Periodic Surges Of Saharan Dust Forecast Over Next 10 Days

A brief surge of Saharan Dust moved across Trinidad and Tobago late Thursday into Friday, with concentrations declining ahead of an approaching tropical wave. Over the next 10 days, while no significant surges of Saharan Dust are forecast to move across the country, periodic moderate to high surges will affect the Lesser Antilles. Trough systems and tropical waves are also forecast to temper the impacts of dust.

Over the last 24 hours, air quality has been good to moderate with visibility outside of showers and thunderstorms between 6 to 10 kilometers across T&T. The Environmental Management Agency (EMA) air quality monitoring stations are recording AQI values at levels that are good in Trinidad and Tobago. 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.

The Saharan Dust Forecast

Peak concentrations have passed across Trinidad and Tobago, with air quality improvements forecast over the next 24-48 hours as Tropical Wave 27 moves across the region.

Following the passage of the tropical wave, Saharan Dust concentrations are forecast to increase on Sunday and remain across T&T through next week, with fluctuating moderate concentrations. Air quality improvement is forecast for next weekend.

Air quality levels will fluctuate between good to moderate through the entire forecast period. On days with peak concentrations, visibility may be reduced between 7-10 kilometers.

00Z 30th July 2021, NASA GEOS-5 Dust Extinction Model Monitoring Tropical Atlantic Dust Aerosol Optical Depth showing Saharan Dust.
00Z 30th July 2021, NASA GEOS-5 Dust Extinction Model Monitoring Tropical Atlantic Dust Aerosol Optical Depth showing Saharan Dust.

What does this mean for you?

For the general population, with moderate to high Saharan dust concentrations forecast, little to no impacts are forecast beyond hazy skies. For sensitive groups, such as children, the elderly, and persons who suffer from respiratory ailments and allergies, you may need to avoid prolonged exertion outdoors on days with high concentrations of Saharan Dust.

We’re in a period where the ITCZ and tropical waves may shield Trinidad and Tobago from significant 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 the strength of the wave 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 dust begin to occur in April and continue through November.

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