Evolving kona low storm system could bring flooding, lightning to Hawaiʻi island

Hawai‘i County urges residents and visitors to prepare for a strong evolving storm system that could bring lightning and heavy flooding rains to Hawai‘i island this weekend and into Monday.

While the exact path and volume of rain from the storm system is still unclear, National Weather Service forecasters issued a statewide flood watch running from late today (Jan. 3) through Monday afternoon (Jan. 5).

“On the Big Island and Maui, the greatest flood risk will be on southeast slopes,” reports National Weather Service.

A kona low — a powerful low-pressure system that can produce strong winds and heavy rain — is expected to develop today north of Kaua‘i and push moist, unstable air across the state from the south and southeast.

Such storms can drop inches of rain in a short time. They also can stall over an area and saturate the ground, increasing the risk of falling rocks or landslides on steep terrain.

“Storms like this are unpredictable and potentially dangerous, so we urge the public to be prepared,” said Hawai‘i County Mayor Kimo Alameda in a Saturday press release. “The picture right now looks like the biggest risk is to Puna and Hilo communities, but that could shift to Ka‘ū or to Kona coast communities by later this weekend.”

Here are additional steps to prepare:

• Consider changing or delaying travel plans or outdoor activities during inclement weather, including routes that have low-lying areas prone to flooding.
• Know areas that are prone to flooding — especially close to your home — and use extra caution near them. Heavy rain uphill from you can cause flooding, even if it’s not raining where you are located.
• Never try to cross moving water — on foot or in a vehicle: “Turn around, don’t drown.”
• Monitor forecasts from reliable sources for the latest information about the storm and its potential hazards.
• If lightning threatens, the safest place to be is indoors. If you’re in a vehicle, stay in the vehicle, but pull off the road if rain is dangerously heavy and it is safe to pull over.
• Have a “go bag” ready in case you have to evacuate the area, especially if your home is in an area prone to flooding. It should include food, water, necessary medication, important documents and other necessities for the members of your household (including pets) if you need to leave in a hurry.
• Check in with neighbors, especially those who might have mobility problems, to make sure they have a safe way to evacuate if flooding strikes.

“This is an evolving storm, so we encourage everyone to stay informed about the forecast; if you haven’t already done so, we encourage you to sign up for emergency alerts at the Hawai‘i County Civil Defense website to receive updates on your cellphone,” said Hawai‘i County Civil Defense Administrator Talmadge Magno.

Visit the National Weather Service Honolulu forecast office website for the most up-to-date forecast and severe weather information, including advisories, watches and warnings.