Tropical Wave 11 Forecast To Bring Inclement Weather To T&T

Tropical Wave 11 will begin affecting Trinidad and Tobago on Sunday morning, with periodic showers and thunderstorms into early Monday.

What you need to know

Saharan Dust: Following Tropical Wave 11, a mild to moderate Saharan Dust surge is forecast to briefly affect T&T on Monday into early Tuesday, ahead of Tropical Wave 12/Invest 94L.
Rainfall: On Sunday through early Monday, periods of light to moderate rain, heavy to violent showers, and isolated thunderstorms are forecast. A resurgence of activity is also forecast on Monday night into Tuesday.
Hazards: The main hazards remain street/flash flooding 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: The Adverse Weather Alert (Yellow Level) was discontinued by the Trinidad and Tobago Meteorological Service at 3:29 PM Sunday. There are now no alerts/watches/warnings in effect for T&T at this time. There are also no tropical storm or hurricane watches or warnings in effect for T&T at this time.

The Forecast

Sunday – Tropical Wave 11 & ITCZ

Sunday – Tropical Wave 11 & ITCZ
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Initially partly cloudy, hazy, becoming overcast as the morning progresses with periods of light to moderate rain, heavy to violent showers and isolated to scattered thunderstorms. Stronger thunderstorms are forecast to affect T&T from the late morning (10 AM onwards), beginning across southeastern areas and gradually spread across the country. Conditions are forecast to gradually settle by the late afternoon with lingering rain and cloudy skies. Isolated thunderstorms and heavy showers are forecast after nightfall, interrupting cloudy skies, Street/flash flooding, gusty winds likely!
Initially partly cloudy, hazy, becoming overcast as the morning progresses with periods of light to moderate rain, heavy to violent showers and isolated to scattered thunderstorms. Stronger thunderstorms are forecast to affect T&T from the late morning (10 AM onwards), beginning across southeastern areas and gradually spread across the country. Conditions are forecast to gradually settle by the late afternoon with lingering rain and cloudy skies. Isolated thunderstorms and heavy showers are forecast after nightfall, interrupting cloudy skies, Street/flash flooding, gusty winds likely!
8/10
Thunderstorm Chances
High – Very High

Monday – Saharan Dust

Monday – Saharan Dust
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Showers and thunderstorms are forecast during the early morning, favoring Trinidad, with isolated activity across Tobago. From daybreak, mostly sunny and hazy skies are forecast through the day with isolated showers and thunderstorm activity developing across mainly western and southern Trinidad by the late morning through the afternoon, settling into the evening. By nightfall, isolated showers and thunderstorms are forecast to return across T&T with heavier activity favoring southern and eastern Trinidad. Street/flash flooding, gusty winds possible!
Showers and thunderstorms are forecast during the early morning, favoring Trinidad, with isolated activity across Tobago. From daybreak, mostly sunny and hazy skies are forecast through the day with isolated showers and thunderstorm activity developing across mainly western and southern Trinidad by the late morning through the afternoon, settling into the evening. By nightfall, isolated showers and thunderstorms are forecast to return across T&T with heavier activity favoring southern and eastern Trinidad. Street/flash flooding, gusty winds possible!
4/10
Thunderstorm Chances
Low – Medium

Tuesday – Approaching Invest 94L

Tuesday – Approaching Invest 94L
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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 partly to mostly cloudy and decreasing hazy skies with initial peak thunderstorm and heavy shower activity during the late morning through the afternoon. Increasing cloudiness, widespread rain, showers (heavy/violent) and thunderstorms are forecast by the evening and persisting into the night with overall heavier activity favoring Tobago, northern and eastern Trinidad. Winds may gust in excess of 65 KM/H particularly across Tobago. Street/flash flooding, landslides, localized wind damage and agitated seas likely!
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 partly to mostly cloudy and decreasing hazy skies with initial peak thunderstorm and heavy shower activity during the late morning through the afternoon. Increasing cloudiness, widespread rain, showers (heavy/violent) and thunderstorms are forecast by the evening and persisting into the night with overall heavier activity favoring Tobago, northern and eastern Trinidad. Winds may gust in excess of 65 KM/H particularly across Tobago. Street/flash flooding, landslides, localized wind damage and agitated seas likely!
8/10
Thunderstorm Chances
High – Very High

Marine: Through early Tuesday, seas are forecast to be moderate, with waves generally between 1.5 and 2.5 meters in open waters. In sheltered areas, waves are forecast to be near 1.0 meter and choppy, particularly during heavy showers or thunderstorms. From mid-Tuesday, open waters particularly east of T&T, will be rough to very rough, with waves up to 4.0 meters, particularly north and east of Tobago. For the remainder of T&T’s open waters, seas will be rough, with waves between 2.5 and 3.0 meters. In sheltered areas, seas will be up to 1.5 meters. For the southwestern Gulf of Paria, seas will be particularly agitated on Tuesday night with waves up to 2.0 meters, while on Wednesday morning, hazardous seas shift to the northwestern Gulf of Paria.

Invest 94L is being monitored by the National Hurricane Center for tropical cyclone formation. Forecast models indicate this system could become a tropical depression or a tropical storm, moving north of Tobago, by Tuesday night into Wednesday morning. Based on the proximity to T&T, Tuesday’s weather and marine forecast may change.

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 30.0°C in Trinidad and Tobago. In urbanized areas like Port of Spain, Scarborough, San Fernando, and Chaguanas, the maximum high temperatures could exceed 30.0°C.

Through Thursday, temperatures are forecast to be cooler due to increased cloud cover and anticipated rainfall.

Forecast Impacts

Flooding

Flooding
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Particularly due to the influence of Tropical Wave 11 and the eventual system that originates from Tropical Wave 12/Invest 94L, significant rainfall is forecast across T&T over the next three to five days. Through Tuesday, before the passage of Invest 94L, Over the next five days, between 25 and 75 millimeters of rainfall is forecast across most of the country. Lower rainfall totals are forecast across northwestern/west-central areas of Trinidad while higher totals are forecast across the eastern and southern halves of Trinidad, as well as Tobago. In isolated areas, overall three-day rainfall totals could exceed 100 millimeters.
Particularly due to the influence of Tropical Wave 11 and the eventual system that originates from Tropical Wave 12/Invest 94L, significant rainfall is forecast across T&T over the next three to five days. Through Tuesday, before the passage of Invest 94L, Over the next five days, between 25 and 75 millimeters of rainfall is forecast across most of the country. Lower rainfall totals are forecast across northwestern/west-central areas of Trinidad while higher totals are forecast across the eastern and southern halves of Trinidad, as well as Tobago. In isolated areas, overall three-day rainfall totals could exceed 100 millimeters.
8/10
Likelihood
High – Very High

There is a high to a very chance of street and flash flooding. While initial chances for riverine flooding remain low, by Tuesday into Wednesday, these chances are forecast to increase across all river basins in Trinidad substantially.

Forecast Rainfall Totals

  • Sunday: Between 5 and 25 millimeters across the country, trending higher across northeastern areas of Trinidad and across Tobago with totals up to and in excess of 35 millimeters. In highly isolated areas, upwards of 35 millimeters are possible, favoring eastern Trinidad and Tobago.
  • Monday: Between 5 and 25 millimeters across the country, trending higher across southern and eastern Trinidad with isolated totals up to 30 millimeters.
  • Tuesday (through midnight): Between 10 and 25 millimeters across the country, trending higher across northeastern areas of Trinidad and across Tobago with totals up to and in excess of 45 millimeters. In highly isolated areas, upwards of 60 millimeters are possible, favoring eastern and southern Trinidad and Tobago.

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
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On Sunday, under a highly favorable atmospheric environment, chances for strong thunderstorms are medium to high.
On Sunday, under a highly favorable atmospheric environment, chances for strong thunderstorms are medium to high.
6/10
Likelihood
Medium – High

With minimal to no wind shear, a highly moist atmosphere, and light low-level winds, strong to severe thunderstorms are possible, with medium to high chances on Sunday. Low to mid-level conditions become drier on Monday into the first half of Tuesday, reducing the severe potential.

Funnel cloud development is possible. 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.

Frequent cloud-to-ground lightning will be possible in thunderstorm activity.

Gusty Winds

Gusty Winds
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While low-level 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 likely. Stronger winds and gusts, up to and in excess of 55 KM/H are possible, accompanying heavy shower or thunderstorm activity.
While low-level 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 likely. Stronger winds and gusts, up to and in excess of 55 KM/H are possible, accompanying heavy shower or thunderstorm activity.
6/10
Likelihood
Medium – High

With wind gusts up to and in excess of 55 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 Monday through the first half of Tuesday, briefly 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 Sunday through Tuesday.

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 11th tropical wave for 2022 (TW11) is along 55/56°W, south of 16°N, moving west at 15 knots (27 KM/H). Scattered moderate to isolated strong convection is ongoing. This wave is forecast to move across Trinidad and Tobago tonight (Sunday night).
  • The 12th tropical wave for 2022 (TW12) is along 40°W, south of 15°N, moving west at 15 knots (27 KM/H). This wave is being monitored for tropical development. As of the 2:00 AM Tropical Weather Outlook from the National Hurricane Center, it has a high chance of development over the next five days. Regardless of development, heavy rainfall and gusty winds will likely affect countries from T&T to St. Lucia on Tuesday evening into Wednesday morning as it moves across the Windwards.
  • The 13th tropical wave for 2022 (TW13) is along 26/27°W, south of 15°N, moving west at 15 knots (27 KM/H). Few showers are observed near the wave axis. This wave is forecast to move across Trinidad, Tobago, and the remainder of the Lesser Antilles on Friday into Saturday.

This forecast discussion will focus on Tropical Wave 11. Follow the latest tropical updates for those interested in Tropical Wave 12/Invest 94L’s possible impacts.

An active tropical wave (TW11) is forecast to move across Trinidad and Tobago later today (Sunday), dragging the Intertropical Convergence Zone across the country and bringing scattered showers and thunderstorms. This wave is being enhanced by an upper-level trough, producing favorable upper-level divergence, leading to stronger shower and thunderstorm activity. Compounding the favorable atmospheric conditions on Sunday are marginal to no vertical wind shear and a highly moist environment.

This wave will move out of the area by Monday morning, with a brief mild to a moderate surge of Saharan Dust sweeping in by mid-Monday, drying out the low to mid-levels of the atmosphere. However, with the Intertropical Convergence Zone remaining nearby and trailing moisture following the wave axis, cloudiness, isolated showers, and thunderstorms remain in the forecast on Monday into Tuesday.

Current model guidance indicates Tropical Wave 12/Invest 94L or whatever tropical system evolves from the tropical disturbance will begin to affect Tobago by Tuesday evening and Trinidad by Tuesday night.

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