The Jan. 4 “bomb cyclone,” a particularly strong nor’easter. (CIRA)

While few and far between this winter, nor’easters and their driving rain, heavy snow, howling winds  and raging seas often leave a big mark on the Mid-Atlantic and Northeast.

A significant nor’easter is likely later this week along the Northeast coast. To better understand these storms, here are some things to know.

1) How does a nor’easter form?

The Gulf Stream provides warm waters along the East Coast from Florida to the Mid-Atlantic states. These waters warm the air above the ocean, as well. When a cold weather system moving off the land clashes with this warm air over the ocean, it creates a type of instability in the atmosphere that powers a nor’easter.


NASA visualization of the Gulf Stream. The turning and twisting orange line off the Southeast coast depicts the Gulf Stream. (NASA)

2) Why “nor’easter”?

Although many think these storms are called nor’easters because they occur in the Northeast, it’s because their winds come from the northeast along the Eastern Seaboard. Sailors identified storms by the direction of the approaching winds and began calling these storms “northeasters.” Captains eventually shortened “northeaster” to “nor’easter.”

3) Where do they hit?

It may not be why we call them “nor’easters,” but they do mostly affect the Northeast. These are storms that develop and move along the East Coast. They hit a densely populated sector. Large cities like Boston, New York City, Philadelphia and Washington, D.C., are all vulnerable to these storms.

4) Different types of nor’easters

There are two kinds of nor’easters. Miller “type A” and Miller “type B,” which are named after J.E. Miller, who first classified these storms in 1946.

1. Miller “type A” storms are also known as “classic” nor’easters. They form along the Gulf Coast, then travel up the East Coast.


Nor’easter, Miller Type A Pattern (NWS)

2. Miller “type B” storms are less traditional nor’easters that form in the Midwest, as ordinary cyclones, and travel east toward the Appalachian Mountains. These storms are disrupted by the mountains, then re-form along the East Coast.


Nor’easter, Miller Type B Pattern (NWS)

5) When do they form?

Nor’easters typically form during the colder months, from around September to April, but they can occur at any time of year. They are more likely to develop during the winter because of the polar jet stream. The jet stream brings cold air from Canada toward the south, then east to the Atlantic Ocean. This provides the perfect combination of cold and warm air to form a nor’easter.

6) Characteristics

Not all nor’easters are snowmakers. They can include heavy rains, strong winds, coastal flooding  and rough seas. Nor’easters are often compared to hurricanes for their strong winds, heavy precipitation and high tides.

Although they may look alike, hurricanes and nor’easters are very different. Unlike hurricanes, which develop in the tropics, nor’easters form in mid-latitudes. Nor’easters form from contrasting air masses and are cold at their core. Hurricanes are warm at their core and are fueled by warm ocean waters, usually at least 80 degrees.

7) Possible dangers

A nor’easter usually lasts a day or two. Heavy rain and snow lead to unsafe driving conditions, and strong winds knock down trees and power lines, causing outages. These conditions can disrupt a community and sometimes bring everything to a halt. Many people are injured during and after nor’easters because of car accidents, slips and falls, hypothermia, trees falling, roofs collapsing, and even snow shoveling. During a nor’easter, it is wise to plan properly, stay home and stay safe.


Ninth and I streets NW in Washington, D.C., during Snowzilla in 2016. (Jaclyn Lippelmann via Flickr)

8) Economic implications

Since these storms tend to force this busy area of the country to pause, there are many economic effects. Flight cancellations and delays are costly. Coastal flooding can result in the inundation of homes and businesses.

People are more likely to stay home, so businesses  suffer. Plus, there are damage costs and recovery after the storm. However, those selling eggs, milk, bread, shovels  and salt all probably reap the economic benefits of nor’easters.


Coastal flooding inundates houses in North Wildwood, N.J., after the January 2016 blizzard. (Robb Nunzio/Associated Press)

9) Is there a nor’easter intensity scale?

Unlike the Saffir-Simpson scale for hurricane intensity, there is no widely used scale for a nor’easter. However, the little-known Dolan-Davis scale, developed by Robert Dolan and Robert Davis in 1992,  classifies nor’easters into five categories based on their wave height. A Class 1 is considered weak and has a mean wave height of two meters. In contrast, an extreme Class 5 has a mean wave height of 6.8 meters. The classes are used to predict beach erosion, dune erosion, overwash and property damage.

10) What are some famous nor’easters?

Historically, nor’easters have been some of the most memorable storms on record in the Northeast. Famous nor’easters include the Blizzard of 1888, the Ash Wednesday storm of March 1962, the Blizzard of 1996, the April 2007 nor’easter, the 2011 Halloween nor’easter, the January 2016 Blizzard, and the January 2018 “bomb cyclone.”

Nor’easters can cripple a community; they can also evoke memories of bundling up in front of a cozy fire or playing in the snow. The more you know about them, the better prepared you will be.

Samantha Durbin is a Capital Weather Gang intern, studying meteorology at the University of Maryland, Baltimore County.