Tropical Update – Weak Tropical Wave To Affect T&T Tuesday Into Wednesday

Tropical Update Overview:
Tropical Wave 01 – This weak tropical wave is now moving across Central America, entering the Pacific Ocean.
Tropical Wave 03 – This tropical wave was added to the NHC’s analysis late Sunday night in the central Caribbean Sea. No threat to T&T.
Tropical Wave 02 – A weak tropical wave is forecast to traverse the Southern Windwards beginning late Tuesday through Wednesday. Increased moisture may fuel heavier showers and thunderstorms across T&T Tuesday into Wednesday. No widespread severe weather forecast.
Impacts to T&T – After midday Tuesday, isolated showers are forecast to increase across T&T with increasing cloudiness. After midnight through Wednesday isolated to scattered showers, isolated thunderstorms, and periods of light to moderate rain are possible, with mostly settled conditions by nightfall. No direct tropical threats to Trinidad and Tobago are forecast over the next week but locally heavy rainfall is possible on Wednesday, 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. A high-pressure system is forecast to bring settled conditions to the region Wednesday night into Thursday.

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 01

Tropical Wave 01 continues westward, entering the Pacific Ocean Sunday Night. The wave, combined with localized activity across the mountainous terrain of Central America has triggered showers and thunderstorms. Credit: Weathernerds

Tropical Wave 01 continues its westward trek, remaining a weak tropical wave through much of its journey across the Atlantic, Caribbean Sea and now Central America.

According to the National Hurricane Center, at 4:00 PM, the axis of Tropical Wave 01 was located along 89W.

While it produced no precipitation across Trinidad, Tobago and the Windwards during its progression across the Eastern Caribbean, it did cause flooding across French Guiana with record breaking rainfall, heavy showers across the Cayman Islands, causing flooding and triggered thunderstorms across Central America, which caused lahars.

This is the final update on the first tropical wave for 2020.

Tropical Wave 03

Tropical Wave 03 was analyzed by the National Hurricane Center Sunday night in the central Caribbean Sea. This wave is weak, with little convection associated with the wave. Credit: Weathernerds

The third tropical wave for the 2020 Atlantic Hurricane Season was added by the National Hurricane Center as of the 4:00 PM Surface Analysis.

According to the NHC, this tropical wave is near 73W from 18N southward, moving west at 10 knots. Convection associated to this wave is limited, but the cyclonic curvature is noted on visible satellite imagery.

Near the wave axis, convection has appeared Sunday night across Colombia and Hispanola, with none across the Caribbean Sea.

No threat to the Lesser Antilles, including T&T.

Tropical Wave 02

Activity associated with Tropical Wave 02 along 45W to 49W in the Atlantic. Credit: Weathernerds

As of the 8:00 PM Tropical Update, the axis of Tropical Wave 02 (added to the NHC’s surface analysis Saturday 23rd May 2020) is approximately along is along 45W to 49W, from 18N southward, moving westward 15 knots (28 KM/H). Scattered moderate convection from 02N-9N between 40W-53W is associated with this broad but weak tropical wave.

Following the passage of Tropical Wave 01, it is fair to be on the conservative side of what impacts this wave can bring to T&T – particularly since the overall dynamics have not significantly changed.

Wind shear, one of the chief factors into last week’s lack of rainfall, remains strong across the region as of Sunday night, between 40 to 50 knots. When this wave moves across the region, Tuesday into Wednesday, wind shear is forecast to remain above 50 knots through the entire period.

Also, model guidance continues to show relatively dry low- to mid-levels of the atmosphere, working against the formation of showers and thunderstorms. However, compared to TW01, this tropical wave has several models supporting showers and isolated thunderstorms beginning Tuesday, particularly on Wednesday. Still, it is not unanimous that heavy precipitation will occur on Wednesday.

Moderate to strong wind shear continues to limit persistent convection, but upper-level divergence and low-level convergence are allowing for isolated pockets of deep convection to develop.

Abundant low-level moisture is forecast, supporting cloudiness and isolated to scattered showers, with thunderstorms possible mainly on Wednesday. The passage of this tropical wave could bring the onset of the 2020 Wet Season. See below for details.

What does all of this mean for Trinidad and Tobago?

T&T’s 5-Day Weather Forecast

Monday: A high-pressure system continues to dominate across the Lesser Antilles, allowing for mostly sunny, breezy, and hot conditions throughout the day. Low-level cloud patches will traverse T&T, bringing brisk isolated showers, accompanied by gusty winds up to 50 KM/H. Mostly settled conditions are forecast during the evening into the night, with the odd isolated showers.

Tuesday: During the first half of the day, the high-pressure system continues to remain dominant, allowing for mostly sunny and hot conditions. Low-level cloud patches will traverse T&T, bringing brisk isolated showers, accompanied by gusty winds up to 50 KM/H. By midday, moisture ahead of the axis of Tropical Wave 02 will begin to affect the Windward Islands, including T&T. Increased cloudiness is likely with isolated showers through the afternoon. Showers to favor eastern areas of Trinidad and Tobago, gradually moving westward. Seas to remain moderate, with waves up to 2 meters in open waters.

Wednesday: The axis of Tropical Wave 02 is forecast to move across Trinidad and Tobago. Winds initially will be out of the east-northeast to the east, with variably cloudy skies after midnight. However, as the early to mid-morning progresses, isolated to scattered showers with periods of light to moderate rain and isolated thunderstorms are forecast to affect Trinidad and Tobago throughout the day. Conditions are forecast to settle by the evening, with a resurgence of showers overnight.

There is the low to medium chance, presently, of locally heavy rainfall, particularly during heavy to violent showers and thunderstorms on Wednesday, with gusty winds up to 60 KM/H. Seas to remain moderate, with waves up to 2 meters in open waters, but may become choppy during heavy showers and thunderstorms. Street/flash flooding and landslides are possible.

With winds mainly from the southeast as Wednesday progresses, moisture moving across T&T will interact with our topography and local climate. Hence, sea-breeze convergence, daytime heating, and orographic effects will trigger showers and isolated thunderstorms.

Thursday: As quickly as the tropical wave came, its influence will leave. A high-pressure system is forecast to regain dominance across the region. This is forecast to allow for mostly sunny, breezy, and hot conditions throughout the day. Low-level cloud patches will traverse T&T, bringing brisk isolated showers, accompanied by gusty winds up to 55 KM/H. Mostly settled conditions are forecast during the evening into the night, with the odd isolated showers. Note that a surge of Saharan Dust is forecast to move across the region by early Thursday.

Friday: A high-pressure system continues to dominate across the Lesser Antilles, allowing for mostly sunny, breezy, and hot conditions throughout the day. Low-level cloud patches will traverse T&T, bringing brisk isolated showers, accompanied by gusty winds up to 50 KM/H. Mostly settled conditions are forecast during the evening into the night, with the odd isolated showers.

Saturday: A high-pressure system regains dominance across Trinidad and Tobago, with a surge in Saharan Dust, allowing for mostly sunny, breezy, and hot conditions throughout the day. Low-level cloud patches will traverse T&T, bringing brisk isolated showers, accompanied by gusty winds up to 50 KM/H. Mostly settled conditions are forecast during the evening into the night, with the odd isolated showers.

Impacts This Upcoming Week

Forecast confidence on the impacts of the upcoming tropical wave, with a low to medium chance for heavy to violent showers and thunderstorms. With those chances, there is the medium potential for street flooding and very low chances for flash flooding. However, there is the low to medium chance for gusty winds in excess of 55 KM/H and the very low to low chance for frequent lightning, due to the suboptimal conditions for thunderstorm development.
Forecast confidence on the impacts of the upcoming tropical wave, with a low to medium chance for heavy to violent showers and thunderstorms. With those chances, there is the medium potential for street flooding and very low chances for flash flooding. However, there is the low to medium chance for gusty winds in excess of 55 KM/H and the very low to low chance for frequent lightning, due to the suboptimal conditions for thunderstorm development.

Winds: Sustained surface winds between 25 KM/H and 45 KM/H with gusts up to 60 KM/H are likely in heavy showers or thunderstorms across Trinidad and Tobago, particularly Tuesday into Wednesday.

With wind gusts up to 60 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, no to trace daily rainfall accumulations are forecast, less than 5 millimeters. On Tuesday into Wednesday, isolated totals between 5-15 millimeters, with in excess of 15-20 millimeters in isolated thunderstorms or heavy/violent 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 to scattered activity is forecast.

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

Tropical Cyclone Climatology

Tropical Cyclone Points of Origin during the month of May. Though much of the points of origin are west or north of T&T as we move into the first 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.

Tropical Cyclone Points of Origin during the month of May. Though much of the points of origin are west or north of T&T as we move into the first 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.

List of names for the 2020 Atlantic Hurricane Season, which will be updated each tropical update as new systems develop.
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