Storm terms: Nor’easter, thundersnow, polar vortex and more explained

A nor'easter blanketed the city in snow on March 7.
A nor’easter blanketed the city in snow on March 7. Photo Credit: Courtesy of Tribeca Film Festival

Thundersnow, “bomb cyclone,” polar vortex — what does it all mean?

It seems that with each passing year (and each passing storm) some new weather term blows the minds of the masses.

Well don’t fret. We’re here to help you sort it all out.

Here’s our guide to winter weather terminology, as defined by the National Weather Service.


There are several conditions that need to be met in order for a snowstorm to be considered a blizzard. First: sustained winds or frequent gusts of 35 mph or higher need to be recorded. Second: there must be considerable falling and/or blowing snow that reduces visibility.


Most common along the East Coast between September and April, a storm is called a nor’easter when winds blow from the northeast.

‘Bomb cyclone’

Technically called bombogenesis, this is a storm system that rapidly intensifies, dropping at least 24 millibars (a measure of atmospheric pressure), over the course of 24 hours. This often occurs when cold and warm air masses collide.


This weather phenomenon occurs when “shallow layers of unstable air lead to enhanced upward motion, increasing snow growth and causing enough electric charge separation for lightning.”

Polar vortex

Though meteorologists haven’t been using this term much this winter, the polar vortex still haunts the dreams of many New Yorkers. The polar vortex is a swath of low pressure and cold air that typically sits near the poles. But sometimes, often in winter, the vortex expands and pushes the frigid air south.

Wintry mix

This commonly used phrase is a succinct way to describe precipitation that could involve snow, sleet, rain and/or freezing rain.

Winter weather warning

A warning means the NWS is predicting winter weather conditions that could endanger life or property.

Winter weather advisory

This is issued by the NWS when a storm is expected to bring a combination of snow, freezing rain and sleet. But while it does present a “hazard,” it does not meet the criteria for a warning.

Winter weather watch

This advisory is intended to alert folks of the potential for dangerous winter weather conditions. A watch may be issued when the likelihood of bad weather has increased but the NWS hasn’t yet pinned down the specifics on the timing and location.

Wind advisory

When sustained winds between 25 and 39 mph are expected or if there are gusts of 57 mph predicted, the NWS will issue this advisory.