As we’ve mentioned over the last week, a significant surge of Saharan Dust was forecast to move across the region at the end of this week. Air quality has plummeted across the Windward Islands over the last 24 hours as the first major surge of dust moved across the region.
Across Trinidad and Tobago, air quality has reached unhealthy levels for the first time for 2020 across both islands, with visibility significantly affected, down to 4 kilometers across Trinidad compared to the usual 10 kilometers and above.
This plume of dust is also affecting the entire Eastern Caribbean, with a number of islands reporting reduced visibility and air quality. The more severely affected islands include Barbados (6 kilometers visibility, moderate air quality based on U.S. Standards) and St. Vincent and the Grenadines (5 kilometers visibility, moderate air quality based on U.S. Standards).
This initial peak of Saharan Dust is forecast to gradually reduce overnight as Tropical Wave 11 moves across the region, bringing thunderstorms and showers mainly north of Trinidad and Tobago. Following the passage of this wave, a more severe and prolonged Saharan Dust surge is forecast to arrive, lingering through the week.
Note that in localized areas, further reduced air quality will occur in areas with smoke, fires, and high vehicular traffic.
The Environmental Management Agency (EMA) air quality monitoring stations are presently recording AQI values at levels that are unhealthy for sensitive groups to unhealthy in Trinidad and Tobago 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.
What we expect
Based on the latest dust modeling, air quality across Trinidad and Tobago is forecast to improve tonight through tomorrow. By Saturday night into Sunday, a more severe and prolonged surge of dust will arrive across T&T and the Lesser Antilles, with the highest concentrations remaining between Tobago and Martinique.
Note that on Sunday into Monday, very unhealthy air quality (for the entire population) is possible, triggering health alerts for some islands as some of the highest concentrations will remain north of T&T. Across Trinidad and Tobago, isolated to scattered showers and isolated thunderstorms may provide some relief, keeping our air quality below that very unhealthy level.
Concentrations are forecast to remain elevated through the upcoming week, with improvement forecast on Thursday as Tropical Wave 13 moves across the islands, but another surge of dust will follow on Friday, leading to a mostly dusty end to June.
Note that this plume of Saharan Dust that follows on Sunday will traverse and affect the entire Caribbean, including the Greater Antilles over the next week, flowing into the United States Gulf Coast and Central America by next week, reducing air quality across those areas.
What does this mean for you?
On Sunday into Monday, health alerts are possible as everyone may experience more serious health effects. A significant increase in respiratory effects in the general population is expected. See the AQI levels versus the above Saharan Dust forecast for more details
We’re in a period where the ITCZ and tropical waves 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 frequent tropical waves also aid in improving 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.
Sensitive groups such as persons with respiratory ailments, children, the elderly and cardiopulmonary disease should take the necessary precautions on days where dust concentrations degrade air quality to moderate and beyond, as there is more Saharan Dust forecast.