Meteorologists have linked the presence of Saharan Air Layer (SAL) or Saharan Dust across the Atlantic Ocean, to the calm currently being experienced for the Atlantic Hurricane Season.
The very dry, dusty layer of warm air occurs when a dust storm develops over Western Africa in the Sahara Desert and gets blown into the Atlantic Ocean by easterly winds.
The Antigua and Barbuda Meteorological Services, which has weather forecasting responsibilities for the BVI, explained that the dust hinders the formation of tropical cyclones by restricting the amount of moisture needed for cyclones to develop.
Director, Antigua and Barbuda Meteorological Services, Keithley Meade stated, “The aerosols within the SAL are thought to inhibit convection by robbing an area of moisture. This can inhibit the development of tropical waves, especially during the early hurricane season”.
Mr. Meade noted that the SAL’s impact on hurricane formation is not a new occurrence.
He said, “SAL’s effect on the 2015 hurricane season has been well documented where many of the developing systems failed to thrive as dry existing air and dust robbed the systems of moisture and provided an atmosphere unsuitable for development”.
Meteorologist with Pennsylvania based weather forecasting service, AccuWeather, Ed Vallee also reported that the Saharan Dust has slowed down hurricane activity for July.
Mr. Vallee said, “There are plenty of tropical waves moving off Africa right now. We aren’t at a loss for energy coming off the continent. It’s the fact that there is this dry Saharan Air Layer.”
He added, “The water temperatures are plenty warm, but the dry, dusty air is really inhibiting development and a heavy wind shear—another tropical cyclone killer, is also occurring with the Saharan Dust”.
Despite the presence of the Saharan dust, the month of July has traditionally been a slow month during annual hurricane seasons, therefore the Department of Disaster Management (DDM) is advising residents to continue to fast track preparations.
Director of the DDM, Sharleen DaBreo stated, “Historically, August and September are peak months for hurricane activity so while the Saharan Dust is contributing to this quiet period this month (July), it cannot be used as a measure for hurricane activity for the remainder of the season”.
She added, “It is therefore imperative that everyone remain vigilant and continue to finalise preparations for the season. I know there is a tendency for persons to become relaxed when they don’t see anything happening but I strongly urge everyone to avoid complacency”.
Saharan Dust can occur throughout the hurricane season with June and July normally being the peak months for heightened activity.
There have been some variations in Hurricane predictions for 2016 by several weather forecasting institutions. On May 27, the National Oceanic Atmospheric Administration issued its forecast saying the season will “most likely be near-normal”. It predicts a 70% likelihood of ten to16 named storms of which four to eight could become hurricanes including one to four major hurricanes.
To date, three storms have developed since the start of the 2016 Atlantic Hurricane Season—Bonnie in late May (a few days before the official start), followed by Colin and Danielle in June. However, months before the prescribed hurricane season, Hurricane Alex formed in January.