Three named storms, two hurricanes including a major one, will occur in the Atlantic basin,scientists forecast on Tuesday.

The Net Tropical Cyclone (NTC) activity will reach 30 this October, well above the mean average value of 18, said William Gray and Phil Klotzbach, hurricane forecasters at the Colorado State University.

The possibility that a named storm will hit US coast will reach 49 percent, much higher than the normal 29 percent based on data from the past 100 years, they said.

Issuing their Forecast of Atlantic Hurricane Activity, the researchers said the hurricane season in year 2005 has already accumulated 183 NTC units which makes it the seventh most active full season since 1950. In an average season, about 80 NTC units occur before the end of September.

"We expect that by the time the 2005 hurricane season is over, we will witness seasonal tropical cyclone activity at near-record levels," their report said.

"It's going to be above average," said Klotzbach, a research associate at the Colorado State University.

"The wind shear is pretty low and the Atlantic is pretty warm, so it will be an active month. You will get a couple of storms before the season is over."

Klotzbach and Gray, both working in the atmospheric science department, said a major hurricane in October may reach category 3 to 5, with wind speed at least 180 km per hour.

October is typically the third most active month for hurricanes,accounting for about 20 percent of the named storms of the season,which runs from June 1 through Nov. 30, the researchers said.

The busiest month is September when 50 percent of named storms occur, followed by August, which sees 25 percent. In this year, devastating Hurricanes Katrina and Rita raided US southern states in August and September, respectively.

Part of the reason for the continued hurricane activity this month is that the temperature of the Atlantic Ocean is about 0.5 to 1 degree Celsius warmer than normal. Warmer water means more hurricanes because that is where they draw their strength.

But the warmer water is not due to global warming, the researchers noted.

"If you look at global tropic cyclones, the number has gone down the last 10 years," he said. "Statistically, if you have global warming, you would see it (the number of hurricanes) go up everywhere."

Instead, the Atlantic Ocean undergoes cycles lasting 20 to 25 years in which the water warms and then cools off. Currently, the Atlantic is in the midst of the warm cycle, with water temperatures rising above average in the past 11 years.

The Atlantic is more prone to these cycles because its water is saltier than that of other oceans, which results in more evaporation than precipitation.

Another reason that more hurricanes are expected in October is that the vertical wind shear is low. Vertical wind shear occurs when there are different wind directions and speeds at various heights in the storm.

The higher the wind shear, the less likely a hurricane will form because the storm will blow apart, according to the report by Klotzbach and Gray.

Source: Xinhua