Showers, Thunderstorms Forecast Over Next 5 Days

Key Messages:
Weather: Over the next 5 days (and likely through next week), periods of showers and thunderstorms with variably cloudy skies are forecast for Trinidad and Tobago. From Thursday through Saturday, activity will be associated with a tropical wave (Tropical Wave 64) while Sunday through next week, a favorable mid to upper-level environment.
Rainfall: Through Tuesday, between 1 to 3 inches (25 to 75 millimeters) are forecast across Trinidad and Tobago with isolated totals between 3 to 5 inches (75 to 125 millimeters). Higher rainfall totals are possible mainly across eastern areas of Trinidad and across Tobago. Note the highest rainfall totals will remain east of T&T. There is an elevated threat of street flooding and flash flooding beginning Thursday evening. Chances of riverine flooding remain very low to low, mainly across eastern areas of Trinidad.
Seas & Tides: King tides are forecast to begin on Thursday through next week which may hinder runoff during high tide periods. However, the overall sea state is forecast to remain slight to moderate.
Winds: Outside of heavy shower and thunderstorm activity, winds are forecast to be light to moderate, 10 KM/H to 30 KM/H. A surge in low-level winds is possible on Monday through Tuesday from the southeast. In thunderstorm activity, gusty winds up to and in excess of 55 KM/H possible. Winds of this strength will produce wind damage including downed trees, utility poles, and roof damage. Localized power outages possible.
Other Impacts: Landslides possible in elevated areas by the weekend. Though unlikely, brief funnel cloud and even tornado development are possible, favoring western areas of Trinidad on days where light winds and sunny mornings occur.

Trinidad and Tobago is under no alerts, watches, or warnings from the Trinidad and Tobago Meteorological Service at this time.

The Forecast

Remainder of Wednesday: Mostly settled conditions across both islands, with brisk isolated showers. Nearing midnight, isolated showers and thunderstorms are possible across both islands, with heavier activity initially favoring eastern Trinidad and our eastern coastal waters.

Thursday: From 12:00 AM through 8:00 AM, much of the shower and thunderstorm activity is forecast to remain east of T&T. Brisk shower and thunderstorm activity may interrupt partly cloudy skies, favoring eastern areas. From 8:00 AM to 12:00 PM, brisk showers continue to interrupt partly to mostly cloudy skies, with increasing coverage and intensity across both islands. After midday through 6:00 PM, isolated showers continue across Trinidad, remaining brisk. Heavier showers and thunderstorms may develop, favoring the western and southern halves of Trinidad, as well as eastern coastal Trinidad. All activity forecast to gradually subside by nightfall, with a resurgence of showers and isolated thunderstorms across Tobago and eastern Trinidad near midnight (after 10:00 PM).

Friday: From midnight through midday, brisk isolated showers are possible, interrupting mostly clear to partly cloudy skies. By midday through nightfall, isolated heavy showers and thunderstorms are possible across Trinidad, favoring the northern and western halves of the island through the afternoon initially settling by nightfall. After 8:00 PM, showers are forecast to begin affecting Tobago and eastern Trinidad, moving westward with heavy showers and thunderstorms possible closer to midnight.

Saturday through Monday: Very mixed conditions are forecast. Brisk heavy showers and thunderstorms, with periods of light to moderate rain, are forecast to interrupt partly to mostly cloudy skies. Generally, heavier showers and isolated thunderstorms are expected during the overnight hours (10:00 PM through 4:00 AM) and during the late morning through the afternoon (10:00 AM through 4:00 PM). Note that Sunday and Monday are forecast to be the wettest of the 5-day period, with heavy rainfall possible on Tuesday.

The Forecast Discussion

As of Wednesday night, the axis of Tropical Wave 64 remains well to T&T’s east along 55W. Preceding an approaching tropical wave is abundant atmospheric moisture at most levels of the atmosphere, with a surface to a low-level confluent pattern (winds slowing down and piling up, causing convergence) across T&T and the Windwards. A marginally favorable upper-level pattern is in place, forecast to enhance convection at low levels of the atmosphere on Wednesday night through Thursday. On Friday, a similar setup is forecast, with a slightly favorable mid to upper-level diffluent pattern (winds move outward, in a ‘fan-out’ pattern), enhancing convection (showers and thunderstorms).

Note that stronger activity associated with tropical waves tend to follow the wave axis, even with a surge is moisture ahead of the wave.
Note that stronger activity associated with tropical waves tend to follow the wave axis, even with a surge is moisture ahead of the wave.

Tropical Wave 64 will slowly inch towards the Lesser Antilles into the weekend, moving across T&T on Saturday. As with most tropical waves, the active weather follows the wave axis on Sunday through Monday and Tuesday. In addition, an upper-level low-pressure system will be favorably positioned northwest of the Windwards, providing greater enhancement for showers and thunderstorms.

Thursday through late Saturday, wind shear is forecast to be weak across the Windwards, between 0 to 15 knots, still mainly from the west, allowing showers and thunderstorms to gain intensity but keeping stronger activity to T&T’s east. Wind shear will only increase Sunday through Tuesday, still from the west to southwest between 10-30 knots, at times up to 50 knots. This will keep stronger activity north and east of T&T by the end of the weekend into next week.

In addition to wind shear, another inhibiting variable will be Saharan Dust, drying out the mid-levels of the atmosphere, something models have not grappled with well for 2020. Given that nearly all models (dust and weather prediction) show minimal dust with heavy precipitation, it is likely Saharan Dust will have a negligible impact on this weekend’s rains.

Temperatures

With increased cloud cover across both islands, the heat will be on the lower side through the weekend, though during the late mornings, particularly on Thursday through Saturday, temperatures will be elevated.

The maximum high for Trinidad is forecast to be near 32.0°C on Thursday through Saturday, and higher in urbanized areas but Sunday through Tuesday, up to 31.0°C but generally remaining much cooler when persisting cloudiness, showers and thunderstorms occur, in the upper twenties.

In Tobago, the maximum high is forecast to be near 31.0°C on Thursday through Saturday and up to 30.0°C Sunday through Tuesday.

Forecast Impacts

Hazards associated with Tropical Wave 64 and a trough system over the next five days.
Hazards associated with Tropical Wave 64 and a trough system over the next five days.

For Trinidad and Tobago, the main hazards will be gusty winds up to and in excess of 55 KM/H and flooding. Street and flash flooding will be likely on Thursday and Sunday through Tuesday, with riverine flooding possible by Sunday (dependent on where overall heavier rainfall totals fall.)

While thunderstorm activity is forecast to be brief, due to strong low-level winds, 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. With rainfall through the weekend, landslides are also possible in elevated areas, particularly beyond Sunday

Though unlikely due to strong low-level winds, brief funnel cloud and even tornado development are possible, favoring western areas of Trinidad.

Winds

Sustained surface winds are forecast to be elevated, beginning on Thursday between 20 KM/H and 50 KM/H at times. In thunderstorm and 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.

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

Rainfall

Through Tuesday, between 1 to 3 inches (25 to 75 millimeters) are possible across Trinidad and Tobago with isolated totals between 3 to 5 inches (75 to 125 millimeters).

Higher rainfall totals are possible mainly across eastern areas of Trinidad and across Tobago. Note the highest rainfall totals will remain east of T&T. There is an elevated threat of street flooding and flash flooding beginning Thursday evening. Chances of riverine flooding remain very low to low, mainly across eastern areas of Trinidad.

Thursday: Between 5 and 15 millimeters across both islands. Across the eastern half of Trinidad and across Tobago, between 15-25 millimeters are possible. In heavier showers and thunderstorms where violent rainfall occurs, isolated totals up to and in excess of 25 millimeters are possible.

Friday: Between 5 and 15 millimeters across both islands. In heavier showers and thunderstorms where violent rainfall occurs, isolated totals up to and in excess of 25 millimeters are possible.

Saturday: Between 5 and 15 millimeters across both islands. In heavier showers and thunderstorms where violent rainfall occurs, isolated totals up to and in excess of 30 millimeters possible.

Sunday through Tuesday: Generally less than 20 millimeters across both islands. In heavier showers and thunderstorms where violent rainfall occurs, isolated totals up to and in excess of 50 millimeters possible.

Other Impacts

Landslides possible in elevated areas, particularly beyond Sunday

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 slight to moderate over the next five days but King Tides may impact runoff.

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 during the next 5 days.

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