Forecast: Cloudy Periods With Isolated Showers, Thunderstorms

Following days of mostly sunny skies, a few showers and isolated thunderstorms are forecast to return on Sunday due to a surface to low-level trough and shearline moving across the Southern Windwards.

With a favorable atmosphere, isolated heavy showers and thunderstorms are possible by the late morning through the afternoon, favoring Trinidad, with brisk showers elsewhere.

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

The Forecast

Partly to mostly cloudy skies across Trinidad and Tobago, interrupted by brisk showers throughout the day. Isolated heavy showers and thunderstorms are possible across Trinidad by the late morning through the afternoon, with brief, heavier activity favoring the western and northern areas of Trinidad and overall higher accumulations across southern and eastern areas.

Marine: Seas are forecast to be slight to moderate. Generally, in open waters, waves are forecast to be between 1.0 to 1.5 meters. In sheltered areas, near calm but choppy at times in heavy shower or thunderstorm activity.


Overview: At the surface to low-levels of the atmosphere, favorable low-level convergence with ample moisture is in place as a surface to low-level trough moved across the Lesser Antilles overnight. This has brought moisture from the equatorial regions across T&T and the Windward Islands. A weak, low-level shearline (a line or narrow zone across which there is an abrupt change in the horizontal winds)

Dominating the overall wind flow, a weak surface to low-level high-pressure system will remain in place through the week. With lighter winds, daytime heating and sea breeze convergence across Western Trinidad, as well as orographic effects along northern Trinidad and the northern coasts of Tobago will allow showers and possible thunderstorms to develop.

At the mid- to upper-level atmosphere, a tropical upper tropospheric trough (TUTT) will strengthen as it meanders closer to the Lesser Antilles, allowing for some development of deep convection (strong showers and thunderstorms). However, very strong wind shear from the west, up to 80 knots, will also limit the intensity and duration of stronger showers or thunderstorms.

Temperatures

Across both islands, cool conditions are forecast on Sunday. The maximum high for Trinidad is forecast to be near 31.0°C, up to 33.0°C in urban and built-up areas, particularly between 9:00 AM and 3:00 PM. In Tobago, the maximum high is forecast to be near 31.0°C.

Temperatures in cities, such as Port of Spain, tend to be much higher than surrounding locations due to a phenomenon called the Urban Heat Island Effect. There are several causes, but the main instigator for this phenomenon tends to be increased dark surfaces such as roads and pavement in cities, which absorb solar radiation more than surrounding areas.

Forecast Impacts

On Sunday, street flooding is possible in thunderstorms and/or heavy showers. With heat-driven showers, gusty winds in downburst-like fashion, up to and in excess of 45 KM/H are possible.

Winds

Sustained surface winds will be light to near calm. During the afternoons, up to 20 KM/H likely. In heavy shower or thunderstorm 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

Across most areas of Trinidad and Tobago, little rainfall is anticipated over the next 24-48 hours, with maximum accumulation totals near 15 millimeters. In areas where isolated heavy showers or thunderstorms occur, accumulations up to 25 millimeters are possible.

Generally, with heavy showers and thunderstorm activity, street flooding, particularly in flood-prone areas or areas with poor drainage, is possible as well as flash flooding in areas where more prolonged heavy rainfall may occur.

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.

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 on Sunday.

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