Saharan Dust Forecast To Follow Tropical Waves Over Next 10 Days

Following the passage of a low-level trough in the last 24-36 hours, Saharan Dust has returned to T&T, reducing air quality across the country.

Through the next 7-10 days, periodic surges of Saharan Dust are forecast to follow the passage of weak tropical waves, typical for this time of year.

Moderate to high concentrations of dust through the next 10 days may cause air quality levels to dip to moderate levels with the lowest visibility at 7-8 kilometers.

The Environmental Management Agency (EMA) air quality monitoring stations are recording AQI values at levels that are good to moderate 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

Through the next 24-36 hours, at least through Saturday night, Saharan dust concentrations are forecast to remain moderate to high but gradually diminishing due to a tropical wave moving across the region Saturday night into Sunday 30th May 2021.

A surge of Saharan dust will move across the region on Monday 31st May 2021, with high concentrations continuing into Tuesday. Dust levels will fluctuate into the end of the week, with another tropical wave arriving sometime between the middle to end of the upcoming week. This will improve air quality levels temporarily before another surge on Friday night into Saturday 5th June 2021. High concentrations will linger through the end of the forecast period.

Longer range modelling show a significant surge of dust arriving across T&T and the Windward Islands by June 12th, lingering into the mid-month.

Air quality levels will fluctuate between good to moderate. By mid-month, air quality may dip further to levels that are moderate to unhealthy for sensitive groups.

On days with peak concentrations, visibility may be reduced between 7-10 kilometers.

00Z 28th May 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.

Closer to the middle of the month, with high concentrations of Saharan Dust forecast, members of sensitive groups may experience health effects. The general public is not likely to be affected though visibility will be reduced due to increased dust. There is an increasing likelihood of respiratory symptoms in sensitive individuals, aggravation of heart or lung disease, and premature mortality in persons with cardiopulmonary disease & the elderly.

We’re in a period where the ITCZ 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 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 Saharan dust begin to occur in April and continue through November.

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