Tag Archives: El Niño

Summer forecast 2016: yo-yo weather

The cold start to June may soon be a distant memory once summer proper gets going in east London. But rather than a succession of prolonged hot, dry spells it’s looking like the season overall will be broadly average – you will hear the old saying: ‘an English summer consists of three fine days and a thunderstorm’ more than once this year.

Heavy shower cloud looking east over Wanstead Flats
Three fine days and a thunderstorm – the typical English summer

Looking at summers back to 1799 I’ve tried to find a pattern linked with a declining El Nino. And failed to find anything conclusive. With ENSO forecast to be approaching neutral by August I decided to discount it completely, instead relying on pattern matching of meteorological data from this area for March, April and May stretching back to 1799.

The mean for the spring season was 10C with 156.4mm of rain and 455 hours of sunshine.

If you take into account all years that were within +/- 10 per cent of these figures, for rainfall and then mean temperature, some 36 ‘best fit’ years emerged, far more than my previous two attempts to forecast summer. The years, ranging from 1805 through to 2007, saw all manner of summers – only one was a real corker, 1825, but most were fairly nondescript average affairs. As an average this summer could be expressed as: Mean: 16.7C (just above average) Rainfall: 166mm (exactly average) Sunshine: 546hrs (about average)

Or, expressed in probabilities, I concluded the following:

summer 2016 probs

 

 

From the above you could deduce that the next three months will be slightly warmer than average, with average rainfall and sunshine.

Last year I tried to decipher, with fair success, when hot spells would occur. However,  looking at the data of these 36 summers very warm, dry spells happened through the three months – it was impossible to find any exact pattern to when it would be warm and dry.

Instead I’ve broken down the summer into June, July and August probabilities.

Looking at June, considering this cool and cloudy start, I would guess that we can look forward to a few very warm, thundery spells – a repeat of the Spanish plumes of the past couple of years.

june 2016 probs

Considering the above data perhaps there is a greater than evens chance of some thundery activity – and the nature of thunderstorms mean you can get a deluge or stay relatively dry / average. Sunshine average.

On to July. After a ‘rather warm’ June I wonder if the ‘return of the westerlies’ will happen just in time to affect this month?

July 2016 probs

The above chart would suggest that July will be classically average overall. Fine, not too hot spells, with occasional depressions bringing cooler weather and showers.

On to August. This month has been a real disappointment the past couple of years. However, I think this year August may offer a bit more in the way of sunny weather.

August 2016 probs

Looking at the above probabilities there seems a fair chance of something average to rather warm overall. With rainfall below average and average sunshine I wonder if there will be two or three fine spells throughout August – perhaps more?

So, all-in-all, summer looks a mixed bag. How this summer will fair obviously only time will tell. One could argue that what I’m forecasting is just climatology which has a good chance of being correct should no external influences, such as a huge eruption on Mount Etna, have a bearing on the end result.

* Taking into account the fact that temperatures in London are up to 0.66C warmer than they were 100 years ago I have added 0.66C to mean temperatures before 1915.

** Obviously, in the event of a series of direct hits from thunderstorms, my rainfall estimate could be hopelessly short – a symptom of abundant solar energy at this time of year which creates a ‘noisy’ atmosphere compared with winter.

*** The 1981-2010 average mean for summer in this region is 17.6C, with 144.9mm of rain and 564 hours of sunshine

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Is London heading for a hot summer?

Before I’m accused of going all Daily Express the following is based on winter statistics for the London area and other variables rather than the latest expert hopecast.

Even before looking at the data in depth the chart below shows that a warmer than average summer is more likely after a mild winter. The winter just gone was the third mildest in a record going back to 1797.

combined

There are some real corkers in that list, including 1995 when this area recorded the driest August on record. Other notable summers included 1990 – England in the semi-finals of the World Cup and another notably fine August: the then hottest UK temperature was set that year when a maximum of 37.1C was recorded at Cheltenham – a record that lasted until 2003. The year 1989 also stands out with a notably sunny summer.

So far, so good. But what about rainfall? Some 145mm of rain fell this winter – pretty much on the nose average for this region. Combining warm winters with similarly average rainfall gives the following list.

with similar rain

Though some years have disappeared there are still some decent summers, and notably sunny too. The year 1975 stands out as does the sunniest summer on record, 1911! Both were also very dry summers.

Altough the teleconnection with El Nino is tentative in our part of the world the winter seemed to follow the pattern of most positive ENSO episodes, so it is worth having a look to see where the data goes. The latest forecast by NOAA suggests:

A transition to ENSO-neutral is likely during late Northern Hemisphere spring or early summer 2016, with a possible transition to La Niña conditions during the fall.*

If the forecast goes to plan the second ‘rainfall list’ would narrow further:

Screen Shot 2016-03-08 at 02.44.05

Viewed by graph reveals that ENSO values of all the years decreased over the course of the year. Series 1 is 1998, series 2 is 1983 etc.

Screen Shot 2016-03-08 at 02.48.01

In conclusion, the results would suggest that there is a 66% chance of a decent summer with below average rainfall and above average sunshine. In terms of details June 1st is still a very long off in meteorological terms – so whether it includes any heatwaves that would put it my premier league of hot spells is anyone’s guess at this range.

If it’s anything like 1959, 1975, 1983 or 1998, however, I think most folk will be happy.

*The above contradicts some forecasts which suggest a continuation of the general pattern that persisted during the winter: warm SSTs in the Atlantic / warm water south of the Grand Banks were largely responsible for the cyclonic westerly type of weather that caused the mild weather. In summer this would cause changeable weather rather than long spells of settled weather.

 

London winter forecast 2015/16

Winter in the London area this year is likely to be average overall, following the pattern of the past two winters that saw little snow.

winter 2015-16A rather mild December, dominated by a SW’ly flow with only brief, cooler, NW’ly incursions, will be followed by a rather cold January and average February. Rainfall throughout is likely to be average or slightly above. Probabilities of this scenario are listed in the tables.

The best chance of any snow is most likely to be at the end of January, though given the generally mild pattern it is not likely to last longer than two or three days.

Much has been said about how El Niño will affect this winter. The more hysterical parts of the media tell us we will see a repeat of 2009-10, a cold winter that saw frequent snowfall. But their assertion ignores the fact that other winters following a strong El Niño have been exceptionally mild.

decThis autumn has shown some striking similarities with 1997, a record El Niño year, that was followed by a very mild winter in this area, the third warmest since 1797. This autumn was also similar to 1994 – another El Niño year – followed by the fourth warmest winter on record.

But just as you think the pattern is the same the El Niño this year is different in that it is an El Niño Modoki – a full-Pacific basin El Niño that differs from the one in 1997. In other words we really are in unfamiliar territory.

janSo before I get too bogged down in finding teleconnections with El Niño, perhaps it is wiser to go back to more traditional ways of trying to predict the coming season.

Before I trawled through the figures my initial gut reaction to this winter was that it would be mild – because of some blocking in September/October.

febAs well as my method of using rainfall and temperature I also considered other methods. One, of which I see mentioned very little these days, was Russian research that states that the weather pattern in the winter will be the opposite to the weather on September 17th and November 7th. This autumn September 17th was NE’ly and November 7th was SW’ly. So, of little use this year.

You can read the method 0f how I reached my conclusion here.

DJF max
This chart shows that the coolest spell is likely to be around January 27th

 

 

Will potent El Niño bring cold winter?

Much of the UK media has been very persistent in the past few months in saying that large positive anomaly El Niño years herald cold winters – basing their assumption on one year: 2009/10.coldandwarmepisodesbyseason

Whilst that winter was very cold, among the top 10 coldest of the last 70 years in this area, another El Niño year, 1997/98 – the strongest in recent history – brought London its third-warmest winter in a record going back to 1797.

When I had a look at ENSO data going back to 1950 a few months ago I found it impossible to find a definitive teleconnection between El Niño and winters in north-west Europe. However, now that we are midway through November, and with a fair impression of how the monthly mean will finish, I had another look.

NOAA data shows that the most similar El Niño years to this are: 1957, 1965, 1972, 1982, 1997, 2002. Taking in to account only mean temperature shows that November values have increased.

new el nino

What does this mean for this winter? It is still impossible to tell and is just another variable to consider when the time comes to predict winter.