MIAMI (Reuters) - Hurricane Igor strengthened rapidly over the Atlantic Ocean on Sunday, becoming a large and dangerous Category 4 storm as it spun menacingly westward.
Igor, capable of causing catastrophic damage, posed no imminent threat to land or energy interests.
But the U.S. National Hurricane Center said Igor was still intensifying with top sustained winds of 150 miles per hour and could become a Category 5 storm on the five-step Saffir-Simpson scale of hurricane intensity on Monday.
"Igor continues to intensify at a rapid pace," the Miami-based hurricane center said.
Behind Igor, the hurricane center said Tropical Storm Julia developed over the far eastern Atlantic Ocean on Sunday, becoming the 10th named storm of the 2010 Atlantic hurricane season.
The hurricane center said Hurricane Igor was located about 1,005 miles east of the Caribbean's northern Leeward Islands at 11 p.m. EDT.
Igor is moving west and is expected to turn toward the west-northwest and slow its pace by late Monday or Tuesday.
"Some fluctuation in intensity is likely during the next 48 hours ... and Igor could become a Category 5 hurricane on Monday," the center said.
Computer models project Igor, which became the fourth hurricane of the 2010 Atlantic season late on Saturday, would stay in the Atlantic for the coming days and not enter the Gulf of Mexico, where U.S. oil and gas operations are clustered.
Veteran forecaster Jeff Masters said on Sunday on his Weather Underground blog (www.wunderground.com) that Igor may threaten Bermuda but had only a small chance of making landfall on the U.S. East Coast or in Canada.
Masters and other forecasters said it was still too early to make any definitive predictions about Igor's long-term fate, however.
Meanwhile, Tropical Storm Julia posed no immediate threat to land and was heading in a westerly direction as it swirled off the Cape Verde islands.
The tropical cyclone was packing top sustained winds of 40 miles per hour, the hurricane center said.
It said the storm was expected to become a low-level Category 1 hurricane by Tuesday while it was still far out in the open Atlantic.
At 11 p.m. EDT, Julia was located about 110 miles southeast of the Cape Verde Islands.
The hurricane center was also monitoring another low pressure system over the east-central Caribbean that it said could develop into a tropical cyclone over the next couple of days.
The 2010 Atlantic hurricane season was predicted to be extremely active by most forecasters. Besides Igor, three hurricanes -- Alex, Danielle and Earl -- formed earlier in the season, the last two reaching Category 4 strength.
Several forecasters have said they expect the season to produce in all some five major hurricanes of Category 3 strength or stronger.
(Reporting by Tom Brown; Editing by Anthony Boadle)