The first named storm of the Central Pacific hurricane season formed overnight, but is expected to pass north of the islands and is “not a significant threat to Hawaii,” forecasters said Thursday morning.

However, what’s left of Tropical Depression Ela will bring muggy weather, locally heavy showers and a slight chance of thundershowers this weekend.

Surf generated by Ela is expected to arrive Friday, prompting the National Weather Service to issue a high surf advisory for east shores of all islands starting 6 a.m. Friday through 6 a.m. Sunday. Waves with heights of 6 to 8 feet are expected. The waves could be dangerous and create strong currents.

As of 5 p.m. Thursday, Ela was headed northwest at 12 mph with wind speeds of 35 mph, just below the minimum for a tropical storm. The center of the storm was about 510 miles east-northeast of Hilo.

Ela is being torn apart by winds coming at it from different directions and altitudes. It’s also moving over cooler waters as it heads north.

“We’re fairly confident that this system will continue to weaken,” said Derek Wroe, a meteorologist with the Honolulu office of the weather service. “The major impact we’re looking at is the potential for heavy rainfall this weekend. So just keep an eye out for it. We could have some thunderstorms.”

Ela is expected to take a turn to the west and pass north of the islands through the weekend. The center of what’s left of the storm is forecast to pass about 150 miles north of Oahu and Kauai Saturday night as a tropical depression or remnant low pressure system.

It’s not likely to bring much wind, but even as a depression or remnant, tropical moisture and rain clouds within the system extend for hundreds of miles and will likely affect Hawaii’s weather through Monday.

Most of the rain is expected Saturday afternoon, and Sunday afternoon through Monday morning.

The Honolulu Department of Emergency Management notified staff to be ready for possible activation this weekend and reviewed emergency plans. The agency also asked the Department of Facility Maintenance to check streams maintained by the city in case of heavy rain.

The U.S. Coast Guard advised the public and mariners to prepare for possible affects of the storm, including extreme sea conditions and high surf throughout the state.

Coast Guard officials said beachgoers should heed all warnings. “Although weather conditions may be good, rip tides and high surf may impact beaches far in advance of the actual storm,” they said in a news release.

Tradewind weather will continue through Thursday and most of Friday across the state, but what’s left of Ela is expected to cut off the tradewind flow this weekend, bringing muggy conditions that will make the temperature feel like it’s in the high 90s or even 100 degrees.

“With the lack of tradewinds and higher humidity, it’s going to be quite uncomfortable out there,” Wroe said.

Tradewinds are expected to return Monday. But with Ela’s moisture to the east and north of the state, the northeast winds could also bring in heavier than usual windward and mauka showers that could spread to leeward areas.

Two other systems are south of the islands.

There’s a medium chance — 60 percent — of an area of low pressure developing into a more organized system within the next two days from a storm about 925 miles southwest of Honolulu. However forecasters expect the system to continue to track west and remain well south of Hawaii.

Another weak surface low-pressure system is about 600 miles south of Hilo. There’s only a 20 percent chance of it developing. But moisture from that system is being pulled up into Ela and will contribute to the muggy and wet weekend weather.