HAWAII — Much of Hawaii is under a flood watch as a new kona storm threatens more rain after a storm from March 10-16 that buckled roadways and collapsed buildings. More than five feet of rain fell in some parts of Maui during the earlier storm, with 33 inches falling in 24 hours at Haleakalā crater near Maui's summit.

"Given the high soil saturation from the recent kona storm, even moderate rainfall rates could pose a risk for rapid runoff and flooding," National Weather Service forecasters said. "It's concerning — we're primed for flooding," said Thomas Giambelluca, Professor Emeritus at the University of Hawaii at Mānoa. "Having this back to back could be bad."

A kona storm is a weather pattern that can cause heavy rainfall on typically dry, leeward areas of the Hawaiian Islands. During a kona storm, a low pressure system draws tropical moisture toward Hawaii, bringing winds from the south that deliver heavy precipitation to areas usually sheltered from rain.

The recent kona storm set daily rainfall records at four official sites in Hawaii and hit regions where wildfires have become more common over the past several decades. Lahaina was one of the areas hit hard by the recent floods. More than 100 people died in a fire in Lahaina, Maui, in 2023.

Rainfall on fire-affected areas triggers runoff and erosion, which can worsen flooding and raise the risk of mudslides. Rain runs off recently burned slopes more rapidly, which can cause more intense flooding. In areas dominated by unburned invasive grasses, the water table is shallower and the soil is less absorptive compared to native forests.

During the recent storms, a condominium building collapsed and roadways failed in Kihei. Some parts of South Maui, including areas of Kihei, are in federally designated floodplains. The County of Maui is working to overhaul drainage systems and improve infrastructure resilience.

"Designing infrastructure capable of fully eliminating flooding during extreme storm events like this recent kona low would require an extraordinarily large and costly system that would not be financially feasible," said Jordan Molina, Director of Maui County's Department of Public Works. On Wednesday and Thursday, the Maui County Public Works Department staged equipment, cleared debris from roads, and inspected drainages for obstructions ahead of the next storm's arrival Thursday night.