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Periods of Heavy Rainfall Forecast Through The Divali Long Weekend

November 10, 2023
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Favorable low-level convergence trailing a low-level trough and favorable upper-level conditions are forecast to create the potential for heavy rain, showers, and isolated thunderstorms. As a result, street/flash flooding will be a concern, particularly on Divali (Sunday), with gusty winds accompanying heavy/violent rainfall.

What you need to know

— Rainfall: Over the next five days, between 40 and 100 millimeters are forecast across T&T, with higher totals trending across eastern Trinidad and Tobago. In isolated areas across eastern Trinidad and Tobago, up to 150 millimeters are forecast over the five days. In highly isolated heavy showers and thunderstorms, 24-hour rainfall totals could exceed 50 millimeters.
— Saharan Dust: There is little to no Saharan Dust forecast across T&T over the next five days.
— Hazards: The main hazards into next week will originate from heavy showers and thunderstorms, producing cloud-to-ground lightning, gusty winds up to 55 KM/H (through Monday), and periods of heavy/violent rainfall, which can trigger street/flash flooding. Though riverine flooding concerns are low presently, eastern river basins and the Caroni River Basin will be monitored closely. In elevated areas of northern Trinidad and eastern Tobago, landslides are also possible, particularly as the weekend progresses.
— Marine: Seas are forecast to be moderate, with waves in open waters generally reaching as high as 2.5 meters by Monday. In sheltered areas, waves are forecast to be up to 1.5 meters and choppy in heavy showers and thunderstorms and along north-facing coastlines of T&T.

Latest Alert

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Trinidad and Tobago is NOT under any tropical storm or hurricane threat, watch, or warning at this time.

The Forecast

Friday night

Friday night
3 10 0 1
Isolated to scattered showers to favor the northern half of Trinidad and Tobago, with isolated heavy rainfall possible, interrupting partly to mostly cloudy skies. For southern Trinidad, partly cloudy with the odd isolated shower.
Isolated to scattered showers to favor the northern half of Trinidad and Tobago, with isolated heavy rainfall possible, interrupting partly to mostly cloudy skies. For southern Trinidad, partly cloudy with the odd isolated shower.
3/10
Thunderstorm Chances
Low

Saturday

Saturday
5 10 0 1
Partly cloudy to cloudy conditions interrupted by passing showers and isolated heavy showers/thunderstorms, generally favoring Tobago and the northern and eastern halves of Trinidad generally during the early morning, and again from the late morning through the afternoon. By the evening and night, partly cloudy conditions with isolated showers favoring eastern Trinidad and Tobago.
Partly cloudy to cloudy conditions interrupted by passing showers and isolated heavy showers/thunderstorms, generally favoring Tobago and the northern and eastern halves of Trinidad generally during the early morning, and again from the late morning through the afternoon. By the evening and night, partly cloudy conditions with isolated showers favoring eastern Trinidad and Tobago.
5/10
Thunderstorm Chances
Medium

Sunday

Sunday
6 10 0 1
Mostly cloudy to overcast with periods of rain and showers across both islands from the early morning and continuing into late afternoon. Isolated thunderstorms are possible across Tobago and east Trinidad during the early morning, spreading across the country through the mid-morning into the afternoon. Heavy/violent rainfall rates likely, particularly across eastern Trinidad and Tobago, accompanied by wind gusts near 55 KM/H. By nightfall, periods of light to moderate rain, isolated heavy showers and the odd thunderstorm possible, interrupting cloudy skies.
Mostly cloudy to overcast with periods of rain and showers across both islands from the early morning and continuing into late afternoon. Isolated thunderstorms are possible across Tobago and east Trinidad during the early morning, spreading across the country through the mid-morning into the afternoon. Heavy/violent rainfall rates likely, particularly across eastern Trinidad and Tobago, accompanied by wind gusts near 55 KM/H. By nightfall, periods of light to moderate rain, isolated heavy showers and the odd thunderstorm possible, interrupting cloudy skies.
6/10
Thunderstorm Chances
Medium – High

Monday

Monday
4 10 0 1
A few early morning showers and offshore thunderstorms to lead to a partly cloudy day. Isolated late morning through afternoon showers is possible across both islands, with heavier activity favoring southern and western halves of Trinidad initially, then across eastern areas toward the evening. A mostly settled evening and night, barring the odd shower favoring eastern areas of T&T.
A few early morning showers and offshore thunderstorms to lead to a partly cloudy day. Isolated late morning through afternoon showers is possible across both islands, with heavier activity favoring southern and western halves of Trinidad initially, then across eastern areas toward the evening. A mostly settled evening and night, barring the odd shower favoring eastern areas of T&T.
4/10
Thunderstorm Chances
Low – Medium

Tuesday

Tuesday
4 10 0 1
A few early morning showers, with the odd isolated thunderstorm, to give way to a partly cloudy day. By the late morning, isolated heavy showers and the odd thunderstorm are possible favoring western Tobago and across Trinidad, settling by the mid-afternoon. A partly cloudy night with the odd shower favoring eastern areas.
A few early morning showers, with the odd isolated thunderstorm, to give way to a partly cloudy day. By the late morning, isolated heavy showers and the odd thunderstorm are possible favoring western Tobago and across Trinidad, settling by the mid-afternoon. A partly cloudy night with the odd shower favoring eastern areas.
4/10
Thunderstorm Chances
Low – Medium

Wednesday

Wednesday
3 10 0 1
A partly cloudy day with a few isolated showers by the late morning through the afternoon, and the odd thunderstorm, generally favoring Trinidad. A slightly hazy, settled night.
A partly cloudy day with a few isolated showers by the late morning through the afternoon, and the odd thunderstorm, generally favoring Trinidad. A slightly hazy, settled night.
3/10
Thunderstorm Chances
Low

Marine Forecast

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Temperatures

Saturday

Low: 24-26°C

High: 29-31°C

Sunday

Low: 23-25°C

High: 28-30°C

Monday

Low: 24-26°C

High: 30-32°C

Tuesday

Low: 24-26°C

High: 30-32°C

Wednesday

Low: 24-26°C

High: 31-33°C

Maximum high temperatures are forecast to remain near to below-average levels for November across Trinidad and Tobago over the next five days due to forecast rainfall and cloudy skies, with actual temperatures reaching as high as 32°C across both islands. Across the country, over the next five days, the heat index, or feels like temperature, is forecast to range between 34°C and 38°C, as some days, particularly Tuesday and Wednesday, partly cloudy skies will allow for warming. Minimum lows are forecast to range between 23°C and 26°C daily but can trend lower in interior areas of the country and across eastern Tobago, where rainfall persists.

Forecast Impacts

Flooding

Flooding
7 10 0 1
Over the next five days, between 40 and 100 millimeters are forecast across T&T, with higher totals trending across eastern Trinidad and Tobago. In isolated areas across eastern Trinidad and Tobago, up to 150 millimeters are forecast over the five days. In highly isolated heavy showers and thunderstorms, 24-hour rainfall totals could exceed 50 millimeters. While these rainfall totals would usually warrant a medium to high risk for flooding, given rainfall across T&T since the start of November, soils are becoming increasingly saturated, raising the flooding risk to high for street/flash flooding, but low to medium for riverine flooding at this time, mainly for eastern river basins, as well as the Caroni River Basin.
Over the next five days, between 40 and 100 millimeters are forecast across T&T, with higher totals trending across eastern Trinidad and Tobago. In isolated areas across eastern Trinidad and Tobago, up to 150 millimeters are forecast over the five days. In highly isolated heavy showers and thunderstorms, 24-hour rainfall totals could exceed 50 millimeters. While these rainfall totals would usually warrant a medium to high risk for flooding, given rainfall across T&T since the start of November, soils are becoming increasingly saturated, raising the flooding risk to high for street/flash flooding, but low to medium for riverine flooding at this time, mainly for eastern river basins, as well as the Caroni River Basin.
7/10
Likelihood
High

Forecast Rainfall Totals

  • Saturday: Across the western half of Trinidad, between 5 and 15 millimeters with isolated totals up to 25 millimeters in areas that experience heavy showers and thunderstorms. Across the eastern half of Trinidad and Tobago, between 10 and 25 millimeters of rainfall, with totals as high as 50 millimeters possible, favoring eastern Tobago and northeastern Trinidad.
  • Sunday: Heavy rainfall is likely across both islands! Across Trinidad and Tobago, rainfall totals between 15 and 35 millimeters are forecast, with totals between 50 and 100 millimeters possible across the eastern half of Trinidad and Tobago and isolated areas of southern/western coastal Trinidad.
  • Monday: Across both islands, between 5 and 20 millimeters of rainfall is forecast, with isolated totals as high as 50 millimeters across Trinidad’s southern and western halves.
  • Tuesday: Between 5 and 15 millimeters across the country and isolated totals up to 25 millimeters favoring eastern Trinidad and Tobago, western areas of Trinidad. Locally higher amounts are possible in areas with persisting heavy showers or thunderstorms.
  • Wednesday: Between 0 and 10 millimeters across the country, with higher totals favoring eastern Trinidad. Locally higher amounts are possible in areas with persisting heavy showers or thunderstorms.

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 Thunderstorms
5 10 0 1
Though strong thunderstorms in the traditional sense (frequent lightning, hail and/or funnel clouds/waterspouts/tornadoes) are not expected, atmospheric conditions will be favorable for efficient rainfall production at the mid-levels of the atmosphere, with strong vertical motion through the atmosphere. Both of these features can produce rainfall rates and wind gusts that can be classed, based on our below definitions, as severe, particularly on Sunday. Hence, chances remain at medium for Sunday and a lesser extent on Monday, but low to very low for Saturday, Tuesday, and Wednesday.
Though strong thunderstorms in the traditional sense (frequent lightning, hail and/or funnel clouds/waterspouts/tornadoes) are not expected, atmospheric conditions will be favorable for efficient rainfall production at the mid-levels of the atmosphere, with strong vertical motion through the atmosphere. Both of these features can produce rainfall rates and wind gusts that can be classed, based on our below definitions, as severe, particularly on Sunday. Hence, chances remain at medium for Sunday and a lesser extent on Monday, but low to very low for Saturday, Tuesday, and Wednesday.
5/10
Likelihood
Medium
What 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 55 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 Winds
5 10 0 1
Mid-level to low-level winds are forecast to remain elevated through Monday, which can translate to the surface in showers and thunderstorms. As a result, through Monday, sustained winds are forecast to reach as high as 35 KM/H mainly in heavy/violent showers or thunderstorms with gusts as high as 55 KM/H. Generally, winds speeds are forecast to reach as high as 30 KM/H outside of rainfall activity, particularly from Tuesday onwards.
Mid-level to low-level winds are forecast to remain elevated through Monday, which can translate to the surface in showers and thunderstorms. As a result, through Monday, sustained winds are forecast to reach as high as 35 KM/H mainly in heavy/violent showers or thunderstorms with gusts as high as 55 KM/H. Generally, winds speeds are forecast to reach as high as 30 KM/H outside of rainfall activity, particularly from Tuesday onwards.
5/10
Likelihood
Medium

With winds gusting to 55 KM/H and occasionally above, 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. Note these impacts are mainly possible ahead of and during heavy/violent showers and thunderstorms.

Other Hazards

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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.

Isolated rainfall is forecast on Tuesday and Wednesday, isolated to scattered rainfall is forecast on Saturday and Monday, and scattered to widespread rainfall is forecast on Sunday.

Forecast Discussion

On Friday night, a low-level to surface trough moved into the Caribbean Sea, with a trailing area of confluence (winds slowing down, piling up like a traffic jam, and creating an area of convergence) that produced a band of rain, scattered showers, and isolated thunderstorms mainly north of Tobago near Barbados. Scattered pockets of convergence have supported scattered light to moderate showers across mainly eastern and northern areas of Trinidad and Tobago. An upper-level trough is forecast to enhance activity (showers, thunderstorms) across the Windwards from Friday night through Sunday.

On Saturday, convergence and confluence trailing the low-level to surface trough will continue to support shower and isolated thunderstorm activity.

Favorable convergence and transport of moisture from the east to southeast will continue on Sunday. However, forecast models indicate quite favorable mid-level conditions that will support fairly efficient rainfall processes that can produce periodic heavy to violent rainfall rates, even in the face of strong to very strong wind shear.

From Saturday through the first half of Monday, low to mid-level winds are forecast to increase, which can make it to the surface in showers or thunderstorms. As a result, forecast winds will reach as high as 35 KM/H and gust to 55 KM/H. On Sunday, with forecast models showing moderate to strong vertical lift in updrafts, gusts can be stronger than 55 KM/H in heavy/violent rainfall.

On Monday, low-level convergence is forecast to weaken, leading to further isolated rainfall as a ridge rebuilds across T&T. This ridge is forecast to establish itself by Tuesday and Wednesday, with T&T remaining on the southwestern periphery, leading to some equatorial moisture moving in from the southeast. However, upper-level conditions are forecast to become increasingly dry, with low levels still remaining relatively dry compared to the prior weekend.

Though heavy rainfall is forecast on Divali (Sunday), this is not expected to be a Divali 2018 repeat, where widespread rainfall accumulations exceeding 75 millimeters within 24 hours occurred, causing significant flooding across Trinidad. Still, flooding rainfall is possible, particularly in northeastern Trinidad.

Note that as an extended forecast goes further into the future, it is normal for the certainty to be reduced relative to the extended time period.

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