Friday, 29 November 2013

What's going on across the stratosphere?

With regard to any significant SSW occurring this winter, its looking very slim in DEC/JAN given the indices on the table this year. For +QBO, -PDO, N/- ENSO and years with the JAN SSN below 95 no significant warming's have even occurred since 1950 in DEC/JAN. In february their are a few exceptions, one begin 08-09 which had a strong East Pac ridge, definitely aiding in the wave 2 response. 00-01 is another example of this, although the PDO was neutral/positive and the QBO was transitioning from positive to negative. The common denominator in these two years is a strong Kamchatka PV lobe and bering sea/GOA ridging. Unless we see an uptick in the PDO/ENSO domains, or a quick downturn in the QBO by feb a major warming in the DJF period is going to be tough to come by. EP heat flux anoms are already starting off winter well below normal ever since the wave 1 response in late october. Our best shot will probably be a wave 2 warming in Feb if we can keep the EPO ridge consistent which becomes more likely given the +QBO/N ENSO and -EPO persistence. If this doesn't work out then their is always the FW question in March/April that should arise with a mean state similar to our current one. This SSW timing is much more favoured given the current setup and could have impacts on spring, especially with the warming ENSO region expected and a transitioning QBO index(favourable for high heights across the NAO/EPO region's).

Feb 2001
Feb 2009

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