Extreme Event
Channel: Tracey's Tracks
Date: 18/01/2013

Sudden Stratospheric Warming Split the Polar Vortex in Two.
the plar vortex was intact at 50 millibars(height in m) on January 1 to 3.

the polar vortex had broken in two (50millibar heights in m) on January 10 to 13

50-hPa Zonal Mean Temperature for 2012 & 2013

The dynamical activity in recent winters reveals that the frequency of MWs (Major Warmings) in the Arctic is increasing (e.g. CharltonPerez et al., 2008). ... 
On average, during 1957/58--1990/91, MWs occurred only once every two Arctic winters (e.g Bancala et al. ´ , 2012; Cohen and Jones, 2011; Andrews et al., 1987). Conversely, no MW occurred in 9 consecutive winters from 1989/90 to 1997/98, except a minor warming in early February 1990 (Manney et al., 2005).

However, there were 7 MWs in 5 out of the 6 winters from 1998/99 to 2003/04. The winter 1999/00 was unusually cold but each other winter was prone to MWs... Furthermore, two MWs were observed in 1998/99 and 2001/02...This warming sequence continued and there were 5 MWs in 5 winters again in 2005/06--2009/10... Many of the MWs in recent years have been atypically early (December/early January) compared to those found before 1990s, which were observed mostly in February.

those found before 1990s, which were observed mostly in February.

Animation of temperature anomalies at the 30mb pressure surface in the stratosphere shows the magnitude of this massive event.

In the Pacific ocean the dynamic interaction of the cold air with abnormally warm water off of the northeast coast of Japan

Meteorologist Ryan Hanrahan predicted this cold outbreak based on the breakdown of the polar vortex 2 weeks ago. 
http://www.dailykos.com/story/2013/01/16/1179397/-Sudden-Stratospheric-Warming-Split-the-Polar-Vortex-in-Two
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