The Washington Post

Is the Atlantic hurricane season winding down?

Tracks of Atlantic tropical systems during 2011 (Unisys Weather)

The Atlantic hurricane season is not over by a long shot. In fact, we’re in the middle of the most active few weeks of the season historically. However, the tropics seem poised to enter a temporary quiet period once tropical storm Maria becomes part of an extratropical rainstorm over the North Atlantic in a couple days. A spell of inhospitable conditions that will shut down storm development is beginning to temporarily settle over Africa and the Atlantic Basin.

To date, this season has produced a lot of hype and very few hurricanes. In all, we’ve seen one tropical depression, 12 tropical storms, and two hurricanes. Though the total storm count is atypically high, only Irene made a North American landfall at hurricane strength - and did so just barely along a small section of North Carolina’s Outer Banks. All other members of the 2011 class so far either made landfall at tropical storm strength or curved out to sea a long way from our shores.

During the next week or so, mechanisms that partly govern the dryness, wind shear, and vertical stability (i.e., resistance to thunderstorm development) over the tropics will conspire to suppress the likelihood of tropical cyclone genesis in the Atlantic Basin. The image below offers a simplistic overview of what’s currently going on.

Areas countered in green are favorable for thunderstorm development, areas countered in brown are unfavorable (NOAA/CPC)

Satellite imagery shows very dry air off the coast of Africa (colored in bronze) which will tend to inhibit the development of tropical systems there. (NOAA/CIMSS)

Indeed, our next named storm may not come until those green lines become more prominently clustered over Africa and/or the Caribbean.

Meteorological guidance from the global weather models and from statistical forecasts of the tropical atmosphere suggests that this general pattern will continue for the next 10 days or so.

Soon thereafter, there are some indications that the pattern will shift in a way that re-activates our hurricane season, possibly in the Caribbean first. The ocean heat content is still sufficiently high in the development regions (including the Gulf of Mexico) to support major hurricanes. And history says we have a long way to go before we can put the season to bed. But until our current pattern flips, easterly waves rolling off of Africa just might travel harmlessly across the Atlantic, and any developments in the Caribbean may very well be squashed by the unfriendly surroundings.

Related links: Hurricane Tracking Center


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