Light winds, strong daytime heating, and high atmospheric moisture forecast to be triggers for showers and possible strong thunderstorms across parts of Trinidad by the late morning through the afternoon. This could bring street/flash flooding and gusty winds to parts of Central and Southern Trinidad. With light winds, funnel clouds are also possible.
1:15 PM Update: The Trinidad and Tobago Meteorological Service has issued an Adverse Weather Alert Yellow Level on Tuesday afternoon at 1:03 PM, which went into effect at 12:40 PM Tuesday 1st September 2020 and will remain in effect through 6:00 PM Tuesday 1st September 2020.
Abundant low-level moisture continues to remain present across Trinidad and Tobago. Very light winds from the south to near calm conditions and a mostly sunny start to the day will produce strong daytime heating across parts of Western and Central Trinidad. By the late morning, these features will trigger shower and thunderstorm development, with activity generally moving toward the north. Favorable low-level convergence and low wind shear will allow for strong isolated thunderstorms and heavy showers mainly across the Western and Northern halves of Trinidad.
A mostly hot and sunny start to Tuesday is forecast, becoming increasingly cloudy as the morning progresses. With light to no winds and sunny skies, temperatures may soar into the mid-thirties, higher in urban areas. However, but the late morning through the afternoon, isolated strong thunderstorms are possible mainly across the Western and Northern halves of Trinidad. These thunderstorms may produce damaging wind gusts, flooding rainfall, and frequent, dangerous lightning.
By the evening, conditions are forecast to settle across the island with clearing but partly cloudy skies. Though light winds persist, the night is forecast to be mostly clear and cool.
Seas forecast to be slight, with waves up to just over 1 meter in open waters. In sheltered areas, near calm but choppy in areas of heavy showers or thunderstorms.
The main hazards include heavy 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 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. Landslides are possible in heavy rainfall, particularly along the southern facing slopes of the Northern Range.
Note that with weak winds, from the south to southeast, with sea breeze convergence, heat, and orographic effects may act as triggers for shower and thunderstorm development across the south-facing slopes of the Northern Range, which could also intensify thunderstorms similar to what occurred early Monday morning.
Across both islands, hot and humid conditions are forecast. The maximum high for Trinidad is forecast to be near 34.0°C, up to 36°C in urbanized 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 very high on Tuesday across Trinidad and Tobago. The heat index and 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, the maximum heat index is forecast to be between 37.0°C and 40.0°C, and even higher in urbanized areas. In Tobago, the maximum heat index is forecast to be between 35.0°C and 38.0°C
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 is generally classified into four categories: caution, extreme caution, dangerous, and extremely dangerous. On Tuesday, the heat index is forecast to be between levels where extreme caution is needed to dangerous levels for sensitive groups. Remain hydrated!
Sustained surface winds will be light to nonexistent. However, during heavy showers and thunderstorms, sustained winds between 25 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, little to no rainfall is forecast, with accumulations less than 5 millimeters. However, across parts of Western and Northern Trinidad, particularly along the south-facing slopes of the Northern Range, rainfall totals of 25 millimeters are possible, with isolated totals up to 50 millimeters, 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. Landslides are possible in heavy rainfall, particularly along the southern facing slopes of the Northern Range.
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 by the late morning through the afternoon on Tuesday.