3 Winter Words You Should Know

Bombogenesis, polar vortex, and williwaw—what do these really mean?

Prospect Point at Niagara Falls State Park covered in snow after the polar vortex.

"Bombo"-what? Bombogenesis. It's not a word you expect to hear from your local meteorologist. So what is it exactly? And what's with the mishmash of strange weather vernacular over the past few months?

On Tuesday, meteorologist John Bolaris at Philly.com was the first to use the term "bombogenesis" to describe the large, fast-moving snowstorm that was heading toward the East Coast. NPR journalist Mark Memmott noticed the unusual word and wrote his own article called "What Is This Bombogenesis And Why Is It Dumping Snow On Us?" Memmott's story went viral and brought national attention to the word.

But these two writers were not the first to use this term and other terms that have been popularized this winter.

The odd collection of weather words used in the media—such as "polar vortex"—are actually advanced technical terminologies for specific weather conditions. "Polar vortex" describes a wind pattern over the North and South Poles. "Bombogenesis" is a slang word used by meteorologists to describe a winter storm that forms quickly.

Why haven't we heard these words before? According to Chris Vaccaro, a spokesperson for the National Weather Service, meteorologists are using these terms to describe weather conditions in areas that don't typically see such events; the use of these words is then accelerated through social media.

"As a result of social media, these terms are picked up and spread much further," said Vaccaro. "Now there are more voices to amplify our weather words."

And even though an odd winter word may first make you go "huh?" it can then teach you about the way weather works. After a while we become more familiar with meteorology terms: "When I hear the term 'polar vortex,'" Vaccaro says, "I remember all of the characteristics I learned about it in school."

That being said, here are three winter weather terms that are particularly apropos this winter.

Polar Vortex

A polar vortex, also known as a circumpolar vortex, is a wind current that circulates above the North and South Poles. The currents sit like spinning hats above the Poles.

During the winter season, the northern polar vortex typically increases in strength as it is blanketed in 24 hours of darkness. Heat from the surface rises into the atmosphere and creates an area of low pressure above each Pole. The warm air becomes colder because of the lack of sunlight and is contained over the polar region by a jet stream.

When the jet stream—a result of colder air over the polar region pushing up against warmer air—is strong, the air stays trapped in the vortex above the polar region. But when the jet stream is weak, undulations or kinks in the jet stream cause polar air streams to travel farther south, an arm of cold air breaking out of an icy circle.

The polar vortex itself is nothing new. It has existed for many years, and "it will continue to be there," says Vaccaro. The term "has appeared in meteorologist glossaries dating back to at least the 1950s."

But this winter, the bitter winds from the polar vortex disrupted areas of the U.S., closing schools and offices in cities like Chicago. This southern dive may be a result of warmer temperatures in the Arctic region, which weaken the polar vortex.

Studies by the National Oceanic and Atmospheric Association (NOAA) suggest that a loss in Arctic sea ice has contributed to a weaker polar vortex, which then brings frigid air farther into North America and Europe, and warmer temperatures to the polar areas. (See related: "Behind Record U.S. Cold Snap: Canadian Air and a Jet Stream Kink.")


A man walks through strong winds and blowing snow in Massachusetts.

Bombogenesis is meteorological slang that describes a rapidly developing storm system as noted by the raid fall of its central pressure. The word originates from "cyclogenesis." Bombogenesis is a form of cyclogenesis. "The so-called 'bomb' is when the barometric pressure drops sharply," said Vaccaro. The lower the barometric pressure, the stronger the storm.

This type of storm is common on the East Coast. For instance, many nor'easters are created through bombogenesis.

The term was popularized on Tuesday when the central pressure of a storm system over the Atlantic dropped sharply in 24 hours. An area of cold air from Canada encountered warm air from the Gulf Stream in the Atlantic to create a textbook example of bombogenesis.

The result was a snowstorm that battered quite a few major cities from Kentucky up to New England. The fast-moving system was so severe in the northeast that New York, New Jersey, and Delaware declared states of emergency. (See "Editor's Picks: Our Favorite Pictures of the Winter Snowstorm.")


An air tanker drops water on a wildfire that was fanned by the Santa Ana winds, which are similar to williwaws.

"Williwaw" describes a violent windstorm created when gravity pulls high-density cold air down from a mountain to the sea. Williwaw is a colloquial word for a katabatic wind in Alaska, where the strong winds can be dangerous for local fishermen.

The origin of the word "williwaw" is unknown; the Oxford Dictionary dates the use of the word back to the middle of the 19th century. And if you want to impress your friends, you should also learn the term "katabatic winds." That's a term meteorologists use to describe gusts of wind associated with the buildup of dense air. And such winds aren't confined to cold areas.

Another famous katabatic wind is known as a Santa Ana, which blows over southern California in autumn and winter. Santa Anas are warm, dry winds created when air is compressed as it moves down a mountain range. These dry katabatic winds are associated with spreading wildfires.

Now to try using these new words in a sentence. (For other interesting meteorology terms, snoop around in the National Weather Service glossary.)

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Correction: An earlier version of this story incorrectly implied that both polar regions are blanketed in 24 hours of darkness. Only one polar region is dark while the other is light, this has been updated for clarity. It also stated that Santa Ana winds are foehn winds. They are actually classified as warm katabatic winds.