Forecast: Strong Afternoon Thunderstorms To Interrupt Sunny Skies

Showers affecting parts of Trinidad on Monday 12th October 2020, taken from Piarco. Strong showers and thunderstorms are forecast today across parts of Trinidad. (Photo: Ainsley Mohamed)

A combination of sea breeze convergence, daytime heating, and orographic effects will trigger strong thunderstorms and showers after midday across parts of Trinidad. With light winds, funnel clouds are possible across western areas of the island.

Higher rainfall accumulations are forecast to favor isolated areas of West-Central and Northern Trinidad, mainly after midday, though rainfall will be brief.

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

Forecast For Wednesday

Forecast: A mostly sunny start to the day will give way to increased cloudiness, showers, and strong thunderstorms after 11:00 AM, developing along the south-facing slopes of the Northern Range and western coastal Trinidad. Rainfall and cloudiness will gradually spread across Eastern and Central Trinidad through the afternoon.

Conditions will gradually settle through the late afternoon, leading to a partly cloudy and cool night across T&T. Overnight thunderstorms are possible, mainly north of Tobago.

Hazards: The main hazards include brief but heavy to violent rainfall, which may reduce visibility and gusty winds up to and in excess of 55 KM/H. Street or flash flooding will be possible in violent showers and thunderstorms. In thunderstorm activity, frequent lightning is also possible. Gusty winds may cause power dips/outages, downed trees, and localized wind damage.

Marine: Seas are forecast to be slight to moderate, with waves below 1.5 meters in open waters. Swells are forecast to be from the east, with a swell period between 8 to 10 seconds. In sheltered areas, near calm. However, in areas where thunderstorms occur, seas can become choppy and locally rough.

Winds are forecast to be light offshore, less than 10 knots prevailing from the southeast.

Forecast Discussion: Tropical Wave 55 (and Invest 93L) will be nearing the Central and Northern Lesser Antilles. A surface to low-level trough extending southwestward from the disturbance’s low-level center will allow for near calm winds across T&T.

Across Trinidad, by the late morning through the afternoon, light winds, daytime heating, and sea breeze convergence will act as triggers for shower and thunderstorm development across western parts of Trinidad, with orographic lift triggering/enhancing showers along hilly topography.

Activity will be enhanced by favorable upper-level conditions due to the positioning of an upper-level trough, as well as a short-wave trough further east of the region. However, strong westerly wind shear will limit persisting deep convection, spreading upper-level clouds eastward.

Sea breeze convergence mechanisms for the Gulf of Paria and the Atlantic Ocean across Trinidad which can produce thunderstorm activity. On Thursday, sea breeze convergence will be possible across all coasts of Trinidad and Tobago due to light to no winds.
Sea breeze convergence mechanisms for the Gulf of Paria and the Atlantic Ocean across Trinidad which can produce thunderstorm activity.


Across both islands, even with the forecast showers and thunderstorms, hot and humid conditions are anticipated. Trinidad’s maximum high is forecast to be near 34.0°C, up to 36.0°C in urban and built-up areas. In Tobago, the maximum high is forecast to be near 33.0°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.

The Heat Index

The heat index will be high across Trinidad and Tobago. The heat index is a combination of air temperature and relative humidity, determining what the air feels like to a person, i.e., how hot it actually feels.

Across Trinidad and Tobago, the maximum heat index is forecast to be between 35°C and 45°C and even higher in urbanized areas.

The heat index is important because of sweating. Your body sweats to cool the skin and maintain a constant, healthy body temperature. This cooling process means that the sweat has to evaporate off the skin to remove heat. However, if the sweat is unable to evaporate, the body isn’t able to regulate temperature.

 Heat Index Values Explained
Heat Index Values Explained

Forecast Impacts


Sustained surface winds will be light, peaking during the afternoon. By the afternoon, sustained winds between 20 KM/H and 35 KM/H with gusts up to and in excess of 55 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.


Across most areas of Trinidad and Tobago, low rainfall accumulations are anticipated, with maximum accumulation totals less than 5 millimeters over the next 24 hours.

In isolated areas across Trinidad, rainfall accumulations up to 25 millimeters are possible. In areas where torrential rainfall occurs with possible severe thunderstorms, accumulations up to 50 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.

Frequent Lightning: 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.

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.

Brief, isolated to scattered rainfall is forecast on Wednesday, interrupting partly to mostly cloudy periods.

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

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