High Saharan Dust Concentrations To Fluctuate Across T&T Over Next 10 Days

A surge of Saharan Dust is moving across T&T following yesterday’s passage of Tropical Wave 18 which brought scattered showers and thunderstorms across the country.

Through the next 10 days, air quality levels are forecast to fluctuate due to passages of tropical waves on Wednesday and Thursday, and again on Sunday.

Over the last 24 hours, air quality has been good with visibility outside of showers and thunderstorms beyond 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

Through today and into tonight, Saharan Dust concentrations are forecast to gradually increase with peak (and significant) concentrations forecast within the next 18 hours. Concentrations will decline into Tuesday and Wednesday as Tropical Waves 19 and 20 move across the region, though moderate dust concentrations will linger.

By Friday, another moderate to high concentration surge of dust will move across the Lesser Antilles. Still, this surge is forecast to be short-lived as a tropical wave traverses the region on Saturday into Sunday. Another moderate to high concentration surge of dust is forecast to arrive late Sunday into next Monday, reducing visibility and air quality.

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.

12Z 11th July 2021, NASA GEOS-5 Dust Extinction Model Monitoring Tropical Atlantic Dust Aerosol Optical Depth showing Saharan Dust.
12Z 11th 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.

For countries in the Leewards, air quality could dip to levels that are unhealthy for sensitive groups.

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.

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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