Hurricane Iselle continues to make its way toward the Hawaiian islands and is expected to weaken to a tropical storm by the time it hits the Big Island and Maui County on Thursday before it progresses across the archipelago Friday.

As of Tuesday afternoon, Iselle was about 1,000 miles away from the Big Island and was steadily weakening, advancing at about 13 mph, according to National Weather Service meteorologist Eric Lau.

“We’re not expecting it to deviate greatly from what we’re forecasting now,” Lau said. “We’re pretty confident it is going to hit the islands.”

Meanwhile, a separate weather system — tropical storm Julio — is moving toward the islands on a similar path, though it was still too far away Tuesday for officials to ascertain its impact. Julio is expected to hit the Big Island on Sunday.

Iselle and Julio head toward Hawaii

National Weather Service

The weather forecast for Iselle is relatively consistent across the main Hawaiian islands: five to eight inches of rain, winds of 45-55 mph and gusts as strong as 65 mph.

All islands face “a major threat for flash flooding,” Lau said. 

Some areas could experience more intense rainfall than others, particularly mountainous regions, Lau said, adding that the winds could be strong enough to knock down branches or even entire trees. 

The Hawaii Department of Education on Tuesday announced the closure of all public schools on the Big Island, Maui, Molokai and Lanai on Thursday. All other schools are expected to remain open and conduct business as usual.

“The force of these storms remain uncertain, however, we do not want to wait until the last minute to close our schools,” said Superintendent Kathryn Matayoshi in a statement, adding that many of the schools are designated emergency shelters. The schools that are designated shelters will also be closed Friday. More information can be found on the DOE’s Twitter page.

The Coast Guard warned Tuesday that the two cyclones are expected to generate extreme sea conditions, including a storm surge and surf of 10-15 feet throughout the main Hawaiian islands on east-facing shores.

As of Tuesday afternoon, the various counties were still developing contingency plans, including procedures for managing tourists and residents without proper shelter such as the homeless, according to Melvin Kaku, Honolulu Department of Emergency Management director.

Government agencies will likely establish emergency shelters when and if the storm hits, Kaku said, adding that the counties are working “very closely” with homeless providers. In the past, the city has provided free bus transportation for people on the shorelines and in other vulnerable areas.  

The most powerful hurricane to hit Hawaii in recorded history was Hurricane Iniki, which devastated Kauai in 1992. The category 4 hurricane had winds of 145 mph and gusts as high as 175 mph. Iniki caused about $1.8 billion in damage and as many as six deaths. 

The most recent serious hurricane to hit Hawaii was Felicia in 2009, according to Kaku. Hurricane Felicia caused severe rainfall and flooding.

Officials warn that if a major disaster were to occur, the state wouldn’t be able to provide extensive emergency relief for a week. As a standard precaution, they’re urging residents to take care of their own emergency needs for at least seven days.

That’s because most Hawaii suppliers do “just in time” shipping, meaning they receive goods only as they’re needed, according to Shelly Kunishige, a spokeswoman for the Hawaii Emergency Management Agency. 

“We’re preparing for the potential disruption in shipping,” Kunishige said, adding that about 80 percent of Hawaii’s shipped goods come through Honolulu Harbor. “Regardless (of what happens), we’re still going to tell people that they can’t depend on the government for everything.”

Residents are urged to have disaster preparedness kits with necessities including food, water and supplies to stay warm. 

Here’s a list of supplies the City and County of Honolulu encourage residents to have on hand:

• Water – One gallon of water per person per day for seven days for drinking and sanitation
• Food – Non-perishable food that does not require cooking. Popular local foods such as Spam, corned beef and Vienna sausage
• Eating Utensils – Plates, mess kits, forks and chop sticks. Don’t forget a non-electric can opener for canned foods
• Radio – Battery-powered or hand crank radio with NOAA Weather alert
• Light – Flashlight and/or a portable fluorescent or LED light
• Spare batteries – Check annually
• First Aid – Get a first aid kit and — in the future — consider enrolling in a certified first aid, CPR and AED course
• Whistle – Important for signaling for help. A whistle carries much farther than the human voice and uses less energy than yelling
• Dust Mask – Helps to filter contaminated air
• Sanitation – Moist towelettes, toilet paper, 5-gallon bucket, garbage bags and plastic ties for personal sanitation
• Tools – Wrench or pliers to turn off utilities, duct tape
• Maps –  Local area maps
• Prescription – Special medications and glasses
• Baby – Infant formula and diapers
• Pets – Pet food and extra water for your pet

Residents should call 911 for emergencies only.

Hawaii’s electric companies are also urging residents to take various safety measures in the event of a disaster or power outage, including unplugging unnecessary electric equipment and appliances and staying away from downed power lines. A full informational handbook can be downloaded here. 

Guidelines for pet owners can be found here. 

The close succession of Iselle and Julio is rare but not unheard of; the onset of the El Nino season means the environment is more favorable for increased tropical cyclone activity, Lau said. The storms, however, aren’t expected to exacerbate each other’s impacts.

The National Weather Services’ Honolulu office will continue to provide updates as the two systems advance toward Hawaii.

Here are some of the places where you can check for updates:

• Nixle
• Reddit
• The National Weather Service Forecast Office
• Twitter: #Iselle or #Julio and the accounts of The National Weather Service and Hawaii State Civil Defense and the Honolulu City and County Department of Emergency Management, among others
• Hawaii Beach Safety