In both Winters of 2009-10 and 2010-11 my long range seasonal forecast turned out successful but last year that success came to a crashing halt. Since then I have been studying the global pattern, ocean sea surface temperatures across the world as well as observing closely what our weather pattern has been telling us ever since last year.

I’ve learned a hard lesson and in this post I will show you where I went wrong last winter and why we missed out. I’ll explain also how my summer forecast should have been clearer rather than having a ‘sit on the fence’ approach depending upon spring rainfall.  When making up a winter or summer forecast, months away from the actual season, you must constantly observe current trends and past trends both regionally and globally as well as understand how they affect the pattern. Feedback is a word you’ll notice a lot.

It’s important to NEVER assume that given what happened last summer or winter will happen again next year. I’m seeing a few comments pop up on facebook making that very assumption. Very foolish. This shows a lack of understanding. The pattern this year is nothing like last year, not in the slightest. Unfortunately, our global climate system is far far more complex than that and like water, it’s moving and changing all the time. It’s my job to keep a close eye on EVERYTHING in order to even attempt on making a seasonal forecast.

For me, one of the hardest jobs is not figuring out what the current signals are, whether it be the El Nino or La Nina but trying to forecast what the pattern both regionally and globally will evolve into 3, 6, 9, 12 weeks down the road and what impacts this will have. This year for example.. How will the El Nino evolve. Will it turn strong, will it’s warmest waters stay in close to the South America coast or will they push out into the heart of the central Pacific? These factors have huge impact throughout the Northern Hemisphere. Take the NAO. Will this past summers trend of a mainly negative signal follow into winter and stay that way like we saw in 2009-10 and for the first part of 2010-12 or will it be like last year?

There are several MAJOR factors which come into play such as what is the current mode of the Pacific, the Atlantic, the ENSO (El Nino-La Nina) as well as pressure indexes such as the NAO (North Atlantic Oscillation), AO (Arctic Oscillation), PNA (Pacific North America Pattern).

The consequences of Pacific cooling and Atlantic warming

In order to fully show you where I am going with this winter, I want to go back to 2007. Of course we had a strong El Nino, the Pacific was ending it’s warm mode (but was still warm) and the winter of 2007-08 was one of the warmest on record for Europe.

Interestingly, once the Pacific Ocean (think of this as a giant thermostat) cooled with it’s ‘official’ return to a cold mode in 2007′, our weather here in the UK changed and so too did it around the world. The atmosphere reacted to this cooling with the onset of an El Nino which turned out to be strong. This ‘basin-wide’ cooling and the reactive El Nino, helped, along with a warm AMO to produce our second wettest summer on record in the UK. That super soaker of a summer started a long-term pattern of cool, rainy summers that we’re still in and likely won’t leave till the Atlantic returns to it’s cold mode.

What’s facinating is that as the Pacific returned to cold in 2007, the Arctic Ocean that summer saw it’s lowest extent of sea ice on record, why? The Maturation of the warm mode in the Atlantic.

Now.. before I go further.. 2007 vs 2012. There’s a link.. this summer was second wettest on record, beating that of 2007. The record of 2007 for minimal sea ice in the arctic was beaten this summer… Also, the Pacific is STRONGLY in a cold mode, shadowed be an El Nino.. The difference is that this Nino is weak as the Pacific is far cooler than when it first flipped in 2007, so no need to worry about this winter ending up like 2007-08..

The first cold winter in years hit both the UK, Europe as well as the United States in 2008-09 when the strong Nino faded during the 2007 summer.

Summer 2008 funnily enough was another cool and wet summer for the UK followed by a cold autumn. Now, what’s worth pointing out is the fact that the summers really from 2002 to 2006 were for the most part warmer and drier than normal. The warm Pacific and warm Atlantic lead to warm, wet winters and warm, dry summers. This would would certainly suggest that the flip in the Pacific is the reason for our wetter weather during the summer months.

In 2009 the El Nino returned but in a much weaker form than back in 2006-07. Keep in mind that El Ninos are STRONGER when the Pacific is warm but weaker when it’s cool.

As the Nino came on with a cold Pacific backdrop, weighed against the warm Atlantic, this meade for another cool, wet summer.. see the trend?

Onset of an El Nino within a colder PDO signal made a world of difference between winters 07-08 & 09-10

The key difference between the onset of Nino in 2006 and the Nino of 2009 was it formed in a far colder overall ocean AND the Atlantic was warmer.

The weak Nino made for the positioning of warmest waters out over the CENTRAL Pacific Ocean, not in close to South America which leads to a ridge and warmth over much of the Lower 48. This also leads to warmth over Western Europe.

This central based Nino allowed a ridge to pump further west (north of Hawaii) and a trough to drop out of the Canada down into the United States. The warm AMO has a tendancy to lead to more BLOCKING over Greenland and across the pole. Stratosphic warming events are tied to warm waters in the North Atlantic. This setup lead to a blockbuster winter for persistent cold and snow on both sides of the pond.

La Nina come on strong in 2010 and 2nd year Nina lead to blocking where we didn’t want it

The summer of 2010 was yet another wet summer but with the demise of the El Nino and the cooling of the equatorial Pacific which brought on the Nina, this lead to drier than normal conditions developing over the UK. A soaking late summer and early autumn with record rains in September was following quickly by another severe EARLY period of winter. The atmosphere was ‘cast’ from the winter before with a warm North Atlantic once again leading to blocking and a negative AO.

The difference between winter 2009-10 and 2010-11 is that the winter hit fast and furous, early on but with the La Nina coming on strong and the atmosphere reacting, the winter died off as fast as it begun by January 1, 2011. 98% of that January and the rest of winter was mild.

The following summer saw a drought continue across much of England which really started following a drier than normal winter overall in 2009-10. These dry conditions and the onset of a La Nina meant the dry conditions from Southern Scandinavia all the way down Southern Spain persisted. These increasingly dry soils lead to feedback. Positive heights began to show during summer 2011 over the drought areas caused by blocking during winter 2009-10 and harnessed by the La Nina.

Drought & back to back La Nina lead to no winter in 2011-12

What I didn’t see or factor into the equation when making up my 2011-12 winter forecast back that summer was the DRIER than normal summer and the back to back La Nina. A second year La Nina is very different to a first year one due to the fact that the La Nina in the 2nd year has also brought drought to places that normally wouldn’t and rains to normally dry places. The atmosphere was ‘cast’ differently because of the feedback. I didn’t realise that this could well lead to blocking further east over the North Atlantic due to the feedback of the drought which set in over Western Europe. Water temperatures were warm and with dry ground and no trough that summer, this meant the ‘block’ sat over the UK and not over Greenland throughout winter 2011-12, however, Europe from Russia to as close by as Belgium and the Netherlands shivered in one of it’s coldest winter spells on record. A stretch spanning late January through late February brought brutal cold and massive snows, yet Scotland in particular basked in mild air. The drought the previous 2 years, started off by the 2009-10 winter and sustained by the 2 year Nina, meant we lost out but only by a mere 200-300 miles. This shows the power of feedback!

The major summer rains herald the return of the El Nino & likely confirmation that a 2011-12 winter should not repeat itself this coming winter

My downfall this summer wasn’t so much the ‘sit on the fence’ approach depending on upon spring rains but I was sidetracked by the drought. I believed a drier and warmer than normal summer was more likely due to the intensity of the drought but what I didn’t account for was the fact that the dry signal (Nina) had gone and the wet signal was returning. The onset of the Nino within the backdrop of the cold PDO and increasingly warm AMO should have told me that a potentially WETTER summer than in 2007 was on the cards, keeping in mind that the warmer AMO could support higher amounts of rainfall within low pressure systems. The onset of the el Nino lead to our wettest summer in 100 years. When looking at history and not so distant history, this should have been seen by me.

However, what this summer has told me is that we shouldn’t have a repeat of last winter’s warmth and persistent Azores high. Why? The summer rains have returned, the trough has been dominant. The soils are wet and with a super warm North Atlantic, this should lead to a wet, stormy autumn which in turn should all lead to cold further down the road. There’s a transitionary feedback during autumn which can bring intense rains during September and November with respite in October and right now that is occuring. We saw respite during August following a super wet June and July, then we had the 1-2 months worth of rain within 24 hours at the close of the month. Record rains occured back in Sept 2009! History repeating itself!

Why should this autumn not be cold and or snowy?

The current pattern is VERY ALIKE to 2009 with the mainly negative summer NAO, the rains and the weak version of the El Nino thanks to the cold PDO.

Why am I shying away from the idea of a cold, snow this October-November, like a few forecasters are going for? History doesn’t agree given the pattern we’re in. Had this been a La Nina year then maybe. I shall keep banging the 2009/2012 correlation. If history is to repeat itself, next month (November) should be very wet and mild with a brief 1-2 weeks of a positive NAO. Back in November 2009 we saw the greatest 24 hour rainfall in the UK on record. Remember the foot which fell at Seathwaite Farm in Cumbria?

What’s different about this year to 2009 is that the Pacific is far colder, and arguably the Nino is even weaker. The Atlantic is much warmer. So, there’s greater contrast plus, if things play out as they should, the WARMER AMO should suggest an even greater liklihood for blocking further down the road which could support a very similar winter both here in Western Europe as well as Eastern North America.

Don’t worry if the NAO flips positive for 2-4 weeks and so too the AO. We need the positives to allow the cold a chance to bundle in it’s source region. The AMO and a positive NAO SHOULD support a few wild storms during November, perhapos extending into early December. Bare in mind, our benchmark winter of 2009-10 started AFTER December 15th, so there’s a while yet. The good news is that we should see a couple of cold shots in between the wetness of November. The end of October may end quite cold.

BTW, I also anticipate a few more days of last minute summer. Perhaps 1-3 days with sun and warmth. Interestingly, models show hints of ridging early next week.

More later!

Tags: europe winter forecast 2012-13, uk winter forecast 2012-13, winter 2012-13, winter forecast 2012-13