Wet Week Forecast For T&T: Cloudy Skies, Showers & Thunderstorms

Showers seen from Mosquito Creek, Southern Trinidad on May 2nd, 2021

A series of low-level troughs, weak winds, and a persisting flow of moisture are forecast to keep rainfall and cloudy skies on tap for Trinidad and Tobago into the weekend.

Overall, heavier rainfall will favor the southern and eastern areas of Trinidad and Tobago. In areas where isolated heavy showers or thunderstorms occur, isolated higher rainfall totals are expected, particularly along Western Coastal Trinidad.

Based on model guidance, through the next 5-7 days, very high accumulated precipitation is forecast for T&T across all locations of the country. Chances of flooding will gradually increase as we head through the week, with the wettest days forecast on Tuesday and then again on Friday into Saturday.

The Trinidad and Tobago Meteorological Service has issued an Adverse Weather Alert (Yellow Level) for Trinidad and Tobago beginning at 5:00 AM through 6:00 PM Tuesday 4th May 2021.

The Forecast

Through the week, the daily forecast will not drastically change. Mostly cloudy to overcast skies are forecast throughout the day, interrupted by intermittent periods of rain and scattered showers across the country. During the mid-morning and late afternoon, partly cloudy skies are possible. During the late morning through the early afternoon, showers can become heavy to violent, with thunderstorm activity favoring Trinidad, generally western coastal areas. Conditions will generally settle into the night, with isolated showers and light rain possible.

Chances for heavy to violent showers and thunderstorm activity are highest on Monday into Tuesday and Friday into Saturday. In addition, gusty winds are more likely from Friday through the weekend.

Note that Saharan Dust levels are forecast to remain low through the week, with no major surges forecast over the next 7 days.

Marine: Seas are forecast to be slight to moderate through the week, with waves up to 1.5 meters and up to 2.0 meters on Tuesday and Friday into the weekend in Trinidad and Tobago’s open waters. Across sheltered coastlines, waves below 1.0 meter to near calm conditions are likely. In heavy showers or thunderstorms, sheltered seas may become choppy. Note that long period swells are forecast to affect T&T’s northern and eastern coastlines from Friday afternoon into the weekend.


Overview: On Monday, the first of a series of weak, low-level troughs are forecast to traverse the Windwards, including T&T. This feature will allow abundant moisture and instability to stream in from the southeast. This pattern of easterly to southeasterly moisture flow is forecast to hold through the next seven days. In fact, forecast models show during this period, high amounts of atmospheric moisture will be present across Trinidad and Tobago, providing fuel for showers and possible isolated thunderstorms.

At the mid-to-upper levels, a trough is gradually lifting through the next 12 hours. Still, mid-to upper-level winds are forecast to continue bringing moisture and cloudiness from the west to southwest across T&T. Ample moisture and instability will remain across T&T through the week.

Through the forecast period, wind shear will be weak to moderate up to 30 knots from the southwest to west, bringing upper-level clouds from South America. This will limit the strength of thunderstorms, keeping heavy showers and thunderstorms relatively brief and most of the heavy rainfall east of T&T. Still, overall high rainfall accumulations are forecast across the country through the week.

With lower wind shear, localized heavy shower and thunderstorm development will be likely due to localized climatic effects such as sea breeze convergence, orographic effects, and daytime heating in the event of partly cloudy skies and heating during the mid-morning.

Temperatures

Across both islands, overnight lows are forecast to be mild, with daytime highs cool due to cloud cover throughout the week. As skies clear somewhat at times through the week, temperatures may trend warmer during the day.

The minimum low for Trinidad is forecast to be near 23.0°C, and as low as 22.0°C in valleys and forested areas. In Tobago, a minimum low near 24.0°C is forecast.

The maximum highs for Trinidad and Tobago are forecast to be near or below 30.0°C, up to 33.0°C in urban and built-up areas, particularly between 9:00 AM and 3:00 PM.

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.

Forecast Impacts

Initially, the main hazards through the first half of the week would be heavy rainfall and gusty winds, particularly in moderate to heavy showers or thunderstorms, bringing the risk of street flooding or flash flooding. By the end of the week, chances for street flooding or flash flooding as well as gusty winds would increase due to persistent rainfall. In addition, depending on the total rainfall that accumulates, riverine flooding, particularly in eastern areas, would be a concern. Landslides will also become a concern by the end of the week as soils become increasingly saturated.

Winds

Sustained surface winds moderate to fresh (20-38 KM/H). In shower activity, gusts up to and in excess of 55 KM/H are possible. Gusty winds are more likely by the end of the week into the weekend.

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.

Rainfall

Over the next 5-7 days, very high rainfall accumulations are forecast. The most likely totals are between 25 millimeters and 100 millimeters for Trinidad and Tobago, with totals between 100 and 175 millimeters across Eastern and Southern Trinidad, as well as Eastern Tobago.

At the extreme end, global models show 200+ millimeters of rainfall falling across the entire country through the next 7 days, with higher totals favoring Tobago. If this materializes, significant flooding will be possible across T&T. This rainfall forecast will be updated daily as more information is available. The wettest days are forecast on Tuesday and then again on Friday into Saturday.

  • Monday: Between 5-15 millimeters are forecast, with isolated totals between 15-30 millimeters across Northern Trinidad and Tobago. Higher totals are possible in areas of isolated heavy showers or thunderstorms.
  • Tuesday: Between 5-25 millimeters are forecast, with isolated totals up to (and in excess of) 35 millimeters across Trinidad and Tobago. Higher totals are possible in areas of isolated heavy showers or thunderstorms. Across Eastern and Southern halves of Trinidad, as well as Tobago, isolated rainfall totals could near and exceed 50 millimeters (2 inches).
  • Wednesday: Between 5-15 millimeters are forecast, with isolated totals between 15-25 millimeters across Trinidad and Tobago. Higher totals are possible in areas of isolated heavy showers or thunderstorms.
  • Thursday: Between 5-15 millimeters are forecast, with isolated totals between 15-25 millimeters across Trinidad and Tobago. Higher totals are possible in areas of isolated heavy showers or thunderstorms.
  • Friday: 10-25 millimeters are forecast, with isolated totals up to (and in excess of) 40 millimeters across Trinidad and Tobago. Higher totals are possible in areas of isolated heavy showers or thunderstorms. Some models are also showing totals in excess of 50 millimeters across Trinidad.
  • Saturday: 10-25 millimeters are forecast, with isolated totals up to (and in excess of) 40 millimeters across Trinidad. Higher totals are possible in areas of isolated heavy showers or thunderstorms. Some models are also showing totals up to 100 millimeters across Eastern Trinidad and 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. Depending on the total rainfall that accumulates, riverine flooding, particularly in eastern areas, would be a concern by mid-week through the end of the week.

Lightning: 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.

Through the week, isolated to scattered rainfall is forecast interrupting mostly cloudy to overcast skies.

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

Facebook Comments