A sudden, violent and frigid windstorm that drops from a mountainous coast onto the sea.
Because williwaws occur when parcels of cold, compressed air in high-altitude snow and ice fields are pulled down to sea level by gravity, they are considered a type of katabatic wind (a meteorological term for any high-density air flowing downhill).
Uncertain, but either of Native American origin or invented by the European seamen and fishermen who encountered the winds off North America’s northwest coast. First recorded uses were by British sailors in the mid-19th century.
The term “williwaw” is used most commonly in the Aleutian Islands and the fiords of the Alaska Panhandle and northwestern British Columbia, but the phenomenon can occur anywhere high-altitude features form the coast, including Baffin Island, Greenland and southernmost South America’s Strait of Magellan.
Williwaws have been clocked at more than 120 knots (about 220 km/h), suddenly stirring up large and potentially deadly waves. Like Chinooks, they are among the few winds frequent and significant enough to have earned a nickname and a kind of legendary status.