Surges of Saharan Dust Forecast To Follow Tropical Waves This Week

Saharan dust concentrations are increasing across Trinidad, Tobago, and the Lesser Antilles briefly ahead of Tropical Wave 16. Over the next 10 days, mild to high concentration surges of Saharan Dust are forecast to move across the Lesser Antilles, following the passages of tropical waves.

Over the last 24-48 hours, air quality has been good, decreasing to moderate with visibility outside of showers and thunderstorms beyond 10 kilometers.

On days with moderate to high concentrations of dust, air quality may reach moderate levels and visibility diminish to moderate levels.

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

Air quality is forecast to improve ahead of Tropical Wave 16, forecast to move across the region late Monday night into Tuesday. Dust concentrations will increase following the passage of the wave, by late Wednesday and decrease yet again as Tropical Wave 17 moves across the region on Friday.

A surge in trade winds is forecast on Saturday into Sunday, ahead of a more prolonged and significant concentration surge of dust that will linger through much of next week, with concentrations declining as the week progresses.

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 05 July 2021, NASA GEOS-5 Dust Extinction Model Monitoring Tropical Atlantic Dust Aerosol Optical Depth showing Saharan Dust.
00Z 05 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

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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