‘We expect an impactful event’: Flash flooding, damaging winds, severe storms possible during next couple of days

Sunrise on Wednesday in Hilo revealed an eerie red sky accompanied by lenticular clouds loitering over Mauna Kea.

The clouds form when strong winds blow over and around a barrier or rough terrain, pushing moisture up and packing it together into vertical stacks. Sunlight reflecting off the lens-shaped atmospheric accoutrements — which are relatively rare in Hawai‘i — caused the day’s fiery first light.

Together, they created a breathtaking yet foreboding crimson perspective, bringing to mind the old — but timely — maritime saying: “Red sky in the morning, sailors take warning.”

“An early indication of the incoming storm,” wrote Instagram user, photographer and videographer 808hiker in a post that included a video of Wednesday’s sunrise.

Hold onto your board shorts and batten down the hatches, Hawai‘i.

There is an unusually strong winter storm expected to pass just north of Kaua‘i as it marches east, bringing with it a significant threat of severe weather during the next couple of days.

The National Weather Service forecast office in Honolulu already issued several weather advisories throughout the state, including for the Big Island and Kaua‘i, in advance of the storm.

They all went into effect Wednesday and run through Friday:

• Flood watch for the entire state, except the summits of Mauna Kea and Mauna Loa on the Big Island.
• High wind watch for lower elevations of the Big Island.
• High wind warning for the summits of Mauna Kea and Mauna Loa.
• High wind warning for Kaua‘i and Ni‘ihau.
• Winter storm watch for summit areas of Mauna Kea and Mauna Loa.

“We expect an impactful event,” said Thomas Birchard, a lead forecaster with the National Weather Service Honolulu forecast office, on Tuesday.

The potent low pressure system will pass within a couple of hundred miles north of Kaua‘i, much closer than normal for this time of year, and likely intensify as it does. Greatest impacts from the storm are expected through the day today and tonight.

A cold front will be dragged eastward through the islands by the storm as its center passes to the north while strong southerly and southweterly kona winds pull up deep tropical moisture into the cold air surrounding the system and providing instability.

That sets up a scenario ripe for hazardous weather, which National Weather Service Honolulu forecaster Robert Bohlin said will likely include the increasing threat of flash flooding from heavy rainfall and strong to severe thunderstorms.

Hawai‘i News Now Chief Meteorologist Jennifer Robbins said in her forecast update Tuesday that some forecast models show parts of the state receiving 5 to 10 inches of rain from the winter storm, with some places getting as much as 12 inches.

“Total rainfall — while a seemingly popular subject of question — is not all that relevant most times,” Birchard said. “It’s high rainfall rates that lead to flash flooding, and all the ingredients are in place to support the development of very high rainfall rates of 2 to 3 [inches] per hour.”

Intense rainfall rates are likely, especially over leeward areas and particularly the typically drier south and southwest areas of the islands, which would include Kaʻū and portions of South Kona and Puna on the Big Island, where the greatest rainfall totals are expected.

The thunderstorm risk is enhanced, with some possibly becoming severe with the potential to produce damaging wind gusts of 50 mph or more.

Even low-level rotation and supercell thunderstorms are a possibility, especially over the western end of the state, with wind gusts of up to 60 mph and isolated waterspouts possible.

Strong and damaging south and southwest winds will also be a threat through Friday, especially for the smaller islands. Birchard said winds will be especially strong in places where they are accelerated by terrain, such as Puna, Kaʻū and Kona.

Those areas could see localized gusts near 60 mph, and winds can be even stronger as they move downslope to the north and northeast. Damaging downsloping winds will be an even greater threat for Kaua‘i and O‘ahu.

“People should be prepared for power outages,” Birchard warned.

Hawai‘i News Now meteorologist Drew Davis said Tuesday night in an Instagram reel that scattered showers and thunderstorms could start developing ahead of the front late Wednesday and early this morning, but they would be forerunners to the main event and more hit or miss, impacting some but not all.

The cold front associated with the low pressure system to the north of the state will move across the islands today and early Friday.

This winter storm is also somewhat unique compared to others during this time of year.

“Typically during the wet season, when we see these heavy rain events, we’re tracking a low pressure system well to the north of the state and we’re impacted by the tail end of the cold front associated with that low pressure system,” explained Davis. “This one, however, is just to our north, intensifying the chance for both heavy rain and thunderstorms.”

Hawai‘i Gov. Josh Green signed an emergency proclamation in advance of the storm to make sure relief and assistance are available in response to any damages, losses and suffering, as well as to protect the health, safety and welfare of the people of the islands.

Young Brothers makes a couple of changes ahead of winter storm

Young Brothers also modified its cargo acceptances at all ports until further notice in anticipation of any impending severe weather.

The shipping company will not be accepting palletized/mixed hazardous material cargo or livestock.

“There are no changes to the acceptance of any other cargo, and we will make every effort to complete sailings as scheduled; however, changes in the forecast and intensity of the storm conditions could have additional effects on our operation,” said Young Brothers in its announcement.

Updated information will be posted on the company’s website.

Customers also are encouraged to sign up for email notifications and follow Young Brothers on social media @youngbrothershawaii/@youngbrothershi.

Hawaiian Electric watching weather, urges customers to prepare

Hawaiian Electric is closely monitoring the weather as well and urges customers to check their emergency preparations and prepare for possible power outages.

Because stormy weather and hazardous conditions can arise with little notice, the elecric utility strengthens and maintains its infrastructure throughout the year by:

• Conducting ongoing vegetation management.
• Inspecting and upgrading poles, power lines, transformers and other equipment.
• Performing ongoing maintenance of generating units.

“Safety is always Hawaiian Electric’s top priority,” said Hawaiian Electric in an announcement about its storm preparations. “We urge customers to make it their top priority, too.”

Here are some ways you can prepare:

• Check emergency equipment such as flashlights, emergency generators, battery-operated (hand-crank or solar) radios, light sticks and lanterns to be sure they are operational. Buy extra batteries.
• Make sure you have a battery-powered radio to listen for updates about weather conditions.
• If someone in your home depends on electrically powered, life-sustaining medical equipment, check backup facilities.
• Plan where to go if an evacuation is ordered. If you need to go to the hospital or other emergency shelter, remember to take your medical equipment and medications with you.
• If you use a portable generator, make sure it is placed in a well-ventilated area outside the home. Be sure to carefully follow all instructions in the manufacturer’s manual.
• Turn your refrigerator and freezer to their coldest settings. If power goes out, this will keep food fresher longer.
• Turn off and unplug any unnecessary electrical equipment, especially sensitive electronics. If an outage occurs, this will prevent damage to the equipment from surges when power is restored.
• Don’t venture out in the dark. Avoid standing water and debris.
• If you see a downed power line, assume it is energized and dangerous. Stay at least 30 feet or more away from all power lines. Warn others to stay away.

Call the Hawai‘i Island trouble line at 808-969-6666 for Hawaiian Electric assistance.

The electric utility will provide updates frequently via the news media and the following resources:

• Hawaiian Electric website.
• Twitter/X.
• Facebook.
• Mobile app: Free download available on Apple Store and Google Play.

Visit the Hawaiian Electric storm center website for additional storm preparation and safety tips.