In today’s post I want to look at the bigger, broader picture. Look at the drivers which bring us the type of winter’s and summer’s we get. Why was winter 2011-12 and 2013-14 a no show while 2009-10 and 2010-11 brutal. Why were the last two summer’s good compared to the previous 6?

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Firstly, let’s look at the solar cycle chart I showed back on Nov 1 in my official winter forecast. You can clearly see the max of cycle 24 last winter. This is likely the primary driver (along with other factors) which drove the past 2 summer’s and last winter’s warmth.

Other factors including the cyclical warming and cooling of the oceans and flexing of the ENSO play significant roles in year by year variability.

In terms of winter, the WARM water in the NE Pacific both last year and this year is likely responsible in bringing the warm-wet winter last year while the Central and eastern side of North America shivered. This increased the baroclinic zone over the eastern United States and in turn forced a far stronger than normal jet stream across the UK. The combination of the SOLAR MAX, west QBO and warm NE Pacific ultimately drove the cold US and warm-wet UK winter.

We also had a neutral and then cold AMO signal.

This year

Last year

Warm/cold pools are similar now vs this time last year though the N Atlantic is warmer further north than this year, the main feedback area/driver is the warm anomaly over the NE Pacific. Despite colder episodes, probably thanks to the warm pool in the central Pacific and strong east QBO as well as solar downturn, there was yet again a stronger than normal trans-Atlantic jet and thus heights were never truly allowed to build over the North Atlantic/Greenland like last year. I believe a lot has to do with the warm pool south of Alaska and the still relatively high solar cycle.

So, what’s the difference between the much colder winter’s of 09-10 and first half of 10-11 compared to this winter and last?

Notice the neutral to BELOW normal SST’s over the NE Pacific and the warmer N Atlantic. This, perhaps driven by a solar min.

For one, last year was a solar max and this year we’re coming off that solar max but as we head towards the minimum over the next few years, then I think waters return to neutral or colder than normal in the N Pacific/warmer again in the N Atlantic which in turn strengthens the Aleutian low/weakens the Icelandic low and there’s increased chance of blocking.

It’s Joe D’Aleo of WeatherBell who pointed out the relationship or teleconnection between the Aleutian and Icelandic lows. When ones weaker (past two winter’s the Aleutian), the other is stronger, hence the lack of N Atlantic blocking.

A colder N Pacific favours a stronger Aleutian low and therefore we have a better chance at seeing a weaker Icelandic low, especially when waters are warmer than normal.

As for spring and summer, well a lot has to do with water temps and how wet the soils are. Have warm waters over the North Atlantic extending into Irish/UK waters are you lower pressures during the summer but colder waters and drier soils during the March-May period and you raise pressures, hence the warmer, drier June-July periods with a turn to wetter in August.

The lower solar, warmer waters and particularly with an El Nino going, there appears to be a far greater chance of seeing wetter and therefore cooler during the warm season.

Let’s wait and see what the March through May period brings. April is often a key month.

2012 was a bust for me in terms of the summer forecast. Back at the end of March I called for the first ‘good summer’ since 2006, however failed to recognise the El Nino that was developing and the fact that the record warm/dry March had significantly heated the waters surrounding us. That was the perfect setup for wet and therefore a disappointing summer.

This year? Cold waters are there, the prospects of a dry March are there, however the El Nino is lurking in the background albeit it’s shifted more into the WEST Pacific with cooler waters near the South American coast. Does this matter? It’s influence over Western Europe may be less but I’m not too sure at this time.

Interesting times ahead for sure. I know winter may be ending but I hope you can stick around and see what spring and summer brings as well as hopefully learn more about the meteorology behind the long range forecast. I will be talking about next winter in the coming months, showing you things you won’t see elsewhere.

Back with more Sunday. Have a great weekend.

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