It may feel like winter is never-ending but today, we can look forward to the warmer weather with my UK & Ireland Summer Forecast 2013.
It seems like a very long time since we enjoyed a decent summer here in the British Isles and Ireland. Recent summers have been very much dominated by excessive rainfall and cooler-than-normal temperatures. A lot of the reason for such wet summers can be attributed to a very warm North Atlantic. Another contributor is the colder-than-normal Pacific.
The warm AMO (Atlantic Multidecadal Oscillation) has been gradually warming over the past 5-10 years while the Pacific has been cooling since 2007 and until the Pacific turned cold, summers here in the UK were warmer and drier for a time (2002, 2003, 2005, 2006). But once the Pacific returned to it’s cold phase and the Atlantic continued warming, this appeared to trigger our summer trend during summers.
Both AMO and PDO (Pacific Decadal Oscillation) peaked last year and it’s been decades since there was such a contrast between very warm AMO and very cold PDO. With the help of a developing El Nino and abnormally warm SST’s surrounding the UK and Ireland, extending back across the Atlantic, I believe these are the reasons why the UK experienced it’s wettest summer in 100 years.
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When looking at the recent trend, which stems back to 2007 when we endured a super-soaker of a summer (wettest in 100 years up until 2012), summers have been largely wetter than normal. So on the face of it, one could assume that summer 2013 will be the same. Our lesson in never assuming can be tied back to last April. After a very dry back end to winter and early spring, the heavens opened and the rains barely ceased through the rest of 2012. Many assumed summer would be drier and warmer than normal, given conditions we endured during March which was third warmest. The reason for the drier than normal conditions was thanks to the La Nina but when that broke down and the El Nino came on, it was like turning on the tap here in the UK.
I learned my lesson as I thought we would be in for a drier, warmer summer but I did sit on the fence and like this season, have been stating the importance of spring precipitation. A drier spring can help greatly in bringing a drier, warmer summer but it goes further than that. Water temperatures, the current and future ENSO status as well as the trend in the NAO/AO must all be considered. What I failed to see last summer was the onset of the El Nino.
That along with very warm SST’s surrounding the UK should have been the giveaway that wetter times were ahead. I’ve learned a lot since then.
Reasons For A Warmer Than Normal Summer Which Goes Against The Current Trend
I don’t believe this summer will be a washout and in fact it may be a fairly dry and warm summer overall this year.
Why do I think that? Let’s look at the current ENSO index. It’s currently at neutral with hints of a La Nina returning. A La Nina favours drier than normal conditions here if we can get a fairly dry spring. Then, with the combination of an oncoming La Nina coupled with dry soils to start summer, this should feedback to the atmosphere and boost pressure heights and therefore surface temperatures.
The last decent summer here in the UK was back in 2006 when we saw a drier than normal spring and early summer. This eventually lead to record high temperatures. Despite the North Atlantic being warmer than normal (I believe it ‘peaked’ last year) and with a slightly cooler AMO this summer along with much colder waters surrounding the UK, coupled with a drier than normal spring, this should lead to a warmer, drier summer with the potential for some significant warm spells.
Correlation Between Cooler April SST’s & Drier Spring, Warmer Summer?
When looking back at early April SST’s, I’ve noticed both last year and 2007 saw very warm SST’s surrounding the UK, coupled with oncoming El Nino’s, summer was a washout but this year SST’s are considerably below normal and back in 2006, the last true warm and drier than normal summer, early April SST’s were cooler than normal. Unfortunately there was no correlation in 2005 and 2003 which were also warmer, drier than normal summers. However, what’s interesting is that before 2007 when the PDO was still warm, the warm AMO and PDO, along with warmer than normal SST’s in April, supported some rather warm summers in the UK but what will be interesting to see is whether there’s a difference this summer with a cooler than normal SST’s, despite a warm AMO and cold PDO. In other words does the cooler SST’s surrounding the UK and Ireland along with a neutral ENSO, help with a drier but also warmer summer ahead.
Check these out….
2012
2007
Both saw warm March’s, wet April’s and abnormally warm SST’s surrounding the UK and eventually two of the wettest summers in the last 100 years for the UK.
Here’s 2006, our last true warm, drier than normal summer.
Here’s SST’s to start April this year!
Cooler March, April and May periods in neutral to eventually La Nina developments have been known to bring warm, dry summers. The trend since the end of January into February has been drier and colder and the rest of spring is looking cooler-than-normal but more importantly, drier than normal too. Supported by the fact a La Nina should come on.
CFSv2 temp anomaly for April
May
The overall trend remains wetter than normal for the UK given the cold PDO/warm AMO but like we saw last winter, there are breaks within multiyear trends and I believe this summer will see that break in our wet trend. Until the AMO cools and that may take another 5-10 years, summers should remain wetter than normal.
So to summarise, summer 2013 should be drier and warmer than normal for the UK but that doesnt mean we won’t get rain. Afterall, we live in the UK but our atmosphere should favour stronger pressure heights. Ireland, Northern Ireland, Scotland, England and Wales should all see a continuation of our cool spring thanks to a largely negative NAO/AO. As the atmosphere transitions into a summer state with high pressure and warmer air building north, the drier soils should encourage pressure heights to rise and will pull the warmer air further north than in recent years.
June, July and August may all produce decent warm spells but there is going to be wet spells in between, perhaps in the form of thunderstorms.
I shall have an update to this forecast in early summer.
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Great question from Gerard. Will post on your question today!
I have looked back at the records of the 1950s and the summer that was really wet like that of 2012 was 1956. This according to historical data by the met office in terms of rainfall. 1956 before 2012 was the second wettest to 1912. What was interesting about this was there was not a summer as wet or wetter than it after 1956 and the AMO stayed warm until 1965. What I would like to know what contributed to the summers progressively getting drier after 1956 in those nine years before the AMO went cold.
Does this also apply Ireland, specifically Northern Ireland? I just find that Englands summer weather tends to be a little better than ours.
So the summer this year in the UK is going to be like that of 2008 or 2010 where there were decent spells of warm weather or something like 2006 or 2003 when it was exceptionally hot?
Great stuff, just to clarify. When you say drier than “normal” do you mean drier than “what has become normal for the last 5 years” or drier indeed than “normal, i.e. since way back when”
Cheers, Calum.
I mean below normal in terms of the 30-year average and not past 5 years. 🙂
Thats brilliant! Can’t wait.
Well you got winter spot on do lets hope you are correct with the summer. Well done with the winter forecast and keep up the fantastic work
On another note can you recommend a half decent weather station. Many thanks
Cheers, Perry,
Not sure about the wx station, will try to get back to you on that one.