What to know about powerful Hurricane Erin as it heads past the US East Coast

ATLANTIC BEACH, N.C. — Hurricane Erin was creating potentially deadly water conditions all along the East Coast days before the largest waves are expected, even as the strength of the storm weakened on Tuesday.

Erin lost some strength and dropped to a Category 2 hurricane with maximum sustained winds of 105 mph, the National Hurricane Center in Miami said.

It was about 650 miles southwest of Bermuda and 690 miles south-southeast of Cape Hatteras, North Carolina. Forecasters said Erin was moving northwest at 9 mph.

Although the weather center was confident Erin would not make direct landfall in the United States, authorities have warned that water conditions along the East Coast remain dangerous. Officials on a few islands along North Carolina’s Outer Banks issued evacuation orders and warned that some roads could be swamped by waves of 15 feet.

Tropical storm warnings were in effect for the southeast Bahamas and the Turks and Caicos Islands, the weather center said.

Here is what to know about Hurricane Erin:

Troubled waters force rescues

Warnings about rip currents have been posted from Bermuda and Florida to the New England coast. The biggest threat is along the barrier islands of North Carolina’s Outer Banks where evacuations have been ordered.

In North Carolina on Monday, at least 60 people were rescued from rip currents in Wrightsville Beach, near Wilmington, officials said.

Bermuda won’t feel the full intensity of the storm until Thursday evening, and the island’s services will remain open in the meantime, acting Minister of National Security Jache Adams said. But storm surge, which could reach up to 24 feet by Thursday, would make waters too dangerous to swim, surf or boat in, Adams said.

Already this year, there have been at least 27 people killed from rip currents in U.S. waters, according to the National Weather Service. About 100 people drown from rip currents along U.S. beaches each year, according to the United States Lifesaving Association. And more than 80% of beach rescues annually involve rip currents.

N.C. Gov. Josh Stein declared a state of emergency.

“Hurricane Erin will bring threats of coastal flooding, beach erosion, and dangerous surf conditions,” said Stein in a news release. “North Carolinians along the coast should get prepared now, ensure their emergency kit is ready, and listen to local emergency guidelines and alerts in the event they need to evacuate.”

The dangers in the Outer Banks

Forecasters say Erin will turn northeast — and away — from the eastern U.S. Still, the storm is expected to bring tropical storm force winds, dangerous waves and rip currents to North Carolina’s coast, said Dave Roberts of the National Hurricane Center. Coastal flooding in North Carolina is expected to begin Tuesday.

Evacuations were ordered on Hatteras Island and Ocracoke Island. The orders come at the height of tourist season on the thin stretch of low-lying barrier islands that juts far into the Atlantic Ocean.

There are concerns that several days of heavy surf, high winds and waves could wash out parts of the main highway running along the barrier islands, the National Weather Service said. Some routes could be impassible for several days.

Deceptively devastating impacts

Storm surge is the level at which seawater rises above its normal level.

Much like the way a storm’s sustained winds do not include the potential for even stronger gusts, storm surge doesn’t include the wave height above the mean water level.

Surge is also the amount above what the normal tide is at a time, so a 15-foot storm surge at high tide can be far more devastating than the same surge at low tide.

A year ago, Hurricane Ernesto stayed hundreds of miles offshore from the U.S. Eastern Seaboard yet still produced high surf and swells that caused coastal damage.

Fluctuating strength

Erin’s strength has fluctuated significantly over the past week.

The most common way to measure a hurricane’s strength is the Saffir-Simpson Scale that assigns a category from 1 to 5 based on a storm’s sustained wind speed at its center, with 5 being the strongest.

Erin reached a dangerous Category 5 status late last week with 160 mph winds before weakening. It dropped to a Category 2 hurricane on Tuesday.

VIDEO: Tuesday’s forecast