The fourth tropical wave for the year is forecast to move across Trinidad and Tobago by late Monday, ushering in a wet period for the country. However, as is typical with these early-season waves, activity tends to be more scattered, mainly staying south and east of Trinidad and Tobago. However, as this and successive waves pull moisture from equatorial regions and the Intertropical Convergence Zone to the south, activity may increase during the pre-dawn through early afternoon hours.
What you need to know
— Rainfall: Over the next five days, through Sunday morning but mainly through Friday night, overall rainfall accumulations across Trinidad and Tobago are forecast to range between 50 and 100 millimeters. Across central, southern, and eastern Trinidad, rainfall of 75 to 125 millimeters is possible, with isolated totals exceeding 125 millimeters along eastern Trinidad.
— Saharan Dust: Significant Saharan Dust concentrations are forecast to decrease overnight tonight, with mild to moderate dust remaining 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 by mid-week. 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
Adverse Weather Alert Issued For T&T As Tropical Wave 04 Nears
Trinidad and Tobago is NOT under any tropical storm or hurricane threat, watch, or warning at this time.
The Forecast
Tuesday
TuesdayWednesday
WednesdayThursday
ThursdayFriday
FridaySaturday
SaturdayMarine Forecast
Agitated Seas Forecast For T&T Over Next 7 Days
Temperatures
Tuesday
Low: 23-25°C
High: 28-29°C
Wednesday
Low: 23-24°C
High: 27-28°C
Thursday
Low: 23-24°C
High: 29-31°C
Friday
Low: 23-24°C
High: 27-29°C
Saturday
Low: 25-26°C
High: 31-32°C
Forecast Impacts
Flooding
Over the next five days, through Sunday morning but mainly through Friday night, overall rainfall accumulations across Trinidad and Tobago are forecast to range between 50 and 100 millimeters. Across central, southern and eastern Trinidad, rainfall of 75 to 125 millimeters is possible, with isolated totals exceeding 125 millimeters along eastern Trinidad.
Street & Flash Flooding
Street & Flash FloodingRiverine Flooding
Riverine FloodingForecast Rainfall Totals
- Tuesday (Tropical Wave 04): Across both islands, between 10 and 25 millimeters of rainfall is likely, with totals of up to 50 millimeters expected in the southern and eastern halves of Trinidad. In persisting, particularly heavy, showers and thunderstorms, localized rainfall totals exceeding 50 millimeters are possible, favoring Trinidad.
- Wednesday (Tropical Wave 05): Across Tobago, between 10 and 25 millimeters of rainfall is forecast. Across Trinidad, between 25 and 50 millimeters of rainfall is forecast. Isolated totals, favoring southern and eastern areas, may exceed 50 millimeters. Flooding is likely.
- Thursday: Across Tobago, between 5 and 10 millimeters of rain is forecast, with isolated totals of up to 20 millimeters. Across Trinidad, between 10 and 25 millimeters of rainfall is expected, with isolated higher totals in the eastern and southern halves of the island, and lower totals in the northern and northwestern areas of Trinidad.
- Friday (Tropical Wave 06): Between 15 and 35 millimeters of rainfall across Trinidad and Tobago, with higher totals favoring the southern and eastern halves of both islands. In isolated areas, higher totals are possible, favoring Trinidad.
- Saturday: Across Tobago, a little to no rainfall is forecast, with less than 1 millimeter of rainfall accumulation expected. Across Trinidad, there was less than 5 millimeters of rainfall accumulation on the island, with locally higher totals in the eastern and southern coastal areas.
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 Tuesday through Friday, scattered to widespread rainfall is forecast, with isolated showers possible on Saturday.
Forecast Discussion
Tropical Waves (As of 2 PM June 9th)
— Tropical Wave 04: Located along 58W from 17N, moving west around 10 to 15 knots (18 to 28 km/h) with scattered showers. This wave, currently 225 kilometers east of T&T, is forecast to move across the country overnight tonight through early Tuesday.
— Tropical Wave 05: Located along 40W from 12N southward, moving west at around 15 knots (28 km/h) with scattered showers and isolated thunderstorms, which are being enhanced by converging tradewinds. This wave, currently 2,200 kilometers east of T&T, is forecast to move across the country Wednesday through Thursday.
— Tropical Wave 06: Located along 20W from 15N southward, moving west at 15 knots. This wave is still over 4,300 kilometers east of Trinidad and Tobago, but forecast models indicate that it will arrive across T&T toward the end of this week, by Friday night into Saturday.
We now have three tropical waves in the Atlantic Basin, with the first forecast to move across Trinidad and Tobago overnight, bringing increased moisture and instability. As a result, an increase in cloudiness, rain, showers, and isolated heavy showers and thunderstorms is likely. Still, strong westerly wind shear will keep the strongest activity east of Trinidad and Tobago.
Ahead of tropical waves, conditions are usually calmer, with active weather following the wave axis. This tropical wave is forecast to be no different, with showers and thunderstorms from Tuesday morning into Wednesday, where another tropical wave is forecast to move into the area.
This second tropical wave has converging trade winds enhancing showers and thunderstorms, which is also forecast to enhance rainfall activity across T&T, mainly on Wednesday. Upper-level conditions are forecast to become increasingly favorable, particularly on Thursday into Friday, when a third 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.
As mentioned in the last forecast discussion, the Trinidad and Tobago Meteorological Service has issued an initial Adverse Weather Alert from 2:00 AM Tuesday through 4:00 PM Wednesday for Trinidad and Tobago and its surrounding waters. However, the latest forecast guidance indicates 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 on Monday 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 likely this week, starting on Tuesday. As a result, multiple periods of heavy rainfall will lead to flooding, resulting in traffic delays (street and flash flooding), and for those in low-lying areas, particularly near watercourses, impacts on homes, lives, and livelihoods are likely. 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 pay close attention to rivers, wider surroundings, as well as the latest weather forecast and conditions in the coming days.
