Adverse Weather Alert Triggered As ITCZ, Tropical Wave 61 Forecast to Bring Inclement Weather

Key Messages:
— An Adverse Weather Alert Yellow Level goes into in effect at 2:00 PM on Tuesday through 7:00 PM on Wedesday for both Trinidad and Tobago. Adverse weather is likely to begin prior to the official start of the alert.
— Through Thursday, 2 to 4 inches (50 to 100 millimeters) are possible across Trinidad and Tobago with heavier totals across Eastern and Southern halves of Trinidad, as well as Tobago. There is an elevated threat of street flooding and flash flooding, particularly across Tobago and the Eastern half of Trinidad.
— Seas will remain moderate to occasionally rough, with waves up to 2.5 meters are possible in open waters, occasionally up to and in excess of 3.0 meters and less than 1.0 meter but choppy in sheltered areas.
— Gusty winds in excess of 55 to 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 5:21 PM Monday as Tropical Wave 61 and the ITCZ approaches Trinidad and Tobago. The alert goes into effect from 2:00 PM Tuesday 5th November 2019 through 7:00 PM Wednesday 6th November 2019. Tropical Wave 61 and its moisture are forecast to affect the region now through Thursday as the ITCZ lingers in the area.

We mentioned the likelihood of this alert being issued in our post on Saturday. Note that inclement weather may begin overnight tonight, well ahead of the official start of the alert.

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 is forecast to begin by the late morning on Tuesday, but showers and isolated thunderstorms are forecast overnight tonight (Monday).

Information from the Trinidad and Tobago Meteorological Service concerning the Adverse Weather Alert for November 5th-6th, 2019.

Periods of showers and thunderstorms, associated with the combination of a tropical wave and the Inter Tropical Convergence Zone (ITCZ), are likely to affect various parts of Trinidad and Tobago. There is also the likelihood of winds gusting in excess of 55km/hr. Street/ flash flooding or landslips may occur in heavy downpours.” 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

Tropical Wave 61 is approaching Trinidad and Tobago, forecast to bring periods of showers and thunderstorms, triggering the Adverse Weather Alert. Credit: Weathernerds
Tropical Wave 61 is approaching Trinidad and Tobago, forecast to bring periods of showers and thunderstorms, triggering the Adverse Weather Alert. Credit: Weathernerds

The axis of Tropical Wave 61 is located along 56W, south of 12N is moving west at 10 knots. This low amplitude wave shows up well in model guidance and satellite imagery. Scattered moderate convection is seen from 07N-12N between 51W-58W.

This wave is forecast to be accompanied by favorable upper-level conditions, which may support deep convective activity (thunderstorms) as it traverses the region.

The Weather Forecast

Tuesday: The ITCZ affects Trinidad and Tobago, with Tropical Wave 61 approaching, moving across the region by nightfall. Isolated showers are forecast to persist through the early morning into daybreak, becoming more scattered to widespread, and a few heavier showers and thunderstorms developing by mid-morning. Scattered showers, rain, and thunderstorms are forecast to persist throughout the day across both islands, with periods of mostly cloudy to overcast skies. Conditions are forecast to become temporarily settled by the evening, with a few lingering showers but activity is forecast to increase again after midnight. Increased wind speeds would result in higher gusts near thunderstorms.

Wednesday: Scattered to widespread rain, showers, and thunderstorms throughout the 24-hour period, with coverage reducing by the late evening.

Thursday: The ITCZ begins to drift southwards, as Tropical Wave 61 moves well west. Heavier showers and thunderstorms forecast to favor Western and Southern Trinidad, mainly during the late morning through the evening.

Impacts This Upcoming Week

Winds: Sustained surface winds between 15 KM/H and 30 KM/H with gusts in excess of 65 KM/H are likely in heavy showers or thunderstorms across Trinidad and Tobago throughout the week.

With wind gusts in excess of 65 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: Throughout the week, daily rainfall accumulations are forecast to be isolated totals of 15-25 millimeters, with in excess of 50 millimeters in isolated thunderstorms or heavy downpours.

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. There is a very low chance of riverine flooding by the end of the week if overall rainfall totals materialize.

Frequent Lightning: In addition, with forecast thunderstorms, frequent lightning is likely. Lightning can cause power outages, voltage dips, damage to life and property, particularly during cloud-to-ground lightning strikes.

Landslides: Particularly across Northwestern Trinidad, soils are very saturated with persistent heavy afternoon thunderstorms since Thursday, with a number of landslides over the last 3 days. With additional rainfall in the forecast, landslides are possible through Tuesday and likely through Thursday in landslide-prone and elevated areas.

Hazardous Seas: An increase in strong low-level winds will keep seas at moderate levels, with waves up to 2.5 meters in open waters and even at rough levels on Wednesday, with waves in excess of 2.5 meters, particularly along the Eastern coasts of both islands. Hence, it is within the realm of possibility another hazardous sea alert for the Eastern coasts of Trinidad and Tobago.

Why I May Not/Will Not See Constant Rainfall?

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. Widespread showers mean that nearly all persons and areas may experience rainfall.

Forecast - Isolated, Scattered, Widespread - What do they mean?

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