The rain-soaked Hawaiian Islands are preparing for another potential flood this Thursday, just days after record-breaking storms wreaked havoc, buckling roads and damaging buildings.
According to the University of Hawaii’s climate data team, certain areas of Maui received over 5 feet of rain from March 10 to 16, with 33 inches falling in a mere 24 hours at Haleakala Crater near the island’s summit.
While this impending storm is expected to be weaker than its predecessors, the National Weather Service (NWS) warns that flooding could return quickly. A majority of Hawaii remains under a flood watch.
“Due to the high soil saturation from the recent Kona storm, even moderate rainfall poses a risk of rapid runoff and flooding,” stated NWS forecasters on Thursday.
Kona storms are pivotal weather patterns in Hawaii, responsible for delivering heavy rain to the island’s typically dry leeward regions. The rainfall anticipated this week is attributed to a new Kona storm.
These storms significantly interact with Hawaii’s wildfire concerns. The areas receiving the Kona storm’s heavy rains have historically also been wildfire-prone. Rainfall in these fire-affected regions increases runoff and erosion, exacerbating flooding and rising landslide risks.
Lahaina, where over 100 lives were lost in the 2023 Maui fires, is significantly impacted by the recent flooding. Joseph Puruta, a Lahaina resident who lost his home in the fire, lamented the debris washing down the burn scar.
“Debris is flowing down the hill into homes, the ocean, and the streets. It’s a dire situation,” Puruta stated.
The extreme rainfall in Hawaii coincides with widespread weather chaos across the U.S. On Wednesday and Thursday, California and Arizona recorded unprecedented high temperatures, with some areas hitting the 90s and even triple digits. Previously, heavy snow impacted Nebraska, which is also battling severe wildfires.
Hawaii is no stranger to rain, primarily caused by a phenomenon known as “orographic lift,” where trade winds encounter the island’s mountainous terrains. This interaction forces air upwards, leading to cooling and cloud formation. Typically, the winds blow from the northeast, keeping most precipitation confined to the upwind regions.
“In upwind areas, the annual average is about 400 inches,” remarked Thomas Giambelka, a professor emeritus at the University of Hawaii at Manoa.
Conversely, the southern and western parts of the island generally stay relatively dry.
However, during Kona Arashi, this norm reverses. Storms arise due to shifts in the jet stream, a high-altitude air flow moving from west to east. In a Kona storm, low pressure drifts away from the jet stream and gathers northwest of the island, pulling moist tropical air toward Hawaii. This results in winds blowing from the south, delivering heavy rainfall to normally dry regions.
Last weekend’s Kona storm set daily rainfall records at four official sites, as reported by the Honolulu National Weather Service.
Maui County spokesperson Lakshmi Abraham indicated that the impact is “unlike anything we’ve encountered in our lifetimes.”
Maui County (via AP)
The Kona storm impacts Maui areas where wildfires are increasingly common. This trend is linked to the spread of non-native, highly flammable grasses, especially on previously cultivated lands.
According to Clay Trauernicht, a wildland fire expert at the University of Hawai’i at Mānoa, the dangers posed by these invasive grasses have been a longstanding concern. The 2023 Lahaina fire brought this issue to the forefront.
However, many people still fail to recognize the close relationship between fires and floods, Trauernicht noted.
Flooding can facilitate the growth of non-native grasses, which subsequently die during droughts.
“This cycle adds more fuel to the situation,” remarked Camilo Mora, a climate scientist and professor at the University of Hawaii at Manoa.
Concurrently, rain can rapidly run off the recently scorched slopes, intensifying flooding risks, Trauernicht explained. Additionally, areas filled with unburned non-native grasses have shallower water tables that are less absorbent than native forests.
“The root structure tends to be matted with shallow roots,” Trauernicht observed. “This contributes to more water flowing over the surface.”
Locations like Lahaina are “extremely vulnerable due to their fire history,” Trauernicht emphasized.
Historically, many areas were susceptible to flooding, even before the wildfire issue escalated. Portions of South Maui are situated in federally designated floodplains, including parts of Kihei. Reports indicate apartment collapses and road deterioration during the recent storm, according to Hawaii News Now.
Maui County Public Works Director Jordan Molina commented on the ongoing upgrades to the region’s drainage systems to enhance resilience against flooding, although recent storms have stressed existing infrastructure.
“Creating an infrastructure capable of entirely mitigating flooding during extreme storms, like this Kona storm, would necessitate a vast and costly system that is financially impractical,” Molina stated via email.
The Department of Public Works prepared equipment on Wednesday and Thursday in anticipation of the next storm, clearing debris from roads and inspecting drainage channels for blockages.
“It’s worrisome, but we are prepared for flooding,” Giambellucci remarked. “Handling this repeatedly could be detrimental.”
Source: www.nbcnews.com
