Forecast: Tropical Wave 09 To Bring Showers, Thunderstorms. Then, Saharan Dust Returns

Tropical Wave 09 is forecast to begin affecting Trinidad and Tobago early Wednesday morning, with periodic showers and thunderstorms into early Thursday. Saharan Dust is forecast to return on Thursday, leading to mostly dry conditions through the weekend.

What you need to know

Saharan Dust: Minimal to no Saharan Dust is present across T&T on Tuesday, with a gradual increase in dust concentrations on Wednesday. By Thursday, moderate to high concentrations of Saharan Dust returns to T&T.
Rainfall: On Wednesday, periods of light to moderate rain, heavy to violent showers, and isolated thunderstorms are forecast, continuing into early Thursday. Highly isolated showers are possible for the remainder of the week.
Hazards: The main hazards remain street/flash flooding on Wednesday, with the gusty wind threat (up to and in excess of 45 KM/H) increasing overnight into Thursday. The chances for riverine flooding across the Caroni and North Oropouche river basins are medium to high, with low to medium chances across the Ortoire, South Oropouche, and other smaller river basins. 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 for the country.

The Forecast

Tuesday – Approach Of Tropical Wave 09

Tuesday – Approach Of Tropical Wave 09
5 10 0 1
Increasing cloudiness with brief passing showers. There is a low to medium chance of an isolated thunderstorm, favoring eastern and southern areas of the country. Street/flash flooding is possible, accompanying heavier showers and thunderstorms.
Increasing cloudiness with brief passing showers. There is a low to medium chance of an isolated thunderstorm, favoring eastern and southern areas of the country. Street/flash flooding is possible, accompanying heavier showers and thunderstorms.
5/10
Thunderstorm Chances
Medium

Wednesday – Tropical Wave 09

Wednesday – Tropical Wave 09
7 10 0 1
Variably cloudy conditions interrupted by light to moderate showers across the country. By the mid to late morning, isolated to scattered heavy showers and thunderstorms are forecast across both islands, with heavier rainfall favoring eastern Trinidad. Lingering cloudiness with light to moderate rainfall forecast into the night with isolated thunderstorms possible. Street/flash flooding, gusty winds likely. Smaller streams and tributaries to the North Oropuche and Caroni Rivers may flood low-lying areas.
Variably cloudy conditions interrupted by light to moderate showers across the country. By the mid to late morning, isolated to scattered heavy showers and thunderstorms are forecast across both islands, with heavier rainfall favoring eastern Trinidad. Lingering cloudiness with light to moderate rainfall forecast into the night with isolated thunderstorms possible. Street/flash flooding, gusty winds likely. Smaller streams and tributaries to the North Oropuche and Caroni Rivers may flood low-lying areas.
7/10
Thunderstorm Chances
High

Thursday – Saharan Dust Surge

Thursday – Saharan Dust Surge
4 10 0 1
Variably cloudy and hazy skies interrupted by passing showers. Isolated showers favoring northern and eastern Trinidad, as well as Tobago could become heavy or thundery. A mostly settled night is forecast, barring the odd shower. Street flooding possible, favoring Tobago. Gusty winds likely to accompany rainfall activity.
Variably cloudy and hazy skies interrupted by passing showers. Isolated showers favoring northern and eastern Trinidad, as well as Tobago could become heavy or thundery. A mostly settled night is forecast, barring the odd shower. Street flooding possible, favoring Tobago. Gusty winds likely to accompany rainfall activity.
4/10
Thunderstorm Chances
Low – Medium

Friday

Friday
1 10 0 1
Hazy, breezy and partly cloudy, interrupted by brief, passing showers favoring eastern and southern areas.
Hazy, breezy and partly cloudy, interrupted by brief, passing showers favoring eastern and southern areas.
1/10
Thunderstorm Chances
Very Low

Saturday

Saturday
1 10 0 1
Hazy, breezy and partly cloudy, interrupted by brief, passing showers favoring eastern and southern areas. Mostly hazy and settled night.
Hazy, breezy and partly cloudy, interrupted by brief, passing showers favoring eastern and southern areas. Mostly hazy and settled night.
1/10
Thunderstorm Chances
Very Low

Sunday

Sunday
1 10 0 1
Hazy, breezy and partly cloudy, interrupted by brief, passing showers favoring eastern and southern areas. Mostly hazy and settled night.
Hazy, breezy and partly cloudy, interrupted by brief, passing showers favoring eastern and southern areas. Mostly hazy and settled night.
1/10
Thunderstorm Chances
Very Low

Marine: Seas are forecast to be mostly moderate, with waves generally up to 2.0 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. King tides are also forecast through Friday, June 17th, 2022. Mariners and beachgoers should exercise caution due to stronger tidal currents.

Temperatures

Through the forecast period, the minimum low in Trinidad and Tobago is forecast to be between 23.0°C and 26.0°C.

Maximum highs across the country are forecast to be generally up to 31.0°C in Trinidad and Tobago. In urbanized areas like Port of Spain, Scarborough, San Fernando, and Chaguanas, the maximum high temperatures could exceed 32.0°C.

On Wednesday, temperatures are forecast to be cooler overall due to increased cloud cover and anticipated rainfall.

Forecast Impacts

Flooding

Flooding
8 10 0 1
Over the next five days, between 10 and 25 millimeters of rainfall is forecast across most of the country. Most of the rainfall is forecast on Wednesday. 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 10 and 25 millimeters of rainfall is forecast across most of the country. Most of the rainfall is forecast on Wednesday. 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.
8/10
Likelihood
High – Very High

There is a high to a very chance of street and flash flooding, mainly on Wednesday, when the heaviest rainfall is expected over the five-day forecast period. Chances of riverine flooding are now at medium to high, particularly across the North Oropuche and Caroni River Basins. Particular attention should also be paid to the Ortoire River Basin, where upwards of 50 millimeters of rain are possible.

Forecast Rainfall Totals

  • Wednesday: Between 5 and 20 millimeters across the country, trending higher across southern and 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.
  • Thursday: Between 5 and 15 millimeters across the country, trending higher across southern and eastern Trinidad with isolated totals up to 20 millimeters.
  • Friday: Less than 5 millimeters of rain across the country, with isolated higher pockets favoring eastern and southern coastal areas.
  • Saturday: Less than 5 millimeters of rain across the country, with isolated higher pockets favoring eastern and southern coastal areas.
  • Sunday: Less than 5 millimeters of rain across the country, with isolated higher pockets favoring eastern and southern coastal areas.

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 highly favorable atmospheric environment, strong thunderstorms are possible during the early morning through the early afternoon.
On Monday, under a highly favorable atmospheric environment, strong thunderstorms are possible during the early morning through the early afternoon.
2/10
Likelihood
Very Low – Low

While thunderstorms are forecast through Thursday, strong wind shear and Saharan Dust (during the latter half of the week) will limit strong thunderstorms from forming.

Funnel cloud development will remain possible as low-level winds continue to be light through Wednesday afternoon but increase by Wednesday night. 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 likely, with heavy to violent rainfall rates in thunderstorms.

Gusty Winds

Gusty Winds
7 10 0 1
Following the passage of Tropical Wave 09 on Wednesday afternoon, low-level winds are forecast to pick back up by Wednesday evening. Sustained winds up to 30 KM/H are forecast, with gusts up to and in excess of 45 KM/H through Friday. Stronger winds and gusts will accompanying heavy shower or thunderstorm activity.
Following the passage of Tropical Wave 09 on Wednesday afternoon, low-level winds are forecast to pick back up by Wednesday evening. Sustained winds up to 30 KM/H are forecast, with gusts up to and in excess of 45 KM/H through Friday. Stronger winds and gusts will accompanying heavy shower or thunderstorm activity.
7/10
Likelihood
High

With wind gusts up to and in excess of 50 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

As rainfall continues through the week and soils become increasingly saturated, landslides are possible across elevated areas of Tobago, eastern and northern Trinidad.

Saharan Dust will increase by late Wednesday into Thursday, 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 Tuesday through Wednesday, becoming isolated by Thursday and highly isolated into the weekend.

Forecast Discussion

Tropical Waves East of T&T: Based on the Tropical Analysis and Forecast Branch’s 18Z surface analysis on June 14th, 2022, as well as the latest satellite and model guidance:

  • The ninth tropical wave for 2022 is along 54/55°W, south of 15°N, moving west at 15 knots (27 KM/H). This wave is forecast to move across Trinidad and Tobago on Wednesday. Scattered moderate to isolated strong convection is ongoing, mainly near the wave axis.
  • The tenth tropical wave for 2022 is along 19°W, south of 15°N, and moving west at 15 knots (27 KM/H). This wave is forecast to move across T&T on Monday, June 20th, 2022. Scattered moderate showers have been noted near the wave axis.

Following a very wet Tropical Wave 08 (TW08) on Monday, sending multiple rivers across eastern and northern Trinidad to threshold levels, Tropical Wave 09 (TW09) is forecast to bring an additional round of rainfall to the country on Wednesday. Overall rainfall totals are forecast to be substantially less than what was recorded on Monday.

The axis of TW09 is forecast to move across the region by Wednesday afternoon. Lingering moisture from TW08 and ahead of TW09 will fuel cloudiness, showers, and thunderstorms from early Wednesday through early Thursday. Upper-level and low-level atmospheric conditions will be slightly favorable, supportive of heavy showers and moderate thunderstorm activity.

Strong westerly to southwesterly wind shear (up to 50 knots) will persist, keeping heavier rainfall, showers, and thunderstorms south and east of the country through Wednesday. On Thursday, wind shear will briefly weaken, allowing showers or thunderstorms to persist. However, the upper-level trough that has lingered for the last several days will begin to move away from the area, reducing favorable upper-level conditions. A deep-layered high-pressure system is forecast to rebuild, particularly by Thursday afternoon into the evening.

This high-pressure system will allow for breezy and mostly stable weather across the country. Saharan Dust concentrations will also increase to moderate/high levels, remaining across the region through the weekend.

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