Adverse Weather Alert – Yellow Level In Effect For Tobago Until 2 AM Due To Tropical Wave 55

Key Messages:
— An Adverse Weather Alert Yellow Level in effect until 2:00 AM Friday for Tobago. Much of the Adverse Weather has subsided as of 8:30 PM.
— Through Sunday, an additional 1 to 2.5 inches (25 to 62.5 millimeters) are possible across Trinidad and Tobago with heavier totals across Northern and Western halves of Trinidad, as well as Tobago. There is an elevated threat of street flooding and flash flooding, particularly across Tobago and Western Trinidad.
— Seas will remain slight to moderate, with waves up to 1.5 meters are possible in open waters and less than 1.0 meter but choppy in sheltered areas.
— Gusty winds in excess of 65 KM/H possible, particularly on Tuesday. 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 an Adverse Weather Alert (Yellow Level) at 6:22 PM Thursday as Tropical Wave 55 continues to affect Tobago. The alert went into effect from 6:22 PM Thursday 17th October 2019 through 2:00 AM Friday 18th October 2019. Tropical Wave 55 and its moisture is forecast to affect the region through Saturday, dragging the ITCZ across the region.

The timing of the adverse weather alert is curious, as much of the inclement weather subsided prior to the issuance of the alert, much like one of those reactionary adverse weather alerts we wrote about of earlier this year.

Weather Conditions at Crown Point International Airport, Tobago between 4:00 PM and 7:00 PM Thursday, with the boxed area showing the peak of this inclement weather event, prior to the Adverse Weather Alert issuance
Weather Conditions at Crown Point International Airport, Tobago between 4:00 PM and 7:00 PM Thursday, with the boxed area showing the peak of this inclement weather event, prior to the Adverse Weather Alert issuance

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

Based on the latest model guidance and analysis, much of the severe weather across Tobago has subsided, with light rain and isolated showers possible through the night.

Information from the Trinidad and Tobago Meteorological Service concerning the Adverse Weather Alert for October 17th-18th, 2019.

Activity associated with the passage of a Tropical Wave is expected to affect Tobago over the next 6 to 8 hours. During this period Tobago can expect periods of heavy showers and thunderstorms which may result in some flooding and landslide/landslips mainly along hilly areas. Gusts of up to 65km/h are likely near heavy downpours. These strong winds can also result in choppy sea conditions. A gradual improvement in conditions can be expected after midnight.” 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 observed.

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

Tropical Wave 55 continues to affect Tobago and the remainder of the Lesser Antilles, bringing periods of showers and thunderstorms as forecast, triggering the Adverse Weather Alert. Credit: Weathernerds
Tropical Wave 55 continues to affect Tobago and the remainder of the Lesser Antilles, bringing periods of showers and thunderstorms as forecast, triggering the Adverse Weather Alert. Credit: Weathernerds

The axis of Tropical Wave 55 is moving across Trinidad and Tobago, affecting much of the Lesser Antilles, north of Trinidad.

T&T is located in an area of favorable upper-level divergence and low-level convergence. Moisture remains abundant throughout all levels of the atmosphere.

An upper-level diffluent pattern spawning most of the island chain will continue to provide favorable upper-level conditions across Trinidad, Tobago, and the region. As a result, scattered showers, rain and thunderstorms will remain likely across the region.

Weather

Thursday (until midnight): Tropical Wave 55. Lingering showers are likely into the night mainly across Tobago, though it is not expected to be severe, as well as Northern and Eastern areas of Trinidad.

Friday (until midnight): Tail End of Tropical Wave 55. Similar conditions to Thursday are forecast. After an initially hot and sunny early and mid-morning, isolated to scattered showers and thunderstorms are likely across both islands, with heavier showers and thunderstorms favoring the Western and Northern halves of Trinidad, as well as Tobago. Conditions are forecast to become settled into the night.

Saturday (until midnight): Lingering moisture & localized climatic effects and the ITCZ. Essentially the same forecast as the two previous days. After an initially hot and sunny early and mid-morning, isolated to scattered showers and thunderstorms are likely across both islands, with heavier showers and thunderstorms favoring the Western and Northern halves of Trinidad, as well as Tobago. Conditions are forecast to become settled into the night.

Sunday (until midnight): Surface to Mid-level Ridge. Much drier conditions are forecast, with isolated late morning through afternoon showers and thunderstorms across Western Trinidad, interrupting hot and sunny skies.

Wind

Peak sustained surface winds of 25 KM/H to 45 KM/H with gusts in excess of 55 KM/H are possible in heavy showers or thunderstorms across Trinidad and Tobago, particularly on Thursday and Friday during heavy shower or thunderstorm activity.

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

Through Sunday, an additional 1 to 2.5 inches (25 to 62.5 millimeters) are possible across Trinidad and Tobago with heavier totals across Northern and Western halves of Trinidad, as well as Tobago.

There is an elevated threat of street flooding and flash flooding due to the slow-moving nature of this activity.

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

Seas are forecast to be 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.

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.

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