Emily became the fifth named storm of the season, marking the first time that so many have developed by early July. Hurricane season runs fromJune 1 to November 30.

"Not only is it unusual, it's unprecedented," said James Franklin, a forecaster at the National Hurricane Centre in Miami.

"Like we've always said, whether it is an active season or an inactive season, you've got to be prepared and keep your eyes on the the sky," said Kim Brabander, a meteorologist with the National Weather Service.

After a 23-year lull, researchers say the cycle of tropical-storm activity shifted in 1995 to a hyperactive period that could last another two or three decades.

Before this season began, National Oceanic and Atmospheric Administration (NOAA) forecasters predicted 12 to 15 tropical storms, with seven to nine that could grow
into hurricanes. Three to five of those hurricanes, they said, were likely to become intense.

Dennis peaked as a strong Category 4 hurricane with 150 mph winds.

That storm was reason for concern, said Stanley Goldenberg, a researcher with NOAA's Hurricane Research Division on Virginia Key.

Dennis was born July 4 from a "tropical wave" – a wind disturbance that originates in Africa and usually spawns most major hurricanes.

"Dennis is the key; it's saying the conditions are ripe," he said. "Since 1995, all the years that have had a system in that area [this early in the season] have been extremely active."

The last time five named storms formed by the end of July was in 1997, which
turned out to be a relatively quiet season.

One important difference between the years: In 1997,many of the storms tended to form in more northern waters in the Atlantic and did not make landfall.

Hurricane Bill, the third named storm in 1997, reached hurricane status on July 12, but curved northward and died in the cold waters off Newfoundland.

In contrast, the third named storm this year, Tropical Storm Cindy, swept the
upper Gulf Coast with heavy rain and gusty winds.

From 1995 to 2003, many storms tended to veer northward away from Florida. But last year, a southerly shift in a massive high-pressure system known as the Bermuda High blocked some tropical storms and hurricanes, funnelling them toward Florida and the Southeast coast.

The storms also have been fuelled by the unusually warm waters of the Atlantic this July.

Adapted from the Miami Herald.