Forecast: Tropical Disturbance Brings Heavy Showers & Thunderstorms

Over the next 48 hours, showers and thunderstorms are forecast to affect Trinidad and Tobago due to the passage of a tropical disturbance, Invest 98L. T&T is set to experience the heaviest rains from this system while the strongest winds generally remain north of the country.

What you need to know

Rainfall: Scattered showers and thunderstorms are forecast through Thursday afternoon, with isolated activity continuing through Friday. Over the next three days, rainfall accumulations between 50 and 125 millimeters are forecast. Higher rainfall totals are generally forecast across Trinidad and Tobago, where isolated totals can reach up to 150 millimeters.
Hazards: Street/flash flooding is expected. Chances for riverine flooding will increase through the next 12-24 hours. Gusty winds in excess of 70 KM/H accompanying heavy showers or thunderstorms are likely, with wind gusts in excess of 55 KM/H expected. Stronger wind gusts are expected across Tobago and northern Trinidad. Lightning will accompany thunderstorms. Landslides are possible in elevated areas. Seas are forecast to become agitated.
Alerts/Watches/Warnings: A Riverine Flood Alert (Yellow Level) went into effect for the South Oropouche River Basin from 9:00 AM Thursday, September 22nd, 2022, and remains in effect through 9:00 AM Saturday, September 24th, 2022, from the Trinidad and Tobago Meteorological Service. A Riverine Flood Alert (Yellow Level) went into effect for the South Oropouche River Basin from 9:00 AM Thursday, September 22nd, 2022, and remains in effect through 9:00 AM Saturday, September 24th, 2022. The Adverse Weather Alert (Yellow Level) was discontinued at 7:37 PM Thursday, September 22nd, 2022, from the Trinidad and Tobago Meteorological Service. There are no tropical storm or hurricane watches or warnings in effect for T&T at this time.
Saharan Dust: Dust concentrations are forecast to gradually diminish over the next 12-18 hours, with no major dust surges across T&T through the next ten days.

The Forecast

Wednesday

Wednesday
9 10 0 1
Intervals of showers and thunderstorms are forecast to interrupt cloudy skies across both islands through the day. Peak intense activity is forecast during the late morning and continue through the night with widespread moderate to heavy showers/rain and thunderstorms. Street/flash flooding, gusty winds, frequent lightning are expected.
Intervals of showers and thunderstorms are forecast to interrupt cloudy skies across both islands through the day. Peak intense activity is forecast during the late morning and continue through the night with widespread moderate to heavy showers/rain and thunderstorms. Street/flash flooding, gusty winds, frequent lightning are expected.
9/10
Thunderstorm Chances
Very High

Thursday

Thursday
9 10 0 1
Intervals of showers and thunderstorms are forecast to interrupt cloudy skies across both islands through the late afternoon, with peak intense activity during the early through mid-morning. A mostly cloudy evening and night is forecast, with isolated showers and thunderstorms persisting but generally remaining offshore. Street/flash flooding, gusty winds, frequent lightning are expected.
Intervals of showers and thunderstorms are forecast to interrupt cloudy skies across both islands through the late afternoon, with peak intense activity during the early through mid-morning. A mostly cloudy evening and night is forecast, with isolated showers and thunderstorms persisting but generally remaining offshore. Street/flash flooding, gusty winds, frequent lightning are expected.
9/10
Thunderstorm Chances
Very High

Friday

Friday
7 10 0 1
A few early morning showers and isolated thunderstorms, favoring Trinidad, is forecast to give way hot and sunny day. By the late morning, showers and isolated thunderstorms are forecast to develop across western and northern halves of Trinidad, persisting through the late afternoon. A mostly settled and partly cloudy night, barring the odd shower or thunderstorm, generally remaining offshore. Gusty winds, street/flash flooding possible.
A few early morning showers and isolated thunderstorms, favoring Trinidad, is forecast to give way hot and sunny day. By the late morning, showers and isolated thunderstorms are forecast to develop across western and northern halves of Trinidad, persisting through the late afternoon. A mostly settled and partly cloudy night, barring the odd shower or thunderstorm, generally remaining offshore. Gusty winds, street/flash flooding possible.
7/10
Thunderstorm Chances
High

Marine: Through Thursday, moderate to locally rough seas are forecast in T&T’s open waters, particularly north of the country. There is a high risk of rip currents along the country’s northern and eastern coastlines with agitated seas initially, with agitated seas in the Gulf of Paria by Wednesday afternoon. Seas are forecast to return to moderate in open waters by Friday, but spring tides begin.

Temperatures

Wednesday

Low: 24-26°C

High: 28-30°C

Increased cloud cover will keep temperatures relatively cool across the country, with heat indices (or feels like temperatures) forecast to be up to 35°C.

Thursday

Low: 23-25°C

High: 28-31°C

After a fairly cool Wednesday, minimum lows are forecast to be slightly cooler. Like the previous day, increased cloud cover will initially keep temperatures relatively cool across the country, with sunshine returning by late afternoon. Heat indices (or feels like temperatures) are forecast to be up to 38°C.

Friday

Low: 24-25°C

High: 32-33°C

As sunshine returns to T&T, heat indices are forecast to be between 35°C and 45°C across the country, with higher temperatures possible across western and urbanized areas of Trinidad.

Forecast Impacts

Flooding

Flooding
10 10 0 1
Over the next three days, overall rainfall totals between 75 and 125 millimeters are forecast across most of the country, particularly across Trinidad. However, isolated totals of up to 150 millimeters of rainfall are possible localized areas of Trinidad.
Over the next three days, overall rainfall totals between 75 and 125 millimeters are forecast across most of the country, particularly across Trinidad. However, isolated totals of up to 150 millimeters of rainfall are possible localized areas of Trinidad.
10/10
Likelihood
Expected

Street and flash flooding is expected across Trinidad and Tobago over the next 48 hours, with increasing chances for riverine flooding across all major river basins of Trinidad by Wednesday night into Thursday morning.

Forecast Rainfall Totals

  • Wednesday: Significant rainfall accumulations are forecast. There is a high chance of impactful street/flash flooding. Between 25 and 75 millimeters of rainfall is forecast across the country, with higher totals generally across Trinidad. Isolated rainfall totals between 75 and 100 millimeters are possible across Trinidad.
  • Thursday: Between 15 and 30 millimeters of rainfall is forecast across both islands, with isolated higher totals up to 40 millimeters favoring eastern and northern Trinidad as well as Tobago.
  • Friday: Less than 10 millimeters across the country with isolated totals favoring western coastal Trinidad up to 25 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
7 10 0 1
Conditions appear favorable for the development of deep convection on Wednesday through early Thursday.
Conditions appear favorable for the development of deep convection on Wednesday through early Thursday.
7/10
Likelihood
High

The chances of strong thunderstorms are high as a highly unstable atmosphere associated with Invest 98L moves across T&T. Though wind shear is forecast to be moderate, high moisture, high instability, and favorable mid to upper-level conditions will support strong shower and thunderstorm activity.

Funnel cloud development is possible through Friday. 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.

Gusty Winds

Gusty Winds
10 10 0 1
Elevated winds associated with Invest 98L are forecast to mainly affect islands north of Trinidad, between Tobago and Martinique. Sustained winds are forecast between 35 KM/H and 50 KM/H, with gusts up to 70 KM/H generally accompanying showers or thunderstorms. By Friday, winds return to seasonal averages, sustained up to 30 KM/H and gusts to 45 KM/H.
Elevated winds associated with Invest 98L are forecast to mainly affect islands north of Trinidad, between Tobago and Martinique. Sustained winds are forecast between 35 KM/H and 50 KM/H, with gusts up to 70 KM/H generally accompanying showers or thunderstorms. By Friday, winds return to seasonal averages, sustained up to 30 KM/H and gusts to 45 KM/H.
10/10
Likelihood
Expected

Possible impacts include localized wind damage to trees, power lines, and small structures. 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

Abundant frequent cloud-to-ground lightning is possible in strong thunderstorm activity.

With the forecast rainfall accumulations, landslides, mudslides, and rockfalls are possible across elevated areas of Trinidad and Tobago.

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.

Widespread rainfall is forecast on Wednesday through early Thursday, where activity becomes increasingly isolated through Friday.

Forecast Discussion

Latest On Invest 98L

On Tuesday, heavy showers and thunderstorms ahead of Invest 98L moved across Trinidad and Tobago associated with a low-level trough trailing Tropical Wave 38. Then, low-level convergence ahead of tropical disturbance Invest 98L maintained cloudy skies, showers, and thunderstorms through the evening.

The main feature forecast to impact Trinidad and Tobago through Thursday remains tropical disturbance Invest 98L. It remains a tropical wave as of early Wednesday morning with no closed circulation. However, north of a 1009-millibar low-pressure area exists an area of 30-knot winds. If convection increases and a closed circulation develops, this disturbance can become a tropical depression as it nears or moves over T&T. Tropical cyclone development chances remain high over the next 48 hours and five days, respectively.

Invest 98L exists in an area with warm sea-surface temperatures between 29°C and 30°C, moderate shear between 10 and 20 knots, favorable upper-level divergence, and protected from dry air to the north due to a favorably positioned upper-level trough.

Over the next 24-48 hours, abundant, deep tropical moisture associated with Invest 98L is forecast to move across T&T with a very unstable atmosphere. A favorably positioned upper-level trough will support stronger convection (showers and thunderstorms), but persistence could be hindered by moderate to strong deep-layered wind shear from the north. Regardless, these conditions are set to support cloudy to overcast skies, scattered to widespread showers/rain, and scattered thunderstorms through the early afternoon on Thursday.

As Invest 98L moves northwestward on Thursday, moisture at the mid to upper levels and instability are forecast to decrease as a high-pressure ridge moves in, while wind shear is forecast to become strong and persist across the region into Friday. This combination will lead to the typical wet season pattern of sunny mornings with isolated afternoon showers and thunderstorms across the western and northern halves of Trinidad.

Stable weather is forecast to remain shortlived as another mid to upper-level trough is set to increase mid to upper-level moisture by Saturday, bringing more showers and isolated thunderstorms.

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