The US authorities have on Saturday said that more than 70,000 customers across its northeast were without power as a powerful nor’easter swept through the region. With hazardous conditions expected to persist throughout the weekend, forecasters warned of gale-force winds capable of bringing down trees, along with heavy rainfall that could cause widespread flooding and leave roads submerged.
A nor’easter is a large, powerful storm system that commonly affects the northeastern US and eastern Canada, particularly along the Atlantic coast. It can bring heavy snow, rain, strong winds, coastal flooding, and dangerous travel conditions. Here is a detailed explainer of this natural disaster, which often wreaks havoc along the northeastern coast of the US.
What are nor'easters and how do they form?
The name “nor’easter” comes from the direction of the winds associated with the storm. As the system intensifies near the East Coast, winds often blow from the northeast toward the coast.
A nor’easter typically develops when different air masses meet and a low-pressure system forms or strengthens near the East Coast. The basic process looks like this:
Cold air moves south
Cold, dry air can move southward from Canada and the interior United States. At the same time, the Atlantic Ocean remains relatively warmer, particularly in autumn and winter.
Warm, moist, air sits over the Atlantic
The ocean provides a source of relatively warm, moist air. This air can move northward toward the developing storm. The contrast between cold continental air and warmer, moist maritime air provides an important source of energy for storm development.
A low pressure system develops
A disturbance in the atmosphere can cause air pressure to fall and a low-pressure system to develop. In the Northern Hemisphere, air around a low-pressure system generally rotates counterclockwise.
Why the storm moves toward the east coast?
Storms can develop or strengthen near the Mid-Atlantic coast, sometimes close to the Carolinas or farther north.
A common pathway takes the storm northeastward along or just offshore of the East Coast.
Why it strengthens rapidly?
Under favorable atmospheric conditions, the central pressure of the storm can fall quickly. Meteorologists sometimes describe this rapid strengthening as “bombogenesis.”
As the pressure difference between the storm and surrounding areas increases, winds can become very strong.
Why it produce percipitation?
The storm draws in moisture from the Atlantic while cold air remains present to the north and west.
Depending on temperatures and atmospheric conditions, precipitation can fall as:
Heavy snow
Rain
Sleet
Freezing rain
A mixture of several types
A small change in temperature can make a major difference in whether a particular location receives snow or rain.
Why the strong norteasterly winds hit the coast?
As the storm strengthens and moves northeastward, its circulation can produce strong winds blowing toward the coast from the northeast.
These winds can push seawater toward the shoreline, contributing to storm surge and coastal flooding.
Does the storm affect a large area?
A major nor’easter can stretch across hundreds of miles.
Areas closer to the storm's cold side may experience heavy snow and blizzard conditions, while locations farther south or near the coast may receive heavy rain and strong winds.
Think of a nor’easter as a giant atmospheric meeting point. Cold air comes down from the north. Warm, moisture-rich air comes up from the Atlantic.
A low-pressure system develops where these ingredients interact.
The storm then intensifies and moves northeastward, while its circulation pulls in more moisture and produces strong winds and precipitation.
Why can nor'easters be so powerful?
Several ingredients can work together:
A strong temperature difference between air masses
A supply of moisture from the Atlantic Ocean
A favorable jet-stream pattern
A developing area of low pressure
Rapid strengthening of the storm
When these ingredients line up, the storm can intensify dramatically.
What does "Bomb Cyclone" have to do with it?
You may sometimes hear a powerful nor’easter called a “bomb cyclone.”
These terms aren't interchangeable.
“Nor’easter” describes a type of storm that commonly affects the northeastern coast.
“Bomb cyclone” describes a storm that undergoes particularly rapid atmospheric deepening. A nor’easter can undergo bombogenesis, but not every nor’easter does.
What is the difference between nor'easters and hurricane?
Both can produce extremely strong winds, heavy precipitation, and coastal flooding, but they are different kinds of storms.
A hurricane is a tropical cyclone that develops primarily over warm tropical or subtropical waters and derives much of its energy from warm ocean water.
A nor’easter is generally an extratropical cyclone. It gets much of its energy from contrasts between different air masses and the larger-scale atmospheric circulation. In other words, a hurricane is a warm tropical ocean that becomes tropical cyclone that often moves toward land. But a nor'easter is contrasting air masses + atmospheric disturbance that becomes extratropical cyclone and it often tracks along the East Coast.
Why does the east coast get so many nor'easters?
The geography of the region is particularly favorable for these storms.
The Atlantic Ocean lies immediately east of the coastline, providing abundant moisture. At the same time, cold air can descend from Canada and the interior United States.
The combination of a cold continental air mass, warmer Atlantic waters, and atmospheric disturbances can create conditions favorable for powerful coastal storms.
A nor’easter is essentially a powerful coastal low-pressure storm that can develop and intensify along the northeastern North American coast. and its most dangerous combination can be: cold air+Atlantic moisture+ low pressure + strong winds, and heavy precipitation+coastal flooding+ damaging conditions.
And the key thing to remember is that a nor’easter isn't defined simply by “a lot of snow.” Some nor’easters produce major snowstorms, while others bring rain, flooding, high winds, or a mixture of precipitation depending on where the storm and its associated temperature boundaries are located.
