Tag Archives: autumn

Late autumn to bring chilly shock

The Met Office’s latest outlook for a relatively high chance of cold weather in the early part of winter has set the internet abuzz with talk that the UK is about to experience its coldest winter in years.

The 3-month outlook, produced by the agency for contingency planners, states:

Lower-than-average temperatures are more probable than higher-than-average values. Overall, the probability that the UK-mean temperature for November-December-January will fall into the coldest of our five categories is 30% and the probability that it will fall into the warmest of our five categories is 10% (the 1981-2010 probability for each of these categories is 20%).

THe ‘30% chance’ for temperatures to be in the coldest of five categories is more significant than it would appear: in this three-year period of mild winters that figure usually hovers far lower.

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The continent is not yet cold enough to get excited about this synoptic chart for Monday, November 7th

The forecast has drawn obvious comparisons with their 2009 ‘barbecue summer’ f0recast but the GloSea5 model has made infinite advances on the old one.

The Met Office’s method, which includes a combination of data such as QBO, ENSO and ground based observations also agrees with my own method of finding local October singularities back to 1797. This month I found that an average or cold November is most likely: average and cold are both 30 per cent probability. Rather cold and severe are both 20%! There appears no chance of anything mild.

So, we can look forward to ‘a reduction in the normal westerly flow across the UK from the Atlantic, with a greater frequency of northerly or easterly winds’.

But what does this mean for the London area? If the near continent is not cold enough northerly and easterly winds could just bring a succession of cold rain in the form of showers off the North Sea with a higher than average frequency of frosty nights: nothing out of the ordinary for a slightly cooler than average November.

To try and second guess proceedings into December I decided to plot all year singularities to find when the cold spells would most likely fall and how severe they could be.

The results for November look unexciting: the coldest day is likely to be around the 19th with a maximum of 6.9C. The best chance for something cold looks to be in December, around 6th to the 11th – but there again highs of 3C or 4C would mean that any snow would be short lived. There appears to be a warm up in time to scotch hopes of a white Christmas before another cool down toward new year.

So, in conclusion, late autumn / early winter is likely to be a lot colder than the past three years. It is perhaps this fact, together with frosty mornings being common, that will make the season feel colder than it actually is.

I will be publishing my usual winter forecast on December 1st.

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The coldest day in November is likely to be around the 19th

 

A warm North Atlantic is cranking autumn into life

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On looking at NOAA’s sea surface temperature anomaly in the North Atlantic tonight there seems to be a lot of orange (warmer than usual) off the coast of Ireland across the pond to the US.
A lot of energy therefore has to be displaced before we can start thinking about any sustained cold weather – and is a big part of the reason why the Atlantic has kicked back into life.

The jet stream is centred over us
The jet stream is centred over us
Expect a succession of depressions, driven along by a brisk jet stream (currently right over us blowing at over 100knts) to whistle across us in the next 10 to 14 days bringing very mild temperatures together with a mix of rain, blustery winds and sunshine. Any HP ridges will probably be short-lived – though equally any rainfall should be average. In these situations most of the rain falls over western parts of the British Isles.

So, in summary, a changeable spell is coming up – just like autumn should be