Tropical Update: The Tropics Winds Down, Weak Mid-Week Tropical Wave

Tropical Update Overview:
— Tropical Wave 62 – This tropical wave moved across the region early Saturday 10th November 2019. Though this wave did not bring persistent showers or thunderstorms to T&T, locally heavy rainfall occurred across Barbados and Northwestern Trinidad, triggering severe street flooding. This wave is now located in the Central Caribbean Sea.
— Tropical Wave 63 – This tropical wave is forecast to move across the Lesser Antilles Tuesday into Wednesday, bringing elevated moisture that may fuel isolated showers and thunderstorms across Trinidad and Tobago.
Impacts to T&T – A mostly hot and sunny week is ahead, with late morning through afternoon showers and possible thunderstorms, favoring Western areas and then isolated overnight showers favoring Northeastern areas. Other notable features are ITCZ lingering across T&T on Monday and Tropical Wave 63 on Tuesday into Wednesday, bringing increased chances for those isolated showers and thunderstorms. No direct tropical threats to Trinidad and Tobago are forecast over the next week but locally heavy rainfall is possible, throughout the week, mainly during the intense afternoon showers and thunderstorms. Street flooding, flash flooding, gusty winds generally between 30-50 KM/H and occasionally in excess of 50 KM/H, landslides and frequent lightning possible.

Before we dive into the Tropical Update, a few notes:

  • Tropical waves are a normal part of the rainy season.
  • Not every tropical wave will form into a tropical cyclone.
  • Weaker tropical waves produce more rainfall across Eastern parts of the islands with mostly cloudy conditions and a few showers across western parts of the islands.
  • Rainfall will be more isolated and intermittent with weaker tropical waves that do not have ITCZ or upper-level support.
  • Saharan Dust may weaken tropical waves.

You can read more about the weather associated with Tropical Waves, as well as what to expect as these waves move through the region below.

Tropical Wave 62

The axis of Tropical Wave 62 is along 70W in the Central Caribbean Sea. Dry air has limited any shower or thunderstorm activity near the wave axis as it progresses westward in the 4:00 PM Tropical Update. Credit: Weathernerds
The axis of Tropical Wave 62 is along 70W in the Central Caribbean Sea. Dry air has limited any shower or thunderstorm activity near the wave axis as it progresses westward in the 5:00 PM Tropical Update. Credit: Weathernerds

As of the 5:00 PM Tropical Update, Tropical Wave 62 is along 70W from 20N southward, moving west at around 15-20 knots. Drier air is present in the eastern Caribbean limiting convection along the wave axis.

This tropical wave dumped over 9 inches (275 millimeters) of rainfall across St. Lucy, Northern Barbados on Saturday, triggering severe street and flash flooding across the area.

While this tropical wave did not bring prolonged rainfall to Trinidad and Tobago as it did Barbados, intense thunderstorms developed across Northwestern and Western Trinidad Saturday afternoon, causing street and flash flooding across parts of San Fernando, Freeport, Carenage and Westmoornings. Gusty winds also accompanied showers and thunderstorms, with gusts at times in excess of 50 KM/H.

Another by-product of the thunderstorms associated with the passage of this tropical wave was the uncommon sighting of a waterspout off the southwestern coast of Tobago.

Tropical Wave 63

 Activity associated with Tropical Wave 63 along 55W in the Central Atlantic. Credit: Weathernerds
Activity associated with Tropical Wave 63 along 53/54W in the Central Atlantic. Credit: Weathernerds

As of the 5:00 PM Tropical Update, the axis of Tropical Wave 63 is approximately along 53/54 west, from 14N southward, is moving W at 15-20 knots. Scattered moderate convection from 10N-16N between 44W-53W.

Strong wind shear continues to weaken showers and thunderstorms as they develop, causing a large canopy of upper-level clouds across the Central Atlantic.

Wind shear will continue to keep convection well east of the wave axis as it moves across the Lesser Antilles Tuesday into Wednesday but abundant low-level moisture is forecast, supporting cloudiness and isolated to scattered showers, with brief thunderstorms. See below for details.

What does all of this mean for Trinidad and Tobago?

Monday: Surface to low-level moisture associated with the ITCZ will linger over the southern Windwards, including Trinidad and Tobago. Conditions are expected to be partly cloudy to cloudy at times with some scattered showers. During the late morning through the afternoon, heavier showers and thunderstorms are forecast to mainly affect the western half of Trinidad. Isolated showers may persist into the night, favoring Eastern areas of both islands.

Tuesday: Similar conditions to Monday with brisk isolated showers across both islands throughout the day, interrupting partly cloudy skies. Heavier activity will favor Western, Southern and hilly areas of Trinidad as well as Tobago. An approaching tropical wave may bring increased cloudiness and isolated showers and thunderstorms, particularly across Eastern Trinidad and Tobago during the second half of Tuesday.

Wednesday: The axis of Tropical Wave 63 is forecast to move across T&T, with showers and thunderstorms developing after midnight, affecting both islands. Periods of showers and thunderstorms are forecast to interrupt partly cloudy to overcast conditions. Note that activity will be intermittent throughout the day. Lingering showers, remaining isolated and interrupting partly cloudy skies, are forecast by the late evening through the night mainly across Eastern Trinidad and Tobago.

Thursday & Friday: Strong wind shear is forecast to subside by Thursday, with low-level wind speeds also weakening. This will allow for hot and sunny early and mid-mornings to lead into showers and thunderstorms developing by the late morning through the afternoon. Intense activity will be possible, favoring Western and Northern Trinidad and Tobago, subsiding by the evening. Winds will be from the northeast, so heavier thunderstorms and showers will favor Southwestern Trinidad.

Impacts This Upcoming Week

Winds: Sustained surface winds between 15 KM/H and 30 KM/H with gusts in excess of 50 KM/H are likely in heavy showers or thunderstorms across Trinidad and Tobago throughout the weekend.

With wind gusts in excess of 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, 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 less than 10 millimeters, with in excess of 20-40 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.

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.

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.

This week, isolated activity is forecast.

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

Tropical Cyclone Climatology

Tropical Cyclone Points of Origin during the month of November. Though much of the points of origin are west or north of T&T as we move into the last month of the Hurricane Season, we still need to pay attention to some of these waves and the ITCZ, which have historically brought major flooding events to T&T, hence all low-pressure systems in the Atlantic should be closely monitored, as we do in the Tropical Update.

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