Next Surge Of Saharan Dust Forecast To Arrive By End Of Week

Concentrations of dust from the significant surge of Saharan Dust that arrived across the Windward Islands last week are on the decline. Across the Windward Islands, Saharan Dust concentrations are forecast to decrease over the next 3-4 days. We continue to monitor the La Soufrière Volcano eruption as volcanic ash can reduce air quality and visibility across islands that experience ashfall.

On Monday morning the Environmental Management Agency (EMA) air quality monitoring stations are recording AQI values at levels that are good to 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 and above.

The Saharan Dust Forecast

Between April 19th and April 22nd, Saharan Dust concentrations will be declining at mild to moderate levels. During this time, air quality will fluctuate between levels that are good to moderate across Trinidad and Tobago

Saharan dust levels are forecast to increase during the morning into the afternoon of April 22nd and linger into next week. During this period, air quality could reach levels that are moderate to unhealthy for sensitive groups. This surge of dust will diminish by Monday 26th April 2021, with another, prolonged surge arriving by late Wednesday 28th April 2021.

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

12Z Sunday 18th April 2021, NASA GEOS-5 Dust Extinction Model Monitoring Tropical Atlantic Dust Aerosol Optical Depth showing Saharan Dust.
12Z Sunday 18th 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 the Grenadines, extending westward into the Caribbean Sea 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. Volcanic eruptions of the La Soufrière Volcano can occur at any time, sending ash across the Windward Islands and reducing air quality depending on the movement of ash clouds.

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