If you live somewhere between Washington and Boston on the United States' East Coast, you will be in one of the most densely populated parts of the world. You will also be among 50 million people to suffer from sudden and ferocious snowstorms that often leave the highways feet deep in snow within just a few hours.
Other parts of the world get these, but nowhere near as many people are affected. Along the Atlantic coast of America they are called nor 'easters, meaning they are brought about by a wind blowing onshore from the northeast.
A nor’easter is a low pressure area that often passes just off the New England and southeast Canada Atlantic coastline. Nor’easters can cause severe coastal flooding, coastal erosion, hurricane-force winds or blizzard conditions.
So how do they happen? It is because in this region something unique occurs. This is where the warm ocean current called the Gulf Stream comes up the coast and starts to make its way across the Atlantic Ocean to the UK and Europe. Just off the coast is also where very cold air is coming southwards from snowbound Canada. When the very cold and dry air rushes southward from Canada, it blows over the warm Gulf Stream current (often near 70F/21C even in mid winter). The lower parts of the cold air warm up and rise, pulling huge amounts of moisture from the ocean. This warm moisture is packed with energy, and it quickly develops into a storm. After that it is directed by the Jet Stream high in the air, so where it makes landfall varies depending on where the Jet Stream happens to be.
These storms rapidly intensify, tracking northward and trapped from going inland by the Appalachian Mountains. So Washington D.C. gets the storm first, then Philadelphia, then New York, and then Boston. The storm then meanders across the North Atlantic, weakens, and finally arrives in the UK. It can last for several weeks.
The effects of a nor 'easter can include high tides and strong winds. Some surfers actually hope for this kind of weather! But for most people, the threat of coastal flooding in winter is not something to look forward to.
