Significant Saharan Dust Forecast Through Next 48 Hours Across T&T

Hazy skies across Port of Spain, Trinidad due to Saharan Dust at approximately 6:00 PM Wednesday 14th April 2021.

A significant surge of Saharan Dust arrived across the Windward Islands over the last 24 hours. High concentrations are forecast to remain across the region through the next 48 hours, bringing additional hazy skies and reduced air quality, exacerbating the impacts of the La Soufrière eruption.

On Thursday morning the Environmental Management Agency (EMA) air quality monitoring stations are recording AQI values at levels that are moderate across 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. Across the Lesser Antilles, mainly islands south of the French Antilles are experiencing degraded air quality.

Visibility at Piarco International Airport, Trinidad, and Crown Point International Airport, Tobago is at 10 kilometers.

The Saharan Dust Forecast

Between April 15th and April 17th, significant concentrations of Saharan Dust are forecast to remain across T&T and the Lesser Antilles. During this period, the air quality will fluctuate between levels that are moderate to unhealthy for sensitive groups.

Milder concentrations are forecast between April 17th through April 20th with generally moderate air quality.

Saharan dust levels are forecast to decline on April 21st through April 22nd, with another surge arriving on April 23rd across the region, particularly T&T.

A high-pressure system dominating across the Atlantic is producing strong easterly trade winds. These winds have become a conveyor belt for a significant and prolonged surge of Saharan Dust through mid-April.

12Z Thursday 15th April 2021, NASA GEOS-5 Dust Extinction Model Monitoring Tropical Atlantic Dust Aerosol Optical Depth showing Saharan Dust.
12Z Thursday 15th April 2021, NASA GEOS-5 Dust Extinction Model Monitoring Tropical Atlantic Dust Aerosol Optical Depth showing Saharan Dust.

What does this mean for you?

Members of sensitive groups may experience health effects. The general public is not likely to be affected. 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.

Saharan Dust outbreaks from December through early April tend to be milder in the Eastern Caribbean compared to late April through November. During the latter period, those dust outbreaks are associated with West African thunderstorms driving dust into the upper atmosphere.

For mariners, an “Ashfall Advisory” is in effect for the marine waters surrounding St. Vincent and extending as far east as east of Barbados from the National Hurricane Center Tropical Analysis and Forecast Branch. Mariners are encouraged to contact the National Hurricane Center at 305-229-4424 if they encounter volcanic ash or floating volcanic debris.

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