Significant Saharan Dust Plume Set To Affect Lesser Antilles From Today

Islands across the Lesser Antilles are bracing for a high-concentration surge of Saharan Dust that is set to affect the region from this (Sunday) afternoon. Meteorological offices in Grenada, Barbados, Antigua and Barbuda, and Trinidad and Tobago have issued statements ahead of the dust surge. Air quality is set to improve by mid-week, with another dust surge arriving by the end of the week.

What you need to know

Saharan Dust Surges: A significant dust surge is forecast to begin affecting the Lesser Antilles today, July 10th, 2022, with peak concentrations through the next 36 hours. Another moderate to high concentration dust surge is forecast across the Lesser Antilles by early Thursday, July 14th, 2022. After some improvement over the upcoming weekend, a third surge of dust is set to arrive by July 19th. In all dust surges, higher concentrations are forecast to remain north of T&T, across the French Antilles and Leewards.
Impacts: Air quality levels across Trinidad and Tobago will vary between good and moderate through the forecast period, dipping to unhealthy levels for sensitive groups on Sunday evening through Tuesday morning.
What Should You Do: Sensitive groups will have brief periods during the upcoming forecast period where good air quality is anticipated. However, they should take the necessary precautions during dust surges. The general population will remain unaffected.

Current AQI Levels Across T&T

The Environmental Management Agency (EMA) air quality monitoring stations at San Fernando, Port of Spain, and Signal Hill have all recorded good to moderate air quality levels over the last 24 hours.

These measurements are based on PM2.5 (particulates the size of 2.5 micrometers and smaller, usually associated with increases in Saharan Dust, vehicle exhaust, and smoke) and PM10 particulates.

Over the last 24 hours, visibility remained near ten kilometers at the Piarco International Airport and A.N.R. Robinson International Airport at Crown Point, Tobago.

Saharan Dust Forecast

00Z Sunday, July 9th, 2022, NASA GEOS-5 Dust Extinction Model Monitoring Tropical Atlantic Sulphates Aerosol Optical Total showing Saharan Dust
00Z Saturday, July 9th, 2022, NASA GEOS-5 Dust Extinction Model Monitoring Tropical Atlantic Sulphates Aerosol Optical Total showing Saharan Dust

New Surge: From Sunday, July 10th, 2022

Following Tropical Wave 17 on today (Sunday), a significant surge of Saharan Dust is forecast to begin moving across the Lesser Antilles, with higher concentrations affecting countries north of Trinidad and Tobago. Peak dust concentrations are forecast between Monday, July 11th, and Tuesday, July 12th, with gradually diminishing dust levels.

Air quality levels will vary from good, mainly across southern Trinidad, and moderate to unhealthy for sensitive groups elsewhere, with the visibility dropping five kilometers outside of shower or thunderstorm activity.

This dust surge is forecast to briefly decrease – but Saharan Dust will not go away – by Wednesday, July 13th, 2022 as an upper-level low pressure that has been anchored across the Central Caribbean Sea pulls west.

Surge #2: Early Thursday, July 14th, 2022

A moderate to high-concentration surge of dust is set to follow on Thursday, July 14th, 2022, and linger through July 17th. Higher dust levels are forecast to remain north of the country.

Air quality levels will vary from good to moderate, with the visibility dropping to six kilometers outside of shower or thunderstorm activity.

Some brief improvement is forecast on Monday, July 18th, 2022 as a tropical wave is modeled to move across the Lesser Antilles then, decreasing dust levels.

Surge #3: Early Tuesday, July 19th, 2022

Following the passage of Tropical Wave 18 and modulation of the Intertropical Convergence Zone across T&T on Friday into the weekend, another moderate to a high-concentration surge of dust is set to follow on Tuesday, July 19th, 2022. Similar to the previous two dust surges, higher concentrations of Saharan Dust are forecast to remain north of Trinidad and Tobago.

Air quality levels will vary from good to moderate, with the visibility dropping to six kilometers outside of shower or thunderstorm activity.

What does this mean for you?

The air quality will be degraded through the forecast period. During high traffic periods, particularly between 6:00 AM and 9:00 AM, and again from 3:00 PM through 6:30 PM, air quality may be further reduced in localized areas.

According to the Trinidad and Tobago Meteorological Service, “the 2022 Saharan Dust Haze Season is likely to peak from June to August with the number of Saharan dust haze days expected to increase significantly. The duration of the plumes of Saharan dust haze visiting both islands is also likely to be more prolonged than earlier in the year, with increased odds for higher dust haze concentration during plumes visitation.”

We’re in a period where the Intertropical Convergence Zone and tropical waves may shield Trinidad and Tobago from the Saharan Dust events. While Tropical Waves play a notable role in moving dust across the Atlantic and the Eastern Caribbean, these periodic tropical waves also improve air quality.

The concentration of the dust that follows the wave depends on its strength as it moves off the West African Coast. This is because of stronger thunderstorms across Central Africa. As strong winds move downward and outward from these thunderstorms, the wind kicks up dust as it moves across parts of the Saharan Desert and transports it into the upper atmosphere. This “plume” of dust follows the axis of the wave as it progresses westward into the Atlantic.

Dust that makes it into the upper levels of the atmosphere can then get transported across the Atlantic Ocean. The plumes of dust eventually affect the Eastern Caribbean.

Larger, more concentrated plumes of Saharan dust begin in April and continue through November.

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