News•February 7, 2013

Life-Threatening Blizzard Poised to Strike New England

A life-threatening and historic blizzard that could rank among the top 10 snowstorms on record in southern New England is poised to plaster the region this weekend with snow that will be measured in feet rather than inches. The storm could also cause major coastal flooding and produce hurricane-force wind gusts, forecasters said.

Graphic depicting the anticipated storm impacts in southern New England.
Click to enlarge the image. Credit: NOAA/NWS.

Beginning on Friday, snow and mixed precipitation is being forecast to move into the heavily populated I-95 corridor between New York City and Boston, and from overnight Friday into Saturday, blizzard conditions are likely across a wide swath of Massachusetts, Rhode Island, and Connecticut. There is an outside chance that blizzard conditions could even make it into New York City, according to the National Weather Service.

The storm will take shape as separate pieces of atmospheric energy join forces off the Mid-Atlantic coast on Friday — a process meteorologists refer to as “phasing” — creating one rapidly intensifying storm center that is expected to move northeastward and park itself for many hours just offshore of Cape Cod. The storm, known in this region as a nor’easter because of its fierce northeasterly winds, is expected to dump anywhere from 1 to more than 2 feet of snow from southern Connecticut to Maine. The highest amounts, perhaps 30 inches or more, are expected to fall in the Boston to Providence corridor, with another bullseye across western Massachusetts and Connecticut. Depending on the ultimate track and intensity of the storm, the areas of maximum snowfall may shift, however.

A wide array of severe weather watches and warnings have been posted for New England, from blizzard watches to hurricane-force wind warnings, all of which highlight the likelihood for a damaging winter storm. While the impacts of the storm are clear for southern New England, the storm is posing a forecasting nightmare for New York, since the city will be right on the line between receiving a moderate snowfall of 4-to-8 inches or getting hit with more than a foot of snow.Cities from Portland, Maine to New York were girding for expected impacts, calling in snow plow drivers and getting cars off streets in anticipation of deep snow drifts.

One unusual characteristic of the storm is how much moisture it is expected to draw in from the Atlantic Ocean, with many computer-model simulations showing that it will produce upwards of 3 inches of liquid precipitation equivalent in the Boston area. If that were all snow, it could exceed 30 inches, which would set a record for the city.

Boston’s all-time heaviest snowstorm dumped 27.5 inches on the city. This storm almost comes 35 years to the day after the infamous 1978 blizzard paralyzed New England under more than 2 feet of snow. At times, this storm is expected to deliver snow at rates of 2-to-3 inches per hour, with thundersnow a distinct possibility, the NWS said.

Sea surface temperature anomalies off the East Coast.
Click to enlarge the image. Credit: Wunderground/NOAA.

As was the case when Hurricane Sandy struck in late October, sea-surface temperatures are running a couple degrees above average off the East Coast, which according to climate scientists may reflect both natural climate variability and the effects of manmade global warming.

The presence of unusually warm waters could aid in the rapid development of the storm system, and infuse it with additional moisture, thereby increasing snowfall totals.

Heavy precipitation events in the Northeast, including both rain and snowstorms, have been increasing in the past few decades, in a trend that a new federal climate report links to manmade global climate change. As the world has warmed, more moisture has been added to the atmosphere, giving storms additional energy to work with, and making precipitation extremes more common in many places. The last major snowstorm to strike southern New England was the unusual Halloween snowstorm in 2011.

One of the nor'easter's multiple hazards is coastal flooding from the combination of strong onshore winds, high waves, and astronomical high tides. Coastal flood warnings are in effect for parts of Massachusetts, Connecticut, Rhode Island, and New York, with major flooding expected in eastern Massachusetts during the Saturday morning high tide. A storm surge of between 2-to-4, and up to 5 feet in some areas, is anticipated on Saturday morning in parts of eastern Massachusetts. The surge will combine with high astronomical high tides and building seas to cause moderate to major flooding, particularly between Boston and Cape Cod Bay.

Sea level pressure and precipitable water forecast valid on Friday afternoon, with an arrow showing the feed of tropical moisture northward into the storm system.
Click to enlarge the image. Credit: Weatherbell.com

According to the NWS, major coastal flooding means that “at least scattered structural damage,” and widespread flooding of vulnerable shoreline areas is anticipated.

Coastal flooding is also a concern in southeastern New York, where strong winds may funnel waters from Long Island Sound into flood-prone areas of northern Long Island and New York City. Up to a 3-to-5 foot storm surge is possible during the times of high tide Friday evening along western Long Island Sound and the Twin Forks of Long Island, which, along with high waves, could cause moderate coastal flooding. Minor to potentially moderate coastal flooding is expected in New York Harbor, but the impacts will depend on the wind direction at the time of high tide.

Seas of greater than 30 feet are expected off the New England coast, prompting the NWS to warn mariners that this “will become a life-threatening storm for anyone caught in its path.”

The coastal flooding threat for this storm in New York pales in comparison to what it was during Hurricane Sandy, when large parts of the city’s iconic subway system flooded in the face of a record storm surge, and many New Yorkers drowned in flood waters.

Rising sea levels due to warming seas and melting ice caps are already making typical nor’easters such as the upcoming event more damaging, since they provide the storms with a higher launching pad for causing coastal flooding. According to the draft National Climate Assessment report released in January, even without any changes in storms, the chance of what is now a 1-in-10-year coastal flood event in the Northeast could triple by 2100, occurring once every 3 years, due to rising sea levels.

According to research by Climate Central scientists, the sea level trend in Boston Harbor from 1959 to 2008 in Boston Harbor has been 2.31 milimeters per year, which is slightly below the global average over the same period. In the past 50 years, the water level has risen by about 4.5 inches at that location, although it has increased much more in other spots along the northeastern coast.

On Nantucket Island, where coastal flooding is anticipated from this storm along with hurricane-force winds, the sea level has risen by about half a foot during the past 50 years.

For the northern hemisphere as a whole, winter storms have become more common and intense during the past 50 years, according to the draft federal report. Observed changes in winter air circulation in the northern hemisphere, possibly related to Arctic sea ice loss, has been linked to large swings in seasonal snowfall from one winter to the next in the Northeast. Other studies indicate that as global warming continues, nor’easters such as the one about to hit New England may become more frequent in this region, and less common in the Mid-Atlantic states, as storm tracks shift closer to the poles.