‘Bomb cyclone’ gets ready to roar across Northeast
A vigorously powerful cyclone was set to 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, which was slated to develop Wednesday afternoon off the Delmarva Peninsula, was expected to rapidly intensify Wednesday evening, its explosive strengthening bringing a significant windstorm to coastal New England.
Across all of Eastern New England, sporadic power outages and tree damage were expected. This was especially true due to the presence of fully leafed trees, which will more efficiently catch the wind like a sail and, in some places, sway or topple.
The coastal storm was set to begin to take shape during the mid-afternoon hours Wednesday, with rain and breezy winds along the coast from Maryland to northern New Jersey and the New York City. Things were forecast to 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 they will see the system’s wraparound rain shield, but lesser in the way of strong winds and dynamics to the east. The National Weather Service called for a broad shot of 1 to 2 inches from the tri-state area up to the Hudson Valley and Catskills, though there are reasons to believe that totals ultimately realized may tend to be less. A few snowflakes could mix in in the Adirondacks.
The bulk of the high impact weather were instead set to target New England overnight. For Connecticut, Rhode Island, and Massachusetts, the worst conditions were expected from about 10 p.m. Wednesday through 5 a.m. Thursday. Also, the bomb cyclone was expected to bring rainy and windy weather to Central Pennsylvania.
A strong low-level jet or wind maximum is forecast to 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. There are indications that rapid changes of air pressure, heavy rainfall and isolated downpour/thunderstorm structures may enhance the odds of some of that strong wind making it down to ground level.
The ingredients that will spin up the storm were already 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. In order 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.