Tropical storms have winds of at least 39 miles (63 kilometers) an hour. Hurricanes have winds of at least 74 miles (119 kilometers) an hour.
The prediction from the National Oceanic and Atmospheric Administration's Hurricane Research Division in Miami is a little less specific than Gray's, but still forecasts a very active season. NOAA expects 12 to 15 tropical storms, resulting in 6 to 8 hurricanes and 2 to 4 major hurricanes.
Meteorologists will adjust their forecasts in August, when the peak of the hurricane season begins.
During the 2003 season 14 tropical storms formed, and 7 developed into hurricanes. Three storms—Fabian, Isabel, and Kate—evolved into major hurricanes.
At one point Hurricane Isabel reached Category Five level. It had winds faster than 165 miles (266 kilometers) an hour, making it one of the most intense hurricanes of the past several decades. But Isabel lost strength and came ashore as a Category Two hurricane just south of Cape Hatteras, North Carolina, on September 18, 2003.
Still, at least 40 people died as Isabel moved up the Atlantic coast. The storm inflicted billions of dollars worth of damage from North Carolina to Canada.
Hurricane Boom Could Last Decades
Chris Landsea, a hurricane researcher at NOAA in Miami, said more hurricanes are forming over the Atlantic Ocean because its water is a bit warmer than it was in the early 1990s.
Hurricanes draw their energy from warm ocean water. Since 1995 the temperature of the Atlantic has been, on average, one-half degree to one degree Fahrenheit (0.3 degree to 0.6 degree Celsius) warmer than was in the early 1990s, he said.
Landsen and Gray, the Colorado State University meteorologist, think the increased number of hurricanes is part of a weather cycle that's been going on for a very long time. "It does appear to be a natural cycle," Landsea said. "We see evidence for this over the last several hundred years. It doesn't seem to be related to any possible greenhouse gas forming."
Gray thinks changes in the salinity of the Atlantic are a major factor in the cycles. When the salt content is higher, the ocean is warmer and more storms form. It takes decades for this cycle to complete itself, he said.
"We see these major storms going up and down on a decadal basis," Gray said. "You can't link it to global warming. It's ridiculous to blame [an increase in hurricanes] on human-induced greenhouse gasses coming up into the atmosphere."
Researchers have used weather records to identify hurricane cycles dating back to at least the late 19th century. But new research is revealing possible clues to hurricane cycles thousands of years ago.
Kam-biu Liu, a professor of geology at Louisiana State University, has concluded that there was a "hyperactive" period of hurricanes affecting what is now the Gulf Coast, lasting from about 3,400 years ago to about 1,000 years ago.
"Since about a thousand years ago, it's gone back to a relatively quiet period," Liu said.
The current increase in hurricanes is only a small fluctuation within this longer millennial cycle, according to Liu. Forecasters can't say exactly how long the current cycle will last. During the past century periods of increased activity have lasted 25 to 30 years.
The Atlantic warmed up in 1926 and stayed warm until the late 1960s, according to Gray. There was a corresponding period of active hurricane seasons. The Atlantic was cooler from the late 1960s until 1995, when it warmed again and started spawning more storms.
Gray thinks the current warming trend could last another 10 or 20 years. That could mean trouble, because coastal development and population growth exploded during the calm summers between 1970 and 1995.
"It's inevitable that we'll see property damage way beyond what we've ever had before," Gray said. "Not so much because more hurricanes will make landfall, but because there's more property there now."
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