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Forecast: Tropical Wave 10 To Bring Rainfall To T&T

June 19, 2022
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Tropical Wave 10 is forecast to begin affecting Trinidad and Tobago late Monday morning, with periodic showers and thunderstorms into early Tuesday. Saharan Dust is forecast to return by Monday night into Tuesday, leading to mostly dry conditions throughout the week.

What you need to know

— Saharan Dust: Mild Saharan Dust is forecast to be present across T&T on Monday, with a gradual increase in dust concentrations overnight into Tuesday. Through the week, moderate to high concentrations of dust are forecast.
— Rainfall: On Monday through mid-Tuesday, periods of light to moderate rain, heavy to violent showers, and isolated thunderstorms are forecast. Highly isolated showers and afternoon thunderstorms are possible for the remainder of the week.
— Hazards: The main hazards remain street/flash flooding on Monday, with gusty winds (up to and in excess of 45 KM/H) accompanying heavy showers or thunderstorms. The chances for riverine flooding remain low. Lightning will accompany thunderstorms.
— Alerts/Watches/Warnings: There are no alerts, watches, or warnings in effect from the Trinidad and Tobago Meteorological Service at this time. There are also no tropical threats facing Trinidad and Tobago over the next five-day period.

The Forecast

Sunday Night – Approach Of Tropical Wave 10

Sunday Night – Approach Of Tropical Wave 10
1 10 0 1
Mostly hazy, breezy, and partly cloudy with brief passing showers.
Mostly hazy, breezy, and partly cloudy with brief passing showers.
1/10
Thunderstorm Chances
Very Low

Monday – Tropical Wave 10

Monday – Tropical Wave 10
7 10 0 1
Mostly sunny initially, with increasing cloudiness by the late morning. Showers and isolated thunderstorms are forecast to begin affecting eastern areas of Trinidad and Tobago from the late morning, gradually spreading across the country shortly before midday. Mostly cloudy to overcast skies are forecast from the afternoon, interrupted by periods of light to moderate rain and isolated heavy/violent showers and/or thunderstorms, persisting into the night. Gusty winds and street/flash flooding are possible.
Mostly sunny initially, with increasing cloudiness by the late morning. Showers and isolated thunderstorms are forecast to begin affecting eastern areas of Trinidad and Tobago from the late morning, gradually spreading across the country shortly before midday. Mostly cloudy to overcast skies are forecast from the afternoon, interrupted by periods of light to moderate rain and isolated heavy/violent showers and/or thunderstorms, persisting into the night. Gusty winds and street/flash flooding are possible.
7/10
Thunderstorm Chances
High

Tuesday – Saharan Dust Surge

Tuesday – Saharan Dust Surge
6 10 0 1
Early morning showers and isolated thunderstorms are forecast to favor offshore areas initially, spreading mainly across the country. Showers and thunderstorms are forecast to interrupt variably cloudy and increasingly hazy skies through the early afternoon, becoming settled mainly by the late afternoon barring the odd shower. A mostly settled and hazy night is forecast, with a low chance of an offshore thunderstorm, especially south/southeast of Trinidad. Gusty winds and street/flash flooding are possible.
Early morning showers and isolated thunderstorms are forecast to favor offshore areas initially, spreading mainly across the country. Showers and thunderstorms are forecast to interrupt variably cloudy and increasingly hazy skies through the early afternoon, becoming settled mainly by the late afternoon barring the odd shower. A mostly settled and hazy night is forecast, with a low chance of an offshore thunderstorm, especially south/southeast of Trinidad. Gusty winds and street/flash flooding are possible.
6/10
Thunderstorm Chances
Medium – High

Wednesday

Wednesday
5 10 0 1
Mostly sunny, hazy across both islands, interrupted by the odd shower. There is a medium chance of an isolated heavy shower or thunderstorm favoring southern and western coastal Trinidad from late morning through the afternoon. A mostly settled night.
Mostly sunny, hazy across both islands, interrupted by the odd shower. There is a medium chance of an isolated heavy shower or thunderstorm favoring southern and western coastal Trinidad from late morning through the afternoon. A mostly settled night.
5/10
Thunderstorm Chances
Medium

Thursday

Thursday
3 10 0 1
Mostly sunny, hazy across both islands, interrupted by the odd shower. There is a low chance of an isolated heavy shower or thunderstorm favoring southern and western coastal Trinidad from late morning through the afternoon. A mostly settled night.
Mostly sunny, hazy across both islands, interrupted by the odd shower. There is a low chance of an isolated heavy shower or thunderstorm favoring southern and western coastal Trinidad from late morning through the afternoon. A mostly settled night.
3/10
Thunderstorm Chances
Low

Friday

Friday
3 10 0 1
Mostly sunny, hazy across both islands, interrupted by the odd shower. There is a low chance of an isolated heavy shower or thunderstorm favoring southern and western coastal Trinidad from late morning through the afternoon. A mostly settled night.
Mostly sunny, hazy across both islands, interrupted by the odd shower. There is a low chance of an isolated heavy shower or thunderstorm favoring southern and western coastal Trinidad from late morning through the afternoon. A mostly settled night.
3/10
Thunderstorm Chances
Low

Marine: Seas are forecast to be mostly slight to moderate, with waves generally up to 1.5 meters, during the forecast period in open waters. In sheltered areas, waves are forecast to be between near calm and 1.0 meter but occasionally choppy during heavy showers or thunderstorms.

Temperatures

Through the forecast period, the minimum low in Trinidad and Tobago is forecast to be between 24.0°C and 26.0°C.

Maximum highs across the country are forecast to be generally up to 32.0°C in Trinidad and Tobago. In urbanized areas like Port of Spain, Scarborough, San Fernando, and Chaguanas, the maximum high temperatures could exceed 33.0°C.

From Monday to Tuesday, temperatures are forecast to be cooler due to increased cloud cover and anticipated rainfall.

Forecast Impacts

Flooding

Flooding
6 10 0 1
Over the next five days, between 25 and 50 millimeters of rainfall is forecast across most of the country. Most of the rainfall is forecast on Monday into Tuesday. Lower rainfall totals are forecast across northwestern/west-central areas of Trinidad while higher totals are forecast across the eastern half of Trinidad. In highly isolated areas, overall five-day rainfall totals could exceed 50 millimeters.
Over the next five days, between 25 and 50 millimeters of rainfall is forecast across most of the country. Most of the rainfall is forecast on Monday into Tuesday. Lower rainfall totals are forecast across northwestern/west-central areas of Trinidad while higher totals are forecast across the eastern half of Trinidad. In highly isolated areas, overall five-day rainfall totals could exceed 50 millimeters.
6/10
Likelihood
Medium – High

There is a medium to high chance of street and flash flooding, mainly on Monday into Tuesday, when the heaviest rainfall is expected over the five-day forecast period. Chances of riverine flooding are very low.

Forecast Rainfall Totals

  • Monday: Between 5 and 20 millimeters across the country, trending higher across eastern areas of Trinidad with isolated totals up to and in excess of 25 millimeters. In highly isolated areas, upwards of 30 millimeters are possible, favoring eastern Trinidad.
  • Tuesday: Between 0 and 10 millimeters across the country, trending higher across southern and eastern Trinidad with isolated totals up to 15 millimeters.
  • Wednesday: Less than 5 millimeters of rain across the country, with isolated higher pockets up to 10 millimeters favoring eastern and southern coastal areas and isolated areas along western coastal Trinidad.
  • Thursday: Less than 5 millimeters of rain across the country, with isolated higher pockets favoring southern coastal areas.
  • Friday: Between 0 and 10 millimeters across the country, trending higher across southern and eastern Trinidad with isolated totals up to 15 millimeters.

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
2 10 0 1
On Monday, under a marginally favorable atmospheric environment, chances for strong thunderstorms remain fairly low.
On Monday, under a marginally favorable atmospheric environment, chances for strong thunderstorms remain fairly low.
2/10
Likelihood
Very Low – Low

While thunderstorms are forecast for Monday through Tuesday, with low chances for an isolated thunderstorm during the week, Saharan Dust will be one of the limiting factors. While wind shear is forecast to be fairly weak on Monday into Tuesday, shear will increase through the week, decreasing persisting convective activity.

Funnel cloud development will remain possible as low-level winds continue to be light through the week. 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.

Throughout the week, frequent cloud-to-ground lightning will be possible in thunderstorm activity.

Gusty Winds

Gusty Winds
6 10 0 1
While winds across the region are forecast to remain light, with under a low-shear and low-wind speed environment, strong gusts could accompany heavier thunderstorms or shower activity. Sustained winds up to 30 KM/H are forecast, with gusts up to and in excess of 45 KM/H possible. Stronger winds and gusts will accompanying heavy shower or thunderstorm activity.
While winds across the region are forecast to remain light, with under a low-shear and low-wind speed environment, strong gusts could accompany heavier thunderstorms or shower activity. Sustained winds up to 30 KM/H are forecast, with gusts up to and in excess of 45 KM/H possible. Stronger winds and gusts will accompanying heavy shower or thunderstorm activity.
6/10
Likelihood
Medium – High

With wind gusts up to and in excess of 45 KM/H, whole trees are expected to be in motion, and there may be some inconvenience when walking against the wind gusts. 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

Saharan Dust will increase on Tuesday and remain at elevated concentrations throughout the week, reducing air quality and affecting visibility.

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 to scattered rainfall Monday through Tuesday, becoming highly isolated into the remainder of the week.

Forecast Discussion

Tropical Waves East of T&T: Based on the Tropical Analysis and Forecast Branch’s 18Z surface analysis on June 19th, 2022, as well as the latest satellite and model guidance:

  • The 10th tropical wave for 2022 is along 53/54°W, south of 16°N, moving west at 10-15 knots (18.5-27 KM/H). Scattered moderate to isolated strong convection is ongoing, mainly near the wave axis. This wave is forecast to move across Trinidad and Tobago on Monday.
  • The 11th tropical wave for 2022, yet to be analyzed by the National Hurricane Center, is along 23/24°W, south of 20°N with a 1010 millibar area of low pressure and embedded within the monsoon trough (similar to the Intertropical Convergence Zone, but with a slightly different motion of wind convergence). This low pressure and wave area are moving west at 15 knots (27 KM/H). This wave is forecast to move across T&T on Sunday, June 26th, 2022.

After a much welcome sunny (albeit hazy) weekend, showers and isolated thunderstorms are forecast to return as Tropical Wave 10 (TW10) approaches Trinidad and Tobago, moving across on Monday.

TW10 is located between two high-concentration areas of Saharan Dust, with deep, tropical moisture moving in tandem with the wave axis. This high moisture area will fuel showers, thunderstorms, and cloudiness through Tuesday. Wind shear will be reduced during the period of this wave passage, between near zero to 20 knots, allowing for persisting shower or thunderstorm activity.

Following the wave’s passage on Monday, a high-pressure ridge will sweep back in on Tuesday evening, leading to mostly settled conditions through much of the week with low-level cloud patches bringing brief showers. Wind shear will also increase to 20 to 30 knots from the west, limiting persisting shower or thunderstorm activity.

While mostly settled conditions are expected, skies will not be entirely clear. A surge of Saharan Dust will be moving in on Tuesday and lingering through the week and weekend with moderate to high concentrations. Both air quality and visibility are forecast to be reduced.

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