[Updated] ITCZ to Affect T&T, Bringing Isolated Showers & Thunderstorms

As we’ve been forecasting over the last few days, down to the last few hours, thunderstorms and showers are anticipated across T&T due to an active ITCZ approaching the region.

The Intertropical Convergence Zone (ITCZ) is forecast to affect Trinidad by 2:00 AM to 3:00 AM, with activity gradually spreading across both islands through Sunday.

Though ominous looking, showers and thunderstorms rapidly diminished as it was just offshore Trinidad, bringing none of the anticipated inclement weather to T&T. However, as favorable dynamics remain in place, showers and thunderstorms remain in the forecast. The TTMS has discontinued the Adverse Weather Alert (Yellow Level).

The Forecast


Sunday – A low-level trough will interact with the ITCZ as both features move across T&T. Abundant low-level moisture, favorable low-level convergence, and upper-level divergence and low wind shear will allow for isolated strong thunderstorms and heavy showers.

AM – After midnight, mainly after 2:00 AM, isolated to scattered showers and thunderstorms are forecast to initially affect the eastern halves of Trinidad and Tobago, gradually moving westward through the early morning. Conditions will gradually settle into daybreak, with variably cloudy skies. Showers and thunderstorms are forecast to return by the late morning, through the afternoon, favoring Trinidad.

PM – Variably cloudy skies may be interrupted by isolated showers and isolated thunderstorms across both islands. Heavier activity to favor Trinidad through the afternoon, with the odd thunderstorm across Tobago. Conditions will gradually settle into the evening and night, with a few isolated showers.

Seas forecast to be moderate, with waves between 1.5 to 2.0 meters in open waters. In sheltered areas, below 1 meter but choppy in areas of heavy showers or thunderstorms.

The main hazards include heavy rainfall, favoring Southern and Eastern halves of Trinidad, reducing visibility, and gusty winds up to and in excess of 55 KM/H. Street or flash flooding will be possible in slow-moving showers and thunderstorms. In thunderstorm activity, frequent lightning is also possible. Gusty winds may cause power dips/outages, downed trees, and localized wind damage.

Note that with weak winds, with sea breeze convergence, heat, and orographic effects may act as triggers for additional shower and thunderstorm development across western and hilly areas.

Possible Impacts From ITCZ

Winds

Sustained surface winds will be weak, generally below 25 KM/H during the afternoon at its peak. However, Gusts up to and in excess of 60 KM/H are possible in heavy showers or thunderstorms across Trinidad and Tobago.

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.

High Wind Event Precautions
High Wind Event Precautions

Rainfall

Overall, less than 25 millimeters are forecast, with areas across southern and eastern Trinidad recording between 25-40 millimeters. Isolated totals up to and in excess of 50 millimeters possible, particularly in slow-moving downpours or thunderstorms.

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. There is a very low chance of riverine flooding.

Frequent Lightning: In addition, with forecast thunderstorms, frequent lightning is likely. 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 Constant 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.

Scattered activity is forecast.

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

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