Tropical Wave 63 To Move Across T&T On Sunday

An active tropical wave, Tropical Wave 63, is forecast to move across T&T and the Eastern Caribbean on Sunday. The passage of this wave will drag the Intertropical Convergence Zone northward of T&T.

Dry air from our surge of Saharan Dust this past week lingers, limiting activity across our country. In addition, strong wind shear has continued to keep stronger showers and thunderstorms well to our east and south.

Still, abundant moisture is forecast to fuel isolated showers, some becoming heavy to violent, and isolated thunderstorms on Sunday into the upcoming week.

Active Tropical Wave 63 east of Trinidad and Tobago (Weathernerds.org)
Active Tropical Wave 63 east of Trinidad and Tobago (Weathernerds.org)

Heavier rainfall will generally favor Tobago and the eastern half of Trinidad, but during the afternoons, the northern and western halves of Trinidad may experience stronger activity. Street/flash flooding and gusty winds are possible over those regions, with light to moderate rainfall and breezy conditions elsewhere.

There are no alerts, watches or warnings in effect for T&T from the Trinidad and Tobago Meteorological Service at this time.

The Forecast

The remainder of Saturday: Mostly settled conditions across Trinidad and Tobago. One or two isolated showers may develop across the country, mainly after midnight. Rainfall activity to be brisk as showers move to the west/northwest.

Sunday: Mostly settled, partly cloudy skies with breezy conditions are forecast through the morning, barring the odd isolated shower and increasing cloudy skies. By the late morning through the afternoon, isolated to scattered showers, and the odd thunderstorm, are forecast across the western and northern halves of Trinidad. In addition, activity east of T&T may begin to drift across both islands. Periodic showers and isolated thunderstorms are forecast to linger across T&T through the night, associated with Tropical Wave 63.

Monday: Overnight showers and isolated thunderstorms are forecast to favor the eastern half of Trinidad, as well as Tobago, briskly moving to the west/northwest. Conditions are forecast to settle after daybreak gradually. By the late morning, through the afternoon, a few isolated showers and the odd thunderstorm may occur across Trinidad’s western coastal areas. A mostly settled night is forecast.

The Forecast Discussion

Contrary to reports over the last week, calling for inclement weather, dry air following our mild Saharan Dust episode this week continues to cap any shower and thunderstorm development across T&T. In addition, persisting strong wind shear has kept much of the activity east of our islands.

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.

The activity in question is associated with an active tropical wave (Tropical Wave 63) interacting with the Intertropical Convergence Zone and a favorably positioned upper-level trough. This wave will move across the region on Sunday, during the first half of the day. This tropical wave is moving to the northwest, so much of the activity directly associated with the wave and the ITCZ will remain to our north.

However, following the passage of the wave, southeasterly winds are forecast to bring increased moisture and instability to T&T, with marginally favorable upper-level conditions, on Sunday which may support heavy showers and thunderstorms across western and northern Trinidad due to sea breeze convergence and orographic effects.

Sea breeze convergence mechanisms for the Gulf of Paria and the Atlantic Ocean across Trinidad which can produce thunderstorm activity.. Note that sea breeze convergence is possible across all coasts of both islands. Diagram: Trinidad and Tobago Weather Center
Sea breeze convergence mechanisms for the Gulf of Paria and the Atlantic Ocean across Trinidad which can produce thunderstorm activity.. Note that sea breeze convergence is possible across all coasts of both islands. Diagram: Trinidad and Tobago Weather Center

On Sunday afternoon, weaker wind shear is forecast across T&T, which could allow for stronger showers and thunderstorms. However, outside of the Sunday afternoon period, generally moderate to strong wind shear will be in place, keeping shower and thunderstorm activity brief.

This southeasterly flow will continue to transport moisture northwest of T&T, but it will also allow for a surface to mid-level ridge pattern to move in across our country during the latter half of the day, with decreasing moisture.

Temperatures

With variable cloud cover across both islands, the heat is forecast remain present across T&T.

The maximum high for Trinidad and Tobago is forecast to be near 32.0°C on Sunday and Monday, and higher in urbanized areas, up to 35.0°C but generally remaining much cooler when persisting cloudiness, showers and thunderstorms occur.

Forecast Impacts

Hazards associated with Tropical Wave 63 over the next 48 hours.
Hazards associated with Tropical Wave 63 over the next 48 hours.

For Trinidad and Tobago, the main hazards will be isolated areas of heavy rainfall producing street/flash flooding and gusty winds up to and in excess of 55 KM/H mainly on Sunday/

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 55 KM/H, and frequent lightning.

Winds

Sustained surface winds are forecast to be elevated, between 20 KM/H and 30 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 morning, between one-half to 2 inches (12.5 to 50 millimeters) are possible across Trinidad and Tobago with isolated totals higher totals possible in localized areas of Trinidad.

There is an elevated threat of street flooding and flash flooding on Sunday. Chances of riverine flooding are very low to zero at this time.

Other Impacts

Landslides are possible in elevated areas. Strong low-level winds will create unfavorable conditions for funnel clouds and tornadoes but Sunday 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.

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 Sunday through Monday.

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