ITCZ To Affect T&T Friday Through Sunday

The Intertropical Convergence Zone (ITCZ) is forecast to affect Trinidad initially after midnight tonight and remaining across our area through the weekend.

Tropical Storm Josephine’s influence on T&T’s wind regime, its moisture, and instability, in combination with the ITCZ, is forecast to create favorable conditions for shower and thunderstorm development, particularly on Friday and Sunday.

Trinidad and Tobago Meteorological Service has no alerts, watches, or warnings in effect for T&T as of 9:00 PM Thursday 13th August 2020.

The Forecast

Friday – Tropical Storm Josephine is forecast to indunce a low-level trough, extending southwestward from the system. Light winds and the ITCZ will be present across T&T.

AM – After midnight Thursday into Friday, isolated showers are forecast to mainly affect southern and eastern Trinidad, gradually moving westward through the early morning. Isolated thunderstorms are also forecast, with heavier rainfall and generally stronger activity favoring Eastern Trinidad, at times across Tobago. 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.

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 isolated 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 shower and thunderstorm development across western and hilly areas.


Saturday – Tropical Storm Josephine will move north of the Leewards. Light winds and the ITCZ will be present across T&T. A pocket of drier air will be moving across the Windwards, particularly during the latter half of the day.

AM – After midnight Friday into Saturday, a few isolated showers and even an isolated thunderstorm is possible, generally affecting eastern coastal areas, with heavier activity remaining offshore. By daybreak, a mostly hot and sunny morning is forecast, with a few brisk isolated showers possible. Partly cloudy skies will build by the late morning, with isolated showers across Trinidad.

PM – Partly cloudy and hot conditions are forecast to be interrupted by isolated showers and isolated thunderstorms, mainly across Trinidad. Heavier activity to favor Trinidad and offshore areas through the afternoon. Conditions will gradually settle into the evening, with showers and thunderstorms favoring Eastern Trinidad and Tobago by the late night.

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 isolated heavy rainfall, 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 shower and thunderstorm development across western and hilly areas.


Sunday – Tropical Storm Josephine will be well north and west of the Lesser Antilles. However, the ITCZ will still be present across T&T, with Tropical Wave 35 approaching the region.

AM – After midnight Saturday into Sunday, isolated showers and thunderstorms are forecast to initially affect the eastern half 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 isolated 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 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 55 KM/H possible in heavy showers or thunderstorms across Trinidad and Tobago.

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.

High Wind Event Precautions
High Wind Event Precautions

Rainfall

Overall, less than 20 millimeters are forecast, with areas across southern and eastern Trinidad recording between 20-30 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 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.

Isolated to scattered activity is forecast.

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

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