Tropical Wave 01

With a number of models forecasting showers and thunderstorms for T&T, the passage of Tropical Wave 01 lacked precipitation for the islands. Instead, T&T recorded its second-highest temperature at Piarco for 2020 to date.

Gusty Winds Move Across Tobago, Trinidad

7:00 PM Wednesday 20th May 2020

Activity associated with Tropical Wave 01 collapsed east of Trinidad and Tobago, even as showers began to move across Tobago.

GOES-EAST Imagery showing the gust front moving across Tobago at 3:30 PM and across Trinidad at 5:30 PM as activity from Tropical Wave 01 collapse.
GOES-EAST Imagery showing the gust front moving across Tobago at 3:30 PM and across Trinidad at 5:30 PM as activity from Tropical Wave 01 collapse.

As showers and thunderstorms dissipated, a gust front was produced, bringing breezy conditions with gusty winds across Tobago between 3:30 PM and 4:30 PM. Sustained winds at Crown Point reached 39 KM/H at 4:00 PM, with gusts at Scarborough rose above 60 KM/H.

Gusty winds move across Tobago, with gusts in excess of 60 KM/H as a gust front resulting from collapsing activity associated with Tropical Wave 01.
Gusty winds move across Tobago, with gusts in excess of 60 KM/H as a gust front resulting from collapsing activity associated with Tropical Wave 01.

As the gust front moved across Trinidad, gusty winds and breezy conditions followed, with gusts generally below 50 KM/H.

Gusty winds move across Trinidad, with gusts up to 50 KM/H as a gust front resulting from collapsing activity associated with Tropical Wave 01.
Gusty winds move across Trinidad, with gusts up to 50 KM/H as a gust front resulting from collapsing activity associated with Tropical Wave 01.
Gusty winds move across Trinidad, with gusts up to 50 KM/H as a gust front resulting from collapsing activity associated with Tropical Wave 01.
Gusty winds move across Trinidad, with gusts up to 50 KM/H as a gust front resulting from collapsing activity associated with Tropical Wave 01.

Showers, Cloudiness Approaching Tobago

3:15 PM Wednesday 20th May 2020

Increased cloudiness and showers are beginning to move across Eastern Tobago, gradually moving westward. Gusty winds up to 55 KM/H are possible, mainly accompanying heavier showers or the isolated thunderstorm.

For Trinidad, sweltering heat continues due to minimal cloud cover across much of the country except Northwestern areas of the island. Temperatures between 33°C to 36°C have been recorded across parts of Central and Southern Trinidad. Increased cloudiness and showers are possible across Trinidad, beginning by 6:00 PM.

3:15 PM Satellite Update, showing cloudiness approaching Tobago with partly cloudy skies across Trinidad.
3:15 PM Satellite Update, showing cloudiness approaching Tobago with partly cloudy skies across Trinidad.

Heavy Downpour Across West Port of Spain

2:10 PM Wednesday 20th May 2020

As a localized shower affected parts of Northwestern Trinidad, weather stations across Woodbrook and Lower Diego Martin picked up rainfall rates that were considered heavy, but accumulations remained below 10 millimeters.

An isolated shower produced brief heavy rainfall across Lower Diego Martin.
An isolated shower produced brief heavy rainfall across Lower Diego Martin.
An isolated shower produced brief heavy rainfall across Western Port of Spain
An isolated shower produced brief heavy rainfall across Western Port of Spain

Showers Ongoing Across Northwestern Trinidad

1:45 PM Wednesday 20th May 2020


The Showers Are Coming

1:30 PM Wednesday 20th May 2020

While it’s getting cloudy outside, it’s still hot and it’s still dry, much to the ire of everyone. Thankfully, showers and isolated thunderstorms are still possible later this evening through tomorrow morning as activity from this tropical wave is finally moving westward.


Tropical Wave 01 Still Moving Across the Lesser Antilles

8:30 AM Wednesday 20th May 2020

With sunny skies prevailing across T&T, its hard to think a tropical wave is moving across the region. Not only has the axis of the wave moved slower than anticipated, but the forecast early morning showers (and isolated thunderstorms) disappointed many.

Weaker tropical waves, such as the first one for the year, this type of low confidence in the forecast is typical, particularly in a high wind shear environment.

Tropical Wave 01 traversing the Lesser Antilles on Wednesday morning.
Tropical Wave 01 traversing the Lesser Antilles on Wednesday morning.

Tropical Wave 01’s structure is relatively typical, with the active weather following the wave axis and now that we have clear, visible satellite imagery (in addition to using reported wind shifts at weather stations across the Eastern Caribbean), the wave is now moving across the islands.

Showers and thunderstorms further north are being aided by favorable upper-level divergence, low-level convergence and relatively favorable mid- to upper-level environment – none of which presently exists across T&T.

However, as the morning progresses, these sunny skies may be the trigger for development of new showers and thunderstorms (not seen in present satellite imagery) particularly with our presently moist atmosphere.

The typical model of a tropical wave, with generally stable conditions ahead of the wave axis and active weather following – similar to Tropical Wave 01

Where are our showers?

7:00 AM Wednesday 20th May 2020

Disappointingly, due to a mostly stable atmosphere across T&T and very strong wind shear, no activity developed across the area overnight, which was a possibility in our forecast.

However, now with a mostly sunny morning, deep tropical moisture still streaming across the islands and near calm conditions, the heat will act as a trigger by the late morning for showers and possible isolated thunderstorms to develop across T&T.

During light wind conditions, locally heavy showers and isolated thunderstorms tend to favor the Western and Northern halves of both islands, with the development of funnel clouds possible. By 10:00 AM, when data from the 7:00 AM atmospheric sounding is processed, we’ll have a better snapshot of what the atmosphere looks like for the remainder of today.


Axis of Tropical Wave Moving Across Lesser Antilles

11:00 PM Tuesday 19th May 2020

At TTWC, we use the Surface Pressure Analysis completed by the National Hurricane Center‘s Tropical Analysis and Forecast Branch, to determine the Tropical Waves for the Hurricane Season.

When it comes to the passage of the wave across the islands, we use all data available, including satellite and other remote sensing data (such as Total Precipitable Moisture – TPW) as well as ground stations and upper-air observations.

Total Precipitable Water Imagery showing the large plume of moisture associated with Tropical Wave 01 moving across the Lesser Antilles. Image: CIMSS
Total Precipitable Water Imagery showing the large plume of moisture associated with Tropical Wave 01 moving across the Lesser Antilles. Image: CIMSS

Based on all available data, the axis of this wave is presently moving across the Lesser Antilles, including Trinidad and Tobago. While this detail is important from a technical standpoint in declaring the onset of the 2020 Wet Season, active weather tends to follow the wave axis.

Moisture from Tropical Wave 01 is beginning to spread across the Lesser Antilles as of 11:00 PM, with the axis still moving across the region.

Wind shear is serving to be the detriment of this wave, with some of the highest wind shear across the Caribbean presently being across the Lesser Antilles, up to 70 knots. Wind shear disrupts the development of updrafts needed to sustain shower and thunderstorm development.

During the late afternoon through the early night, convective activity tends to be at a minimum. With tropical waves and the Intertropical Convergence Zone, activity tends to flare up during the early morning – which is when we forecast the first round of activity to move across Tobago and Eastern Trinidad initially, gradually spreading westward.

Shower and thunderstorm activity associated with Tropical Wave 01 remaining short-lived as strong wind shear continues to disrupt convection as this wave nears the Lesser Antilles. Image: Weathernerds
Shower and thunderstorm activity associated with Tropical Wave 01 remaining short-lived as strong wind shear continues to disrupt convection as this wave nears the Lesser Antilles. Image: Weathernerds

Even with the highly disruptive vertical wind shear, periods of rain, isolated to scattered showers and isolated thunderstorms remain in the forecast over the next 24 hours due to marginally favorable low-level convergence and upper level-divergence, in addition to the deep tropical moisture streaming across the islands.

On top of the tropical wave, a mid-level trough just east of the region may provide some support for shower and thunderstorm development.

The Forecast

The first round of activity is possible by the early to mid-morning (beginning at 4:00 AM). However, much of the showers and thunderstorms, instead of moving across T&T, have shifted north. By daybreak, if these showers do not materialize – a mostly hot and sunny start is expected. This may seem like a busted forecast for the remainder of the day but heat allows for the destabilization of our atmosphere.

By the late morning (10 AM), whether or not we have early morning showers, additional activity (showers and isolated thunderstorms) are forecast to develop across T&T with variably cloudy intervals through the mid-afternoon (3-4 PM).

Conditions are forecast to settle by the evening (6 PM) with isolated showers occurring across both islands by the late night Wednesday into Thursday, with negligible chances for thunderstorm activity onland across T&T.

Winds: Sustained surface winds between 25 KM/H and 45 KM/H with gusts up to 55 KM/H are possible in heavy showers or thunderstorms across Trinidad and Tobago, particularly on Wednesday.

With wind gusts up to 55 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: On Wednesday, accumulated totals are forecast to be between 10-15 millimeters, with 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 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?

Axis of TW01 Approaching T&T

1:00 PM Tuesday 19th May 2020

As of 1:00 PM, the leading edge of the plume of moisture associated with Tropical Wave 01 was just 125 kilometers east of T&T, with the axis of the wave nearly 400 kilometers east of the region.


TW01 Triggers Street/Flash Flooding Across French Guiana

Monday 18th May 2020

The passage of the first tropical wave across French Guiana triggered intense thunderstorms across coastal areas between 12:00 PM and 1:00 PM local time. These thunderstorms produced one-hour rainfall totals at the Cayenne-Rochambeau Airport of 78.2 millimeters, breaking the one-hour rainfall record at the station since 1946.

ℹ️ Pour info et pour illustrer l’orage violent qui s’est abattu sur l’île de Cayenne et St Laurent du Maroni. Quelques…

Posted by Météo-France Antilles-Guyane on Monday, May 18, 2020

Tropical Wave 01 Forecast to Traverse T&T Tuesday Night Into Wednesday

Sunday May 17th 2020

The first tropical wave for 2020 is forecast to move across the Southern Windwards, including Trinidad and Tobago, on Tuesday night into Wednesday. Note that much of the “active” weather is forecast to occur on Wednesday.


2020’s First Tropical Wave

Saturday May 16th 2020

The first tropical wave moved off the African coast on Wednesday May 13th into Thursday May 14th 2020.


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