Adverse Weather Alert Updated As Tropical Wave 61 Moves West, ITCZ Continues to Affect T&T

Key Messages:
— An Adverse Weather Alert Yellow Level is in effect from 2:00 PM on Tuesday through 4:00 PM on Wedesday for both Trinidad and Tobago.
— 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 updated the Adverse Weather Alert (Yellow Level) at 3:00 PM Tuesday as Tropical Wave 61 moves west of Trinidad and Tobago while the ITCZ continues to affect the region. The alert remains in effect through 4:00 PM Wednesday 6th November 2019. Quite a bit of the moisture associated with this tropical wave remains east of Trinidad and Tobago, yet to affect the region.

We mentioned the likelihood of this alert being issued in our post on Saturday. Note that inclement weather may continue beyond the end of the adverse weather alert’s end time.

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 occur overnight Tuesday through mid-Wednesday, with lingering showers and thunderstorms into Wednesday night.

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

The Tropical Wave is now west of the Islands, however with the presence of the ITCZ, showers and thunderstorms remain in the forecast. There is a high possibility of street/flash flooding and gusty winds in excess of 55km/hr in areas of 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 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

 MIMIC-TPW2 shows total precipitable water (TPW) across the Atlantic Basin, where we can see the moisture in the entire atmospheric column associated with the ITCZ and Tropical Waves 61, 62 and 63 in the Atlantic Basin. Image: University of Wisconsin-Madison
MIMIC-TPW2 shows total precipitable water (TPW) across the Atlantic Basin, where we can see the moisture in the entire atmospheric column associated with the ITCZ and Tropical Waves 61, 62 and 63 in the Atlantic Basin. Image: University of Wisconsin-Madison

The axis of Tropical Wave 61 is approximated to be along 61W from 12N
southward, moving W 10 to 15 knots. Scattered moderate to strong convection (showers and thunderstorms) are within 300 nautical miles to the east of the tropical wave.

Though the axis of Tropical Wave 61 has moved west of Trinidad and Tobago, weather behind the axis in addition to the ITCZ is forecast to bring periods of showers and thunderstorms, triggering the Adverse Weather Alert. Credit: Weathernerds
Though the axis of Tropical Wave 61 has moved west of Trinidad and Tobago, weather behind the axis in addition to the ITCZ is forecast to bring periods of showers and thunderstorms, triggering the Adverse Weather Alert. Credit: Weathernerds

The axis of this wave moved across both islands between 11:00 AM and 3:00 PM with the characteristic wind shifts seen at Crown Point, Tobago as well as numerous weather stations across Trinidad and Tobago, with winds shifting from the east-northeast, then northeast, then east, and then to the southeast/east-southeast.

Activity associated with this wave and the ITCZ is supported by favorable upper-level divergence and low-level convergence. Strong low-level winds and very strong wind shear will keep showers and thunderstorms moving briskly westward, and limit the strengthening of convective activity.

The Weather Forecast

Tuesday Evening: The ITCZ affects Trinidad and Tobago, with the tail-end of Tropical Wave 61 affecting the region. Isolated showers and thunderstorms are forecast to continue interrupting partly cloudy to cloudy skies through the late afternoon into the evening. Increasing cloudiness and showers are forecast by nightfall with thunderstorms likely after 9:00 PM. Increased wind speeds would result in higher gusts near thunderstorms and heavy showers.

Wednesday: Scattered to widespread rain, showers, and isolated to scattered thunderstorms throughout the morning into the late afternoon, with lingering showers into the late evening and night.

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 35 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. No riverine flooding is expected.

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 at the end of the last week. 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.

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?
Facebook Comments