Tropical Wave 55 Brings Thunderstorms, Heavy Showers to T&T. Additional Isolated Activity Forecast Over Next 24-48 Hours.

Key Messages:
— A tropical wave is moving across the Lesser Antilles, with much of the activity across the Leewards and Northern Windwards. Localized climatic effects triggering heavy showers and thunderstorms across T&T.
— Through Friday, 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 Western, Northern Trinidad and Tobago. There is an elevated threat of street flooding and flash flooding due to the slow moving nature of this activity.
— Seas will remain slight to moderate, with waves up to 1.5 meters and 2.0 meters are possible in open waters and choppy in sheltered areas. Swells are forecast to persist through Wednesday.
— Gusty winds in excess of 55 KM/H possible, particularly on Thursday afternoon. Winds of this strength will produce wind damage including downed trees, utility poles and roof damage. Localized power outages possible.
— Frequent Lightning is expected.
— Landslides possible in elevated areas.

Trinidad and Tobago is NOT under any alerts, watches or warnings AT THIS TIME.

What We Know

A tropical wave located along 60W is influencing our local wind regime, triggering severe thunderstorms across Trinidad and Tobago, with much of the activity associated with this wave remaining north of T&T.  Additional showers and thunderstorms forecast. Credit: Weathernerds
A tropical wave located along 60W is influencing our local wind regime, triggering severe thunderstorms across Trinidad and Tobago, with much of the activity associated with this wave remaining north of T&T. Additional showers and thunderstorms forecast. Credit: Weathernerds

As of 1:00 PM Thursday, the 55th tropical wave of the 2019 Atlantic Hurricane Season is moving across the Lesser Antilles. Much of the activity is moving across the Leewards and Northern Windwards. However, the winds are near stationary across Trinidad, to lightly from the south and southeast.

From the Trinidad and Tobago Meteorological Service, a feature we’ve explained prior, orographic precipitation is ongoing. “Due to the passage of a Tropical Wave over the area, winds near the surface are coming from the south. Since our ranges are oriented east to west (particularly the northern range), these southerly winds are forced to rise and cool when they meet the foothills. Combined with daytime heating for extra lift, heavy showers, and thunderstorms formed at the foothills of the northern and central ranges.

T&T is located in an area of favorable upper-level divergence and low-level convergence, combined with low wind shear across Trinidad and Tobago and deep tropical moisture across the region have allowed for strong thunderstorms and heavy showers to develop across both islands this afternoon.

Sea breeze convergence, where trade winds from the east meet winds from the west, moving onshore from the Gulf of Paria, is also ongoing. This causes locally heavy showers and thunderstorms across the Western halves of Trinidad and Tobago.

1:00 PM Thursday 17th October 2019 Radar Update: Heavy showers and thunderstorms ongoing across Western and Northern Trinidad, as well as Tobago. Conditions forecast to continue through the afternoon, settling by the late evening. Image: Trinidad and Tobago Meteorological Service
1:00 PM Thursday 17th October 2019 Radar Update: Heavy showers and thunderstorms ongoing across Western and Northern Trinidad, as well as Tobago. Conditions forecast to continue through the afternoon, settling by the late evening. Image: Trinidad and Tobago Meteorological Service

Isolated to scattered heavy showers and thunderstorms are ongoing across the Western and Northern halves of Trinidad, as well as Tobago, as forecast. This activity is forecast to subside by the late evening, with a few lingering showers into the night as this tropical wave progresses westward.

Weather

Thursday (until midnight): Tropical Wave 55. Periods of showers and possible thunderstorms are likely across both Trinidad and Tobago, with the heaviest activity ongoing through the afternoon, across Western and Northern halves of Trinidad as well as Tobago. This activity will interrupt partly cloudy to mostly cloudy skies and will likely be accompanied by gusty winds. While conditions may become more settled by the late evening, lingering showers are likely into the night, mainly across Tobago.

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. 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 Friday, 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 Western, Northern Trinidad and 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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