The Atlantic basin hurricane season officially ended on Nov. 30, marking yet another year that the U.S. coast avoided the landfall of a major hurricane. It has been more than 10 years since that happened — since Hurricane Wilma in 2005 — the longest such “drought” on record, eclipsing the previous record of eight years set from 1861 to 1868.
Major hurricanes are defined only by their maximum winds — any storm that’s a Category 3 or stronger — but say nothing about a hurricane’s impacts. Certainly, despite the dearth of strong storms, the United States has experienced significant hurricane damage over the past 10 years; notably, Gustav and Ike in 2008; Irene in 2011; and Sandy in 2012, all of which caused considerable loss of life and huge financial losses.
But there is no denying that there is something significant about this drought, and it’s leading atmospheric scientists to ask why it’s happening.
Obviously, there is a considerable component of luck at play here. Cuba, a mere 150 miles south of Florida, has been devastated by several major hurricanes during the same time period. It also may come as a surprise that 27 major hurricanes have formed in the Atlantic Ocean since Wilma, about a dozen of which made landfall as major hurricanes in places outside the United States.
In addition, some of the hurricanes that have made landfall in the past 10 years have been just below the Category 3 threshold. Two memorable examples of this are Hurricane Ike, which made landfall as a powerful Category 2 with a very large wind field in 2008, and Hurricane Arthur in 2014, which made landfall in North Carolina around the Fourth of July holiday. Others have just barely missed the U.S. coast, such as Hurricane Earl in 2010.
But it’s not only luck that has been saving our coastlines from major hurricane damage. Over the past 10 years, there has tended to be an area of stronger-than-normal low pressure over the East Coast at the mid-levels of the atmosphere (about 18,000-feet high) during hurricane season.
This is an important feature because the winds at these levels steer hurricanes and determine the final path they take. Winds around this low pressure area help to push storms toward the north where they are picked up by the jet stream and carried away from the United States and out to sea.
It’s not just the major hurricane landfall drought that leads us to believe this low-pressure anomaly has been influencing our hurricanes.
The United States is also in a 10-year low in hurricanes that have impacted the coast. These numbers include storms that might not have made landfall — the center of the storm did not cross the coastline — but still brought hurricane-force winds to land.
Only eight hurricanes have made impact with the United States in the past 10 years, and there have been zero major hurricane impacts. This ties the old record for impact drought set from 1973 to 1982.
Our current drought is really put into perspective when you compare it to the most active periods in the historical record: 27 U.S. hurricane impacts from 1879 to 1888, and eight major hurricane impacts last achieved from 1999 to 2008.
And perhaps an even more impressive hurricane streak is the fact that Florida has not been impacted by a hurricane of any strength since Wilma in 2005. Their current ten-year string of good luck doubles the previous record set between 1980 and 1984.
Of course, the current drought is just the recent part of a longer-term downward trend in hurricane activity for the East Coast and the Florida peninsula. Over the past 50 years, only eight major hurricanes have made impact, compared with 20 major hurricanes during the previous 50 years. If a similar active period for landfalling major hurricanes were to occur in this region, damage would be catastrophic given the large population increase in coastal communities.
So if this recurring low-pressure pattern over the East Coast has helped prevent hurricanes from making landfall, then what does the new high pressure pattern over the Eastern United States mean for next hurricane season? Might 2016 bring a reversal in fortunes?
It’s still far too early to say what the predominant steering patterns will be during next year’s hurricane season. But the good news is there’s very little connection between wintertime and summertime weather patterns, so this winter’s high pressure doesn’t necessarily portend a big U.S. hurricane season in 2016.
This post has been updated to reflect recent changes in the historical hurricane database (HURDAT2) from 1951 to 1955.