Tropical Wave 05 Forecast To Continue Bringing Flooding Rainfall To T&T

What you need to know:
— Widespread rain with isolated heavy showers and thunderstorms remain in the forecast for Trinidad and Tobago through Saturday, becoming isolated to scattered on Sunday. Additional rainfall accumulations range from 25 millimeters to 50 millimeters, with isolated higher totals.
— The inclement weather is due to the influence of Tropical Wave 05 (now well west of T&T) combined with a highly favorable atmospheric setup, not a tropical storm.
— An Adverse Weather Alert (Yellow Level) remains in effect for Trinidad and Tobago through 12:00 AM Sunday.
— A Riverine Flood Alert (Yellow Level) remains in effect for northern and central Trinidad through 12:00 PM Sunday.

The Forecast

Saturday: Periods of rain, numerous showers, and isolated to scattered thunderstorms are forecast to affect T&T from midnight throughout the day. Rainfall will interrupt mostly cloudy to overcast skies. Heavier showers and thunderstorm activity are forecast mainly from dawn through the afternoon across both islands. Overall higher rainfall accumulations are forecast north of Trinidad and across the eastern and southern halves of Trinidad. Conditions will gradually settle into the night with few brisk overnight showers.

Sunday: A partly cloudy and breezy day, with brisk cloudy periods and isolated showers favoring the morning through the early afternoon. There is a low chance of a thunderstorm. Increasingly hazy skies are forecast through the afternoon into Monday, with breezy and mostly settled conditions into the overnight hours, barring the odd isolated shower.

Marine: Seas are forecast to be moderate over the next 48 hours, with waves between 1.5 to 2.0 meters in Trinidad and Tobago’s open waters. Across sheltered coastlines, waves below 1.0 meter are likely. In heavy showers or thunderstorms, sheltered seas may become choppy.

Forecast Discussion

As of 1:00 AM, Tropical Wave 05 has been analyzed at 68W, south of 12N, moving westward at 10 to 15 knots (18 to 27 KM/H). This wave is well west of Trinidad and Tobago, but its large plume of moisture and instability remains across the Windward Islands.

Near Trinidad and Tobago, there is abundant moisture at all levels of the atmosphere, favorable low-level convergence, upper-level divergence, and moderate wind shear. These factors will persist through the next 12-24 hours, allowing for abundant cloudiness, showers, and thunderstorms across Trinidad, Tobago, and the Windward Islands. The worst of the weather is forecast to favor Trinidad.

On Sunday, the low to mid-levels of the atmosphere are forecast to dry due to a mild surge of Saharan Dust, limiting further significant rainfall. However, Tropical Wave 04 will be affecting the region from late Monday into Tuesday, bringing another round of showers and possible thunderstorms early next week.

Total precipitable water imagery showing high levels of atmospheric moisture approaching Trinidad and Tobago as a tropical wave moves across the region. (CIMSS, Space Science & Engineering Center, University of Wisconsin – Madison)

Why is Tropical Wave 05 west of Tropical Wave 04? Our numbering system is based on when these waves are analyzed. Tropical Wave 05 was added by the National Hurricane Center after Tropical Wave 04 left the west coast of Africa, resulting in a wave further east with a lower “wave number.”

Temperatures

Across both islands, overnight lows are forecast to be mild, with daytime highs cool due to increased cloud cover.

Over the next 48 hours, the minimum low for Trinidad and Tobago is forecast to be between 22.0°C and 25.0°C. The maximum high for Trinidad and Tobago is forecast to be between 26.0°C and 29.0°C. Temperatures are forecast to be warmer on Sunday due to more sunshine, with maximum highs in the low thirties.

Forecast Impacts

Over the next 24 hours, the main hazards include heavy rainfall triggering additional street flooding and flash flooding, as well as there is the medium to high risk of riverine flooding, favoring Central and Northern Trinidad. Lightning and gusty winds up to and in excess of 55 KM/H may accompany thunderstorms or heavy showers and cause power dips/outages, downed trees, and localized wind damage. Landslides may be possible due to saturated soils.

On Sunday, the main hazards are gusty winds accompanying brisk showers and reduced air quality due to a slight increase in Saharan Dust.

Winds

Sustained surface winds up to 35 KM/H. In shower activity, gusts up to and in excess of 55 KM/H are possible. With wind gusts 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.

Rainfall

Rainfall accumulations across Trinidad and Tobago on Friday 4th June 2021 following the passage of Tropical Wave 05.
Rainfall accumulations across Trinidad and Tobago on Friday 4th June 2021 following the passage of Tropical Wave 05.

Over the next 48 hours, overall higher rainfall is forecast to favor eastern Trinidad and Tobago with accumulations between 20 to 50 millimeters. However, localized totals up to and in excess of 75 millimeters are possible in prolonged heavy showers or isolated thunderstorm activity. Note that highly isolated areas across western and northern areas of Trinidad may exceed daily forecast totals.

  • Saturday: Between 20 to 40 millimeters across the country, with higher rainfall totals favoring the eastern half of Trinidad, up to 75 millimeters. In isolated areas, rainfall accumulations may exceed 75 millimeters. Across Tobago, between 15 to 40 millimeters are possible. Note that the GFS model remains the outlier, showing widespread totals up to 125 millimeters across the country. If that materializes, severe flooding is possible, but this output remains the outlier amongst the suite of models consulted for this forecast.
  • Sunday: Between 5-15 millimeters across the country, with higher rainfall totals favoring eastern and southern halves of Trinidad, in excess of 20 millimeters.

Over the next 24 hours, the main hazards include heavy rainfall triggering additional street flooding and flash flooding, as well as there is the medium to high risk of riverine flooding, favoring Central and Northern Trinidad. The Trinidad and Tobago Meteorological Service has issued a Riverine Flood Alert (Yellow Level) remains in effect for northern and central Trinidad through 12:00 PM Sunday.

Other Adverse Weather Impacts

Lightning: Lightning is possible in thunderstorm activity. Lightning can cause power outages, voltage dips, damage to life and property, particularly during cloud-to-ground lightning strikes.

Landslides: With saturated soils by Saturday and the threat of additional rainfall, landslides are possible in elevated areas, particularly hilly areas in southern and northeastern Trinidad.

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.

On Saturday, scattered to widespread rainfall is forecast. On Sunday, isolated rainfall is forecast

Forecast - Isolated, Scattered, Widespread - What do they mean?

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