A vigorously powerful cyclone will impact the Northeast on Wednesday night into Thursday, bringing a burst of damaging winds, heavy rainfall and perhaps setting all-time minimum air pressure records for the month of October in eastern New England. The lower the pressure, generally the stronger the storm.
The storm, slated to develop Wednesday afternoon off the Delmarva Peninsula, will rapidly intensify Wednesday evening, and as it explosively strengthens, it will bring a significant windstorm to coastal New England.
Across all of eastern New England, sporadic power outages and tree damage can be expected. The fully leafed trees in those areas will more efficiently catch the wind like a sail and, in some places, sway or topple.
Timing and impacts
The coastal storm will begin to take shape during the midafternoon hours Wednesday, with rain and breezy winds along the coast from Maryland to northern New Jersey and the Big Apple. Things will really get going around sunset, especially for Long Island and the southern New England coast, where winds may gust above 40 mph.
Rainfall forecasts for New York City and adjacent suburbs are challenging, given those areas will receive the system’s wraparound rain shield, but the winds there may be a bit less even though rain will still be decent. The National Weather Service is calling for a broad shot of one to two inches from the Tri-State area up to the Hudson Valley and Catskills, although totals ultimately may tend to be less. A few snowflakes could mix in the Adirondacks.
The bulk of the high-impact weather will instead target New England overnight. For Connecticut, Rhode Island and Massachusetts, the worst conditions are expected from about 10 p.m. Wednesday through 5 a.m. Thursday.
A strong low-level jet or wind maximum will be racing just overhead, with 80- to 85-mph winds soaring just a couple thousand feet above the surface. It’s a challenge to gauge exactly how much of that momentum will “mix down” to the surface. Strong thunderstorm downdrafts could enhance the odds of some of that strong wind making it down to ground level.
This will probably be a widespread and significant windstorm for hundreds of thousands of New England residents.
Expect building winds, especially east of Interstate 84 and south of the Mass Pike, around nightfall. As the low-level jet, a river of swiftly moving air several thousand feet above the ground, sweeps overhead around midnight, wind gusts could top 55 to 60 mph in coastal Rhode Island, Narragansett Bay, Buzzards Bay and southeastern Massachusetts. Because these winds are southerly and southeasterly, the entirety of the eastern New England coastline — from the Outer Cape to Downeast Maine — will be exposed to very high winds “off the deck.” As the low-level jet works its way up the coast, there’s nothing over the open water to slow the ferocious gales it brings to the coast.
There are signs that point to the winds from this storm being even stronger than forecast. It’s not out of the question that a few gusts up to hurricane-force may sneak into the mix Wednesday night in far eastern New England, although the chance of that happening in any one given location is relatively slim.
Farther west, 40- to 55-mph gusts are possible inland for the Boston to Providence corridor, and the Blackstone Valley to the Connecticut River Valley could see 45-mph gusts. A bit of terrain influence may bring a few gusts to 50 mph in the Worcester Hills. Winds will taper off as one approaches the Berkshires and noticeably west of there.
For rainfall, two bull’s-eye zones appear favored: one east of Interstate 91, and the other in the 495 belt of MetroWest. More than two inches is forecast there, with even some isolated three- to four-inch totals possible. In between, around an inch and a half appears to be in the offing.
Amounts may drop some over southeastern Massachusetts, where people may spend more time in the rain-free “dry slot” than the system’s wraparound moisture.
The system will lash Maine with about an inch of rain early Thursday morning, bringing a 60-mph wind-gust threat to the coast.
The ingredients that will spin up the storm were coming together Wednesday morning. A batch of heavy rainfall was splayed from the nation’s capital southwestward to the Appalachians, soon to shift off the Mid-Atlantic coastline. Meanwhile, an invigorating shot of mid-level energy over the Great Lakes was barreling eastward, set to trigger the growth of a low-pressure zone east of the Chesapeake Bay.
This low will rapidly develop, its central air pressure dropping at a rate sufficient to make it a “bomb cyclone,” wrote the National Weather Service in Boston. To classify for that tier, a cyclone’s core surface pressure must drop by 24 millibars in 24 hours; this one will do it by at least 30. The greater the difference in pressure over a certain area, the stronger the winds. It’s akin to damming a river; the greater the height that the water falls from one side of the dam to the other, the more intensely the water wants to rush across the dam.
As a result, the system may be an overachiever in terms of both wind and rainfall.
Behind the storm
Light showers and some cloudiness will linger across much of southern and central New England on Thursday before the region clears southwest to northeast during the afternoon. Behind the powerful front associated with the storm, breezy winds gusting 35 to 40 mph can be expected during the day from Washington, Philadelphia and Baltimore all the way up through the Canadian border.
Cooler, drier air in the storm’s wake will set us up for a picture-perfect weekend.