Skip to main content

Earth from Orbit: Kona Low Slams Hawaii

December 9, 2021

This week, NOAA satellites monitored a large “kona low” storm system that on Saturday began drenching Hawaii with heavy rains, leading to significant flooding and property damage. The system moved directly over the islands on Monday, prompting the state’s governor, David Ige (D), to declare a state of emergency that is set to remain in effect through Friday, Dec. 10.

 “Hawaii is in danger of a disaster occurrence of heavy rains, flooding, high winds, and high surf, which are forecast to continue through December 8, 2021,” he stated in the proclamation, “with anticipated localized flooding, lingering saturated ground conditions, and periods of heavy rains and flooding which are expected to cause extensive damage.”

A kona low, or kona storm, tends to form in the winter months and is a type of seasonal subtropical cyclone. The word “kona” means “leeward” in Hawaiian, which refers to the side of an island that is usually sheltered from prevailing trade winds and associated rainfall. In Hawaii’s case, these usually come from the east-northeastern direction. Instead, a kona low brings cooler, moisture-rich winds to the islands from the south to southwest, which can lead to torrential rainfall and even heavy snow accumulation across the highest volcanic peaks of the Big Island (Mauna Kea and Mauna Loa). In fact, blizzard conditions were reported on these two mountain summits, and a blizzard warning ran through Monday morning. 

Since the leeward side of the islands don’t get as much rain, they tend to be drier with less vegetation and shallower soil. These conditions make these areas more vulnerable to floods,  along with landslides and mudslides, especially in mountainous areas with steep, sloping inclines. The state’s Big Island has endured some of the worst impacts after experiencing “catastrophic flooding” where two feet of rain fell in some areas and knocked out power throughout the islands. 

The GOES West satellite, also known as GOES-17, provides geostationary satellite coverage of the U.S. West Coast, the Pacific Ocean, Alaska and Hawaii. Launched in March 2018, the satellite became fully operational in February 2019.

The NOAA-20 satellite and Suomi-NPP satellite are part of the Joint Polar Satellite System (JPSS). JPSS is the nation’s advanced series of polar-orbiting environmental satellites. JPSS represents significant technological and scientific advancements in observations used for severe weather prediction and environmental monitoring. These data are critical to the timeliness and accuracy of forecasts three to seven days in advance of a severe weather event. JPSS is a collaborative effort between NOAA and NASA.