‘Kona Low’ Douses Hawaii With Heavy Rains

Hawaii may be a tropical paradise most of the time, but the U.S. state was recently hit by a tropical cyclone, causing flooding and power cuts.

Hawaii is made up of over 100 islands, but there are just eight major ones. The Big Island, Maui, and Molokai were hit first by the heavy rain and gusty winds, with the storm then moving over Oahu. According to NASA’s Earth Observatory, “The storm also brought … flash flooding, along with reports of landslides, downed trees, and power outages. Some roads and schools were closed.”

At least a foot of rain fell over Maui over 24 hours, while Honolulu saw its wettest December day on record. Areas suffered from flash floods – a type of flood that occurs very quickly as there is too much water that can’t drain away quickly enough.

The state’s governor, David Ige, declared a state of emergency due to the storm conditions. “Now is the time to make sure you have an emergency plan in place and supplies ready should you need to move away from rising water,” he warned residents.

A Very Hawaiian Storm

This is not just any old storm, though. It’s called a “kona low,” a type of cyclone specific to Hawaii.

“Kona” is a native Hawaiian language term. It means “leeward,” a word that refers to something that is downwind, or facing the same direction that the wind is blowing. It is the opposite of “windward” when something faces into the wind.

That National Ocean Service describes Hawaii’s leeward and windward sides:

“An island’s windward side faces the prevailing, or trade, winds, whereas the island’s leeward side faces away from the wind, sheltered from prevailing winds by hills and mountains. As trade winds blow across the ocean, they pick up moist air from the water …

“An island’s windward side is wetter and more verdant than its drier leeward side … As an example, the Hawaiian Islands have damp windward sides and drier leeward sides most of the time as a result of the Pacific Ocean’s northeasterly trade winds. Windward locations are generally lush and green. Famously sunny beaches like Oahu’s Waikiki and Maui’s Wailea are found on the islands’ more sheltered leeward sides.”

The leeward side of Hawaii’s islands is to the west, while the wind normally comes from the east. However, during Kona storms the wind direction changes and starts to blow from the west – hitting the areas of the islands that are normally protected.

Kona lows normally form during the winter months, and Hawaii can experience a few each year. The cyclones can last for several days or over a week. They can cause heavy rain, hail, high winds, snow on the mountains, floods, and landslides.

As well as floods, Hawaii faced a blizzard warning during the storm. Snow fell on the Mauna Kea and Mauna Loa volcanoes. In fact, enough snow fell that people were seen skiing on the volcanoes, making a different picture than the sun and surf people usually imagine when thinking of Hawaii!