Id like to draw peoples attention to the 2 nd part of last years big freeze at this time , frist the crew over on the strat forum on netweather said there was nout on cards before it came as in strat warming etc , so this shows us you cant just go by strat warming for a dip in the AO index . Another point is look how cold strat is yet we have had some very cold weather dublin has been colder then germany , warsaw , stockholm this past week .
Below is what a us forecaster thinks
However, I mentioned that the La Niña's influence would be weak. The true drivers of the long-term pattern will be the Arctic Oscillation, the North Atlantic Oscillation, and the East Pacific Oscillation. A negative summer AO and NAO is associated with a negative AO and NAO the following winter. This past summer the AO was the third lowest it has ever been, and the NAO was the second lowest it has ever been. In addition, both indexes were solidly negative for each of the months of June, July, and August. This would support a solidly negative AO and NAO this winter. Solar geomagnetic activity is still low, which would suggest enhanced chances of strong blocking (negative AO). The QBO is turning from positive to negative, which could bring an interesting situation, with the AO being forced farther down by the –QBO at 30mb without the enhanced southeast ridge that a –QBO at 50mb would bring. The summer SST configuration in the north Atlantic is pointing towards a negative NAO, though not as much as it did last year. However, a deeper look reveals that this pattern is very strongly pointing towards a negative west-based NAO, that is, a blocking high between Baffin Island and Greenland. This supports cold in the eastern US way more than a negative east-based (high between Greenland and Iceland) or neutral-based (high right over Greenland) NAO does. There is some speculation that the eruption of Eyjafjallajökull slightly reduced the NAO and AO during 2010-2011. If so, then it is likely that this year's eruption of Grímsvötn will have a similar effect this winter. There is currently record cold air over Alaska and Canada, and it is only a matter of time until the pattern changes and brings this cold air down to the United States. The final consideration of these three is the EPO. A first glance at the current pattern shows that the EPO is strongly positive and has been for quite a while, with a very powerful vortex over Alaska. However, that is not supported at all by the increasingly obvious east basis of the La Niña. I expect the vortex to become a bit weaker, and, more importantly, to retrograde toward the Aleutian Islands as the month of December progresses. This seemingly small change makes a world of difference for the pattern, as it would switch the EPO from strongly positive to strongly negative once an upper-level high takes the vortex's place.
Last edited by mcriot29; 17-12-2011 at 14:27.