Two Significant Surges Of Saharan Dust Forecast Across T&T Over Next 7 Days

Over the next seven days, two plumes of Saharan Dust are forecast to move across the Windward Islands, reducing air quality and visibility. Across Trinidad and Tobago, the first surge will begin to move across the country by late Monday, with the second surge arriving by Friday. However, overall peak concentrations are forecast on Sunday.

Saharan Dust concentrations are forecast to remain at moderate to high levels across Trinidad and Tobago at least through the next two weeks.

With the first surge of Saharan Dust, air quality levels may dip to moderate levels, at times, unhealthy for sensitive groups. However, by this weekend, with the second surge of dust, air quality may dip to unhealthy levels into next week.

The Environmental Management Agency (EMA) air quality monitoring stations are recording AQI values at levels that are good in Trinidad and Tobago as of Monday morning 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

Over the next 24 hours, Saharan Dust concentrations are forecast to gradually increase. Air quality levels will reduce from good levels to moderate. The initial peak of the first surge of dust is forecast on Tuesday, with air quality dipping further to levels that are unhealthy for sensitive groups.

Through the week, air quality levels will fluctuate between moderate to unhealthy for sensitive groups until Friday, with Saharan Dust concentrations are forecast to increase yet again. Through the weekend, particularly on Sunday, air quality may reach unhealthy levels.

On days with peak concentrations, visibility may be reduced between 7-10 kilometers particularly on Tuesday, and 5-10 kilometers over the weekend.

00Z 9th May 2021, NASA GEOS-5 Dust Extinction Model Monitoring Tropical Atlantic Dust Aerosol Optical Depth showing Saharan Dust.
00Z 9th 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 through the next 48 hours, 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.

Beginning Tuesday, 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. 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 a ridge of high pressure stays over the central Sahara Desert. The Intertropical Convergence Zone (ITCZ) also remains over the Gulf of Guinea. The Harmattan wind accelerates when it blows across the mountain massifs of Northwest Africa. If its speed is high enough and it blows over dust source regions, it lifts the dust and disperses it.

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.

However, as we progress through May, 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.

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

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