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Atlantic Hurricane Season has Officially Descended on US

If it seems that there have been more hurricanes crossing the Atlantic in the past few years, it's because it's true.

The Atlantic hurricane season started early this year and so far has produced two powerful storms. In the Pacific, a severe typhoon hit China causing more than a million people to flee their homes.

The U.S. National Weather Service has documented higher than normal numbers of hurricanes for the last 10 years. The weather service is part of the National Oceanic and Atmospheric Administration.

"Generally, on the average, the long-term average, we'll see about 10 main storms, tropical storms or hurricanes a year, and now we're looking at 13-15 this year. We had 15 last year. We're certainly in a period of heightened tropical cyclone activity," said Scott Kiser, who oversees the tropical cyclone program says.

Hurricane Emily, the fifth Atlantic storm since June first, smashed into the popular beach resorts on Mexico's Yucatan Peninsula July 18th, forcing thousands of tourists into emergency shelters.

It is the first time since forecasters began record keeping that so many storms have formed so early. "Really, what you have is a combination of a lot of favorable factors hitting the Atlantic right now, setting up for a very, very active year, which has really already started now," explained Stan Goldenberg, a meteorologist with the U.S. National Oceanic and Atmospheric Administration.

"Those upper level winds can tear storms apart or help them grow," said Mr. Kiser.

Once the storm takes shape, it is carried along by prevailing winds. The winds determine where, when and if the hurricane makes landfall. Sim Aberson, a hurricane researcher at the U.S. National Oceanic and Atmospheric Administration, make clear, "It's the flow around that storm that's pushing it. And you can liken that to putting, say, a marble on your dining room table and blowing on the marble."

Tropical storms are cyclones that form in the tropics using the steamy water below as fuel. "The waters in the Atlantic have been above normal. So we have ample energy for those to form," said Mr. Kiser in describing the role of water temperature.

Hurricanes are becoming even more intense, and more destructive because the Atlantic Ocean is warming. The Geophysical Fluid Dynamics Lab, a research branch of the National Oceanic and Atmospheric Administration, has data to support this.

"Those storms that do occur, are going to have the potential to be significantly stronger in a warmer climate," said climate modeller Tom Knutson, who led a study that used a computer to simulate 1,300 virtual storms.

If his model is correct, by the end of the century, average hurricane strength will increase by half a category in the five-step scale used to measure intensity.

Mr. Knutson says average wind speed could jump four kilometers an hour, rainfall by five centimeters, and storm surge by several meters.

"It could be the difference between say a roof staying on a house and the roof being ripped off," said Bob Tuleya, at the Old Dominion University Center for Coastal Physical Oceanography in Norfolk, Virginia.

Mr. Kiser says avoiding injury or death and reducing property damage all comes down to preparedness. "How well constructed are the homes, what types of emergency management arrangements they have made for evacuations and proper sheltering," he said.

And that goes for any tropical storm, even those that do not reach hurricane or typhoon strength. The experts say there will be more of those storms and they, too, will be more destructive.