Why The Atlantic Basin Is As Hostile To Hurricane Formation As Possible Right Now

Jon Erdman
Published: August 10,2015

Monday, Aug. 10, marked the date by which you typically have seen the first hurricane of the Atlantic hurricane season, according to the National Hurricane Center.
Given the setup right now, the season's first Atlantic hurricane remains a remote chance until further notice.
How is it that the Atlantic's activity lately has been so squashed?

How Dry It Is!

First, there is currently an expansive area of dry air in the deep tropical Atlantic Basin, particularly from the Lesser Antilles east.

Water Vapor Satellite Image

Tropical cyclones form from a feedback mechanism when thunderstorms are able to remain clustered around an area of low pressure near the surface.
Dry air impedes this by encouraging the development of stronger thunderstorm downdrafts, which then either squelch nearby thunderstorms from forming or push them away.
This dry air is also stable, meaning it suppresses upward vertical columns of air needed to maintain or form new thunderstorms.
Known to meteorologists as a Saharan Air Layer, this dry air in the deep tropical Atlantic Basin comes from Africa's Saharan Desert. Saharan dust can be carried thousands of miles in this dry, stable layer of sinking air across the Caribbean Sea into the U.S., at times.
Over the first two-plus months of the hurricane season, abnormally dry air has been in place from the southern Gulf of Mexico to well east of the Lesser Antilles, as the first plot in this tweet from the NWS office in Tallahassee shows.
(MORE: Puerto Rico's Punishing Drought)

The Shear Magnitude

Dry air isn't the only suppressing factor, though.
Tropical cyclones like uniform winds through a depth of the atmosphere, in order to keep the convection colocated with the center of circulation, concentrating the energy given off in this "heat engine."
When winds strongly change with height, either in speed and/or direction, convection can get blown away from the center. This wind shear can keep tropical cyclones from forming and can rip apart any existing storms, as we've seen in the Pacific with Guillermo as it neared the Hawaiian Islands in August 2015.
Right now, wind shear is strong, as it has been much of the season so far, over the Caribbean Sea as well as parts of the Gulf of Mexico, far western and eastern Atlantic.

Current Wind Shear

As Colorado State University's Dr. Phil Klotzbach wrote in a recent Wunderground blog, July wind shear over the Caribbean Sea set a record high.
The still-intensifying El Nino is thought to be responsible for the increased wind shear in the Caribbean this summer.
So, if you took a chance and booked a Caribbean getaway over the next week or two, it appears a hurricane will be the least of your worries.

It Only Takes One

The Atlantic may be suppressed now, but that doesn't mean the entire season will remain that way.
"We're standing on the verge of the typical rapid escalation into the peak of the season," said senior meteorologist Stu Ostro in a Monday tropical update.
(MORE: Heart of the Hurricane Season Starts Now)

The number of both tropical storms and hurricanes in the Atlantic Basin typically begins its ramp up in August and peaks in September.

Ostro says regardless of whether this pattern is largely forced by El Nino, it doesn't mean the pattern couldn't change as we continue heading into the peak of the season, or that strong tropical cyclones couldn't develop in areas of atmospheric conditions more conducive to development.
So far this season, all three named storms have developed close to the U.S. Two of these, Ana and Bill, had significant U.S. impacts.

2015 Atlantic hurricane season tracks, so far.

As the cliché goes, "It only takes one" destructive hurricane or tropical storm landfall to erase any notion of a "quiet season."
Stay prepared and check back with us at The Weather Channel, weather.com and Weather Underground for the latest on the tropics this season.

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