The timing on yesterday’s wind and rain was ideal…clearing out for Halloween!  I’m calling it an event; it was a fall storm, but you might have heard it referred to as a Nor’easter.  Technically, it was not a true Nor’easter.

Let’s have a look at what makes a storm a Nor’easter:

Nor'easters occur along the eastern seaboard any time between October and April, when moisture and cold air are plentiful. They often dump heavy amounts of rain and snow, producing hurricane-force winds, and creating high surfs that cause severe beach erosion and coastal flooding.

There are two main components to a Nor'easter: a Gulf Stream low-pressure system and an arctic high-pressure system.  Gulf Stream lows develop off the coast of Florida. (Late Saturday, remnants of tropical storm Philippe supplied that needed energy). The low circulates off the southeastern U.S. coast, gathering warm air and moisture from the Atlantic. Strong northeasterly winds at the leading edge of the storm pull it up the east coast.

That’s where the Arctic high comes into play.  As the strong northeasterly winds pull the storm up the east coast, it meets with cold Arctic air blowing down from the north. When the two systems collide, the moisture and cold air produce a mix of precipitation.  The resulting precipitation depends on how close you are to the converging point of the two systems.

Here’s where yesterday’s storm differs from a text-book Nor’easter.

A Nor'easter is named for the winds that blow in from the northeast and drive the storm up the east coast along the Gulf Stream.  So to be a nor'easter, the predominant wind direction during the height of the event should be from the northeast, not the northwest or southeast.  Yesterday, our winds blew from the SE then turned to the SW where they sit right now.

Those SW winds continue to serve up milder than normal weather! It should be a lovely night for trick-or-treating!

 

Chief Meteorologist

Cindy Day