecast to be near 30.0°C on Monday and Tuesday, with highs near 32.0°C Wednesday onwards.

Forecast Impacts

Hazards associated with Tropical Wave 65 and a trough system over the next five days.

For Trinidad and Tobago, the main hazards will be heavy rainfall, mainly across eastern halves of both islands producing flooding, as well as gusty winds up to and in excess of 55 KM/H. Street and flash flooding will be likely on Monday and Tuesday, with riverine flooding possible by early Tuesday (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 55 KM/H, and frequent lightning. Landslides are also possible in elevated areas, particularly Monday and Tuesday.

Winds

Outside of heavy shower and thunderstorm activity, winds are forecast to be light to moderate, 10 KM/H to 25 KM/H. Across Trinidad, gusts up to and in excess of 55 KM/H are possible, and across Tobago, gusts up to and in excess of 60 KM/H are possible.

With wind gusts in excess of 55 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 Wednesday (when most of the rainfall through the forecast period is anticipated), between 1 to 2 inches (25 to 50 millimeters) are forecast across Trinidad and Tobago with isolated totals up to and in excess of 3 inches (75 millimeters).

Higher rainfall totals are expected across eastern areas of Trinidad and across Tobago. Note the highest rainfall totals will remain east of T&T. There is an elevated threat of street flooding and flash flooding. Chances of riverine flooding remain very low to low, mainly across eastern areas of Trinidad.

Remainder of Sunday: Generally, less than 5 millimeters across the western half of Trinidad, while across Eastern Trinidad and Tobago, less than 10 millimeters.

Monday: Between 5 and 20 millimeters across both islands. In heavier showers and thunderstorms, mainly across Eastern Trinidad and Tobago, and where violent rainfall occurs, isolated totals up to and in excess of 50 millimeters are possible.

Tuesday: Between 5 and 15 millimeters across both islands. In heavier showers and thunderstorms where violent rainfall occurs, isolated totals up to and in excess of 25 millimeters possible, mainly across Eastern Trinidad and Tobago.

Wednesday: Generally less than 10 millimeters across both islands, with higher totals across eastern areas of both islands, as well as southwestern Trinidad.

Thursday onwards: No significant rainfall is forecast. Isolated totals may reach up to 5 millimeters in highly localized areas.

Other Impacts

Landslides possible in elevated areas, particularly Monday through the first half of Wednesday.

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 slight to moderate over the next five days but King Tides may impact runoff through Wednesday.

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 during the next 2-3 days, with highly isolated rainfall Wednesday through Friday.

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

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