Forecast: Back-to-back Tropical Waves Bring Inclement Weather To T&T

On Monday, due to Tropical Wave 08 and favorable atmospheric conditions, periods of heavy to violent rainfall are forecast associated with thunderstorms and showers. Another, less impactful tropical wave is forecast by Wednesday, with the return of Saharan Dust shortly after.

What you need to know

Saharan Dust: Low levels of Saharan Dust are forecast from Monday through late 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 Monday, periods of light to moderate rain, heavy to violent showers, and isolated thunderstorms are forecast, continuing into early Tuesday. Isolated to scattered showers are possible again on Wednesday, with rainfall subsiding by the latter half of the week.
Hazards: The main hazards remain street/flash flooding from Monday through Wednesday. The chances for riverine flooding across the country remain low at this time. Close attention should be paid to the North and South Oropouche River Basins, as well as the Ortire River Basins through Tuesday. Gusty winds are possible through Wednesday, up to and in excess of 45 KM/H accompanying heavy showers or thunderstorms. Lightning will accompany thunderstorms.
Alerts/Watches/Warnings: The Adverse Weather Alert (Yellow Level) has been discontinued by the Trinidad and Tobago Meteorological Service at 2:34 PM Monday. There are no alerts, watches, or warnings in effect for T&T at this time.

The Forecast

Sunday Night – Approach of Tropical Wave 08

Sunday Night – Approach of Tropical Wave 08
7 10 0 1
Variably cloudy and hazy skies interrupted by light to moderate showers, favoring Trinidad and eastern Tobago. Isolated heavy showers and thunderstorms are also forecast, mainly favoring southern Trinidad initially, gradually spreading across the country overnight. Gusty winds likely. Street flooding possible.
Variably cloudy and hazy skies interrupted by light to moderate showers, favoring Trinidad and eastern Tobago. Isolated heavy showers and thunderstorms are also forecast, mainly favoring southern Trinidad initially, gradually spreading across the country overnight. Gusty winds likely. Street flooding possible.
7/10
Thunderstorm Chances
High

Monday – Tropical Wave 08

Monday – Tropical Wave 08
9 10 0 1
Variably cloudy conditions, interrupted by periods of light to moderate rain, heavy to violent showers and isolated to scattered thunderstorms. Peak inclement weather is forecast from the early morning through the early afternoon. Conditions to gradually improve through the late afternoon into the evening with cloudy skies persisting. Lingering showers/rain to favor southern and eastern Trinidad, as well as Tobago. Street/flash flooding is highly likely, with gusty winds possible, accompanying heavier showers and thunderstorms.
Variably cloudy conditions, interrupted by periods of light to moderate rain, heavy to violent showers and isolated to scattered thunderstorms. Peak inclement weather is forecast from the early morning through the early afternoon. Conditions to gradually improve through the late afternoon into the evening with cloudy skies persisting. Lingering showers/rain to favor southern and eastern Trinidad, as well as Tobago. Street/flash flooding is highly likely, with gusty winds possible, accompanying heavier showers and thunderstorms.
9/10
Thunderstorm Chances
Very High

Tuesday – Lingering Influence Of Tropical Wave 08

Tuesday – Lingering Influence Of Tropical Wave 08
8 10 0 1
Early morning showers and isolated thunderstorms to favor northern and offshore areas of Trinidad, as well as Tobago, gradually increasing through the day, interrupting partly to mostly cloudy skies. By the late morning, isolated heavy showers and thunderstorms are forecast to develop along northern and western Trinidad, as well as across Tobago, gradually spreading across the country. Lingering showers are forecast through the evening and night, with isolated thunderstorms favoring eastern coastal areas of Trinidad and Tobago. Street/flash flooding is highly likely, with gusty winds possible, accompanying heavier showers and thunderstorms.
Early morning showers and isolated thunderstorms to favor northern and offshore areas of Trinidad, as well as Tobago, gradually increasing through the day, interrupting partly to mostly cloudy skies. By the late morning, isolated heavy showers and thunderstorms are forecast to develop along northern and western Trinidad, as well as across Tobago, gradually spreading across the country. Lingering showers are forecast through the evening and night, with isolated thunderstorms favoring eastern coastal areas of Trinidad and Tobago. Street/flash flooding is highly likely, with gusty winds possible, accompanying heavier showers and thunderstorms.
8/10
Thunderstorm Chances
High – Very High

Wednesday – Tropical Wave 09

Wednesday – Tropical Wave 09
7 10 0 1
Variably cloudy skies interrupted by isolated early morning showers and thunderstorms to favor offshore areas, gradually spreading across the country. By the late morning through the afternoon, isolated to scattered heavy showers and thunderstorms are forecast across the northern and western halves of Trinidad, as well as Tobago. Increasingly hazy and breezy conditions are forecast into the evening, with lingering showers through the night. Isolated thunderstorms to favor offshore areas. Street/flash flooding is likely. Gusty winds are possible through the day, becoming likely with overnight showers or thunderstorms.
Variably cloudy skies interrupted by isolated early morning showers and thunderstorms to favor offshore areas, gradually spreading across the country. By the late morning through the afternoon, isolated to scattered heavy showers and thunderstorms are forecast across the northern and western halves of Trinidad, as well as Tobago. Increasingly hazy and breezy conditions are forecast into the evening, with lingering showers through the night. Isolated thunderstorms to favor offshore areas. Street/flash flooding is likely. Gusty winds are possible through the day, becoming likely with overnight showers or thunderstorms.
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. 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. Street flooding possible, favoring Tobago. Gusty winds likely to accompany rainfall activity.
4/10
Thunderstorm Chances
Low – Medium

Friday

Friday
3 10 0 1
Hazy, breezy and partly cloudy, interrupted by brief, passing showers. There is a low chance of an early morning isolated thunderstorm, favoring southwestern areas into the Gulf of Paria.
Hazy, breezy and partly cloudy, interrupted by brief, passing showers. There is a low chance of an early morning isolated thunderstorm, favoring southwestern areas into the Gulf of Paria.
3/10
Thunderstorm Chances
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 the next five days. 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 22.0°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.

Over the next five days, temperatures are forecast to be cooler overall due to increased cloud cover and anticipated rainfall.

Forecast Impacts

Flooding

Flooding
9 10 0 1
Over the next five days, between 25 and 100 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/north-central areas of Trinidad while higher totals are forecast across the southern and eastern half of Trinidad. In highly isolated areas, overall five-day rainfall totals could exceed 150 millimeters.
Over the next five days, between 25 and 100 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/north-central areas of Trinidad while higher totals are forecast across the southern and eastern half of Trinidad. In highly isolated areas, overall five-day rainfall totals could exceed 150 millimeters.
9/10
Likelihood
Very High

There is a 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 now at medium, particularly across the North Oropuche and Ortoire River Basins as well as the eastern extent of the Caroni River Basin. Particular attention should also be paid to the South Oropouche River Basins, where upwards of 75 millimeters of rain are possible on Monday into Tuesday.

Forecast Rainfall Totals

  • Monday: Rainfall accumulations from 15 to 45 millimeters are forecast across most of the country, trending as high as 75 millimeters across southern and eastern areas of Trinidad and eastern areas of Tobago. Across the southern and eastern halves of Trinidad, rainfall totals could reach or exceed 150 millimeters.
  • Tuesday: Between 5 and 15 millimeters across the country, trending higher across northern and western areas of Trinidad and across Tobago with isolated totals up to and in excess of 25 millimeters.
  • Wednesday: Between 5 and 15 millimeters across the country, trending higher across northern and western areas of Trinidad with isolated totals up to and in excess of 25 millimeters. Across Tobago, isolated totals could reach/exceed 30 millimeters.
  • Thursday: Between 5 and 15 millimeters across the country, trending higher across eastern Trinidad and Tobago with isolated totals up to 25 millimeters. Across Tobago, isolated totals could exceed 25 millimeters.
  • Friday: 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
5 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.
5/10
Likelihood
Medium

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

On Monday, a highly favorable low-level environment will be in place initially, with an increasingly favorable mid- to upper-level environment by the latter half of the day. These conditions may support stronger or severe thunderstorm activity on Monday morning through the early afternoon.

Additionally, funnel cloud development will be possible on Monday through early Wednesday, with light low-level winds and a supportive environment for thunderstorm activity. 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
Low-level winds are forecast to diminish through Wednesday, picking back up by Wednesday night. Sustained winds up to 35 KM/H are forecast, with gusts up to and in excess of 45 KM/H through early Wednesday and up to and in excess of 50 KM/H by late Wednesday through Thursday. Stronger winds and gusts will accompanying heavy shower or thunderstorm activity.
Low-level winds are forecast to diminish through Wednesday, picking back up by Wednesday night. Sustained winds up to 35 KM/H are forecast, with gusts up to and in excess of 45 KM/H through early Wednesday and up to and in excess of 50 KM/H by late Wednesday through Thursday. 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, southern 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.

Scattered to widespread rainfall is forecast on Monday, isolated to scattered rainfall Tuesday through Wednesday, becoming isolated by Thursday and highly isolated by Friday.

Forecast Discussion

Tropical Waves East of T&T: Based on the Tropical Analysis and Forecast Branch’s 18Z surface analysis on June 12th, 2022, as well as the latest satellite and model guidance:

  • The eighth tropical wave for 2022 is along 55/56°W, south of 20°N, moving west at 20 knots (37 KM/H). This wave is forecast to move across Trinidad and Tobago overnight tonight (Sunday) into Monday. Scattered moderate to isolated strong convection is ongoing, mainly near the coast of South America.
  • The ninth tropical wave for 2022 is along 35°W, south of 14°N, and moving west at 20 knots (37 KM/H). This wave is forecast to move across T&T late Tuesday, June 14th, 2022, into Wednesday, June 15th, 2022. Few showers have been noted near the wave axis.

Trinidad is set to see some of the highest 24-hour rainfall totals for 2022 to date on Monday as a highly moist and favorable environment associated with the approach and passage of Tropical Wave 08 will fuel heavy showers and thunderstorms.

The wave has a large moisture envelope. Low-level conditions will be favorable through Monday morning. In contrast, upper-level conditions become increasingly favorable as the day progresses due to an upper-level trough drifting westward, placing T&T and much of the Windwards under an upper-level diffluent pattern (winds move away and apart, enhancing convection).

Lingering, abundant moisture from Tropical Wave 08, favorable upper-level conditions, and a weakening of low-level winds will allow for additional, slow-moving showers and thunderstorms on Tuesday.

Strong westerly to southwesterly wind shear (up to 60 knots) will persist, keeping heavier rainfall, showers, and thunderstorms south and east of the country through Tuesday.

Tropical Wave 09 is forecast to enter the region by Wednesday, under similar conditions as the last two days, and bring additional inclement weather and increased low-level winds by Wednesday evening. However, most rainfall is set to occur north of Trinidad, potentially placing Tobago in the crosshairs of additional flooding rainfall by Wednesday into Thursday.

From here, uncertainty increases. Dust models show a gradual rise in Saharan Dust from Wednesday, with high concentrations returning by Thursday. Saharan Dust negatively impacts rainfall, resulting in cloudy and hazy but dry weather. The ECMWF shows precipitation still occurring as Tropical Wave 09 moves west, but much lower overall rainfall totals. The GFS, on the other hand, shows higher rainfall totals both on Wednesday and Thursday, with a trailing band of showers and thunderstorms mainly affecting Northern Trinidad and Tobago, seemingly unphased by the increase in dust. For now, the forecast for Wednesday into Thursday lies closer to the GFS solution, as other top global models, like the UKMET and Australia’s ACCESS-G, indicate a similar setup to the GFS.

By Friday into the weekend, though, the atmosphere dries out as a deep-layered high-pressure ridge returns, along with our dusty norm – Saharan Dust.

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