Trough Forecast To Produce Showers, Thunderstorms Into Monday

A surface to a low-level trough that has been affecting the region this weekend is forecast to continue producing cloudiness, showers, and thunderstorms on Sunday night through Monday morning. While moisture will linger, a surface to mid-level high-pressure system will be in place from late Monday through Wednesday, with sunshine and heat returning to the region.

Heavy rainfall will favor Tobago and the eastern half of Trinidad, with street/flash flooding and gusty winds most likely over those regions, with light to moderate rainfall and breezy conditions elsewhere. Chances of riverine flooding remain very low across the country, and low across Eastern areas through Monday.

As of 10:30 AM November 2nd, 2020, the southern half of Trinidad is under a Localized Flood Alert (Yellow Level) from the Trinidad and Tobago Meteorological Service.

The Forecast

Remainder of Sunday: Mostly cloudy to overcast skies are forecast across Trinidad and Tobago, with moderate to violent rainfall across Tobago, northern and eastern areas of Trinidad with heavy to violent showers and isolated thunderstorms.

Monday: Moderate to heavy rainfall forecast to interrupt mostly cloudy to overcast skies with isolated violent showers and thunderstorms through the predawn hours. Similar activity is forecast during the late morning through the afternoon, interrupting partly cloudy skies. Conditions are forecast to gradually settle through the late afternoon into the night with skies clearing.

The Forecast Discussion

Instability due to the passage of a surface to low-level trough, coupled with favorable low-level convergence and upper-level divergence has continued to produce mostly cloudy to overcast skies across T&T.

With abundant moisture in place overnight through the first half of Monday, showers, and thunderstorms are likely across both islands. Strong wind shear from the northwest to the north has kept activity offshore and east of T&T. Hence, the heavier activity will mainly affect the eastern halves of both islands.

On Monday, mainly from the second half of the day through Tuesday, a surface to low-level ridge will build across the region. Still, surface to low-level confluencing (winds slowing down and pilling up like cars in a traffic jam) will allow for brisk shower and thunderstorms. Moisture will be capped to the low-levels, keeping brisk activity weak and inhibiting most cloud development.

Tropical Wave 61 is forecast to move across the region on Friday into the weekend, with a heavy rainfall event possible beginning Saturday into the following week.

Temperatures

With decreasing cloud cover across both islands, the heat will increase across T&T from the second half of Monday through mid-week.

The maximum high for Trinidad is forecast to be near 33.0°C on Monday, and higher in urbanized areas, up to 35.0°C but generally remaining much cooler when persisting cloudiness, showers and thunderstorms occur.

In Tobago, the maximum high is forecast to be near 32.0°C on Monday through midweek.

Forecast Impacts

Hazards associated with a low-level through over the next 48 hours
Hazards associated with a low-level through over the next 48 hours

For Trinidad and Tobago, the main hazards will be gusty winds up to and in excess of 60 KM/H overnight and flooding. Street and flash flooding will be likely across Eastern areas of both islands, mainly on Sunday night and possible across Trinidad on Monday from the late morning through the afternoon.

While thunderstorm activity is forecast to be brief, due to strong wind shear, frequent lightning will still be possible as upper-level enhancement may trigger locally severe thunderstorm activity. This means violent rainfall, gusty winds in a downburst-like fashion, up to and in excess of 60 KM/H, and frequent lightning. Landslides are also possible in elevated areas.

Winds

Sustained surface winds are forecast to be elevated, between 20 KM/H and 50 KM/H at times. In thunderstorm and shower activity, gusts up to and in excess of 60 KM/H are possible.

With wind gusts in excess of 60 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.

For unsecured roofs, and weaker structures, wind damage will be likely.

Rainfall

Through Tuesday morning, between one-half to 4 inches (12.5 to 100 millimeters) are possible across Trinidad and Tobago with isolated totals higher totals across eastern areas of the islands

There is an elevated threat of street flooding and flash flooding on Sunday night. Chances of riverine flooding remain low to very low.

Other Impacts

Landslides possible in elevated areas. Strong low-level winds will create unfavorable conditions for funnel clouds and tornadoes but on days with sunny mornings, funnel clouds are possible.

Frequent 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.

Seas will be moderate over the next five days.

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 is forecast overnight through Tuesday.

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