Tropical Wave 19 Forecast To Bring Showers, Thunderstorms Over Next 24 Hours

An active and well-defined tropical wave and a surge of trade winds are forecast to move across Trinidad and Tobago this afternoon through Tuesday morning, bringing periods of cloudiness, showers, and thunderstorms. By Tuesday afternoon, a surge of Saharan Dust and winds is forecast to lead to a breezy but mostly settled middle to end of the week.

What you need to know

Rainfall: Through the next 48 hours (Wednesday morning), forecast models indicate, between 15 and 35 millimeters of rainfall are possible across both islands, with totals across eastern and southern halves of Trinidad and eastern Tobago between 35 and 75 millimeters. Isolated rainfall accumulation could reach and exceed 75 millimeters, particularly across the eastern and southern areas of Trinidad. For the five-day period through Saturday morning, overall rainfall accumulations are forecast to be between 20 to 50 millimeters across both islands, trending higher between 50 and 75 millimeters across the southern and eastern halves of Trinidad and Tobago, with isolated higher totals exceeding 125 millimeters.
Saharan Dust: A surge of Saharan Dust is forecast to move across the country by mid to late Tuesday, lingering through Friday.
Hazards: Through late Tuesday, street/flash flooding and gusty winds are forecast to be the main hazards in heavy showers and thunderstorms. In and ahead of heavy showers or thunderstorms, sustained winds can reach 35 KM/H and as high as 45 KM/H on Monday into Tuesday. Wind gusts are expected to exceed 45 KM/H in heavy showers/thunderstorms, and through Wednesday, higher gusts to 55 KM/H are likely. There is the potential for landslides in elevated areas, particularly in areas that receive persisting rainfall. Chances for riverine flooding are low to medium as of Monday afternoon.
Marine: Seas are forecast to be agitated and moderate, with waves in open waters ranging between 2.0 and 2.5 meters, occasionally above, while in sheltered areas, up to 1.0 meter and choppy through mid-week.

Latest Alerts

Adverse Weather Alert Discontinued For T&T

The Trinidad and Tobago Meteorological Service (TTMS) has discontinued the Adverse Weather Alert for Trinidad and Tobago. — What has happened: Fast-moving showers and thunderstorms affected…

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

The Forecast

Monday

Monday
8 10 0 1
Generally sunny, hazy and breezy with increasingly cloudy conditions from the late morning, but particularly from the afternoon. Conditions are set to deteriorate from the afternoon through the night with cloudy and breezy conditions and periods of showers/rain and scattered thunderstorms. Street/flash flooding, gusty winds likely.
Generally sunny, hazy and breezy with increasingly cloudy conditions from the late morning, but particularly from the afternoon. Conditions are set to deteriorate from the afternoon through the night with cloudy and breezy conditions and periods of showers/rain and scattered thunderstorms. Street/flash flooding, gusty winds likely.
8/10
Thunderstorm Chances
High – Very High

Tuesday

Tuesday
7 10 0 1
Cloudy and breezy/windy with scattered showers, periods of rain and scattered thunderstorms subsiding by the mid-afternoon. Increasingly settled, hazy and breezy night with the odd isolated shower. Gusty winds to accompany rainfall, street/flash flooding likely.
Cloudy and breezy/windy with scattered showers, periods of rain and scattered thunderstorms subsiding by the mid-afternoon. Increasingly settled, hazy and breezy night with the odd isolated shower. Gusty winds to accompany rainfall, street/flash flooding likely.
7/10
Thunderstorm Chances
High

Wednesday

Wednesday
2 10 0 1
Mostly sunny, hazy, breezy/windy with the odd isolated shower. Mostly settled, hazy and breezy night.
Mostly sunny, hazy, breezy/windy with the odd isolated shower. Mostly settled, hazy and breezy night.
2/10
Thunderstorm Chances
Very Low – Low

Thursday

Thursday
2 10 0 1
Mostly sunny, hazy, breezy/windy with the odd isolated shower. Initially settled, hazy and breezy night, with isolated showers nearing midnight.
Mostly sunny, hazy, breezy/windy with the odd isolated shower. Initially settled, hazy and breezy night, with isolated showers nearing midnight.
2/10
Thunderstorm Chances
Very Low – Low

Friday

Friday
4 10 0 1
A few early morning showers and isolated thunderstorms favoring eastern offshore areas to give way to partly cloudy day. Isolated late morning through afternoon showers and thunderstorms possible across Trinidad, favoring western and hilly areas. A partly cloudy and settled evening and night.
A few early morning showers and isolated thunderstorms favoring eastern offshore areas to give way to partly cloudy day. Isolated late morning through afternoon showers and thunderstorms possible across Trinidad, favoring western and hilly areas. A partly cloudy and settled evening and night.
4/10
Thunderstorm Chances
Low – Medium

Marine Forecast

Temperatures

Temperatures are forecast to be warm throughout the week, with marginally cooler conditions on Tuesday due to increased cloud cover.

Wednesday through Sunday

Low: 24-27°C

High: 29-33°C

Maximum high temperatures are forecast to range between 29°C to 32°C, with higher temperatures across urbanized areas of Trinidad, where in built-up areas, maximum high temperatures could exceed 33°C from Wednesday. Minimum lows are forecast to remain mild, ranging between 24°C and 27°C in Trinidad and Tobago, trending cooler in interior areas. The heat index will generally be near or above 34°C on Monday and again from Wednesday.

Forecast Impacts

Flooding

Flooding
9 10 0 1
Through the next 48 hours (Wednesday morning), forecast models indicate, between 15 and 35 millimeters of rainfall are possible across both islands, with totals across eastern and southern halves of Trinidad and eastern Tobago between 35 and 75 millimeters. Isolated rainfall accumulation could reach and exceed 75 millimeters, particularly across the eastern and southern areas of Trinidad. For the five-day period through Saturday morning, overall rainfall accumulations are forecast to be between 20 to 50 millimeters across both islands, trending higher between 50 and 75 millimeters across the southern and eastern halves of Trinidad and Tobago, with isolated higher totals exceeding 125 millimeters. The chances for street/flash flooding is very high, while riverine flooding is low to medium, particularly across the South Oropouche River Basin.
Through the next 48 hours (Wednesday morning), forecast models indicate, between 15 and 35 millimeters of rainfall are possible across both islands, with totals across eastern and southern halves of Trinidad and eastern Tobago between 35 and 75 millimeters. Isolated rainfall accumulation could reach and exceed 75 millimeters, particularly across the eastern and southern areas of Trinidad. For the five-day period through Saturday morning, overall rainfall accumulations are forecast to be between 20 to 50 millimeters across both islands, trending higher between 50 and 75 millimeters across the southern and eastern halves of Trinidad and Tobago, with isolated higher totals exceeding 125 millimeters. The chances for street/flash flooding is very high, while riverine flooding is low to medium, particularly across the South Oropouche River Basin.
9/10
Likelihood
Very High

Forecast Rainfall Totals

  • Monday: Between 5 and 15 millimeters across the country, with totals between 10 and 25 millimeters across the southern and eastern halves of Trinidad, and isolated higher amounts in localized areas of eastern and southern areas
  • Tuesday: Between 10 and 25 millimeters across the country, with totals between 25 and 50 millimeters across Tobago, and the southern and eastern halves of Trinidad.
  • Wednesday: Little to no rainfall across the country, with isolated totals across eastern areas up to 5 millimeters.
  • Thursday: Little to no rainfall across the country, with isolated totals across eastern areas up to 5 millimeters.
  • Friday: Between 5 and 15 millimeters across the country, trending higher across the southern and eastern halves of Trinidad.

Understanding Rainfall Rates

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
With veering (clockwise) turning winds through the atmosphere on Monday night into Tuesday, coupled with favorable mid to upper-level conditions, there is the medium potential for strong convection and severe thunderstorms, particularly overnight.
With veering (clockwise) turning winds through the atmosphere on Monday night into Tuesday, coupled with favorable mid to upper-level conditions, there is the medium potential for strong convection and severe thunderstorms, particularly overnight.
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
8 10 0 1
In and ahead of heavy showers or thunderstorms, sustained winds can reach 35 KM/H and as high as 45 KM/H on Monday into Tuesday. Wind gusts are expected to exceed 45 KM/H in heavy showers/thunderstorms, and from Monday, higher gusts to 55 KM/H are likely. Higher wind gusts are likely across Tobago, elevated areas of both islands, and associated with stronger thunderstorms.
In and ahead of heavy showers or thunderstorms, sustained winds can reach 35 KM/H and as high as 45 KM/H on Monday into Tuesday. Wind gusts are expected to exceed 45 KM/H in heavy showers/thunderstorms, and from Monday, higher gusts to 55 KM/H are likely. Higher wind gusts are likely across Tobago, elevated areas of both islands, and associated with stronger thunderstorms.
8/10
Likelihood
High – Very High

Possible impacts, particularly on Monday and Tuesday, include localized wind damage to trees, power lines, and small structures. Small potted plants may blow over with light outdoor objects becoming airborne in stronger gusts. Tents may jump. Localized power outages are possible.

Other Hazards

Saharan Dust Forecast

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.

On Monday into Tuesday, scattered to widespread rainfall is forecast across the country, with isolated rainfall forecast through the end of the week.

Forecast Discussion

Tropical Wave 19 is approaching Trinidad and Tobago with a favorable mid to upper-level pattern enhancing showers and thunderstorms on its approach. The tropical wave is embedded within the Intertropical Convergence Zone, leading to the enhancement of showers and thunderstorms during the predawn and early afternoon hours associated with the peak ITCZ activity periods. Additionally, this wave is moving westward in tandem with a surge in low-level winds between 20 to 30 knots (37 to 65 KM/H).

As a result, widespread cloudiness, scattered showers, and thunderstorms are forecast to affect T&T after midday on Monday through the first half of Tuesday, with peak inclement weather conditions forecast overnight Monday through early Tuesday. Wind shear will be light to moderate, generally coming out of the west, keeping higher rainfall accumulations east and south of T&T.

By mid to late Tuesday, a surge of Saharan Dust is forecast to move across T&T and linger through the end of the week, gradually reducing in concentrations. Low to mid-levels are forecast to become increasingly drier as a surface-to-mid-level ridge establishes itself across the region again.

By late Thursday, Tropical Wave 20 will be approaching the region, with isolated showers and an increase in cloudiness forecast by Friday, where localized climatic effects – sea breeze convergence and daytime heating – may trigger a few late morning through afternoon showers and thunderstorms.

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