The Mid-Atlantic and Northeast are in for a wild ride during the next few days as a nor’easter rapidly intensifies off the East Coast of the U.S. The storm will bring with it an array of life-threatening hazards, from record-breaking coastal flooding and hurricane force winds, to cement-like wet snow that will bring down trees and power lines.
The storm will undergo bombogenesis, a process in which the minimum central air pressure will drop by at least 24 millibars in 24 hours. In general, the lower the pressure, the stronger the storm.
The rapid drop in air pressure will kick up extremely strong winds, which will help bring air travel to a halt in some of the biggest cities in the country, from Boston to Washington, D.C., due to high winds and heavy precipitation.
Along the Massachusetts shoreline, coastal flooding is likely to exceed all of the benchmark floods of the past, including the Blizzard of 1978, and possibly the highest water level on record in Boston, which was set earlier this winter.
Up and down the coast of eastern Massachusetts, a 3-to-5-foot storm surge on top of high astronomical high tides, coupled with angry seas with building waves, will do significant damage to shoreline infrastructure, including homes and businesses.
On Jan. 4 of this year, Boston saw its highest water level on record when the “Bomb Cyclone” hit the city. That storm flooded a subway station and shut down portions of the city. This event has the potential to do even more damage in the low-lying, coastal city.
Communities to the north and south of Boston, will also see major coastal flooding on par with some of the biggest coastal storms on record. Cape Cod looks to be in line for some of the highest winds and waves, and its beaches are prone to erosion.
The overall weather pattern in which this nor’easter is forming is going to prevent the storm from skipping east, out to sea, quickly. This will heighten the storm’s impacts, making coastal flooding last through multiple high tides, as east to northeast winds drive water ashore in Massachusetts, parts of Long Island, New Jersey, New York, Connecticut, and Rhode Island.
A sprawling, intense area of high pressure parked over Greenland is serving as a giant stop sign in the atmosphere, pinning storms like this close to the U.S. coast. Such a high pressure area is known as a “Greenland block,” and it’s a prerequisite for producing a severe winter weather event in the Mid-Atlantic and Northeast.
Here’s what to expect in the big cities of the Northeast, along with more details on the threat of heavy, wet snow making it all the way to the coast, which could spread power outage closer to highly populated areas.
Washington, D.C., Baltimore, and Philadelphia:
In these cities, heavy rain on Thursday night and Friday, along with extremely windy conditions on Friday will be the biggest impacts from the storm. Some coastal flooding is possible in the Philadelphia area as well. Wind gusts could exceed 60 miles per hour on Friday in the D.C. area, as the region will be located between the deepening low pressure area offshore and high pressure to the west, causing a wind tunnel effect.
New York City:
In New York, the official forecast is for a sloppy, messy, windswept rainstorm. The precipitation may mix with or change to snow at times, but any accumulations are highly uncertain at this time. It’s possible that the storm will manufacture enough cold air through dynamical cooling to turn the rain to heavy snow late on Friday into Saturday morning, which would create a host of problems in the city and nearby suburbs, but this is not a high-confidence forecast scenario.
Winds will gust to at least 50 to 60 miles per hour along the coast, and moderate to major coastal flooding is possible at high tides, which is also the case in coastal New Jersey.
Heavy rain and snow is expected from late Thursday night through Saturday in Hartford. Snowfall amounts, however, hinge on how much temperatures cool down during the storm, with anywhere from 3 to 6 inches of snow to a foot of heavy, wet snow possible. Snowfall exceeding 3 inches could cause widespread power outages, given the weight of the wet snow on trees and power lines. The Halloween nor’easter of 2011 dumped about a foot of snow in Hartford, causing a weeklong power outage.
The strongest winds, most severe storm surge, and historic coastal flooding all appear to be focused on Beantown and other locations in eastern Massachusetts. Winds could gust to hurricane force — 75 miles per hour — in the area, and a combination of high astronomical tides, a 3-to-5-foot storm surge, and destructive waves are likely to produce historic coastal flooding in many areas during multiple high tides.
[COASTAL FLOOD WARNING] 9 am Friday → 3 am Sunday; severe damage to shoreline structures; some homes may be destroyed; widespread inundation of coastal roads, basements; LIFE THREATENING SITUATION! Many neighborhoods may be at risk of being cut off for a time. pic.twitter.com/3IeOWcEilh
— NWS Boston (@NWSBoston) March 1, 2018
Like in New York City, there is also a wild card of precipitation type in Boston, with some computer models suggesting that heavy rain will change to accumulating snow on Friday night and Saturday, as the center of the storm drifts further to the south.
The National Weather Service is using strong language to warn people about the likelihood of potentially historic coastal flooding from this nor’easter, calling it a “LIFE THREATENING SITUATION.”
It’s not a coincidence that Boston may set back-to-back records for its highest water level in the same year.
Coastal flooding is an increasing hazard in the Mid-Atlantic and Northeast in part because of sea level rise caused by global warming.
Higher background sea levels make it easier for storm surges to break records and do more damage. This is similar to basketball players competing on a court with a steadily rising floor, making it easier for them to dunk.
Over 40-feet significant wave height now forecast by ECMWF model for massive Nor’easter. Seas dramatically build in Friday unfortunately with long duration component of direction perpendicular to the coast.
The worst waves look to impact Bermuda, too. pic.twitter.com/7JSRoGYQWs
— Ryan Maue | weather.us (@RyanMaue) March 1, 2018
Other noteworthy aspects of this storm:
This nor’easter will churn the waters of the Western Atlantic, creating waves higher than 40 feet across a vast swath of the ocean, from Nova Scotia to Massachusetts, southward all the way to Bermuda.
Just off the Massachusetts coast, waves may tower up to 35 feet, and some of the highest swells in years are likely well offshore.
Any ships caught in its path could be in trouble, as high winds and waves present a serious hazard. Cruise ships in particular have had a habit recently of sailing directly into powerful East Coast storms, hopefully that won’t happen again this time.