UPDATE: 11:30 p.m. Monday

Hurricane Walaka, a dangerous Category 5 storm, maintained its intensity as it continued on a course toward Johnston Atoll, far southwest of the main Hawaiian islands.

At 11 p.m. Monday, Walaka was 210 miles south of Johnston Island, the largest of the four islands of Johnston Atoll. Walaka had maximum sustained winds of 160 mph and was moving north-northwest at 8 mph, according to the Central Pacific Hurricane Center. Hurricane-force winds of 75 mph or more extend out 45 miles from the center while tropical storm-force winds of more than 39 mph extend out 185 miles.

The storm was centered 955 miles west-southwest of Honolulu and is not expected to threaten the main Hawaiian islands.

Johnston Atoll is under a hurricane warning, while Papahanaumokuakea Marine National Monument — from Nihoa to French Frigate Shoals to Maro Reef — is under a hurricane watch.

Walaka is expected to pass just to the west of Johnston Island on Tuesday.

5 p.m.

Massive Hurricane Walaka is expected to pass dangerously close to the tiny Johnston Atoll Tuesday as a Category 5 storm.

At 5 p.m., Walaka had maximum sustained winds of 160 mph and was centered 240 miles south of Johnston Island, the largest of the atoll’s four islands, and about 965 miles southwest of Honolulu. The storm was moving northwest at 7 mph, according to the Central Pacific Hurricane Center.

Some strengthening is expected tonight before Walaka starts weakening, forecasters said. Hurricane-force winds extend out 50 miles from the center and tropical storm-force winds extend out 185 miles.

Johnston Atoll remains under a hurricane warning, and Papahanaumokuakea Marine National Monument — from Nihoa to French Frigate Shoals to Maro Reef — is now under a hurricane watch. Walaka is expected still be a major hurricane when it reaches the monument, northwest of the main Hawaiian islands, by Wednesday night.

Four members of a U.S. Fish and Wildlife Service biology field crew are working on Johnston Island, a wildlife refuge. A spokeswoman for the Fish and Wildlife Service said the “on-island staff are sheltering in place at a steel and concrete structure built to withstand hurricanes.”

2:25 p.m.

Hurricane Walaka is now a Category 5 hurricane, with maximum sustained winds of 160 mph, and is expected to intensify further as it threatens tiny Johnston Atoll, far southwest of Hawaii.

Johnston Atoll is one of the most isolated atolls in the world, located between Hawaii and the Line Islands.

Four members of a U.S. Fish and Wildlife Service biology field crew are working on Johnston Island — one of four islands that make up Johnston Atoll, home to the Johnston Atoll National Wildlife Refuge.

“In preparation for any possible impacts from Hurricane Walaka, the field biology crew secured the year-round field camp,” Megan Nagel, a spokeswoman for the U.S. Fish and Wildlife Services Pacific Region, told the Honolulu Star-Advertiser in an email. “Currently, on-island staff are sheltering in place at a steel and concrete structure built to withstand hurricanes.”

The refuge is within the Pacific Remote Islands Marine National Monument; its boundary includes Johnston Island and extends 12 miles from the shorelines.

The Central Pacific Hurricane Center said this afternoon that Walaka was centered 265 miles south of Johnston Island and 965 miles southwest of Honolulu, moving west-northwest at 9 mph.

The storm is expected to make a turn to the north and pass just to the west of Johnston Island on Tuesday. Some strengthening is expected through early Tuesday before Walaka starts a gradual weakening trend.

Hurricane-force winds extend out 50 miles from Walaka’s center while tropical storm-force winds extend 185 miles.

Tropical storm-force winds, of more than 39 mph, are expected to reach Johnston Island starting late tonight or early Tuesday, with hurricane conditions expected by Tuesday afternoon, forecasters said. Large surf and heavy rain is also expected to start hitting the island tonight.

The storm is expected to peak Tuesday with 165 mph maximum sustained winds, which would make it the strongest Central Pacific storm since Hurricane Ioke in 2006.

Johnston Island is a U.S. possession located 825 miles southwest of Honolulu. The atoll is a wildlife refuge that was had been used by the U.S. military to store chemical weapons.

Johnston Atoll, which is now under a hurricane warning, has been hit several times by hurricanes, including Ioke in 2006, Dora in 1999 and John in 1994.

Hurricane center forecasters also said that “interests in the Papahanaumokuakea Marine National Monument (northwest of the main Hawaiian islands) should monitor the progress of Walaka.”

11:50 a.m.

Hurricane Walaka is bearing down on Johnston Atoll as a powerful Category 4 storm, with maximum sustained winds of 150 mph that are expected to continue strengthening.

By late this morning, the storm was 950 miles southwest of Honolulu and 265 miles south of Johnston Island, moving northwest at 10 mph, according to the Central Pacific Hurricane Center in Hawaii.

Johnston Atoll is under a hurricane warning and Walaka is expected to approach the island Tuesday as a Category 5 hurricane with maximum sustained winds up to 165 mph.

“A turn toward the north is expected late tonight through Tuesday with a gradual increase in forward speed,” forecasters said late this morning. “On the forecast track, the center of Walaka is expected to pass just to the west of Johnston Island on Tuesday.”

Hurricane-force winds extend out 50 miles from Walaka’s center and tropical storm-force winds extend out up to 160 miles.

“The northeastward track after Tuesday is also expected to take the hurricane across the Papahanaumokuakea Marine National Monument between French Frigate Shoals and Laysan Island on Thursday, and a hurricane watch may be needed for these locations later today or tonight,” forecasters said.

8 a.m.

Now a Category 4 storm, Hurricane Walaka is continuing to strengthen southwest of the Hawaiian islands.

Located about 940 miles southwest of Honolulu and 290 miles south of Johnston Atoll at 8 a.m., Walaka was packing maximum sustained winds of 145 mph and is headed west-northwest at 10 mph, according to the Central Pacific Hurricane Center.

A hurricane warning is in effect for Johnston Atoll. A turn toward the northwest is expected to begin later today, followed by a turn toward the north late tonight through Tuesday night with a gradual increase in forward speed, weather officials said.

Rapid intensification is expected to continue today into tonight, with little change in intensity forecast Tuesday and Tuesday night.

Hurricane-force winds extend outward up to 35 miles from the center and tropical-storm-force winds extend outward up to 140 miles.

5 a.m.

Hurricane Walaka continued to strengthen overnight and is now a Category 3 storm southwest of the Hawaiian Islands.

Located about 925 miles southwest of Honolulu and 315 miles south-southeast of Johnston Atoll at 5 a.m., Walaka was packing maximum sustained winds of 125 mph and is headed west-northwest at 10 mph, according to the Central Pacific Hurricane Center.

A hurricane warning is in effect for Johnston Atoll. A turn toward the northwest is expected to begin later today, followed by a turn toward the north late tonight through Tuesday night with a gradual increase in forward speed, weather officials said.

Rapid intensification is expected to continue today into tonight, with little change in intensity forecast Tuesday and Tuesday night.

Hurricane-force winds extend outward up to 35 miles from the center and tropical-storm-force winds extend outward up to 140 miles.

11:20 p.m Sunday

Hurricane Walaka grew to a powerful Category 2 storm with maximum sustained winds of 105 mph, and while it poses no threat to the main Hawaiian islands, Johnston Atoll is under a hurricane warning.

As of 11 p.m. Sunday, Walaka was 905 miles southwest of Honolulu and 355 miles south-southeast of Johnston Island, moving west at 12 mph. Hurricane-force winds extend up to 30 miles from the storm’s center while tropical storm-force winds of more than 39 mph extend out up to 125 miles, according to the Central Pacific Hurricane Center in Honolulu.

Walaka is expected to grow to a major Category 4 hurricane — with maximum sustained winds of 155 mph — by Tuesday, as it moves northward and passes near Johnston Atoll, forecasters said.

The warning for Johnston Atoll calls for tropical storm-force winds late Monday night or early Tuesday, and hurricane conditions by Tuesday afternoon. High surf and heavy rainfall may reach the atoll starting Monday night.

In addition, forecasters warn that “interests in the Papahanaumokuakea Marine National Monument (northwest of the main Hawaiian islands) should monitor the progress of Walaka.”

By the end of the week, Walaka is expected to weaken to a tropical storm as it moves north over cooler water far from the main Hawaiian islands.

5:20 p.m.

Walaka has strengthened into a hurricane, centered 860 miles southwest of Honolulu but moving away from the islands.

At 5 p.m., the hurricane had maximum sustained winds of 75 mph and was moving west, further away from the state, at 12 mph. Hurricane-force winds extend outward up to 25 miles from the center and tropical storm-force winds of more than 39 mph extend out up to 90 miles.

A turn to the north is expected in the next two days, putting Johnston Atoll in Walaka’s path, prompting a hurricane warning for the tiny northwestern islands.

“A warning is typically issued 36 hours before the anticipated first occurrence of tropical-storm force winds, conditions that make outside preparations difficult or dangerous,” forecasters with the Central Pacific Hurricane Center in Honolulu said. “Interests in the Papahanaumokuakea Marine National Monument should monitor the progress of Walaka.”

Johnston Island can expect tropical storm-force winds starting early Tuesday, and hurricane conditions by Tuesday afternoon. Large surf will reach the Johnston Atoll reefs and shorelines starting Tuesday, forecasters said.

2:30 p.m.

Walaka’s maximum sustained winds continue to strengthen as the tropical storm keeps moving further away from the islands.

As of 2 p.m., Walaka was 845 southwest of Honolulu and had sustained winds of 65 mph as the storm moved west at 18 mph, according to the Central Pacific Hurricane Center.

Forecasters expect Walaka to become a hurricane as early as tonight and be a major hurricane Monday through Wednesday when it is projected to be hundreds of miles west of Kauai.

“With the official forecast track bringing the center of Walaka very near Johnston Atoll on Tuesday, a hurricane watch remains in effect there,” forecasters said today.

Walaka is expected to weaken back to a Category 1 hurricane later in the week as it moves north over cooler water.

12:30 p.m.

Walaka remains a tropical storm as it moves on a western track that keeps it well south of Hawaii.

At 11 a.m. today, Walaka was about 810 miles southwest of Honolulu and 410 miles southeast of Johnston Atoll and moving west near 18 mph with sustained winds of 65 mph. Tropical-storm-force winds extend up to 70 miles from the center.

National Weather Service forecasters based at the Central Pacific Hurricane Center in Honolulu expect the storm to slow and turn nortwest on Monday, followed by a more northernly turn on Tuesday.

Walaka is forecast to become a hurricane later today and continue to rapidly intensify through Monday night. Wind shear will begin to affect the storm starting late Tuesday or Wednesday, and it will begin to weaken by the end of the week.

Johnston Atoll is currently under a hurricane watch.

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Tropical Storm Walaka intensified overnight, but remains well southwest of the main Hawaiian Islands.

As of 5 a.m. Sunday, Walaka was located about 770 miles south-southwest of Honolulu and 510 miles southeast of Johnston Atoll, where a hurricane watch is now in effect. The storm is moving west near 16 mph and is expected to continue in that direction through the evening with a decrease in forward speed; maximum sustained winds are near 60 mph, with higher gusts.

Walaka is expected to take a turn toward the northwest on Monday, then make another turn northward on Tuesday, bringing it very close to Johnston Atoll. Tropical-storm-force winds extend 70 miles from the center.

According to the National Weather Service’s Central Pacific Hurricane Center in Honolulu, Walaka is expected to rapidly intensify through Monday night and become a major hurricane. Wind shear will begin to affect the storm starting late Tuesday or Wednesday, and it will begin to weaken by the end of the week.