A powerful storm could develop into a rare September nor’easter later this week, raising concerns about coastal flooding, wind damage and rain in parts of the Northeast.
A quick refresher: A nor’easter is a strong coastal storm that gets its name from the direction its punishing winds blow, which is the northeast. Nor’easters typically occur off the East Coast between Georgia and southern New England, and are most common from mid-fall to mid-spring. Usually, storms bring heavy snowfall in the winter, but that wasn’t the factor this time.
⛈️ ️In areas at risk? Track storms, find out local risk, and get more detailed times from our meteorologists with the CNN Weather app ⛈️.
At this point, the possibility of a nor’easter is just a glimmer in the atmospheric eye. It is expected to form off the coast of the Carolinas or Virginia on Wednesday or Thursday.
The momentum will probably build from there and reach its climax this weekend. But where exactly the storm will track as it heads north remains a question.
Regardless of the path, some coastal flooding problems are guaranteed, even in the early stages of a storm. The broader impact will depend largely on how closely it borders the East Coast.
There are two main scenarios we are currently monitoring.
Some weather models envision the storm strengthening rapidly in mid-to-late week, sliding up the East Coast and staying near the coasts of New Jersey and Long Island, New York this weekend.
The storm’s intensification closer to the coast means powerful wind gusts could hit nearby areas, including Boston, the rest of southern New England, New York City and even parts of the mid-Atlantic.
It’s too early to say exactly how strong these wind gusts will be, but they could reach up to 80 mph, especially from Friday into Saturday. These winds will also significantly roughen the oceans, intensifying coastal flooding and raising tide levels 2 to 3 feet above normal.
There is a chance of rain, but it is difficult to determine if there is a risk of flooding. In some areas, even moderate rain may not be absorbed as much as normal. Parts of the Northeast and Mid-Atlantic have been inundated in recent weeks, and dangerous flooding occurred in New Jersey and Connecticut earlier this month.
The storm could then wander just off the coast into next week. The longer it exists, the longer it will have an impact.
In this scenario, Nor’easter would spend an extended period of time anchored in warmer-than-normal waters off the coast. A nor’easter is not a tropical system fueled by warm water like a hurricane, but if it stays above warm water long enough, it can become a hybrid system, providing both ocean heat and atmospheric energy, or a full tropical system.
It’s unlikely this year’s nor’easter will be tropical, but it’s not impossible. Even if that were to happen, the impact would not be much different. The National Hurricane Center just has to watch.
Other forecast models predict a powerful storm but keep it far from the East Coast.
Although rough seas and similar coastal flooding are still possible in this scenario, the threat of wind and rain will not be as strong as in scenario 1.
In this scenario, the timing of the storm’s development and generally northeasterly track will be similar, but where it is likely to remain will differ.
The most significant impacts are likely to occur along the southern New England coast through Friday.
The storm could persist off the coast of southern New England until at least Sunday, and coastal flooding problems could persist, especially around Cape Massachusetts.
Autumn cold and full moon cause coastal flooding
Even if the nor’easter stays further offshore, coastal flooding is occurring this week, and two other factors pose a threat.
The first is a strong area of high pressure that develops over eastern Canada, sending fresh, cold air to the northeast. As a result, high temperatures in the region are expected to only reach the 60s through the weekend.
If a nor’easter forms off the Mid-Atlantic coast on Wednesday or Thursday, the air will become compressed between the newly formed storm and high pressure further north, increasing wind speeds along the East Coast.
The second factor is the full moon. The tides rise each day and reach their monthly peak around the full moon on Saturday. Rising water levels and strong winds can lead to serious coastal flooding.
Coastal areas from Virginia to New Jersey could begin experiencing high tide flooding as early as Tuesday evening, with some gauges indicating they could reach major flood stage by Thursday morning.
Flooding problems could peak this weekend or early this weekend in many locations, with slow relief possible next week if the nor’easter lingers near the coast.
