A multi-day rainfall event began on Tuesday with the passage of Tropical Wave 47 and is set to continue into the weekend. Additional rainfall is forecast associated with the Intertropical Convergence Zone interacting with Tropical Wave 48 by late Friday under favorable upper-level conditions. Unsettled conditions are also forecast to continue into the weekend and next week.
What you need to know
— Rainfall: Through Friday, a combination of cloudy skies, broad areas of rain, scattered showers, and thunderstorms are forecast across the country, with isolated to scattered activity over the weekend, but rainy and cloudy conditions return by Monday. Over the next five days, between 50 and 150 millimeters of rainfall is forecast across both islands with totals nearing 200 millimeters, favoring Tobago, eastern and southern areas of Trinidad. In isolated areas across both islands, totals may reach or exceed 200 millimeters.
— Hazards: Over the next five days, the main hazards will be street/flash flooding, gusty winds, and landslides. Mainly through Friday, wind gusts up to 45 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 possible from Thursday.
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
Thursday
ThursdayFriday
FridaySaturday
SaturdaySunday
SundayMonday
MondayMarine: Through Friday, moderate seas are forecast in open waters with waves up to 2.5 meters. In sheltered areas, waves are forecast to be below 0.5 meters with spring tides. Sheltered areas may 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.
Thursday and Friday
Low: 23-24°C
High: 27-29°C
With cloudy to overcast skies on Thursday and Friday, maximum high temperatures are forecast to struggle to reach 30°C on both days. The heat index will remain below 32°C.
Saturday and Sunday
Low: 24°C
High: 30-32°C
Partly cloudy to mostly cloudy skies are forecast over the weekend, allowing some sunshine to increase temperatures across both islands. Heat indices (or feels-like temperatures) are forecast to be between 32°C and 42°C. Locally higher heat indices are possible in urbanized areas like Port of Spain, Chaguanas, and San Fernando.
Monday
Low: 23-24°C
High: 28-30°C
Cloudy skies with rainfall are set to return by Monday, but a partly cloudy (meaning sunshine) morning could still bring temperatures near or even above 30°C before rainfall begins. Heat indices (or feels-like temperatures) are forecast to reach as high as 35°C.
Forecast Impacts
Flooding
FloodingStreet/flash flooding is very likely across both islands through the next five days. Importantly, the sole model (GFS) that has been showing apocalyptic rainfall totals with this rainfall event has received a dose of reality and fallen in line with the rest of the leading global models and with its overall rainfall totals lowered. Regardless, this heavy rainfall event poses a riverine flooding threat from Thursday. Smaller watercourses may reach threshold levels by Friday, particularly across eastern and southern areas of Trinidad.
Forecast Rainfall Totals
- Thursday: Between 15 and 35 millimeters of rainfall across both islands. Higher totals are forecast to trend across the eastern and southern halves of Trinidad and along the western coastal areas of Trinidad, reaching or exceeding 75 millimeters.
- Friday: Between 5 and 15 millimeters of rainfall across both islands. Higher totals of up to 40 millimeters are forecast to trend across the eastern and southern halves of Trinidad and along the western coastal areas of Trinidad, reaching or exceeding 50 millimeters.
- Saturday: Between 5 and 15 millimeters across both islands, with isolated totals up to or exceeding 25 millimeters favoring the eastern half of Trinidad.
- Sunday: Between 15 and 35 millimeters across both islands, with isolated totals exceeding 50 millimeters favoring Trinidad.
- Monday: Between 10 and 15 millimeters across both islands, with isolated totals exceeding 25 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.
Widespread activity is forecast on Thursday and Friday. Over the weekend, isolated activity is forecast. By Monday, rainfall becomes isolated to scattered.
Forecast Discussion
Tropical Waves (and other notable weather features) near and east of T&T: Based on the Tropical Analysis and Forecast Branch’s 00Z surface analysis on October 27th, 2022, as well as the latest satellite and model guidance:
- The 47th tropical wave for 2022 (TW47) moved across Trinidad, Tobago, and the Lesser Antilles on Tuesday, October 25th, 2022, and continues its westward path, interacting with a deep-layered trough across the eastern Caribbean Sea.
- The 48th tropical wave for 2022 (TW48) is along 45°W, south of 17°N, moving west at 15 knots (27 KM/H). At this time, no deep convection has been noted with this wave except where the axis interacts with the Intertropical Convergence Zone. This wave is forecast to interact with a deep-layered trough and the ITCZ as it nears T&T on Friday, producing an additional round of inclement weather.
- Area of interest in the Caribbean Sea: The National Hurricane Center is monitoring this area for tropical cyclone development over the next five days. An area of low pressure is expected to form, possibly from an existing trough of low pressure over the area or the approach of TW48 by this weekend. Conditions appear conducive for development in the eastern/central Caribbean Sea, and the NHC notes a tropical depression could form by early next week as it moves westward into the central Caribbean Sea.
On Wednesday, moisture trailing Tropical Wave 47 and the Intertropical Convergence Zone sustained showers and isolated thunderstorms across Trinidad and Tobago. To the northwest, a deep-layered trough is now interacting with the ITCZ as it moves across T&T, supporting cloudy skies, periods of rain, showers, and thunderstorms which are all forecast to continue from Thursday into Friday. Tropical Wave 48 is forecast to traverse the islands on Friday into Saturday. Additionally, favorable low-level convergence and upper-level divergence remain in place with deep-layered moisture present.
The sole limiting factor through the next 48-72 hours is moderate to potentially strong wind shear, which the GFS model may have finally taken into account, bringing down its overall rainfall totals compared to earlier model runs over the last three to five days. With shear generally from the west to northwest, overall heavier rainfall is forecast to affect southern and eastern areas of Trinidad and Tobago.
Marginally drier air at the low and mid-levels on Saturday, combined with increased wind shear, will limit showers/thunderstorms through the weekend. However, weak low-level winds through the weekend will allow for daytime heating, sea breeze convergence, and orographic effects to prevail, trigger/enhance showers, and isolated thunderstorms across both islands.
By Sunday, deep-layered moisture returns to Trinidad and Tobago as the ITCZ flares up yet again, producing showers and thunderstorms during the second half of the day into Monday.
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 end of the month, promoting rainfall activity.
