Kona storms (also called Kona lows) are a type of seasonal

cyclone In meteorology, a cyclone () is a large air mass that rotates around a strong center of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above (opposite to an an ...

in the

Hawaiian Islands The Hawaiian Islands ( haw, Nā Mokupuni o Hawai‘i) are an archipelago of eight major islands, several atolls, and numerous smaller islets in the North Pacific Ocean, extending some from the island of Hawaii in the south to northernmost ...

, usually formed in the winter from winds coming from the westerly "kona" (normally

leeward Windward () and leeward () are terms used to describe the direction of the wind. Windward is ''upwind'' from the point of reference, i.e. towards the direction from which the wind is coming; leeward is ''downwind'' from the point of reference ...

) direction. They are mainly

cold core A cold-core low, also known as an upper level low or cold-core cyclone, is a cyclone aloft which has an associated cold pool of air residing at high altitude within the Earth's troposphere, without a frontal structure. It is a low pressure syste ...

cyclones, which places them in the

extratropical cyclone Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth. Extratropical cyclones are capable ...

rather than the

subtropical cyclone A subtropical cyclone is a weather system that has some characteristics of both tropical and an extratropical cyclone. As early as the 1950s, meteorologists were uncertain whether they should be characterized as tropical or extratropical cyclon ...

category. Hawaii typically experiences two to three annually, which can affect the state for a week or more. Among their hazards are heavy

rain Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...

hail Hail is a form of solid precipitation. It is distinct from ice pellets (American English "sleet"), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailstone. Ice pellets generally fal ...

storms,

flash flood A flash flood is a rapid flooding of low-lying areas: washes, rivers, dry lakes and depressions. It may be caused by heavy rain associated with a severe thunderstorm, hurricane, or tropical storm, or by meltwater from ice or snow flowing ...

s and their associated

landslide Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated slope failures, mudflows, and debris flows. Landslides occur in a variety of environmen ...

s, high elevation

snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughou ...

, high winds which result in large surf and swells, and

waterspout A waterspout is an intense columnar vortex (usually appearing as a funnel-shaped cloud) that occurs over a body of water. Some are connected to a cumulus congestus cloud, some to a cumuliform cloud and some to a cumulonimbus cloud. In the ...

Origin of term

Kona is a

Hawaiian language Hawaiian (', ) is a Polynesian language of the Austronesian language family that takes its name from Hawaii, the largest island in the tropical North Pacific archipelago where it developed. Hawaiian, along with English, is an official language ...

term (related to similar words in other Polynesian languages) for the western (to southwestern) side of an island. The

Kona District Kona is a ''moku'' or district on the Big Island of Hawaii in the State of Hawaii, known for its Kona coffee and the location of the Ironman World Championship Triathlon. In the current system of administration of Hawaii County, the ''moku'' o ...

for example on the

Big Island of Hawaii Hawaii ( ; haw, Hawaii ) is the largest island in the United States, located in the state of Hawaii. It is the southeasternmost of the Hawaiian Islands, a chain of volcanic islands in the North Pacific Ocean. With an area of , it has 63% of t ...

still uses this name. Although normally dry and

, the traditional easterly (to northeasterly) tradewinds slacken and reverse during one of these cyclones.

Character of the cyclones

Once termed as

s, a change in the definition of the term during the early 1970s makes categorization of the systems not straightforward. Kona lows are typically cold core, making them

s. However, they generally share the subtropical cyclone characteristic of losing their associated

weather fronts A weather front is a boundary separating air masses for which several characteristics differ, such as air density, wind, temperature, and humidity. Disturbed and unstable weather due to these differences often arises along the boundary. For ins ...

with time, since the cyclones tend to retrograde slowly. Otkin and Martin identified three types of kona storms: cold-frontal cyclogenesis cyclones (CFCs), trade wind easterlies, and cold-frontal cyclogenesis/trade wind easterlies cyclones. Of the three, CFC cyclones are the most common. Rainfall in a Kona storm is more pronounced than a cold front storm, and most intense from south to east of the storm and in front of the storm's center. Steady rains may last from several hours to days, with longer lasting storms typically interrupted by intervals of lighter rain and partial clearing. Intense showers may appear on more moderate but steady rain.Climate of Hawaii
on Western Regional Center web site

Frequency and effects

Some winters occur without a single Kona storm, with a high of four or five. Hawaii typically experiences two to three annually between October and April.Steven Businger and Thomas Birchard, Jr
A Bow Echo and Severe Weather Associated with a Kona Low in Hawaii.
Retrieved on 2007-05-22. The cyclone events for Hawaii can be long-lived, affecting the state for a week or more.Steven Businger
Kona Lows in Hawaii.
Retrieved on 2007-05-22. Kona lows produce a wide range of weather hazards for Hawaii. Among them are heavy rain, hailstorms, flash floods and their associated landslides, high winds which result in large surf and swells, waterspouts, and heavy snows on the higher mountains.

Kona winds

Kona winds are associated with cyclones with central pressures below which pass within 500 miles/820 km northwest of the Hawaiian Islands. Strong Kona winds usually last for a day. Considerable damage is caused to boats lying southwest of the islands. On land, trees are uprooted and roofs can be blown off homes. When passing through mountain gaps and over mountains, downsloped winds gust over 100 mph/165 km/h, which causes much of the destruction.

Examples

The most powerful Kona storm in the last fifty years struck the Hawaiian islands between 8 January and 11 January 1980. The low pressure primarily responsible for the severe conditions had a barometric pressure of 975mb on January 8, while passing north of the state, one of the lowest pressure readings ever recorded in Hawaiian waters as a result of an extratropical storm.

Retrieved on 2007-11-23. The storm caused severe weather across the entire state, forcing the closure of all airports. Rainfall from the storm was extremely heavy, surpassing twenty inches in many locations, particularly on the Big Island and Maui. High surf from the storm caused extensive damage, particularly along the Kona coast of the Big Island, where the towns of Kailua-Kona and Puako received extensive damage. Winds from the storm averaged around 40-50 mph on the open ocean, but varied tremendously on land due to unique geographic features. Some areas experienced wind gusts well over hurricane force, including a low altitude gust of on Lahaina Roads, Maui. Haiku, on the windward coast of Maui, experienced a wind gust of . On the high mountain summits of the Big Island and Maui, winds of over were recorded. Damage from the storm was estimated at between $25 and 35 million (in 1980 dollars). In December 2008, lightning strikes from a Kona storm caused the entire power grid of the island of Oahu to black out, while then President-elect,

Barack Obama Barack Hussein Obama II ( ; born August 4, 1961) is an American politician who served as the 44th president of the United States from 2009 to 2017. A member of the Democratic Party (United States), Democratic Party, Obama was the first Af ...

was visiting."Major Power Outage in Honolulu as Obama Visits"
in Time Magazine, December 27, 2008 In December 2010, a Kona storm became fully subtropical and eventually became

Tropical Storm Omeka Tropical Storm Omeka was the latest forming Pacific hurricane, Eastern Pacific named storm since reliable records began in the 1960s. The storm was part of the 2010 Pacific 2010 Pacific typhoon season, typhoon and 2010 Pacific hurricane season, ...

In popular culture

The fourth episode of the sixth season of Magnum, P.I. is entitled "The Kona Winds."

References

{{DEFAULTSORT:Kona Storm Types of cyclone Weather events in Hawaii Storm Extratropical cyclones Subtropical cyclones