Tropical Wave 36, ITCZ To Bring Showers, Thunderstorms

The Intertropical Convergence Zone (ITCZ) is forecast to affect Trinidad and Tobago overnight, with showers already ongoing across parts of eastern Trinidad and Tobago.

Activity will be enhanced by the passage of Tropical Wave 36, though much of the heavier showers and thunderstorms will remain offshore, north of T&T, gradually affecting the northern and eastern halves of Trinidad and across Tobago.

Because of the threat of adverse weather impacts, the Trinidad and Tobago Meteorological Service has issued another Adverse Weather Alert (Yellow Level) beginning at 11:00 PM Sunday through 11:00 AM Monday. Adverse weather is forecast to continue through the afternoon, mainly across the western half of Trinidad.

The Forecast

Abundant low-level moisture associated with the ITCZ and Tropical Wave 36 will be moving across T&T. Favorable low-level convergence, and upper-level divergence and low wind shear will allow for isolated strong thunderstorms and heavy showers, in addition to a surface to mid-level confluence (where winds slow down and enhance convergence).

Isolated showers are forecast to affect mainly parts of Eastern and Northern Trinidad, as well as Tobago overnight, with isolated thunderstorms possible. Partly to mostly cloudy skies and near calm conditions are forecast elsewhere.

After midnight, isolated to scattered showers and thunderstorms are forecast to develop and mainly affect Tobago, with heavy rainfall forecast through daybreak. Conditions will gradually subside through the morning, with lingering light to moderate rain, but isolated thunderstorms and showers may return near midday through the afternoon.

In Trinidad, conditions forecast to remain mostly settled and variably cloudy across most areas. Parts of Northern and Eastern Trinidad may continue to see periods of showers and the odd thunderstorm, gradually moving westward across the island. By daybreak, conditions will initially settle across the island, but closer to midday, through the afternoon, a resurgence in showers and thunderstorms are forecast across the western half of Trinidad.

A mostly settled evening into the night is forecast across both islands.

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 Northern and Eastern halves of Trinidad as well as across Tobago. Rainfall may reduce 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. Particularly across Tobago, landslides are likely in heavy rainfall.

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 of Trinidad, particularly on Monday afternoon.

Possible Impacts From ITCZ & Tropical Wave 36


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 are 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


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 and across Tobago.

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.

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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