The researchers, now led by Gray protege Philip Klotzbach, said five of the hurricanes were likely to be "intense" or "major" with top sustained winds in excess of 111 mph (170 kph).

Major hurricanes are those that are ranked from Category 3 to Category 5 on the five-step Saffir-Simpson intensity scale.

Two of the five storms that have already formed this year -- Bertha and Dolly -- reached hurricane strength with winds in excess of 74 mph (119 kph) before fading over the open Atlantic and washing up on the shores of south Texas respectively.

On Tuesday, Tropical Storm Edouard -- the fifth of the season -- came ashore on the upper Texas coast.

The unusually early and vigorous storm activity this year made last month the third-stormiest July since the recording of Atlantic hurricane seasons began in 1851.

That has given storm experts reason to believe that predictions of above-normal storm activity this season could turn out to be accurate.

An average Atlantic storm season has around 10 storms, of which six become hurricanes. The record-busting 2005 season, which included Hurricane Katrina, spawned 28 storms.

Klotzbach said the team raised its forecast because of the large number of storms so far and because sea surface temperatures and sea level pressure conditions in the Atlantic were favorable for tropical storms.

But he added there was a possibility of El Nino conditions forming in the Pacific Ocean late in the season. The El Nino phenomenon, a periodic warming of waters in the equatorial Pacific, tends to make Atlantic atmospheric conditions unfavorable for tropical storms. (Reporting by Michael Christie; Editing by John O'Callaghan)