As the Intertropical Convergence Zone continues to produce rainfall across Trinidad and Tobago, a well-defined tropical wave is forecast to move across the region beginning Sunday night, bringing gusty winds and locally heavy rainfall to the islands.
What you need to know
— Rainfall: Over the next five days, through Wednesday night, overall rainfall accumulations are forecast to range between 25 and 50 millimeters across both islands. Across Eastern Tobago, the eastern and southern halves of Trinidad, and localized western coastal areas, totals between 50 and 125 millimeters of rainfall are forecast. Isolated higher totals are possible, favoring northeastern Trinidad.
— Saharan Dust: Moderate, but decreasing, concentrations of Saharan Dust are forecast through the weekend, with mild concentrations between Sunday and Monday. Another dust surge arrives by mid-Tuesday.
— Hazards: The main hazards over the next five days will be gusty winds exceeding 50 km/h, particularly from Sunday night through Tuesday morning, as well as the threat of street or flash flooding, both of which are likely to occur mainly in association with heavy showers and thunderstorms. Increased low-level winds, combined with gusts in heavy showers and thunderstorms, may cause weaker and/or larger trees to fall. There is an overall low risk of riverine flooding, with particular attention needed in the North Oropouche River Basin.
— Marine: Moderate seas are forecast in Trinidad and Tobago’s open waters, while choppy conditions are forecast in sheltered areas. Seas across northern areas may become rough from Sunday night through Tuesday. All marine interests are advised to exercise caution in the vicinity of heavy showers and thunderstorms.
Latest Alert
There are no alerts, watches, or warnings in effect for Trinidad and Tobago from the Trinidad and Tobago Meteorological Service at this time.
Trinidad and Tobago is NOT under any tropical storm or hurricane threat, watch, or warning at this time.
The Forecast
Saturday
SaturdaySunday
SundayMonday
MondayTuesday
TuesdayWednesday
WednesdayMarine Forecast
Agitated Seas Forecast To Continue Into Next Week
Temperatures
Saturday
Low: 25-26°C
High: 30-31°C
Sunday
Low: 24-26°C
High: 30-31°C
Monday
Low: 23-25°C
High: 27-29°C
Tuesday
Low: 23-25°C
High: 30-31°C
Wednesday
Low: 24-26°C
High: 31-32°C
Forecast Impacts
Flooding
Over the next five days, through Wednesday night, overall rainfall accumulations are forecast to range between 25 and 50 millimeters across both islands. Across Eastern Tobago, the eastern and southern halves of Trinidad, and localized western coastal areas, totals between 50 and 125 millimeters of rainfall are forecast. Isolated higher totals are possible, favoring northeastern Trinidad.
Street & Flash Flooding
Street & Flash FloodingRiverine Flooding
Riverine FloodingForecast Rainfall Totals
- Saturday (Tropical Wave 07): Across Tobago, less than 5 millimeters with isolated higher totals across the eastern half of the island. Across Trinidad, up to 10 millimeters across the island, with totals between 10 and 25 millimeters favoring southern and eastern coastal areas.
- Sunday: Across the western half of Trinidad, up to 10 millimeters, while across the eastern half of Trinidad and Tobago, between 5 and 15 millimeters, with isolated totals to 25 millimeters. Note that most of Sunday’s rains are forecast to begin after the mid-afternoon period.
- Monday (Tropical Wave 08): Between 10 and 25 millimeters of rainfall across both islands, with totals between 25 and 50 millimeters across the eastern half of Trinidad and localized areas of Tobago. Isolated totals, particularly across eastern areas, may exceed 50 millimeters.
- Tuesday: Across the eastern and southern halves of Trinidad, between 5 and 15 millimeters of rainfall, with localized higher totals. Elsewhere, up to 10 millimeters.
- Wednesday: Less than 5 millimeters across the country, with isolated higher totals favoring eastern Trinidad.
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
Moderate, but decreasing, concentrations of Saharan Dust are forecast through the weekend, with mild concentrations between Sunday and Monday. Another dust surge arrives by mid-Tuesday.
Saharan Dust Forecast
Saharan Dust Forecast To Stay Generally North of 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.
Through the forecast period, isolated to scattered rainfall is forecast.
Forecast Discussion
Tropical Waves (As of 8:00 PM June 20th)
— Tropical Wave 07: Located along 55W from 16N, moving west around 15 knots (28 km/h) with scattered showers. This wave is approximately 600 km east of T&T on Friday night, forecast to move across the country overnight into Saturday morning.
— Tropical Wave 08: Located along 44W from 15N southward, moving west at around 10-15 knots (18 to 28 km/h). This well-defined wave is forecast to move across T&T on Sunday night into Monday morning, dragging the ITCZ northward ahead of its passage. A significant surge of Saharan Dust will follow on Tuesday.
— Tropical Wave 09: Located along 26W, moving west at 10 knots (18 km/h). This wave is still over 3,770 kilometers east of Trinidad and Tobago.
Back-to-back tropical waves have continued to affect Trinidad and Tobago over the past week, bringing the Intertropical Convergence Zone (ITCZ) near and at times across the country. A similar pattern is forecast to continue not only through the next five days but also for the remainder of this month.
However, our focus is on the next five days. On Saturday, the axis of Tropical Wave 07 will move west, away from T&T. This wave, interacting with the ITCZ, has brought anomalously moist air to the region, leading to ample instability and the rain, showers, and thunderstorms experienced over the last 18 hours, which are expected to continue through early Saturday morning. A brief ridge pattern is likely to return by Saturday afternoon, accompanied by the ever-present but declining Saharan Dust, resulting in partly cloudy and hazy skies.
On Sunday, the well-defined Tropical Wave 08 is forecast to move westward toward T&T and the Windward Islands. This wave is forecast to bring another round of anomalously moist air (99.5 percentile), instability, and gusty winds to T&T and the southern Windwards. Sunday is forecast to initially be a settled day, as the approaching tropical wave erodes that ridge. From the afternoon, increased cloudiness and breezy to windy conditions are expected to begin, moving in from the east.
While current forecast guidance does not develop this wave into an organized tropical system, strong wind gusts, particularly for the southern Windwards, are likely. For T&T, the most likely gusts are between 50 km/h and 65 km/h between Sunday night and Tuesday morning. For islands between Grenada and St. Vincent, as well as Barbados, gusts between 60 and 70 km/h are likely to accompany heavy showers and thunderstorms. The probability of wind gusts exceeding 65 km/h for islands between Grenada and St. Vincent ranges from 20% to 30%. For T&T, the probability is less than 1%.
Rainfall-wise, between Sunday evening and Tuesday morning, maximum 24-hour rainfall totals peak between 50 and 62.5 millimeters, generally along Trinidad and Tobago’s eastern coastlines. Multi-model consensus aligns with this total, and using ensemble guidance, there is a 50% to 60% chance of rainfall totals along T&T’s eastern coastline reaching or exceeding 100 millimeters of rainfall during the Sunday PM to Monday PM timeframe. Based on the current guidance, this is not forecast to be a similar rainfall event compared to the June 10th-13th deluge that led to the Caroni River overtopping. However, based on current model guidance and trends, an Adverse Weather Alert (or even a High Wind Alert) may be issued by the TTMS at some point for Sunday night through Tuesday morning. A reminder that alerts, watches, and warnings for T&T are entirely the prerogative of the forecasters at the Trinidad and Tobago Meteorological Service.
By Tuesday daybreak, another high-pressure ridge moves back across the Windwards, and a significant surge of Saharan Dust follows, with higher dust levels staying north of T&T. As a result, a mostly dry, dusty and hazy end to Tuesday is forecast, continuing into Wednesday.
