On Thursday the forecasters increased their predictions for an unusually active Atlantic hurricane season, noting the number of storms so far and atmospheric and oceanic conditions that favour hurricane development.

There is an 85-per-cent chance of an above-normal hurricane season, an increase from a May prediction of a 65-per-cent chance, the National Oceanic and Atmospheric Administration's Climate Prediction Centre said.

An average season has 11 named storms, including six hurricanes for which two reach major status.

The hurricane season lasts from June through November, and the latest predictions are timed to coincide with the most active hurricane period from August through October.

There is a 67-per-cent chance that 14 to 18 named storms will develop, including seven to 10 hurricanes, the prediction said. Three to six of those hurricanes could be major, reaching category 3 or higher, the centre said.

It had earlier called for 12 to 16 named storms, with six to nine hurricanes and two to five major hurricanes.

There have been five named storms so far this season, including Tropical Storm Arthur, which pounded Mexico's Yucatan Peninsula in late May and early June, and Hurricane Dolly, which hit the US- Mexican border late last month. The most recent, Tropical Storm Edouard, dumped heavy rain on Texas earlier this week. None of the storms to date have been rated a category 3 or higher.

Tropical cyclones have been responsible for killing millions of people and causing significant property damage. Hurricane Katrina killed over 1,800 people in the U.S. and cause damage estimated at $100 billion.