Atlantic Tropics Update

Andrea, Barry, Chantal, Dorian -- these are the four named storms, so far, in this 2013 Atlantic hurricane season.{ } As of the last day of July, there are no storms that the National Hurricane Center is watching for possible tropical development.{ }

So does this mean we're in for a quiet rest of the hurricane season?{ } Not so fast.{ } The Atlantic hurricane season starts June 1st and lasts all the way through November 30th.{ } The peak of the Atlantic hurricane season doesn't occur until the beginning of September.{ } By then, ocean temperatures are usually warm enough to support tropical development.{ } Remember, tropical storms and hurricanes feed off of warm waters (around 80° F), saturated air, and low vertical wind shear.{ } Large bodies of water take much longer to heat compared to land, which is why Atlantic tropical storms and hurricanes are much more common in the early fall.{ }


The National Hurricane Center prediction for the Atlantic hurricane season estimates (prediction from May 2013) a 70% probability of 13-20 named storms, 7-11 hurricanes, and 3-6 major hurricanes.


As for any immediate tropical development, it looks rather unlikely.{ } One of the main reasons is because of the Saharan Air Layer (SAL).{ }{ } The SAL is a mass of very dry, dusty air that forms over the Sahara Desert during the late spring, summer, and early fall and usually moves out{ }over the tropical North Atlantic Ocean every 3-5 days.{ }{ }This dry air can have a negative imact on tropical cyclone development because of the very dry air in the mid levels of the atmosphere, as well as the strong winds associated with this layer which makes for a very hostile enviornment for tropical wave development.{ } Check out the latest satellite imagery depicting the very dry air (bright yellow and orange colors) off the west coast of Africa.

A neat simulation via NOAA visualization{ }that uses a recently enhanced version of the NOAA NGAC aerosol model to show how the plume is expected to travel across the Atlantic Basin over the next four days.

Here's another image of the SAL moving off the west coast of Africa via a NASA MODIS image.{ }

MODIS - TERRA satellite

More research is being done on the effect of the Saharan Air Layer on tropical cyclone formation and intensification.{ } With this very dry air mass moving off the west coast of Africa, and looking at the latest computer model guidance, there does not seem to be any tropical development within the next 7 days.{ } As always, the StormWatch7 weather team will keep you updated with tropical updates right here on our our weather homepage.