Tuesday, January 7, 2014

COLD!

Doesn't get much colder than this around here. Take a look at the current temps from all the weather stations across our region along with the wind chills. Temps are in black, the wind chills are in blue. Temps negative to single with wind chills in negative double digits. This is a record breaking cold spell, but not for all areas. It has gotten this cold before. Its not common, but it happens. 



The term polar vortex was so misused yesterday by the media. It always exists and usually is located over the pole. However, it is known to get displaced form the pole when the stratosphere warms causing it to split. There are numerous times where it has dropped down into America or Europe during a winter because of this. This time, it happens to have our area at ground zero. You can see the vortex below. This is at 5000 ft in the atmosphere. 




Following my video, I still like the trends for a stormy return to winter after January 15th. More on that as the days go on. You can see the video on the post below. 



2 comments:

  1. Silly question, but how do you interperet the map above with the vortex? Are those the temperatures at 5,000 feet? Not sure what GPM is.

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  2. Good question.The map above is basically showing you how many meters at a given location (geopotential meters labeled GPM) it takes to get up to the pressure level of 500mb. 500mb is roughly halfway up in the atmosphere which under neutral conditions is 18,000 feet and will vary based on the temperature of the air. Cold air is denser than warm air so in areas where the air is colder than normal it actually take less vertical distance to reach the pressure level of 500mb due to cold air being dense. Warm air expands so it takes up more space thus the vertical distance to reach the 500mb level becomes higher than normal. In this map it is showing you the deviation from average around the country to reach 500mb. Colder air can be seen by the blues, thus lower than normal heights or distance to get to 500mb and warmer air by reds which is higher than normal geopotential meters to get to the 500mb pressure level. This map is not a map of the atmosphere at 5000ft that would be the 850mb map but it still shows the cold air associated with the polar vortex that by definition is a semi-permanent low pressure center that sits at 5000ft. The air above the surface drives our weather patterns. The 500mb map is useful because it shows troughs and ridges in the jet stream which result in high pressure or low pressure areas developing at the surface. The surface low or high however is not in the same exact location as its corresponding low or high pressure center at 500mb. Hope this clears things up a little.

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