Periods of Rain, Showers & Thunderstorms Forecast Over the Next 24-72 Hours. Elevated Flooding Threat.

Adverse Weather Alert – Yellow Level is in effect for Trinidad and Tobago from 11:00 AM Tuesday through 8:00 PM Wednesday. Inclement Weather possible into Thursday.

What We Know

The axis of Tropical Wave 47 is along 67W with much of the active weather between 65W and 60W. The Center of Invest 97L is located along  12.7°N and 43.5°W, well north and east of Trinidad and Tobago. Image: Weathernerds
The axis of Tropical Wave 47 is along 67W with much of the active weather between 65W and 60W. The Center of Invest 97L is located along 12.7°N and 43.5°W, well north and east of Trinidad and Tobago. Image: Weathernerds

The axis of Tropical Wave 47 is now well west of Trinidad and Tobago. However, the active weather associated with this wave continues to affect much of the Lesser Antilles, dragging the ITCZ across the Southern Windwards.

The ITCZ has remained across our region over the last 24 hours and is forecast to continue producing inclement weather over the next 24-72 hours across Trinidad and Tobago.

Favorable mid-level and upper-level conditions, a southeasterly flow of moisture and low wind shear are allowing heavy showers and thunderstorms to flourish as it moves across T&T.

Showers and thunderstorms remain ongoing across various parts of Trinidad and Tobago, with generally cloudy periods. Much of the heavier showers and thunderstorms have focused along the Northern and Eastern halves of Trinidad, with more intermittent activity across the Southern half of Trinidad and Tobago.

Rainfall began across Trinidad and Tobago generally around 5:00 AM. Between 5:00 AM and 9:00 AM, between 15-30 millimeters of rainfall has fallen across Northern Trinidad.

An important note: Invest 97L (Soon to be designated Tropical Depression Ten or Tropical Storm Imelda) east of the Lesser Antilles, is forecast to take a northwesterly path and will not directly affect Trinidad and Tobago. The inclement weather over the next few days are due to the ITCZ and NOT this tropical system. We will not be under any tropical storm watches or warnings. However, as the flood threat increases, flood alerts may be issued for parts of T&T.

What We Expect (For T&T)

Impacts & Flooding

The Takeaway: Periods of rain, showers and thunderstorms are forecast across both islands over the next 48-72 hours, interrupting cloudy skies. Conditions may become more settled during the evening hours, with lingering isolated showers, intensifying during the overnight hours into the morning.

There is the elevated threat for street, flash and riverine (more prolonged) flooding, in addition to gusty winds, power outages, landslides and downed trees and utility poles.

Severe weather is likely, mainly on Tuesday and Wednesday.

Tuesday 17th September 2019: Periods of rain, showers, and thunderstorms across Trinidad and Tobago, interrupting cloudy skies. Heavier showers and thunderstorms are forecast to favor Northern and Eastern halves of Trinidad. Across Southwestern Trinidad, partly cloudy to cloudy skies with isolated showers are likely. Conditions are forecast to become more settled by the evening, with lingering showers. Activity is forecast to ramp up after midnight. Adverse Weather Alert in effect from 11:00 AM. Seas are forecast to remain moderate in open waters with waves up to 2.5 meters while remaining near 1.0 meters in sheltered areas, but choppy during heavy showers and thunderstorms.

Wednesday 18th September 2019: Another round of rain, showers, and thunderstorms across Trinidad and Tobago interrupting cloudy skies. Heavier activity will continue to favor Northern and Eastern halves of Trinidad, as well as Tobago. Conditions are forecast to become settled yet again by the late evening, with lingering showers across both islands. The Adverse Weather Alert is set to expire at 8:00 PM. Seas are forecast to remain moderate in open waters with waves up to 2.5 meters while remaining near 1.0 meters in sheltered areas, but choppy during heavy showers and thunderstorms.

Thursday 19th September 2019: Though more isolated to scattered, compared to the previous two days of possible widespread activity, showers and thunderstorms are forecast through the afternoon across both islands. Partly cloudy to cloudy skies are also forecast. The threat of riverine flooding and landslides will be at its highest on Thursday, although the Adverse Weather Alert is set to expire on Wednesday. Seas are forecast to remain moderate in open waters with waves up to 2.5 meters while remaining near 1.0 meters in sheltered areas, but choppy during heavy showers and thunderstorms.

 9:00 AM Tuesday 17th September 2019 Radar Imagery from the Trinidad and Tobago Meteorological Service showing scattered showers and thunderstorms across Trinidad, nearing Tobago.
9:00 AM Tuesday 17th September 2019 Radar Imagery from the Trinidad and Tobago Meteorological Service showing scattered showers and thunderstorms across Trinidad, nearing Tobago.

Locally Heavy Rainfall & Flooding: Next 72 hours – Based on the latest model runs on Tuesday morning, from Tuesday (2:00 AM) through Friday (2:00 AM), generally, over the 72 hour period, models are in agreement of fewer than 50-60 millimeters across Trinidad and Tobago with isolated totals up to 90 millimeters across the Northern half of Trinidad.

06Z GFS Model Run showing a possible scenario of total accumulated precipitation across Trinidad and Tobago over the next 3 days as of Tuesday 17th September 2019
06Z GFS Model Run showing a possible scenario of total accumulated precipitation across Trinidad and Tobago over the next 3 days as of Tuesday 17th September 2019

Reiterating, as we progress through the week, soils are forecast to become more saturated, leading to more runoff and increasing that flooding threat.

Street flooding, particularly in flood-prone areas or areas with poor drainage, is likely as well as flash flooding in areas where more prolonged heavy rainfall while riverine flooding is possible.

Frequent Lightning: In addition, with thunderstorms, frequent lightning is likely. Lightning strikes have the potential to cause power dips and outages, destroy trees, utility poles and cause harm to life and property.

Gusty Winds: Gusty winds, generally between 40 and 55 KM/H are possible Gusty winds are most likely prior to, in the vicinity of, or occur during heavy showers or thunderstorms. With wind gusts up to 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.

High Wind Event Precautions
High Wind Event Precautions

Landslides: Heavy showers across the Northern Range may trigger landslides in landslide-prone areas. Particularly in areas that receive heavy rainfall, landslides and/or mudflows may occur across both islands. These landslides, in addition to gusty winds, may down trees, utility poles and impede traffic on roadways. There will be an elevated threat of landslides on Wednesday into Thursday.

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