Scattered Showers, Isolated Thunderstorms As Tropical Wave 22, ITCZ Affects T&T.

There is no alert, watch or warning in effect for Trinidad and Tobago at this time.

What We Know

The axis of Tropical Wave 22 is just east of Barbados and Trinidad and Tobago. This wave is forecast to move across T&T overnight through Wednesday, bringing showers and possibly thunderstorms embedded within the ITCZ across the islands. Most of the "active" weather is forecast across Trinidad on Wednesday and the northern half of Trinidad and Tobago on Thursday. Credit: Weathernerds.org
The axis of Tropical Wave 22 is just east of Barbados and Trinidad and Tobago. This wave is forecast to move across T&T overnight through Wednesday, bringing showers and possibly thunderstorms embedded within the ITCZ across the islands. Most of the “active” weather is forecast across Trinidad on Wednesday and the northern half of Trinidad and Tobago on Thursday. Credit: Weathernerds.org

The axis of Tropical Wave 22 is along 58W from 08N- 25N, moving west at 10-15 knots. Scattered showers are noted over the southern portion of the wave mainly south of 11N (i.e. south of Barbados).

This tropical wave developed through non-traditional means, via a mid-latitude trough. The southern half of the wave is embedded within the ITCZ, dragging it across T&T on Wednesday.

High total precipitable moisture, favorable upper-level divergence but unfavorable low-level convergence is present east of Trinidad.

Tropical Wave 23, on the heels of TW22, axis is along 46W from 07N-20N, moving west at 10-15 kt. Scattered showers prevail along the wave axis and south of 11N, also south of Barbados.

What We Expect

Impacts

The Takeaway: On Wednesday, intermittent showers are forecast to begin across Trinidad mainly after 2:00 AM through much of the day, interrupting mostly cloudy skies. By the late morning, showers are also forecast across Tobago. Isolated thunderstorms possible.

On Thursday, mainly the Northern half of Trinidad and Tobago are forecast to experience showers and isolated thunderstorms, interrupting partly cloudy skies.

Generally, widespread or scattered severe weather is not likely. Localized severe weather reports are possible, with locally (isolated) heavy rainfall.

 GOES-East GEOCOLOR (CIRA) Satellite Imagery showing scattered convection (showers and thunderstorms) east of Trinidad and Tobago. Tropical Wave 22, 23, and the ITCZ are approaching the Lesser Antilles, forecast to bring showers and isolated thunderstorms to the islands beginning Wednesday morning through Thursday. Street/Flash Flooding, Gusty Winds possible. The heaviest rainfall and thunderstorms likely across Eastern Trinidad.
GOES-East GEOCOLOR (CIRA) Satellite Imagery showing scattered convection (showers and thunderstorms) east of Trinidad and Tobago. Tropical Wave 22, 23, and the ITCZ are approaching the Lesser Antilles, forecast to bring showers and isolated thunderstorms to the islands beginning Wednesday morning through Thursday. Street/Flash Flooding, Gusty Winds possible. The heaviest rainfall and thunderstorms likely across Eastern Trinidad.

Generally, increasing cloudiness is forecast to begin overnight tonight, with isolated showers occurring by early Wednesday. A few isolated thunderstorms and locally heavy showers are possible by daybreak, mainly across Trinidad. Street/Flash Flooding and gusty winds possible.

On Wednesday, generally cloudy skies are forecast with scattered intermittent showers during the late morning through the afternoon. A few thunderstorms may develop across Trinidad, producing locally heavy showers.

7:45 PM Tuesday 16th July 2019 Radar Imagery from the Trinidad and Tobago Meteorological Service showing scattered light showers mainly occurring east of Trinidad and south of Tobago with settled skies across both islands.

As Tropical Wave 22 progresses westward, the ITCZ is forecast to drift west-northwestward across the Northern half of Trinidad and Tobago late Wednesday through Thursday.

Based on the latest model guidance, this activity is likely to linger into Thursday with intermittent showers and isolated thunderstorms across the aforementioned areas.

Mostly drier conditions are forecast across much of Trinidad on Thursday, while across Tobago, an increase in showers is forecast with the low-medium chance of a thunderstorm.

Locally Heavy Rainfall & Flooding: Based on the latest model runs on Tuesday, from Wednesday (2:00 AM) through Friday (2:00 AM), generally, over the 48 hour period, models are in agreement of fewer than 15 millimeters across Western halves of Trinidad and Tobago and between 20-40 millimeters across the Eastern halves of both islands. Isolated rainfall totals up to 50 millimeters are possible across Eastern coastal Trinidad and Tobago. Much of the heaviest showers and thunderstorms are forecast to occur just offshore Eastern Trinidad and south of Tobago.

Generally, with heavy showers and thunderstorm activity, street flooding, particularly in flood-prone areas or areas with poor drainage, is possible as well as flash flooding in areas where more prolonged heavy rainfall may occur, based on the above-mentioned forecast rainfall totals.

Frequent Lightning: In addition, with thunderstorms, frequent lightning is likely. Thunderstorms are likely to begin on Wednesday through Thursday.

Gusty Winds: Gusty winds, generally between 40 and 50 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 50 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.

High Wind Event Precautions
High Wind Event Precautions

Landslides: Though there is a low chance of 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.

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 these tropical waves, mostly scattered showers are forecast. Hence, we are likely to see intermittent showers and thunderstorms, interrupting partly cloudy to overcast skies between Wednesday and Thursday.

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