A much warmed and disorganized Polar Vortex created a steady deeper cooling at its center.

~Stable warming of the Polar Vortex is seldom uniform in shape or temperatures.  

~This warming can cause a sudden cooling zone anywhere with very long exposures to the frozen ground and of course by prolonged cloudless air

~Recently we have had a very neat example.  

           Early may 2012 Arctic weather was incredibly warm,  this warming has not stopped,  it kept shrinking  a mangled Arctic Polar Vortex,  but suddenly 1 week later ,  under an even warmer rising sun,  what appears to be impossible occurred:

A small deep cooling area appears near the Pole May 10 (still with a low sun),  it moved over the Canadian Arctic Archipelago where the air was clear,  notice its temperature colder than about 2 weeks prior  (May14) ,  although much smaller, it is strikingly keeping cool despite the P.V. even more dismembered and severely encroached by warmer air all around its perimeter.    What happened is a classic Geophysical phenomena, under certain conditions atmospheric temperatures may drop if  the weather is right,  despite the rapidly approaching summer, despite over all abnormal warming.

This feature can be observed at any time of the P.V. existence.  For instance,  the Northern US can

be coldest place of winter to date more than anywhere else in the Northern Hemisphere.  Notice I use use 600 mb temperature because it is the closest pressure level representing the temperature of the entire troposphere.  500 millibars is more representative of the entire atmosphere, on occasions the stratosphere can be unusually warm or cold,  and can distort tropospheric tendencies if judged by 500 mb maps. WD May 16, 2021