While the pattern remains quite benign I thought I would post a little on the pattern over the next few weeks and basically through the first half of October.

Firstly here is the NAO and AO indexes and it’s clear to see where they are at right now.

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As your well aware, I am going for a cold October overall and although a negative NAO/AO does not mean it has to get cold in western Europe, especially this early in the autumn, I do however expect it to be a little cooler given the indexes but if I’m being honest, there is NO model guidance that suggests cold gets into western Europe over the next 2, 3 even 4 weeks and that’s including the ECMWF Control and Monthly. Yes there’s plenty of cold for the east but not the west. Both GFS and ECMWF keep the ridge pumping mild air north in the west including the UK while the east gets the cold northerly.

Here’s the ECMWF chart Friday. Note 3 key features. 1) the upper low SW of the UK which is supporting the UK ridge and stopping 3) the Scandinavia trough from dropping the cold air further south. It’s instead forcing it SSE.

By next Monday the upper low has opened up bringing much more unsettled weather into the UK but it’s also allowing a Greenland trough to deepen and thus the UK ridge is forced NNE into Scandinavia. Now you’d think that would be a good indicator of cold air driving west, especially with the cold building over Scandinavia but this is not winter and also heights are simply too strong from the Azores across to Spain and north up into the UK so therefore any cold that’s replaced by warm air, i.e the Scandinavia trough is replaced by the ridge, where does the cold go? Into SE Europe.

By next Thursday the trough deepens over Greenland down into Iceland, a much more positive NAO signal and the ridge really pokes it’s nose into Scandinavia but the trouble is the ridge is no cut off in which the cold air now driving south over eastern Europe can go west underneath. The ridge basically extends from  Africa to northern Norway and Sweden and with that setup, it’s stays relatively stable over the UK.

As far as I am concerned, this does not look like a negative NAO pattern for Europe, it’s more positive. What will be interesting to see is whether both ECMWF and GFS stick to this solution as heights are simply too strong over the west right now for us to see any real chill in here any time soon, who knows. Perhaps I’m too fast at bringing in the cold, especially given the warm waters.

In saying this, I’m merely showing both sides of the coin and I’m not ready to abandon ship. I still believe that this pattern has the ability to flip around with heights building more to the north and if ridges can cut off, then we’ll get more pronounced height falls further south that would allow the cold air westward.

Interesting seeing the 500mb height anomalies off the CFS for October with a positive to the NW, negative to the south. That indicates a fight, BUT this model is back and forth and has little guidance just like the CFSv2 right now. At the moment I ask myself, do I go with what I’ve forecasted since mid-August or do I look at what the models are showing me.

October temps.

Autumns which follow warm summers can be tough to forecast especially with a neutral ENSO, warm AMO, cold PDO.

Let’s see if the GFS and ECMWF stick with the current idea over the next 7 days and if it persists, then I guess I may need to look at things more closely.

Just to be clear however, remember that I have went with a cold October but nothing extreme. Spells of cold with frost and potential early snows but I’ve always said that I believe warmer weather would return with flooding rains. This IS NOT my idea of winter beginning but perhaps an early taster. This winter has the potential to be a slow starter just like 2009-10 was when we had a warmer start to December.

Here’s the CFS November 500mb heights

Here’s December

Will have a closer look at winter in the next couple of days.. Stay tuned.

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Tags: Europe Autumn forecast 2013, us october forecast