U.S. again lucky during active hurricane season

The hurricane season that ends today marks the second consecutive year when an above-average number of storms have formed and most of them stayed harmlessly offshore from the U.S. coast.

“Enjoy it while you can,” said Jeff Masters, meteorological director for the website Weather Underground. “It will not last forever.”

The 2011 hurricane season was among the most active on record, producing 19 named storms and three major hurricanes. But the U.S. Gulf and Atlantic coasts were very lucky. Only one hurricane — Hurricane Irene — made a U.S. landfall, and by the time that storm came ashore in North Carolina in late August, it had lost much of its power and was not a major hurricane.

Two other tropical storm systems made landfall in the U.S., but neither approached hurricane strength when it came ashore. Tropical Storm Don made landfall on the southern Texas coast in July. And in September, Tropical Storm Lee came ashore in Louisiana. Neither storm had winds exceeding 50 mph at landfall.

The 19 storms put the 2011 season in a tie for the third-most active season on record. Three other seasons — 2010, 1995 and 1887 — had the same number of storms.

Meteorologists William Gray and Phil Klotzbach at Colorado State University concurred that the U.S. has been lucky during recent hurricane seasons.

“The primary reason why we believe that the U.S. has been so fortunate is due to mid-level steering currents that have in recent years tended to steer storms away from the U.S.,” Gray and Klotzbach said in their summary of the 2011 hurricane season that was released today.

These mid-level currents have been in place during the past six summers, Gray and Klotzbach wrote. The trend began one year after the raucous, record-setting summer of 2005, when 28 named storms formed and four major hurricanes made a U.S. landfall.

It’s been six years since a major hurricane — that is, a storm with peak winds exceeding 110 mph — has struck the U.S. The last major hurricane was Hurricane Wilma, which struck the Florida Keys in October 2005. Klotzbach and Gray noted that the U.S. has not gone six years without a major hurricane making landfall since at least 1878.

The storm that became Hurricane Irene formed just east of the Caribbean Sea on August 20. As it moved northwestward, it strengthened into a major hurricane and struck the Bahamas with peak winds of about 115 mph. Irene caused an estimated $3 billion in damage in the Caribbean and the Bahamas.

Even though Hurricane Irene’s top winds had weakened to about 85 mph when it made landfall near Cape Lookout, North Carolina on August 27, it caused havoc as it roared up the Atlantic Coast. The storm touched the New Jersey coast and made a third landfall at New York City with winds just below hurricane-force.
Irene’s damages in the U.S. totaled at least $10 billion and could have been as much as $15 billion.

Mexico was hit by four tropical storms this summer that caused a total of 33 deaths. Two storms struck the Canadian Maritime Provinces, but no deaths were reported.

Masters thinks the trend of active hurricane seasons that began in 1995 will continue next summer. Hurricanes draw their energy from warm seawater, and the temperature of the Atlantic Basin — which includes the Caribbean Sea and Gulf of Mexico — will again be above average.

Changing Planet

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Willie Drye is an award-winning author and a contributing editor for National Geographic News. He and his wife live in Wilmington, North Carolina.