Residents of the Hawaiian Islands are bracing for severe weather as the region prepares for the impact of an unusually strong low-pressure system expected to traverse north of the state this week. Heavy rainfall, strong winds, and flash flooding pose significant risks, especially to the islands of Oahu and Kauai.
The National Weather Service (NWS) reported potential rainfall accumulations impacting several basins, and as local meteorologist Robert Ballard noted, "What really matters for flash flooding is how hard it is coming down, and a rainfall rate of two to three or four inches per hour. That brings the water up quickly, and the basins can't handle it so streams, creeks, and urban drainage fill up very quickly." This combination creates the perfect storm for hazardous conditions.
Overnight rainfall this past weekend dumped approximately seven inches on parts of Windward Oahu, leading to urban flooding and power outages. Hawaiian Electric reported multiple outages due to downed trees and branches contacting power lines, leaving thousands without electricity.
Conditions are expected to deteriorate from Wednesday night through Thursday. Current forecasts indicate damaging southwest winds, with gusts possibly reaching 50 to 60 mph, increasing the chances of downed trees and more outages. Ballard explained, "Once we get this event, we could see wind gusts of 50 to 60 mph from southwest winds as they go up and over the islands and then accelerate as they come down."
The NWS has issued flood advisories and special weather statements advising residents across multiple islands to stay prepared. With the storm system arriving this week, officials are especially concerned about low-lying areas prone to flooding and treacherous travel conditions.
"The outages were all largely weather-related...we're talking about the impacts from heavy rain and severe weather such as downed trees or other objects coming in contact with the lines," said Darren Pai, spokesperson for Hawaiian Electric. Residents are urged to secure outdoor items, and avoid unnecessary travel during the storm.
While some respite from heavy rain was anticipated with the arrival of calmer conditions, attention has already shifted to the severe winter low developing off the western coast. This low-pressure system is expected to bring periods of heavy rain and thunderstorms, potentially exacerbated by flash flooding throughout the islands.
The NWS warned, "An unusually strong storm low will develop several hundred miles west-northwest of Kauai, which poses an uncommon strength for storms at this latitude." Communities are urged to remain vigilant, especially as flash floods can occur even without heavy rain falling locally. Ballard stated, "You don't want to be near creeks and streams. It doesn't have to be heavy rain where you are to get flash flooding. If you hear thunder or see signs of heavy rain, you need to take immediate precautions."
Three teenagers recently learned this lesson the hard way when they became trapped by rapidly rising water in Iao Valley on Maui, leading to their airlift rescue by local fire crews.
Water safety and preparation are core focuses for emergency management agencies as they brace for the impending storm. Elton Ushio, administrator of Kaua‘i Emergency Management, advised residents, saying, "Given the nature of heavy rain events on Kaua‘i, we urge everyone to stay vigilant and avoid outdoor activities in flood-prone areas like roadways, hiking trails, rivers, streams, and low-lying areas." Anyone planning travel or activities during the storm should reconsider their plans.
Forecasts suggest the worst of the storm will occur overnight Thursday, with conditions finally improving by Friday as the low system clears to the northeast. Rainfall, wind, and potential flooding remain prominent concerns as over 20% of typically flood-prone areas could see significant impacts.
While the heavy rainfall can help relieve drought conditions, Ballard warned of runoff issues; "It will help the drought situation, but it’s also not all going to soak in effectively, and much of it will turn to runoff." The risk for urban flooding and power outages remains heightened with local forecasts of severe thunderstorms and strong winds.
With the winter season proving unusually active, Hawaii residents are reminded about the importance of preparedness. Should residents prepare for power outages, they are advised to stock non-perishable food, batteries, and fuel for generators. Local government agencies continue to monitor and advise as Hurricane season concludes but winter storm preparation has now taken precedence as conditions develop.
Hawaii’s vulnerable weather patterns remind residents to stay informed through services like the National Weather Service's updates and alerts to navigate potential hazards safely. The coming days will require constant vigilance as the islands face the potential impacts of this multifaceted storm system.