Tropical Wave 04 brought persistent rain and showers, along with isolated thunderstorms, to Trinidad and Tobago on Tuesday. This resulted in rising river levels, localized flooding, and gusty winds that brought down trees in Tobago and northern Trinidad.
Up next, a low-level trough is expected on Wednesday, and another tropical wave is set to arrive by Friday, pulling moisture from equatorial regions and the Intertropical Convergence Zone to the south. As a result, activity may increase during the pre-dawn through early afternoon hours.
What you need to know
— Rainfall: Over the next five days, through Monday morning but mainly through Friday night, overall rainfall accumulations across Trinidad and Tobago are forecast to range between 80 and 175 millimeters. Isolated totals exceeding 175 millimeters are likely along eastern Trinidad.
— Saharan Dust: Mild to moderate dust will remain present through the next five days. Higher dust levels are likely to be present across Tobago compared to Trinidad.
— Hazards: With heavy showers and thunderstorms, as well as periods of rain, many of the typical Wet Season hazards are on the table for the next five days. Street and flash flooding is likely in heavy rain, showers, and thunderstorms, accompanied by wind gusts exceeding 50 km/h, and lightning during thunderstorm activity. From Wednesday, as soils become increasingly saturated, landslides are possible in elevated areas. As river levels rise, smaller watercourses may approach their threshold levels from late Wednesday. Spring tides may lead to reduced runoff during high tide periods, and elevated low-level winds are also forecast to agitate marine conditions.
— Marine: Moderate seas are forecast in Trinidad and Tobago’s open waters, while choppy conditions are forecast in sheltered areas. All marine interests are advised to exercise caution in the vicinity of heavy showers and thunderstorms.
Latest Alerts
Caroni River Basin Under Riverine Flood Alert
Adverse Weather Alert Extended For T&T Through 4 PM Thursday
Trinidad and Tobago is NOT under any tropical storm or hurricane threat, watch, or warning at this time.
The Forecast
Wednesday
WednesdayThursday
ThursdayFriday
FridaySaturday
SaturdaySunday
SundayMarine Forecast
Agitated Seas Forecast For T&T Over Next 7 Days
Temperatures
Wednesday
Low: 24-25°C
High: 27-28°C
Thursday
Low: 23-24°C
High: 29-31°C
Friday
Low: 24-25°C
High: 27-29°C
Saturday
Low: 25-26°C
High: 31-32°C
Sunday
Low: 25-25°C
High: 31-33°C
Forecast Impacts
Flooding
Over the next five days, through Monday morning but mainly through Friday night, overall rainfall accumulations across Trinidad and Tobago are forecast to range between 80 and 175 millimeters. Isolated totals exceeding 175 millimeters are likely along eastern Trinidad.
Street & Flash Flooding
Street & Flash FloodingRiverine Flooding
Riverine FloodingForecast Rainfall Totals
- Wednesday (Low-level trough): Across Tobago, between 15 and 35 millimeters of rainfall is forecast. Across Trinidad, up to 50 millimeters of rainfall is forecast, favoring southern and eastern halves of the island, as well as localized areas of western Trinidad. Isolated totals may exceed 50 millimeters, favoring Trinidad. Flooding is likely.
- Thursday: Across Tobago, between 5 and 15 millimeters of rain is forecast, with isolated totals of up to 25 millimeters. Across Trinidad, between 15 and 25 millimeters of rainfall is expected, with higher totals in the eastern and southern halves of the island, where localized amounts could reach 50 to 75 millimeters.
- Friday (Tropical Wave 05): Between 10 and 25 millimeters of rainfall across Tobago and much of the western half of Trinidad. Across the eastern half of Trinidad, as well as isolated areas of north-central and southern Trinidad, totals between 20 and 50 millimeters are possible. Isolated regions, particularly in eastern Trinidad, may experience rainfall totals exceeding 50 millimeters.
- Saturday: Across Tobago, a little to no rainfall is forecast, with less than 1 millimeter of rainfall accumulation expected. Across Trinidad, less than 5 millimeters of rainfall accumulation on the island, with locally higher totals in the eastern and southern coastal areas.
- Sunday: Across both islands, little to no accumulating rainfall, with isolated totals favoring eastern and southern Trinidad up to 10 millimeters.
Understanding Rainfall Accumulations
Putting the rainfall forecast into context, rainfall rates in excess of 50 millimeters per hour or areas that receive in excess of 25 millimeters within an hour tend to trigger street flooding across the country or flash flooding in northern Trinidad. For riverine flooding to occur, a large area of the country (not just in highly localized areas of western coastal Trinidad) would have to record upwards of 75 millimeters within 24 hours, and rainfall would have to fall across major rivers’ catchment areas.
Strong Thunderstorms
Strong ThunderstormsWhat is a strong or severe thunderstorm?
Given how rare these types of thunderstorms are in our region – we classify a severe or strong thunderstorm as one that produces any of the following:
- Damaging wind gusts exceeding 63 KM/H;
- Frequent lightning (more than 30 cloud-to-ground strikes within a 10-minute period);
- Hail (of any size);
- Rainfall of more than 50 millimeters or more within an hour or exceeding 75 millimeters or more within three hours;
- The sighting of a funnel cloud or touchdown of a waterspout/tornado associated with the thunderstorm.
Gusty Winds
Gusty WindsWith wind gusts exceeding 50 KM/H, whole trees can be in motion, with larger trees and weaker branches falling. Light outdoor objects can topple or become airborne, such as garbage cans, loose galvanize, construction material, and outdoor furniture. Tents may also jump.
Other Hazards
Mild to moderate levels of Saharan Dust are forecast across Trinidad over the next five days, with generally higher concentrations favoring Tobago and the remainder of the Windward Islands.
Saharan Dust Forecast
Saharan Dust Concentrations Forecast To Fluctuate Across T&T Over Next 7 Days
Why I May Not/Will Not See Rainfall?
A frequent complaint is that 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 for isolated activity. Widespread showers mean that nearly all people and areas can expect rainfall.
On Wednesday through Friday, scattered to widespread rainfall is forecast, with isolated showers possible on Saturday and Sunday.
Forecast Discussion
Tropical Waves (As of 2 PM June 9th)
— Tropical Wave 04: Located along 62W from 17N, moving west around 10 knots (18 km/h) with scattered showers. This wave moved across T&T on Tuesday.
— Low-level trough: Located along 55W from 11N, moving west around 15 knots (28 km/h) with scattered showers. Located approximately 650 kilometers east of Trinidad and Tobago, this trough is forecast to move across T&T on Wednesday.
— Tropical Wave 05: Located along 48W from 12N southward, moving west at around 10 to 15 knots (18 to 28 km/h) with scattered showers and isolated thunderstorms, which are being enhanced by converging tradewinds. This wave, currently 1,400 kilometers east of T&T, is forecast to move across the country on Friday.
— Tropical Wave 06: Located along 20W from 15N southward, moving west at 10 knots (18 km/h). This wave is still over 4,300 kilometers east of Trinidad and Tobago.
We now have two tropical waves in the Atlantic Basin, following the passage of Tropical Wave 04 on Tuesday, but a low-level trough is forecast to bring additional moisture and instability on Wednesday. As a result, an increase in cloudiness, rain, showers, and isolated heavy showers and thunderstorms is likely, mainly by Wednesday morning. Still, strong westerly wind shear will keep the strongest activity east of Trinidad and Tobago.
This second tropical wave is moving in tandem with converging trade winds, which will enhance showers and thunderstorms. This is also forecast to increase rainfall activity across T&T, mainly on Friday. Upper-level conditions are forecast to become increasingly favorable, particularly on Thursday into Friday, when this tropical wave is forecast to move across T&T.
With a favorable upper-level environment, combined with an already favorable lower-level environment, ample moisture and instability, periods of moderate to occasionally heavy showers and thunderstorms are becoming increasingly likely, particularly on top of increasingly saturated soils.
The combination of these factors is likely to result in daily rainfall accumulations exceeding 25 millimeters in many locations. In some isolated areas, places may even experience daily rainfall totals between 50 and 75 millimeters.
Tropical Wave 04 produced significant rainfall accumulations across eastern Trinidad and across Tobago. Parts of northeastern Trinidad recorded between 50 and 125 millimeters, while across Tobago, between 50 and 75 millimeters were recorded. As a result, soils have become increasingly saturated with river levels elevated, particularly the North Oropouche River, the upper Caroni River, and associated tributaries in the area.
The Trinidad and Tobago Meteorological Service maintained an Adverse Weather Alert from 2:00 AM Tuesday through 4:00 PM Wednesday for Trinidad and Tobago and its surrounding waters. The latest forecast guidance continues to indicate potentially inclement weather continuing through Friday night. A reminder that alerts, watches, and warnings for T&T are entirely the prerogative of the forecasters at the Trinidad and Tobago Meteorological Service.
Compounding this flood threat are spring tides that began on Sunday, June 8th, and will persist through Saturday, June 14th. These higher-than-normal high tides will slow runoff, while the lower-than-normal low tides will lead to quicker runoff. The issue arises when heavy rainfall coincides with high tide periods, and when upstream runoff reaches the lower river basins simultaneously with high tides, leading to flooding in both scenarios.
Additionally, low-level winds are forecast to be elevated through Wednesday, and again from Friday into the weekend. In heavy showers and thunderstorms, wind gusts are likely to exceed 50 km/h, with the potential for gusts exceeding 60 km/h, particularly in elevated and coastal areas. As soils become increasingly saturated, falling trees and resulting downed utility poles and power outages are likely to occur as the week progresses.
By the weekend, a ridge pattern returns, leading to a fairly dry and slightly hazy weekend, as even with the forecasted rainfall, Saharan dust remains present.
The takeaway: A multi-day, heavy rainfall event is underway. As a result, multiple periods of heavy rainfall will lead to flooding, resulting in traffic delays (including street and flash flooding). For those in low-lying areas, particularly near watercourses in northeastern regions, close attention must be paid to river levels. However, this is not expected to be a Greenvale (October 2018) level event, which saw upwards of 250 millimeters of widespread rainfall in three days. Those living in elevated areas, as well as those in low-lying areas near watercourses, should closely monitor the rivers, their surrounding areas, and the latest weather forecasts and conditions in the coming days.
