A potent and rapidly strengthening storm system socked southern New England and the New York tri-state area, bringing flooding rains, a dangerous storm surge and destructive winds gusting between 60 and 100 mph overnight Tuesday. The nor’easter knocked out power to more than half a million customers and forced school cancellations in eastern Massachusetts.

Due to the storm’s breakneck pace of intensification, it qualified as a “bomb cyclone.”

High winds had been the concern of forecasters leading up to the storm’s arrival, but the swiftly strengthening ocean storm overachieved. More than a dozen counties in southeastern Massachusetts and Rhode Island were 75 percent in the dark, with winds gusting to 94 mph on Martha’s Vineyard.

A “bomb cyclone” brought heavy floods, winds and widespread damage across New England in late October. (The Washington Post)

The fierce winds also whipped up a 3- to 4-foot ocean surge, or storm-driven rise in water above normally dry land, which was considerably more than what was anticipated, but low astronomical tides precluded a more serious impact. Two weeks from now, the same spike in sea levels would have spelled devastating coastal flooding.

According to PowerOutage.us, the bulk of the outages were focused in Massachusetts, with near half a million customers in the dark Wednesday morning, corresponding to about one-fifth of the Bay State. Hardest hit was Plymouth County, which was 90 percent in the dark. Around 85,000 were without electricity in Rhode Island and another 25,000 combined in Connecticut and Maine.

What happened with the storm and what comes next

The brunt of the storm blasted eastern New England on Tuesday night and, as of Wednesday morning, conditions were beginning to ease. Still, bands of light to moderate rain were continuing to pinwheel ashore from the east-northeast in eastern Massachusetts, along the New Hampshire Seacoast and across parts of south coastal Maine on Wednesday morning. Winds were still gusting to around 60 mph in coastal areas.

The center of low pressure, which “bombed out” as air pressures plummeted, was about 130 miles south of outer Cape Cod.

More than 100 school cancellations or closings were reported, particularly on Cape Cod, where concern existed over strong winds blowing horizontally across the main spans of the Sagamore and Bourne bridges — the only two vehicle routes connecting the cape to the mainland.

An aircraft was reported damaged at New Bedford Regional Airport, apparently pushed off the runway; both wings were damaged and its nose squashed. In Hingham, Mass., a two-foot-diameter tree narrowly missed a home as it toppled, taking wires down with it.

The Steamship Authority, which operates ferry service from Hyannis, on the cape, to Nantucket and Martha’s Vineyard, shuttered operations Wednesday due to dangerous marine conditions. Twenty- to 30-foot waves were present just offshore.

“All service is suspended until further notice,” Steamship wrote on its website. Winds were continuing to gust upward of 55 mph from Maine through Cape Ann in Massachusetts, with 65 mph gusts on the South Shore and winds approaching hurricane force near the coastline.

The next high tide in Boston comes at 4:33 p.m.; a coastal flood advisory is in effect there, with a coastal flood warning on the cape.

“Numerous roads may be closed,” wrote the National Weather Service. “Low-lying property including homes, businesses and some critical infrastructure will be inundated. Some shoreline erosion will occur.”

Ocean waters pushed over Route 6A in Barnstable between High Street and Sandwich Line.

Andrew Loconto, a meteorologist at the Weather Service in Boston, noted that the region dodged a bullet in comparison to what could have been.

“The surge has been anywhere between 3 to 4 feet, which is pretty significant, but fortunately astronomical tides were just so low,” he said. “If this was a full or new moon, the impacts would have been pretty substantial. We have waves 20 to 30 feet just offshore [that are] really helping to lead to some beach erosion.”

Rain will continue rotating ashore through the early afternoon in eastern Massachusetts and adjacent Rhode Island, but most impacts will remain inside of Intestate 95. The low will withdraw to the southeast during the afternoon, allowing winds to relax below 50 mph shortly after lunchtime and fall beneath 40 mph during the evening hours. Most of the precipitation will fade during the afternoon with only lingering patches of drizzle.

Thursday should be a typical fall day with seasonable temperatures and a blustery onshore wind.

Wild winds

When the storm was at its peak Tuesday night into early Wednesday, the winds were a force, their impact accentuated by the presence of partially- to fully-leafed trees.

Deer Island, just offshore of Boston, recorded a gust of 74 mph, while Chatham on the cape hit 76 mph. Woods Hole on the inner cape near Falmouth gusted to 79 mph, and Scituate, Mass., about 20 miles south-southeast of Boston, saw a screaming 87 mph gust.

On the outer cape, Dennis gusted to 84 mph, Wellfleet to 83 mph and Hatch Beach to 81 mph.

The strongest winds occurred on the islands, with winds reported between 88 and 94 mph on Martha’s Vineyard and up to 70 mph on Nantucket.

The winds appeared 10 to 15 mph more intense than even weather models were simulating, perhaps a product of better “mixing” of momentum down to the surface. Weather models also often fail to adequately capture the role of precipitation drag in autumn Southern New England storms, which further helps yank down stronger winds from aloft.

“Maybe mixing was a factor, but sometimes the pressure gradient is so tight with this, you get these strong winds and that can overdo it a little bit,” said Loconto, referring to a change of air pressure with distance; high pressure is located in Canada currently. “It was probably a combination of the two.”

Residents compared the damage to what they had experienced during brushes with tropical storms in the area, like Irene and Sandy, as well as some of the more formidable winter storms that had lashed the region in recent years.

The storm’s central pressure, which dropped to a record-setting low of 977 millibars on Nantucket, was comparable to that in many Category 1 and 2 hurricanes. The lower the pressure, the stronger the storm.

Rainfall totals

Rainfall amounts in New England, meanwhile, proved less serious than predicted, a welcome respite for a waterlogged region. Boston has seen roughly 31 inches of rain since the start of the summer.

“We haven’t really heard of any inland flooding,” Loconto said. “While they did come up, the rains have been mostly wind-driven with amounts in the 1- to 3-inch range across Massachusetts, Rhode Island and northern Connecticut. That’s really helped to taper the flooding impacts.”

To the south, however, rainfall was much more substantial, with totals of 3 to 6 inches in northeast Pennsylvania, northern New Jersey, southern and interior New York state, and Long Island. These amounts caused numerous instances of flooding, mostly during the day Tuesday. New York City registered 3.66 inches.