With only a few days having passed since the last Kona low storm, Hawai’i is once again bracing for more rain, wind and thunderstorms.
Starting on Wednesday, April 8, a flash flood watch will be in effect for all islands.
The recorded rainfalls in March were historic in some areas across the state, with some parts seeing as much as five feet of rainfall. A total of two trillion gallons of rain soaked the islands over 14 days.
To learn more about the upcoming storm, HPR spoke with Thomas Giambelluca, a University of Hawaiʻi Climatologist.
Giambelluca is in charge of the Climate Data Portal and the director of a statewide network of weather stations called the “Mesonet,” and he also previously served as director of the Water Resources Research Center.
Interview Highlight
On forecasting floods in Hawaiʻi
GIAMBELLUCA: The models are good at telling us that we're going to have potentially heavy rain in the Hawaiian Islands. But especially if it's out a day or two or longer, it's very unlikely those models can say exactly where the heaviest rain is going to occur. They may be able to identify by island, but not by watershed. So as the storm develops, as we start seeing how the atmosphere is evolving, we'll have a better idea. But yeah, it's very hard to predict exactly which watershed is going to get the maximum rainfall. Our watersheds are very narrow, very steep. They can flood very quickly, and so forecasting floods in Hawaiʻi is very difficult.
On rainfall measuring technology
GIAMBELLUCA: The rainfall is one, and it's a very important one. But we also measure air temperature, relative humidity, wind speed, wind direction, air pressure. And we make measurements below ground of soil moisture at three depths. We measure soil temperature, we measure the amount of heat going into the soil. And we measure radiation, solar radiation coming in, how much of it, that radiation is reflected out, and also long wave radiation coming down and going out. And so this provides information for many applications in weather forecasting, but also in agriculture and water resource management and so forth.
... This network is designed to provide real time information, or near real time. We measure, we scan the sensors every second or two, and then use that information to record data at a five minute interval. And we collect the data from all of our stations, currently, 77 stations every 15 minutes. So it's very up to date.
On preparing for the upcoming storm
GIAMBELLUCA: I would just say to be aware, especially if you're living or working in low lying areas, listen to the alerts from National Weather Service, and if it's time to get out of that area, do so. I just wish everyone the best. We're in a situation now where we've had a long period of heavy rain, and so the ground is saturated in many areas, and we have forecast for more heavy rain and prolonged rain over the next few days, and so we could be seeing some really devastating floods. So I just would urge everyone to be aware and be ready to take action as needed.
Giambelluca is the director of the Mesonet, which is part of the Hawaiʻi Climate Data Portal. More information about their work can be found on their website here.
This story aired on The Conversation on April 7, 2026. The Conversation airs weekdays at 11 a.m. Jinwook Lee adapted this story for the web.
