Image courtesy Jeff Schmaltz, MODIS/NASA

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Hurricane Karl approaches Mexico's Gulf Coast on September 17, 2010.

Image courtesy Jeff Schmaltz, MODIS/NASA

2010 Hurricane Season "Strange"

Storms were numerous, but U.S. had "hurricane repellent," expert says.

If you think the 2010 Atlantic hurricane season was a quiet one, think again: This year's season, which ends today, has actually been one of the most active on record, experts say.

The 2010 season produced 19 named tropical storms, tying this season with 1995 and 1887 for the third-most active since record-keeping began. (See before-and-after pictures of sites affected by Hurricane Katrina.)

A dozen of the 2010 storms developed into hurricanes, with winds of at least 74 miles (119 kilometers) an hour. Five of those hurricanes became major storms, with winds exceeding 110 miles (177 kilometers) an hour.

But tropical storm Bonnie—which crossed southeastern Florida in late July and then dissipated in the Gulf of Mexico—was the only 2010 storm to touch the U.S. coastline. That's because persistent low-pressure systems moving off the U.S. East Coast steered the storms away.

"This was a strange, strange season," said Keith Blackwell, a meteorologist at the University of South Alabama's Coastal Weather Research Center in Mobile.

"It was almost like we had a hurricane repellent over the U.S. East Coast and Gulf Coast. The storms were out there, but they just didn't approach the U.S."

Lots of Hurricanes, Few U.S. Landfalls

During the early part of the 2010 season in June and July, upper-level winds known as wind shear hindered the development of tropical storms.

Wind shear diminished as the hurricane season reached its peak in mid-August, and a flurry of storms formed. But low-pressure systems kept the storms at sea.

This year was the first time in recorded history that as many as 12 named hurricanes formed in the Atlantic without at least one of them making a U.S. landfall, said forecasters Phil Klotzbach and William Gray at Colorado State University.

"That stands out as the most remarkable feature of the 2010 season," said Jeff Masters, meteorological director for the Weather Underground website.

"Normally you'd expect four hurricanes to hit the U.S. with that kind of activity."

Canada, Mexico Took Hurricane Hits

The Coastal Weather Research Center's Blackwell said he wasn't sure why so many low-pressure systems developed in the Atlantic. But even with such systems in play, luck was also a factor in the lack of U.S. landfalls.

In some cases, even a few days' difference in when the storms formed would have led to very different outcomes, he said. For example, Hurricane Earl, which gave North Carolina a near-miss in early September, could have made landfall if it had approached the Outer Banks a day or two earlier.

"We were just very fortunate," Blackwell said.

Canada and Mexico weren't so lucky, however. In Mexico, Hurricane Alex caused more than a billion U.S. dollars in damages in early July, and Hurricane Karl left thousands homeless in mid-September.

Canada's Maritime Provinces also took hits from hurricanes. After missing the U.S. coast, Hurricane Earl made landfall on Nova Scotia as a weakened tropical storm.

And in late September Hurricane Igor's winds reached 155 miles (250 kilometers) an hour as it churned across the Atlantic and turned toward Canada.

The storm stayed well off the U.S. coast and weakened as it moved northward, but Igor dealt a punishing blow to Newfoundland and Labrador (map) when it made landfall there on September 21. (See "Hurricane Igor Now Strongest Storm—But U.S. Spared Again?")

"Igor was the worst hurricane in memory in Newfoundland," Weather Underground's Masters said.