What Is the Jet Stream and Why Is It Important?

2013-02-22 18:36:40.000 – Mike Dorfman,  Summit Intern

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Mount Washington is the location of the world’s fastest surface wind ever recorded by man. In April of 1934, a wind speed of 231 miles per hour was recorded by the summit crew. Holed up in a wooden house chained to the summit, the observers strained to hear the clicks of the old-fashioned anemometer, which indicated wind speed. One of the observers on the summit even had to go out and clear ice off of the anemometer immediately before the record gust.

Fly a kite high enough (20,000-40,000 feet in the air…that would require a lot of string) and in the right location, and you could likely hit wind speeds exceeding those that hit the summit on that windy day. A river of air rushes around the upper latitudes, powered by differences in temperature between the cold poles and the warm mid-latitudes. Travelling up to 300 miles per hour, and sometimes even faster, the jet stream has winds equivalent to an extremely strong category 5 tornado. Airplanes use these jet streams to make flight times shorter and save on fuel costs, but these jet streams are also extremely important in governing our weather.

Low pressure systems often form when the jet stream bends, allowing warm air to move north in front of the system and allowing colder air to move south behind the system. These areas of warm and cold air give rise to the warm and cold fronts that spin around low pressure systems. These fronts allow precipitation to fall and clouds to form.

Now, why do some of these storms bring us feet of snow while some just bring a dusting? It all depends on how much water is in the air that makes up these storms. A storm which evolved and traveled over land is often moisture starved and will not bring much in terms of precipitation. On the contrary, a storm that brings heavy snow often originated over water and contains more moisture. Powerful Nor’Easters form when the jet stream dips down towards the Gulf of Mexico and rises back up just offshore in the Atlantic, allowing the low pressure system to tap into moist air over the Atlantic and travel up the coast. These storms eventually deposit this moisture in the form of rain or snow on the northeast.

A handy way to see what the jet stream is doing is to look at model maps on various websites, such as Unisys, Wunderground or the weather gun (amongst others). Go ahead and take a look!

Mike Dorfman,  Summit Intern