A multi-day rainfall event last Tuesday with the passage of Tropical Wave 47. As forecast, rainfall returned on Saturday evening across the country. An unstable atmosphere with multiple weather features, including the Intertropical Convergence Zone (ITCZ), are forecast to produce additional rainfall over the next five days.
What you need to know
— Rainfall: Through Thursday, a combination of cloudy skies, periods of rain, scattered showers, and thunderstorms are forecast across the country. Over the next five days, between 50 and 150 millimeters of rainfall is forecast across both islands, with totals nearing 200 millimeters, favoring eastern and southern areas of Trinidad. In isolated areas across both islands, totals may reach or exceed 200 millimeters. The wettest day is forecast to be today (Sunday, October 30th, 2022) of the five-day forecast period.
— Hazards: Over the next five days, the main hazards will be street/flash flooding, localized gusty winds, and landslides. Wind gusts up to 50 KM/H are very likely, with gusts up to or over 55 KM/H possible in heavy showers or thunderstorms. Lightning will accompany thunderstorms. Riverine flooding, particularly near smaller watercourses across southern and eastern areas, is also very likely.
Latest Alerts
Riverine Flood Alert Discontinued For South Trinidad
Adverse Weather Alert Discontinued For T&T
Trinidad and Tobago is NOT under any tropical storm or hurricane threat, watch, or warning at this time.
The Forecast
Sunday
SundayMonday
MondayTuesday
TuesdayWednesday
WednesdayThursday
ThursdayMarine: Through Thursday, moderate seas are forecast in open waters with waves up to 2.0 meters. In sheltered areas, waves are forecast to be less than 1.0 meter. However, long-period swells through Wednesday may cause larger, battering waves along northern coastlines. Sheltered areas may also occasionally become choppy during showers and thunderstorms.
Temperatures
Generally, over the next five days, with increased cloud cover, maximum highs and minimum lows are forecast to be cooler than usual. However, marginally increased sunshine over the weekend could lead to warmer days.
Sunday through Thursday
Low: 23-24°C
High: 28-30°C
With mostly cloudy skies over the next five days, maximum high temperatures are forecast to struggle to reach 30°C, with minimum lows remaining near 23°C to 24°C in Trinidad and near 24°C to 25°C in Tobago. The heat index will generally remain below 34°C.
Forecast Impacts
Flooding
FloodingStreet/flash flooding is very likely across both islands through the next five days. Riverine flooding is also very likely across the North Oropouche, Ortoire, Nariva, South Oropouche, and Caroni River Basins. Smaller watercourses of the Caroni and South Oropouche Rivers are already outside of their banks following the last five days of heavy rainfall.
Forecast Rainfall Totals
- Sunday: Between 25 and 75 millimeters of rainfall across both islands. Higher totals are forecast to trend across the eastern and southern halves of Trinidad and Tobago, reaching or exceeding 125 millimeters.
- Monday: Between 5 and 15 millimeters of rainfall across both islands. Higher totals of up to 25 millimeters are forecast, trending across the eastern and southern halves of Trinidad and along the western coastal areas of Trinidad. Isolated higher totals are possible.
- Tuesday: Between 5 and 15 millimeters of rainfall across both islands. Higher totals of up to 25 millimeters are forecast, trending across the eastern and southern halves of Trinidad and along the western coastal areas of Trinidad. Isolated higher totals are possible.
- Wednesday: Between 5 and 15 millimeters of rainfall across both islands. Higher totals of up to 35 millimeters are forecast, trending across the eastern and southern halves of Trinidad and along the western coastal areas of Trinidad. Isolated higher totals are possible.
- Thursday: Between 15 and 35 millimeters across both islands, with isolated totals exceeding 50 millimeters across both islands in persisting heavy shower/thunderstorm activity.
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 ThunderstormsStrong thunderstorms can produce frequent lightning, gusty winds, and violent rainfall rates. Short-lived funnel cloud development is possible, particularly on Saturday and Sunday when low-level winds weaken. If a funnel cloud touches down on a body of water, it becomes a waterspout; if it touches down on land, it becomes a tornado.
Gusty Winds
Gusty WindsPossible impacts include localized wind damage to trees, power lines, and small structures. 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.
Other Hazards
With forecast rainfall accumulations, landslides are likely across both islands over the next five days.
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.
Over the next five days, isolated to scattered rainfall is forecast
Forecast Discussion
Tropical Waves (and other notable weather features) near and east of T&T: Based on the Tropical Analysis and Forecast Branch’s 06Z surface analysis on October 30th, 2022, as well as the latest satellite and model guidance:
- The 48th tropical wave for 2022 (TW48) dissipated east of the Lesser Antilles on Saturday, October 29th, 2022.
- The 49th tropical wave for 2022 (TW49) is along 47°W, south of 18°N, moving west at 15 knots (27 KM/H). Scattered moderate convection has been noted with this wave where the axis interacts with the ITCZ. This wave is forecast to interact with the ITCZ as it moves across T&T on Tuesday night into Wednesday.
- Invest 95L: The National Hurricane Center is monitoring this area for tropical cyclone development over the next five days. This broad area of low pressure is moving west-northwest away from the Lesser Antilles. Conditions appear conducive for gradual development in the central/western Caribbean Sea, and the NHC notes a tropical depression could form by early next week. Chances for development are medium over the next 48 hours and high over the next five days. This area of low pressure is influencing the ITCZ across T&T at this time.
Over the last five days, Trinidad and Tobago has been affected by a tropical wave, a series of different troughs, and a persistent Intertropical Convergence Zone. As seen above, widespread rainfall totals of up to 100 millimeters have been recorded across the country, with isolated totals nearing 150 millimeters and, in fewer areas, exceeding 250 millimeters. These five-day rainfall totals have led to multiple rivers and tributaries breaking their banks and landslides across both islands. Over the next five days, additional and similar rainfall totals are forecast.
Presently, a mid-level trough is interacting with the ITCZ, producing scattered to widespread rain, showers, and thunderstorms across Trinidad and Tobago. The ITCZ is forecast to remain near and across the country over the next five days, with the passage of a tropical wave (TW49) on Tuesday into Wednesday and trailing convergence on Thursday, supporting additional rainfall.
Generally, a very moist and unstable atmosphere is forecast to remain across T&T through the next five days. Wind shear, however, is forecast to remain at moderate levels between 10-25 knots from the west to west-northwest, keeping stronger convection (showers and thunderstorms) east of T&T. This will result in with overall heavier rainfall favoring southern and eastern areas of Trinidad and across Tobago. Latest model guidance is in fairly well agreement with this outcome.
The Larger-Scale Cause Of Our Prolonged Rainy Spell
Overarching the next five days will be a series of larger-scale features supporting shower and thunderstorm development. The convectively active phase of a Convectively-Coupled Kelvin Wave (CCKW) is forecast to remain across the region through the end of the month. CCKWs are huge impulses spanning thousands of miles, moving west to east through the stratosphere, typically rolling along at about 30 to 40 mph. Like a giant chimney, each CCKW has a broad zone of rising air at its heart, tilted toward the west as you move up. As low-level air converges, the resulting circulation favors the development of showers and thunderstorms ahead of the CCKW.
Another factor aiding shower and thunderstorm development will be the convectively active phase of the Madden-Julian Oscillation (MJO). Like the CCKW, the MJO is a large-scale rising air area promoting shower and thunderstorm development. This convectively active phase of the MJO is also forecast to remain across T&T and the Caribbean region through the next two weeks, promoting rainfall activity.
