After a fly-through of the storm by the U.S. Air Force’s Hurricane Hunters, it’s officially Hurricane Nolo.

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After a fly-through of the storm by the U.S. Air Force’s Hurricane Hunters, it’s officially Hurricane Nolo.

Nolo strengthened into a category-1 hurricane on Thursday evening as it continued to approach the Big Island from the south, and is expected to become a major hurricane by Saturday.

Forecasters are predicting heavy rainfall — 20 or more inches in some locations — and high winds for the next several days.

A tropical storm warning and a hurricane watch were in effect Thursday for the Big Island.

A tropical storm warning means tropical storm-force winds of between 39 mph and 73 mph are expected within the next 36 hours. A hurricane watch is issued when hurricane-force winds (greater than 74 mph) are possible within the next 48 hours.

“(Nolo) continues to strengthen and threaten Hawaii Island,” said Mayor Kimo Alameda. “We are looking at both the possibility of life-threatening flash flooding and strong, damaging winds, and we encourage everyone to complete their preparations, stay connected to official alerts and weather updates, and secure safe shelter before flooding strikes.”

For members of the public who want to track the storm, the University of Hawaii has launched a website with up-to-date access to rainfall and wind observations statewide.

The Nolo weather tracker — at www.hawaii.edu/climate-data-portal/nolo-mesonet-viewer/ — was developed by UH’s Hawaii Mesonet-Hawaii Climate Data Portal team.

“The goal is to make the observations collected by the Hawaii Mesonet readily accessible during the storm, so that people can quickly see where rainfall and strong winds are occurring and how conditions are changing over time,” said Matt Lucas, who, along with Cherryle Manzano, developed the Nolo weather tracker.

The website provides two tools for monitoring the storm: current storm conditions and storm evolution.

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While UH focuses on real-time info for public consumption, other entities are making their preparations with an eye to Nolo’s actual effect on the island and its residents.

Hawaiian Electric on Thursday urged customers to prepare for the possibility of extended power outages due to the powerful storm system that is nearing the state.

“In the past 24 hours, we’ve increased our staffing and have teams standing by to restore power as quickly as possible,” said Jim Alberts, Hawaiian Electric’s senior vice president and chief operations officer. “As long as it’s safe, we’ll work continuously after the storm clears until all customers have power again.”

The company is maintaining a 24-hour watch on Nolo’s path in order to position crews and equipment in areas most likely to be affected. Customers should also prepare their own homes and properties, HECO said, recommending trees be trimmed to provide a minimum of 10 feet clearance from power lines. That includes removal of damaged or dying vegetation that could be at risk of falling during strong winds.

All county and state parks and most government offices are closed today on Hawaii Island. County solid waste facilities also are closed today and Saturday.

Hawaii Volcanoes National Park also is closed.

The county is opening five additional shelters today, in addition to the four opened Wednesday night.

Shelters opening today at 6 a.m. are: Honokaa Gym, 45-541 Lehua St. in Honokaa; Papaaloa Park Annex, 35-1994 Government Main Rd. in Papaaloa; Puueo Community Center, 145 Wainaku St. in Hilo; Kahilu Town Hall, 67-1182 Lindsey Rd. in Waimea; and Ocean View Community Center, 92-8924 Leilani Circle in Ocean View.

Shelters that opened Wednesday night are: Yano Hall, 82-6156 Mamalahoa Hwy. in Captain Cook; Naalehu Elementary School G ym, 95-5545 Mamalahoa Highway in Naalehu; Robert N. Herkes Gym, 96-1219 Kamani St. in Pahala; and Keaau Armory, 16-512 Volcano Rd. in Keaau.

Shelter occupants are encouraged to bring their own food, water and any necessary medicine. Shelters are pet friendly, but bring your own carrier and leash.

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Email John Burnett at [email protected].