Forecast: Shearline To Bring Showers Mainly To Tobago

A shearline is set to bring cloudy periods with passing showers, accompanied by gusty winds, mainly to Tobago from Thursday evening into Friday. At the same time, mostly sunny conditions continue across most of Trinidad. As the weekend progresses, increasingly breezy to windy conditions are forecast across T&T and the remainder of the Lesser Antilles.

What you need to know

Rainfall: Over the next five days, across most areas of Trinidad and Tobago, most areas are set to receive between 0 and 15 millimeters of rainfall, with areas of northern and eastern Trinidad, as well as Tobago, accumulating up to 25 millimeters. Most of this rainfall is forecast on Thursday night through Friday night, mainly across Tobago.
— Saharan Dust: Little to no Saharan Dust is forecast over the next five days.
— Hazards: The main hazards, primarily from Saturday, will be elevated sustained winds, up to 35 KM/H, and gusts between 45 KM/H and 55 KM/H, particularly in showers/rain. Though the threat remains low, there is the possibility of short-lived street flooding across Tobago on Thursday night through Friday.
— Marine: Seas are forecast to be moderate, becoming moderate to rough from Saturday night, with waves in open waters generally between 2.0 and 2.5 meters. In sheltered areas, waves are forecast to be up to 1.5 meters and choppy in showers.

Latest Alert

Hazardous Seas Alert Discontinued For T&T

The Trinidad and Tobago Meteorological Service has discontinued the Hazardous Seas Alert for the country on Sunday at 12:04 PM. Over the last four days, northerly long-period swells have…

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

The Forecast

Thursday

Thursday
1 10 0 1
For Trinidad, a misty and cool morning leading to a mostly clear, sunny start to the day, with breezy and partly cloudy conditions developing by midday. There is a low chance of one or two isolated showers, favoring eastern and northern areas, by midday through the evening, spreading across the northern half of Trinidad by nightfall. For Tobago, a misty and cool morning, with increasingly cloudy skies, breezy conditions, and intervals of brief showers, accompanied by gusty winds mainly by the late morning into the night. One or two of these showers may be heavy.
For Trinidad, a misty and cool morning leading to a mostly clear, sunny start to the day, with breezy and partly cloudy conditions developing by midday. There is a low chance of one or two isolated showers, favoring eastern and northern areas, by midday through the evening, spreading across the northern half of Trinidad by nightfall. For Tobago, a misty and cool morning, with increasingly cloudy skies, breezy conditions, and intervals of brief showers, accompanied by gusty winds mainly by the late morning into the night. One or two of these showers may be heavy.
1/10
Thunderstorm Chances iThunderstorms not expected.
Very Low

Friday

Friday
1 10 0 1
Variably cloudy and breezy conditions with brief showers moving across both islands, favoring Tobago, northern and eastern Trinidad. One or two of these showers may be moderate/heavy, favoring Tobago. For the southern Trinidad, a mostly sunny and breezy day with the odd shower. Mostly settled night across both islands.
Variably cloudy and breezy conditions with brief showers moving across both islands, favoring Tobago, northern and eastern Trinidad. One or two of these showers may be moderate/heavy, favoring Tobago. For the southern Trinidad, a mostly sunny and breezy day with the odd shower. Mostly settled night across both islands.
1/10
Thunderstorm Chances iThunderstorms not expected.
Very Low

Saturday

Saturday
1 10 0 1
A few early morning and mid-afternoon showers favoring Tobago and eastern Trinidad to interrupt a mostly sunny and breezy day across the country. Nighttime showers are possible, favoring Tobago and eastern Trinidad, particularly near and after midnight.
A few early morning and mid-afternoon showers favoring Tobago and eastern Trinidad to interrupt a mostly sunny and breezy day across the country. Nighttime showers are possible, favoring Tobago and eastern Trinidad, particularly near and after midnight.
1/10
Thunderstorm Chances iThunderstorms not expected.
Very Low

Sunday

Sunday
1 10 0 1
A few early to mid-morning showers to interrupt a mostly sunny and breezy day across both islands. An initially settled night, with isolated showers developing near and after midnight, favoring Tobago and northern/eastern Trinidad.
A few early to mid-morning showers to interrupt a mostly sunny and breezy day across both islands. An initially settled night, with isolated showers developing near and after midnight, favoring Tobago and northern/eastern Trinidad.
1/10
Thunderstorm Chances iThunderstorms not expected.
Very Low

Monday

Monday
1 10 0 1
Mostly sunny and breezy conditions interrupted by passing cloudy periods with brief light to moderate showers, accompanied by gusty winds.
Mostly sunny and breezy conditions interrupted by passing cloudy periods with brief light to moderate showers, accompanied by gusty winds.
1/10
Thunderstorm Chances iThunderstorms not expected.
Very Low

Marine Forecast

Seas Forecast: Moderate Seas, Reduced Visibility

While no hazardous marine events are forecast over the next seven days, marine interests, particularly small craft operators, will need to exercise caution from this weekend due to a…

Temperatures

Thursday

Low: 19-24°C

High: 30-32°C

Friday

Low: 21-24°C

High: 30-31°C

Saturday

Low: 21-25°C

High: 30-32°C

Sunday

Low: 22-25°C

High: 30-32.5°C

Monday

Low: 20-24°C

High: 30-32.5°C

More information

Cool Nighttime Temperatures Forecast For T&T Tonight

A cool and dry airmass with origins from North America settled across Trinidad and Tobago on Wednesday, leading to possible cooler-than-normal nighttime temperatures forecast for both islands…

Forecast Impacts

Flooding

Flooding
2 10 0 1
Over the next five days, across most areas of Trinidad and Tobago, most areas are set to receive between 0 and 15 millimeters of rainfall, with areas of northern and eastern Trinidad, as well as Tobago, accumulating up to 25 millimeters. Most of this rainfall is forecast on Thursday night through Friday night, mainly across Tobago. With the possibility of isolated heavy rainfall in localized areas Tobago and northeastern Trinidad on Thursday night into Friday night, there is a very low to low chance of street/flash flooding on both days. From on Thursday and from Saturday, street/flash flooding is not expected.
Over the next five days, across most areas of Trinidad and Tobago, most areas are set to receive between 0 and 15 millimeters of rainfall, with areas of northern and eastern Trinidad, as well as Tobago, accumulating up to 25 millimeters. Most of this rainfall is forecast on Thursday night through Friday night, mainly across Tobago. With the possibility of isolated heavy rainfall in localized areas Tobago and northeastern Trinidad on Thursday night into Friday night, there is a very low to low chance of street/flash flooding on both days. From on Thursday and from Saturday, street/flash flooding is not expected.
2/10
Likelihood
Very Low – Low

Forecast Rainfall Totals

  • Thursday: Little to no rainfall across both islands, with less than 5 millimeters across Tobago, mainly from the late afternoon into the night.
  • Friday: Across Trinidad, little to no rainfall, with isolated accumulations of up to 5 millimeters in northeastern areas. For Tobago, between 10 and 20 millimeters, with isolated totals up to 25 millimeters, particularly on windward-facing coasts.
  • Saturday: Little to no rainfall across Trinidad, with isolated totals up to 5 millimeters across northeastern Trinidad and southwestern Tobago.
  • Sunday: Little to no rainfall across the country with trace accumulations.
  • Monday: Little to no rainfall across T&T, with isolated totals up to 5 millimeters eastern areas of both islands.

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
1 10 0 1
Strong thunderstorms are not forecast.
Strong thunderstorms are not forecast.
1/10
Likelihood
Very Low
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
4 10 0 1
Mid-level to low-level winds is forecast to increase from Saturday, which can translate to the surface in showers and rain. As a result, sustained winds are forecast to reach as high as 35 KM/H, and even higher in showers with between 45 KM/H and 55 KM/H, especially from Sunday.
Mid-level to low-level winds is forecast to increase from Saturday, which can translate to the surface in showers and rain. As a result, sustained winds are forecast to reach as high as 35 KM/H, and even higher in showers with between 45 KM/H and 55 KM/H, especially from Sunday.
4/10
Likelihood
Low – 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.

Other Hazards

Saharan Dust Forecast

Major Saharan Dust Surge Now Moving Across T&T

Air quality monitoring stations across Trinidad and Tobago are detecting a major surge of Saharan Dust moving in from the east as forecast. Air quality is quickly dropping across Tobago and…

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.

Highly isolated rainfall is forecast throughout the next five days, with isolated to scattered rainfall across Tobago on Thursday night into Friday night.

Forecast Discussion

On Wednesday night through Thursday, a dry airmass with North American origins, brought southward by a prevailing surface-to-mid-level high-pressure system, will lead to mostly clear and cool conditions across both islands.

However, a shearline north of the country will also be sagging southward on Thursday, leading to increased cloudiness with periods of rain/showers across Tobago from mid-Thursday and, to a lesser extent, northern and eastern Trinidad from Thursday night into Friday. A shearline is a line or narrow zone across which there is an abrupt change in the horizontal wind direction, which is typically accompanied by areas of low-level convergence, shallow showers/rain and cloudiness.

This shearline is forecast to weaken on Saturday, with the prevailing Atlantic high-pressure system strengthening. Low-level winds are forecast to increase from Saturday. These two features will generally dominate for the remainder of the forecast period with pockets of low-level convergence and moisture within the moderate to strong easterly trade wind flow, bringing brief cloudy periods, sharp showers with gusty winds, and generally breezy to windy conditions.

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

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