I think the stratosphere is now in a new phase as the polar westerly zonal wind anonalies that have influenced our weather over recent months are now flushed out of the system. Therefore the stratosphere is going to be warmer overall from here on in as recurrent series of wave breaking under the new strengthening easterly QBO regime assert themselves instead. With that in mind I think the day to day stratospheric forecasts from the models should be used in terms of watching the overall trend rather than day to day variances. Much as looking for longer term trends in the tropospheric model thread
Following the second warming due in the next week, it might not be a bad thing if there is a pause and some relative cooling at the top layer as this might actually assist in knocking the top warming lower down to increase the influence on the overall weather patterns. This can be said on the basis of anticipating a fresh surge of wave breaking that is likely to occur thereafter (months end) to reinforce the momentum from the top level again - as part of the longer term trend as described above. It lends itself to an eventual complete breakdown of the polar vortex as less and less impact is required from these warming injections to break up the remaining weakening vortices.
Bear in mind that whilst we saw quick results from the SSW in late Jan 2009, this came unexpectedly as part of an unfavourable polar westerly stratospheric background, thus the short sharp warming was a one off and therefore the polar vortex quickly re-grouped, despite being blown apart as a result of the one off shock to the atmosphere. And look how late, in the end, the final warming of the stratosphere was back then. The situation this time round is quite the opposite, and although it is a slower less dramatic development, it is a much more sustained one in terms of the background pattern assisting further warmings to prolong the potential effects in weeks to come.
So from my humble viewpoint I'm less concened with apparent water treading of the situation in the very short term and much more encouraged by what the medium and longer term looks to bring from end of January onwards. Of course we cant guarantee anything, but the prognosis for February and beyond can only get better in terms of chances from a cold point of view so plenty of winter left. As we know, we have historically seen potent Feb cold spells. so as the days get longer, the cold can get stronger for sure
Also the implications are that the start to Spring may also be very different to last year
Edited by user
12 January 2012 10:33:22
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