Weekend Forecast: Isolated Showers Before Dense, Saharan Dust Arrive

Weekend Weather Forecast

For the remainder of Friday, increased low level moisture associated with an approaching easterly wave, will bring some isolated showers, interrupting mostly cloudy skies.

Precipitable water at low levels of the atmosphere (below 850 MB) is at elevated levels to due an approaching easterly wave. Total precipitable water, a measure of the moisture content of the entire atmosphere is also elevated. However, much of the moisture will be confined to low levels of the atmosphere, inhibiting convective (thunderstorm) activity. Image: CIMSS/SSEC/UWM

This increased low-level moisture will bring some isolated shower activity across mainly Trinidad over the next 24 hours. These showers will be light to moderate, as moisture remains capped at low levels of the atmosphere, interrupting mostly cloudy and hazy skies. These conditions will persist through Saturday evening.

By late afternoon on Saturday, Saharan dust concentrations are forecast to rapidly increase across Trinidad and Tobago. Peak concentrations are forecast Saturday night into Sunday morning. Air quality levels are forecast to be at unhealthy levels solely based on Saharan Dust concentrations for the first time in 2019.

Satellite overview of weather conditions in the Eastern Caribbean.

A weak surface to low level ridge will build behind this easterly wave, with increasing wind speeds generally remaining 15-30 KM/H and gusts to 40 KM/H. By Monday, wind gusts may reach 50 KM/H.

Temperatures

Minimum low temperatures across Trinidad and Tobago through the weekend are forecast to be between 23°C-25°C and likely lower across inland and mountainous areas.

Maximum high temperatures across both islands are forecast to be mild, between 30°C-32°C.

Seas

Seas are forecast to remain moderate in open waters. Waves in open waters are forecast to be between 1.5 meters to 2.0 meters. In sheltered areas, seas are forecast to remain smooth, below 1.0 meters.

Winds are forecast to be from the east to northeast, at 15 to 20 knots.

Saharan Dust

The big weekend weather story will be the dense Saharan dust making its way across T&T’s atmosphere. On late Saturday and throughout Sunday, some of the highest concentrations of Saharan Dust will be present in the atmosphere. Dust models continue to indicate this as of Friday morning.


Saharan Dust forecast from the University of Athens SKIRON model, valid on 0Z UTC 15th March 2019 for Monday 18th March 2019.

Generally, the fluctuating, mild concentrations of Saharan Dust is present today (Friday). Good to moderate air quality levels across both islands. For the better part of Saturday, this will also hold true. However, sensitive groups may experience respiratory effects.

However, beginning after midday on Saturday, concentrations of Saharan Dust will begin to rapidly increase across Trinidad and Tobago,.

For the first time for 2019, air quality levels are forecast to be reduced to unhealthy levels solely because of Saharan Dust concentrations. Throughout the year, Saharan Dust concentrations have generally been reduced to unhealthy for sensitive groups, with the possibility of being reduced to unhealthy levels due to bushfires.

Unhealthy Air Quality Forecast

Saharan Dust Concentration Forecast. EPA AQI colours indicated.

Peak concentrations are forecast on Saturday and Sunday. Models continue to indicate that moderate to high concentrations of Saharan Dust will remain in the atmosphere through the first half of next week. Concentrations will decrease as the week progresses.

EPA Air Quality Index Risk Levels

Generally, PM2.5 levels (dust or particulate matter (PM) with a diameter of less than 2.5 micrometers) are forecast to remain at unhealthy levels beginning Saturday night through Tuesday of next week, at minimum.
PM10 levels (dust or particulate matter (PM) with a diameter of less than 10 micrometers) are forecast to remain at unhealthy healthy for sensitive groups during the peak of the event, returning to moderate levels by the end of the forecast period.

At unhealthy levels: There will be increased aggravation of heart or lung disease. Possible premature mortality in persons with cardiopulmonary disease and the elderly. There will also be increased respiratory effects in the general population. People with respiratory or heart disease, the elderly and children should avoid prolonged exertion. Everyone else should limit prolonged exertion

Related: Saharan Dust

At unhealthy for sensitive groups: There is the increasing likelihood of respiratory symptoms in sensitive individuals. Aggravation of heart or lung disease and possible premature mortality in persons with cardiopulmonary disease and the elderly. People with respiratory or heart disease, the elderly and children should limit prolonged exertion.

Larger, more concentrated plumes of Saharan dust begin to occur in April, and continue through November. This is due to stronger thunderstorms across interior Africa sending dust into the upper atmosphere.

Trinidad and Tobago won’t be the only islands affected. Grenada, St. Vincent and the Grenadines as well as Barbados will also experience unhealthy air quality at times.

Persons with respiratory ailments are advised to take the necessary precautions, not limited to those listed below.

Saharan Dust Precautions
Saharan Dust Precautions
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