Published on 26 Jan 2015

US blizzard: potentially historic snowfall for north east

The north east of the US is bracing itself for a blizzard that is being described as ‘potentially historic’, with as much as 2-3 feet of snow falling between Monday and Wednesday.

An area stretching from Philadelphia to New York City to Maine is covered by blizzard and storm warnings, with the impacts described as ‘life-threatening’ by the US National Weather Service.

Much of the north east of the US has seen below average snowfall so far this winter, but the amount of snow that’s forecast will be enough to shut down major cities – including New York City – at least temporarily.

Around 600 flights have already been cancelled, with that number expected to increase significantly once airlines finalise their plans.

What’s causing the snow storm?

It doesn’t happen that often in the meteorological world, but this really does look to be the perfect setup for a blizzard that will challenge the record books.

At the moment, the jet stream is dipping southwards over the eastern US, producing a U-shaped pattern in the winds of the upper atmosphere – something known in the meteorological world as an upper trough.

newyork_blizzard_g_wp

This simply means that air in this area is much more prone to rising than usual, which causes air to be sucked upwards in the atmosphere faster than it can be replaced at the surface.

As a result of this process, a deep area of low pressure forms very quickly and is then pushed north eastwards along the east coast of the US, taking wind and moisture with it.

Why so much snow?

During the weekend, an area of high pressure just north of the Great Lakes has been feeding cold, arctic air southwards into the north east of the US.

The storm is going to collide with this cold air, so what would normally fall as rain, will instead fall as copious amounts of snow.

Another factor that will help to enhance the amount of snow falling is a strong onshore wind, pumping lots of additional moisture into the storm from off the Atlantic Ocean.

The latest predictions from the US National Weather Service have 18-24 inches of snow widely across the NE of the US, but the potential for more, with snow drifts in excess of 3 feet.

newyork_snowdepths_NOAA_wp

This also includes New York City and will challenge the greatest amount of snow from a single blizzard for the city’s Central Park, which stands at 26.9 inches, set on 11-12 February, 2006.

Wind and flooding additional hazards

Whilst it will be snow that has the potential to cause the greatest amount of disruption, strong winds and coastal flooding will be an additional concern.

Winds around the northern and eastern side of the storm will gust 50-65mph, with gusts to near hurricane force for the east of Long Island.

This will not only cause near-zero visibility when combined with heavy snow, but also bring the risk of trees and power lines being blown down.

The strong north easterly wind will also push water onshore, giving a risk of a storm surge of 2-4 feet along coast, bringing a risk of coastal erosion and flooding.

I’ll be keeping a close eye on the blizzard in the coming days and posting regular updates on Twitter – @liamdutton

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