Hurricane Dennis could be an ominous sign of tempestuous times ahead, with more storms than usual set to pummel the Atlantic, British scientists warn.
Hurricane Dennis's early arrival is highly unusual
Researchers from the Benfield Hazard Research Centre in London used a new model to predict a very active season.
Between July and October, they say, nine hurricanes will probably hit the Atlantic basin as a whole.
The main driving force is likely to be unusually warm sea temperatures in the tropical North Atlantic.
If the predictions come true, this will be the Atlantic's second bumpy year in a row, after 2004 saw hundreds killed and billions of dollars worth of damage caused by Charley, Frances, Ivan and Jeanne.
"Following the ravages of 2004, the current and projected climate signals now suggest that we should prepare for another exceptionally active Atlantic season in 2005, a factor which underlines the ongoing need for vigilance on the part of government and citizens alike," Mark Saunders of the Benfield Hazard Research Centre (BHRC) said.
To predict the ferocity of the forthcoming hurricane season, the team studied the July-September forecasts for wind speed and surface water temperatures through the Caribbean and tropical North Atlantic.
These two factors are important because warm surface waters can trigger hurricanes, while wind speeds dictate how savage they become and whether or not they head inland.
Based on current and projected climate signals, the Tropical Storm Risk (TSR) consortium, which is led by the BHRC, predicts:
- A 97% probability of an above-normal Atlantic hurricane season
- 15 tropical storms for the Atlantic basin as a whole, with nine of these being hurricanes and four intense hurricanes
- Five tropical storm strikes on the US, of which two will be hurricanes
- Two tropical storm hits, including one hurricane on the Caribbean Lesser Antilles.
The forecast spate of hurricanes in 2005 is part of a multi-decadal cycle of fluctuating sea temperatures.
"It is a natural cycle of a period of about 50 or 60 years," Professor Saunders told the BBC News website.
"The last peak of activity was in the 1950s and scientists have mapped this pattern of warming and cooling of Atlantic sea temperatures back about 150 years, so they have two or three cycles of it."
A hurricane is a spinning vortex of winds swirling round a eye of very low pressure
Warm, moist air is drawn upwards around the eye
Cooler dry air is sucked downwards by the low pressure centre
Banks of thunderstorms surround the edges
However, Professor Saunders believes that global warming might be contributing to the problem.
"I think one has to wonder whether at least part of this activity could be due to global warming," he said. "Certainly, sea temperatures where hurricanes form have been the warmest on record over the last year or two."
Indeed, Dennis's early arrival is very irregular, and is yet another indication of the rough ride ahead.
"This year is quite unusual in that there is so much early activity," Professor Saunders said. "Dennis is only the second major hurricane to strike America in July. The other one happened in 1916.
"Often seasons which have high activity in July tend to be active for the whole season."