METEOROLOGIST JEFF HABY
Nor’easters are a type of mid-latitude cyclone that can bring enormous changes to the weather. They are most common in the cool season (colder
half of the year) and they derive their energy from two sources which include the temperature gradient between cold and warm air masses and also
the latent heat energy supplied by warm ocean currents. The location they occur is along and near the East Coast of North America and they get
their name from the northeast wind direction that is experienced along and near the coast. Locations that are noted for receiving these storms
include U.S. states and Canadian Provinces that border the Atlantic Ocean and with the influence extending one to several hundred miles
inland. Since they are more common in the cooler part of the year (mid-Fall to mid-Spring), these storms can produce significant snow
accumulations. They can be referred to as “white hurricanes” since characteristics include strong surface winds and heavy snow. The low
pressure structure differs from a hurricane though in that Nor’easters take on the low pressure structure of an intense mid-latitude
cyclone with differential advections.
Nor’easters can range from wet Nor’easters to white Nor’easters depending on how much cold air is in place and how much cold air is advected
into the system. Commonly Nor’easters produce both heavy rain and heavy snow with a tendency for snow to be more prevalent in the direction
of the colder air advecting into the system. In the case of a wet Nor’easter, most of the heaviest precipitation falls as rain. Coastal areas
receive significant rainfall with snow more likely further inland closer to the cold air source. In the case of a white Nor’easter, heavy
snow is experienced even at coastal locations and areas out over the ocean. Another tendency is that snow is more likely to occur at the
coast the farther north a location is (higher latitude). Each Nor’easter is different though in that certain areas will tend to be favored
for the heaviest rain or snow in any one event. The heavy precipitation tends to fall in bands. If the Nor’easter is slow moving, huge
rainfall and snowfall accumulations can occur at certain locations.
The dramatic weather changes that can occur make Nor’easters a significant weather changer. They can cause coastal beach erosion, heavy
flooding rain, travel crippling snowstorms, dangerous sea waves, and structure / tree damaging wind. Like hurricanes, Nor’easters can explode
in intensity in the span of a few hours. The interaction between latent heat energy from the Gulf Stream, the low pressure center and cold
air advecting toward the coast can create a rapidly developing intense storm system. As they develop and mature they tend to move toward
the north, northeast or east from the influence of the polar jet stream mid-latitude winds. They can leave behind significant damage
and precipitation totals.