Tropical Update: Saharan Dust “Stifles” Tropical Waves in the Eastern Atlantic. First Heavy Rainfall Event for 2019 Possible Next Week

Tropical Weather Update:
Tropical Wave 04 & Tropical Wave 05: Both waves moved across Trinidad and Tobago with a few scattered showers and isolated thunderstorms favoring Trinidad over the last week. These weaker waves have not produced any significant rainfall to date since the rainy season was declared.
Tropical Wave 06: The axis of this “moisture-starved” tropical wave moved across Trinidad and Tobago overnight. There has been an increase in convection east of the wave axis with some thunderstorm activity occurring. If this activity holds together, it will mainly impact Southern and Central Trinidad later this afternoon through the evening.
Tropical Wave 07: This wave is completely devoid of activity due to its location in a dense Saharan Dust plume. There is some surge in total precipitable water and the axis of the wave is forecast to move across T&T on Saturday into Sunday. Favorable atmospheric conditions are likely as this wave moves across the Southern Windwards, forecast to produce scattered showers and thunderstorms beginning Saturday.
Tropical Wave 08: This tropical wave is confined to the ITCZ presently. It is forecast to move across T&T on Sunday into Monday. Based on present model guidance, this wave, as well as TW07, is forecast to shift the ITCZ closer to Trinidad and Tobago, creating a fairly wet pattern through early Thursday of next week. Scattered to widespread showers as well as isolated to scattered thunderstorms are possible. In addition, street/flash flooding may become likely if models maintain their trends on rainfall.
Tropical Wave 09: This tropical wave is just moving off the West African coast with deep tropical moisture, but also a dense plume of Saharan dust to its north. Regardless, this wave is forecast to move across T&T next Tuesday with activity continuing through Thursday (i.e. just under a week away), bringing increased low-level moisture likely to bring showers, thunderstorms and possibly, the first heavy rainfall event for 2019.
No Tropical Development forecast elsewhere across the Atlantic basin over the next 5 days as of the latest tropical update.

Tropical Wave (04) & Tropical Wave (05)

The fourth and fifth tropical waves of the 2019 Atlantic Hurricane Season moved across Trinidad and Tobago last Friday and Sunday. Isolated to scattered showers with a few heavy pockets did occur, with heavier showers generally occurring across Eastern parts of Trinidad, as expected. A few areas across Central and Western Trinidad did see some brief showers, though it was fairly light to moderate. Thunderstorm activity generally remained east and south of Trinidad.

These waves are now well west of Trinidad moving towards the Pacific ocean. Following the passage of these waves, a dense plume of Saharan dust followed, reducing air quality to its lowest levels across T&T since March 2019.

Tropical waves typically have fair weather ahead of the wave axis, though other features in the area such as surface troughs, increased atmospheric moisture, and local climatic effects, to name a few, may trigger showers and the odd thunderstorm. Following the passage of the wave, much of the active weather typically associated with a tropical wave occurs.
Tropical waves typically have fair weather ahead of the wave axis, though other features in the area such as surface troughs, increased atmospheric moisture, and local climatic effects, to name a few, may trigger showers and the odd thunderstorm. Following the passage of the wave, much of the active weather typically associated with a tropical wave occurs.

Why did I not experience 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. Generally, because of winds associated with weak tropical waves, showers and thunderstorms tend to follow a west-northwest track, generally missing areas across Southwestern Trinidad and even Northwestern Trinidad – though activity due to local climatic effects such as daytime heating may trigger shower and thunderstorm development across these areas. See the below graphic for a simple explanation.

Tropical Wave 06

The axis of this weak tropical wave moved across Trinidad, Tobago and the Southern Windwards overnight. Due to a dense Saharan Dust plume present across the Eastern Caribbean, dry mid-levels of the atmosphere has restricted shower and thunderstorm development, though an increase in low-level moisture is present.

As with most tropical waves, favorable low-level convergence and upper-level divergence follow the wave axis. This, in combination with a surge in low-level moisture, is presently supporting some isolated to scattered showers east of Trinidad and southeast of Tobago. Wind shear remains highly unfavorable for the present convection to persist as it moves westward.

However, additional convection is forecast to develop as this cluster moves across mainly Trinidad later this morning through the evening.

10:45AM Radar Update: Scattered moderate to heavy showers approaching Eastern Trinidad as the "active" weather of this tropical wave approaches Trinidad. Light to moderate showers are occurring across parts of Tobago. Showers to continue through the evening.
10:45 AM Radar Update: Scattered moderate to heavy showers approaching Eastern Trinidad as the “active” weather of this tropical wave approaches Trinidad. Light to moderate showers is occurring across parts of Tobago. Showers to continue through the evening. Radar Image: Trinidad and Tobago Meteorological Service

This wave is not forecast to produce widespread or scattered severe weather, nor is it forecast to produce widespread heavy rainfall. However, locally heavy rainfall is possible in heavy showers and/or thunderstorms. This “active” weather is forecast to subside overnight.

Very little rainfall accumulation is forecast, with overall 24 hour totals forecast to be between 0-5 millimeters across both islands, with totals up to 10 millimeters possible across Eastern and Southern Trinidad. Gusty winds may occur in the vicinity of heavy showers and/or thunderstorms.

Following the passage of this tropical wave, another surge of Saharan Dust is forecast to move across the Eastern Caribbean on Friday, though this surge is forecast to be short-lived.

Tropical Wave 07

This wave has fallen victim to the dense plume of Saharan dust present across the Atlantic Ocean presently. This tropical wave is very weak, with no discernable convective activity surrounding the wave axis, though there is a subtle surge in low-level moisture associated with the wave axis. The wave axis extends along 45W/46W from 04N to 11N, moving west at 15 to 20 knots as of the latest tropical update.

As unimpressive as this wave is currently, it is still forecast to retain it’s tropical wave characteristics as it progresses westward. As it nears (Saturday) and moves across (Sunday) Trinidad and Tobago over the weekend, this wave will interact with a forecast upper-level trough creating a diffluent pattern over the Southern Windwards. This may enhance shower development, creating some heavy pockets and thunderstorm activity.

This wave is not forecast to produce widespread or scattered severe weather, nor is it forecast to produce widespread heavy rainfall. However, locally heavy rainfall is possible in heavy showers and/or thunderstorms. This “active” weather is forecast to mainly occur on late Saturday into Sunday.

Rainfall accumulation is forecast to be between 5-10 millimeters across West-central and Northwestern parts of Trinidad as well as Western Tobago, 10-20 millimeters across most of Southern, Central and North-central Trinidad as well as Tobago and up to 30 millimeters possible across Eastern T&T. Generally, street flooding is possible, particularly in areas that experience isolated heavy showers or thunderstorms. In addition, gusty winds are possible in the vicinity of heavy showers and/or thunderstorms.

Note that this tropical wave, as well as the following two waves are to move across Trinidad and Tobago in close succession of one another, producing a fairly wet pattern next week.

Tropical Wave 08

This tropical wave remains closely confined to the ITCZ as of the latest tropical update. The axis of this wave extends along 30W/31W from 02N to
10N, moving west at 10 to 15 knots. Scattered moderate convection is ongoing from 03N to 06N between 25W and 35W, related to the tropical wave and the ITCZ.

This wave is forecast to remain near the ITCZ as it progresses westward, with its axis forecast to move across Trinidad and Tobago Sunday into Monday. Moisture from the previous tropical wave will still be present. Hence, based on the present models, showers and thunderstorms are likely both prior and proceeding the passage of the wave.

This wave is not forecast to produce widespread or scattered severe weather, nor is it forecast to produce widespread heavy rainfall. However, locally heavy rainfall is possible in heavy showers and/or thunderstorms. This “active” weather is forecast to mainly occur on late Sunday into Monday.

Rainfall accumulation is forecast to be between 5-10 millimeters across West-central and Northwestern parts of Trinidad as well as Western Tobago, 10-20 millimeters across most of Southern, Central and North-central Trinidad as well as Tobago and up to 30 millimeters possible across Eastern T&T. Generally, street flooding is possible, particularly in areas that experience isolated heavy showers or thunderstorms. In addition, gusty winds are possible in the vicinity of heavy showers and/or thunderstorms.

Tropical Wave 09

An Atlantic Ocean tropical wave has an axis along 16W/17W from 06N to 12N, moving west at 10 to 15 kt. No significant weather is noted near the wave axis at this time. While deep layer moisture is abundant along the wave axis, Saharan dust is noted north of 12N, emerging into the Atlantic off the coast of Senegal.

This wave is several days away and based on current model guidance is forecast to move across Trinidad and Tobago on Tuesday into Wednesday. It is still over 6 days away, so impacts would become clearer as we near Tuesday. However, based on present model guidance, this is shaping up to be the first heavy rainfall event of the year.

Models show the ITCZ lingering across Trinidad and Tobago as the prior two waves brought the ITCZ closer to the Southern Windwards, with very high total precipitable moisture values and favorable atmospheric conditions, particularly on Tuesday through Thursday.

From Monday through Thursday, scattered severe weather is possible. This means scattered heavy rainfall, with the possibility of street/flash flooding, gusty winds, landslides/landslips are all in the realm of possibility, mainly across Trinidad. As a result of this, downed trees and/or utility poles are possible, which may produce localized power outages. Seas may become locally rough in the vicinity of heavy showers or thunderstorms.

24-hour rainfall accumulation for each day (Tuesday, Wednesday, Thursday) is forecast to be between 15-20 millimeters across both Trinidad and Tobago and up to 50 millimeters possible across Eastern and Southern T&T.

If models continue to trend with heavy rainfall totals for next week, more than likely, an Adverse Weather Alert/Watch/Warning may be issued by the Trinidad and Tobago Meteorological Service by early next week. Updates will be posted in subsequent tropical updates and forecasts.

Tropical Cyclone Climatology

Tropical Cyclone Points of Origin during the month of June. Though attention is usually placed on the Western Caribbean, Gulf of Mexico and the Western Atlantic, a few storms have developed east of Trinidad and Tobago during the month of June, most recently and notably – Tropical Storm Bret in 2017.

In June, we turn our eyes to the Western Caribbean and the Gulf of Mexico for the formation of tropical cyclones in the Atlantic Basin, historically. However, tropical cyclones can form in the Atlantic Basin, without regard for the location once conditions support development.

There are NO tropical cyclone threats to the Eastern Caribbean, including Trinidad and Tobago at this time.

No areas forecast for development in the latest tropical update
No areas forecast for development in the latest tropical update
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