If you’ve noticed the hazy skies increased today (Saturday) and questioning whether it could be Saharan Dust or rain, you’re not wrong with either guess. While showers did affect parts of Trinidad on Saturday, a moderate surge of dust moved in late Friday and will linger through tonight.
Multiple surges of dust are forecast over the next 10 days, generally following tropical wave activity.
What you need to know
— Saharan Dust Surges: After the ongoing dust surge, new surges of dust are forecast by late Sunday, July 18th, 2022; late Thursday, July 21st, 2022; and Tuesday, July 26th, 2022.
— Impacts: Air quality levels across Trinidad and Tobago will vary between good and moderate through the forecast period, dipping to unhealthy levels for sensitive groups mainly across the Leewards and French Antilles.
— What Should You Do: Sensitive groups will have brief periods during the upcoming forecast period where good air quality is anticipated. However, they should take the necessary precautions during dust surges. The general population will remain unaffected.
Current AQI Levels Across T&T
The Environmental Management Agency (EMA) air quality monitoring stations at San Fernando, Port of Spain, Point Lisas, and Signal Hill have all recorded good to moderate air quality levels over the last 24 hours.
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.
Over the last 24 hours, visibility remained near ten kilometers at the Piarco International Airport and A.N.R. Robinson International Airport at Crown Point, Tobago.
Saharan Dust Forecast
Ongoing Surge: Through Tonight, Saturday, July 16th, 2022
A brief surge of Saharan Dust followed Tropical Wave 19, arriving last evening across Trinidad and Tobago.
This dust surge is forecast to briefly decrease tonight as Tropical Wave 20 nears.
Surge #2: Sunday, July 17th, 2022
A moderate concentration surge of dust is set to follow Tropical Wave 20 on Sunday, July 17th, 2022, during the afternoon and linger through Wednesday, July 20th, 2022. Higher dust levels are generally forecast to remain north of Trinidad and Tobago.
The Intertropical Convergence Zone is forecast to remain near Trinidad and Tobago over the week and is forecast to produce intervals of showers and isolated thunderstorms, with brief air quality improvement. Still, air quality levels will vary from good to moderate, with the visibility dropping to eight kilometers outside of shower or thunderstorm activity.
Tropical Wave 21 will bring improvement in dust levels from Wednesday through early Thursday.
Surge #3: Late Thursday, July 21st, 2022
Following the passage of Tropical Wave 21 and the modulation of the Intertropical Convergence Zone across T&T, a moderate to high-concentration surge of dust is set to arrive by late Thursday, July 21st, 2022. Some improvement is forecast by Sunday, July 24th, 2022 due to another tropical wave (yet to leave the African Coast) moving across the region on Sunday into Monday, July 25th, 2022.
Surge #4: Early Tuesday, July 26th, 2022
Following the passage of what will be Tropical Wave 22, another moderate to high-concentration surge of dust is set to arrive by early Tuesday, July 26th, 2022.
What does this mean for you?
The air quality will be degraded through the forecast period. During high traffic periods, particularly between 6:00 AM and 9:00 AM, and again from 3:00 PM through 6:30 PM, air quality may be further reduced in localized areas.
According to the Trinidad and Tobago Meteorological Service, “the 2022 Saharan Dust Haze Season is likely to peak from June to August with the number of Saharan dust haze days expected to increase significantly. The duration of the plumes of Saharan dust haze visiting both islands is also likely to be more prolonged than earlier in the year, with increased odds for higher dust haze concentration during plumes visitation.”
We’re in a period where the Intertropical Convergence Zone 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 its strength 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 in April and continue through November.