Wednesday, February 26, 2014

Winter in the Northeast my have been cold but ...

While the temperatures in most of eastern half of the United States have been colder than normal  ...

... the western side of the country has been warm, really warm in some places.

The seemingly weird extremes are directly related to the position of the jet stream. The western and eastern sides of the US fall on opposite sides of a big loop in the jet stream,  which is keeping the west hot and dry, while on the eastern side of the country cold air is descending from the Arctic and freezing us.

Source (
The cold air mass that circles around the North Pole is bounded on the south by a jet stream, or a fast moving, narrow air current in the atmosphere that is located near the tropopause (the boundary between the troposphere - where we live - and the stratosphere).  Jet streams typically have a meandering or wiggly shape that bobs up and down in latitude depending on a variety of factors. Sometimes the jet stream can be really strong, with only little wiggles, and sometimes it weakens and the meanders can get really large. When the later happens, a mass of frigid air can drop south - an event that can be called a polar vortex. 

You can see this better in this NASA video ...

This unusual behavior lead to possibly the best winter jet stream map I have ever seen ...
Source (

So when you average things out, nationally January 2014 was the 347th consecutive month (or about 29 years) with temperatures above the 20th-century average! So - stinks for us locally, but nationally things are still warmer than average. And for the earth as a whole, it was the fourth-warmest January on record.

If you want more information,

Visit the NOAA State of the Climate website (

and Phil Platt is all over this, as usual, at Bad Astronomy

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