Adverse Weather Alert In Effect As Tropical Wave 52 Approaches T&T

Key Messages:
— No tropical cyclone formation forecast. This is just an active tropical wave. An Adverse Weather Alert Yellow Level goes into effect at 2:00 AM Thursday through 2:00 PM.
— Between 1 to 2 inches (25 to 50 millimeters) are possible across Trinidad and Tobago with isolated totals up to 3 inches (75 millimeters) across Eastern Trinidad. There is an elevated threat of street flooding and flash flooding.
— Seas will remain moderate, with waves between 1.5 meters and 2.0 meters are possible in open waters and choppy in sheltered areas.
— Gusty winds 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.
— Landslides possible in elevated areas.

The Adverse Weather Alert

The Trinidad and Tobago Meteorological Service has issued the Adverse Weather Alert (Yellow Level) as an active tropical wave nears Trinidad, Tobago, and the Southern Windwards. The alert goes into effect from 2:00 AM Thursday 3rd October 2019 through 2:00 PM Thursday 3rd October 2019. This is forecast to be a low to medium impact event.

Trinidad and Tobago is NOT under any tropical storm watch or warning AT THIS TIME.

Based on the latest model guidance and analysis, these showers, with scattered heavy showers and thunderstorms, are forecast to produce severe weather across Trinidad and Tobago. This activity is forecast to begin mainly after midnight tonight through Thursday evening, though the Adverse Weather Alert begins at 2:00 AM Thursday and ends at 2:00 PM.

Street flooding and flash flooding are possible. Gusty winds are likely. These gusty winds and heavy rainfall will be capable of triggering landslides in landslide-prone areas, as well as downing trees and utility poles. See below for more details on what impacts to expect.

Information from the Trinidad and Tobago Meteorological Service concerning the Adverse Weather Alert for October 3rd, 2019.

The passage of a tropical wave tomorrow is expected to produce periods of showers or rain with the 60-80% chance of heavier showers or thunderstorm activity. Due to prior rainfall events, some ground surfaces are still saturated at this time resulting in the heightened risk of street/flash flooding. Gusty winds in excess of 55km/h may accompany heavy downpours and landslides/landslips are possible in areas so prone.” according to the Trinidad and Tobago Meteorological Service. This “alert” status takes into account the possibility of the event occurring. This adverse weather event is likely.

The color of the alert indicates the severity of the event and the probability of the event occurring. Currently, the alert level is at Yellow. This means that the hazard is possible to be aware of the impacts of Street/Flash Flooding and Gusty Winds in your area. Areas prone to landslides should also be aware of the hazard and impacts.

Image Credit: Trinidad and Tobago Meteorological Service
Image Credit: Trinidad and Tobago Meteorological Service

What We Know

 An active tropical wave located along 56/57W producing scattered showers and thunderstorms, forecast to move across T&T over the next 24-36 hours. Adverse Weather Alert in effect. Credit: Weathernerds
An active tropical wave located along 56/57W producing scattered showers and thunderstorms, forecast to move across T&T over the next 24-36 hours. Adverse Weather Alert in effect. Credit: Weathernerds

An Atlantic tropical wave with axis along 56/57W S of 15N is moving W at 10-15 knots. Scattered moderate to isolated strong convection is seen from 07N-12N between 52W-60W. Enhanced rainfall is likely for the southern Windward Islands and SE Caribbean tonight and Thursday, according to the National Hurricane Center.

Based on our counts, this is the 52nd tropical wave of the 2019 Atlantic Hurricane Season. This wave is not forecast to develop.

This wave is located in an area of favorable upper-level divergence and low-level convergence. There is a good amount of heavy thunderstorm and shower activity, which was slowing increasing in intensity and areal coverage on Wednesday evening, as seen on satellite imagery.

Wind shear remains minimal to negligible, with moist low, mid and upper levels of the atmosphere – optimal for heavy shower and thunderstorm development.

Impacts From Tropical Wave 52

Wind

Peak sustained surface winds of 25 KM/H to 35 KM/H with gusts in excess of 55 KM/H are possible in heavy showers or thunderstorms across Trinidad and Tobago.

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.

High Wind Event Precautions
High Wind Event Precautions

Rainfall

Between 1 to 2 inches (25 to 50 millimeters) are possible across Trinidad and Tobago with isolated totals up to 3 inches (75 millimeters) across Eastern Trinidad. There is an elevated threat of street flooding and flash flooding.

Because of the particularly wet period we’ve had over the last several weeks, it will not take much rainfall to trigger street flooding or flash flooding.

Thunderstorms and Lightning

With thunderstorms, locally severe wind (in excess of 55 KM/H), violent rainfall rates (in excess of 50 millimeters per hour) and lightning are all possible.

Gusty winds and lightning pose a threat to our power grid, causing localized power outages. Lightning may also strike trees, homes or utility poles causing damage to property. Lightning can also be deadly to persons outside during a thunderstorm.

Seas and Surf

Long-period swells have subsided, though seas remain moderate in open waters with waves between 1.5 to 2.0 meters. In sheltered areas, seas are near 1.0 meters, but choppy, particularly during heavier showers or thunderstorms.

What’s Next?

After the heavier showers and thunderstorms move out of the region on Thursday, lingering moisture associated with this tropical wave will fuel activity on Friday. Conditions will be mainly hot and sunny on Friday, but locally heavy showers and thunderstorms will be possible across parts of Northern and Western halves of Trinidad, as well as Western Tobago.

Why I May Not/Will Not See Constant Rainfall?

Tropical waves typically have fair weather ahead of the wave axis, though other features in the area such as surface troughs, increased atmospheric moisture, and local climatic effects, to name a few, may trigger showers and the odd thunderstorm. Following the passage of the wave, much of the active weather typically associated with a tropical wave occurs.
Tropical waves typically have fair weather ahead of the wave axis, though other features in the area such as surface troughs, increased atmospheric moisture, and local climatic effects, to name a few, may trigger showers and the odd thunderstorm. Following the passage of the wave, much of the active weather typically associated with a tropical wave occurs.

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.

Generally, because of winds associated with tropical waves, showers and thunderstorms tend to follow a west-northwest track, generally missing areas across Southwestern Trinidad and even Northwestern Trinidad – though activity due to local climatic effects such as daytime heating may trigger shower and thunderstorm development across these areas. See the below graphic for a simple explanation.

With this tropical wave (Tropical Wave 52), mostly scattered showers are forecast. Hence, we are likely to see intermittent showers and thunderstorms, interrupting partly cloudy to overcast skies on Thursday.

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