MIAMI (Bloomberg)—Earl, one of the two strongest hurricanes of the Atlantic season, headed toward the U.S. East coast after passing north of Puerto Rico today packing sustained winds of 135 mph.

The “powerful” hurricane, the second-highest on the five-step Saffir-Simpson scale, was 175 miles north-northwest of Puerto Rico moving west-northwest at 13 mph, the U.S. National Hurricane Center said on its website at 7 a.m. Miami time.

The storm may strike North Carolina's Outer Banks by Sept. 3 while a “major” hurricane with winds of at least 111 mph, the center predicted. Tropical storm conditions are likely to affect the Turks and Caicos Islands Tuesday as heavy winds subside in the Virgin Islands and Puerto Rico, it also said.

Earl's northward march poses “a serious threat to the East coast as we approach the Labor Day weekend,” Jim Rouiller, senior energy meteorologist at the commercial forecaster Planalytics Inc., said in an e-mail. U.S. East coast beaches are often crowded for the Sept. 6 Labor Day holiday.

The hurricane center's forecast maps show Earl is likely to pass east of the U.S. Eastern seaboard, though a direct hit remains possible with any deviation from the current track.

“Residents and tourists anywhere from North Carolina up to new England should keep track of this storm,” Robbie Berg, a hurricane specialist at the center, said Tuesday in a telephone interview from Miami. “It's too early to tell what kind of impact will occur.”

North Carolina hurricanes

In 2003, Hurricane Isabel struck the Outer Banks of North Carolina as a Category 2 storm on the five-step Saffir-Simpson scale, killing at least 16 people and causing $3.4 billion of damage, half of it to insured property, according to the center.

Hurricane Fran was a major hurricane when it hit North Carolina in 1996, causing $1.6 billion of damage to insured property, the bulk of it there and in Virginia, according to National Hurricane Center records.

Earl is being followed by Tropical Storm Fiona, which formed Monday over the Atlantic Ocean, and remained a “weak” system Tuesday with sustained winds of 40 mph, the hurricane center said.

Fiona was 500 miles east of the Leeward Islands heading west-northwest at 24 mph, the center said at 8 a.m. Miami time. The storm is predicted to pass to the northeast on a course between Bermuda and the U.S. East coast. A hit on Bermuda remains a possibility, graphics on the center's website show.

Earl, Danielle

Tropical storm watches, which indicate such conditions are expected within two days, were issued Tuesday for Antigua, Barbuda, Montserrat, St. Kitts, Nevis, Anguilla, Saba and St. Eustatius. A tropical storm warning is in place for St. Martin and St. Barthelemy.

Earl's winds have reached the same intensity as Danielle at its peak. Danielle late Monday weakened to 70 mph over the North Atlantic as the system became a post-tropical storm, an indication it no longer derives its energy from warm waters. Earl's tropical storm-force winds extended up to 200 miles from its eye and hurricane-force winds reached 70 miles.

Tropical storm warnings were lifted for Puerto Rico, the U.S. and British Virgin Islands after Earl passed. The Turks and Caicos remain under a tropical storm warning, while the southeastern Bahamas are under a tropical storm watch.

Hovensa L.L.C.'s St. Croix refinery in the U.S. Virgin Islands operated though the island ports were shut as Earl passed to the east. The refinery sends finished products including heating oil and gasoline to the U.S. Gulf and East coasts, according to the company's website.

‘Outer rain bands’

“The outer rain bands of Hurricane Earl will continue to bring periods of torrential rainfall and tropical storm-force wind gusts across sections of Puerto Rico and the U.S. Virgin Islands through the morning hours,” the National Weather Service said in a local advisory at 6:24 a.m. Miami time. “Due to very saturated soils across the local islands, flash flooding as well as mudslides can be expected with the heavier showers.”

The Atlantic hurricane season runs from June through November, with the coming weeks usually the most active.

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