Autumn Forecast issued 29/08/2014

Issued 29/08/2014 on my Facebook page - posted here for posterity and easy access...

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Autumn Forecast

I will start with the usual caveat that seasonal forecasts can and do go wrong. Predicting 5 days ahead is difficult enough – giving an exact forecast for a particular weekend in November right now is impossible. However I can give a guide as to what I am expecting.

My summer forecast was issued on June 3rd and is available for review if you scroll down quite a way - and I have posted on my old blog for easy access - http://jameswinfieldweather.blogspot.co.uk/2014/08/summer-forecast-2014.html.

My headline was for an above average summer in terms of temperatures, but also rainfall. Sunshine at least slightly above average. And the best chance of significant thunderstorms in our area for some years.

Amongst the things that I feel I got right were no month-long heatwave for July but good spells of hot weather - sunshine and temperature predictions for June and July, thunderstorm potential. August was furthest from being accurate, in particular by predicting average rainfall when we received well-above average though at least I stated that the month would be more unsettled in the second half which it has been. And I did have low confidence in my August forecast.

I am happy with the overall accuracy and will look to build in what I have learnt for next summer.

The headline for this autumn is for a dry September and October, often with above-average temperatures. A gradual breakdown to unsettled conditions in November with above average rainfall and an early taste of winter to finish.

September will begin with high pressure over the UK, or drifting to the east. This will bring lots of warm or possibly hot sunshine. There is the potential for it to briefly drift west bringing a cooler flow and perhaps some showers around 7th - 10th September. I then expect high pressure to move back over the UK to bring further warm sunshine for the rest of the month. Depending on the exact position of the high pressure, there could be some chilly nights in the second half of the month. Rainfall to be very low, perhaps as few as 3-4 days with rain falling, mostly from weak weather fronts toppling over areas of high pressure occasionally.

Overall I expect well-above average sunshine amounts, above-average temperatures and below-average rainfall.

I am 90% confident of this outcome.

October has a strong signal for high pressure to be to our east and this has been something that I have been confident about for several months now, which will mean southerly winds and well above-average temperatures at times, especially in the first half of the month.

The second half of the month is most likely to see the Atlantic high come into effect, bringing cooler north-westerly or northerly winds and occasional showers or weak weather fronts, but mostly dry.

Overall I expect above-average sunshine amounts, slightly-above or above average temperatures and below-average rainfall.

I am 70% confident of this outcome - less confident about the second half.

November will see the return of low pressure systems, though I expect the Jetstream to be tracking slightly north of here, say over Scotland so although rainfall will likely be regular, I expect that we will miss the heaviest of the rain. High pressure will likely nudge into the south at times so there will be a couple of 3-4 day drier spells.

I do feel that there is a chance of a brief cold spell towards the end of the month.

Overall I expect slightly below-average sunshine amounts, slightly above-average temperatures and above-average rainfall.

I am 80% confident of this outcome.

Early signs for winter are for a generally mild winter, and a wetter than average winter although there are no signals for it to be as extreme as last winter – in fact high pressure should nudge up from the south-west at times.

However, there are conflicting signals that it could be a very cold and very snow-filled winter, at least for January onwards. Certainly there is a much higher chance of snow this winter than last winter – which is something I stated before last winter. Added on volcanic uncertainty in Iceland and potential effects in the unlikely, but possible, event of a really major eruption and this winter is definitely one to watch.

Thankfully my winter forecast is still 3 months away!

If you have made it this far then it would be appreciated if you could share the forecast and/or invite friends. A lot of love and effort goes into this forecast and they are normally a reasonable indicator of the upcoming season.

Enjoy autumn

— in Reading.

Summer Forecast 2014

Posted here after summer to create an easily viewable link.

Original on Facebook, post date 3rd June 2014.

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Welcome to my Summer 2014 Forecast

I begin, as always with a caveat that long-term forecasting is horrendously difficult and can only really be produced in terms of the most-likely expected patterns.

My long-term followers will know I got my summer 2013 forecast pretty spot on – predicting a month-long heatwave in July when most other forecasters were expecting another washout. However this winter I underestimated the amount of rainfall (slightly above average was my prediction), my spring and autumn forecasts were reasonable though a long way from perfect.

The headline is for an above average summer in terms of temperatures, but also rainfall. Sunshine at least slightly above average. And the best chance of significant thunderstorms in our area for some years.

This is what I believe is the most likely outcome – it doesn’t mean a washout or a long heatwave won’t happen.

So onto my monthly breakdown.

June is most likely to see a strong area of high pressure develop to our north-east over Scandinavia, particularly in the second half of the month, when I also expect the Jetstream to be running south, bringing very wet conditions to France, for example. Both will be major factors in our weather here in Berkshire.

The first half of the month will be characterised by low pressure to our south-west, often bringing heavy showers for several days at a time. However the wind direction will be favourable for temperatures and should bring at least one very short spell of very warm/hot weather in the first half of the month – but only for 1-2 days before thundery rain arrives once more.

Assuming high pressure builds over Scandinavia as expected during the second half of the month, this should reverse the script to several warm, settled days, though morning cloud often taking a while to clear, interspersed with shorter spells of heavy showers – potentially some cracking thunderstorms, and then the pattern repeating itself.

The first half of the month will have around 10 days of rain falling, the second half around 6.

Overall I expect above-average rainfall, above-average temperatures and around average sunshine, perhaps slightly below average.

80% confident on this outcome.

July is most likely to see high pressure taking more of an influence over our weather, with both high pressure to our east, and also the Azores high nudging in from the south-west.

However, unlikely last year I do not expect any long heatwaves.

The first week of July (give or take) I believe will be sunny and hot. This then being followed by a thundery outbreak from the south which again could potentially bring some very high rainfall totals.

Once this system clears out of the way I expect fresher conditions with ridges of high pressure building from the south-west (the Azores high) – but this not being especially strong, so a few fine and fairly warm days will be interspersed with showery days, this pattern continuing for much of the month.

Overall I expect slightly above-average rainfall (though below average if we miss the early-mid month thunderstorms), slightly above average temperatures and slightly above average sunshine amounts.

65% confident on this outcome.

August has no clear signals, which is particularly unhelpful.

My suspicion is that we will see drier, sunnier weather in the first half, perhaps just touching the hot category for a while.

The second half being slightly more unsettled in terms of afternoon showers/thunderstorms developing but still some decent sunshine around.

Overall I expect above average temperatures, above average sunshine and average rainfall.

50% confident on this outcome.

So not bad at all, especially when you compare it to the summers of 2007 to 2012.

That said, things do change, and I will regularly update you on my long-term thoughts as summer goes on.

It would definitely be appreciated if you would like/share and invite friends.

Looking further ahead, and the early signs are for an unsettled September, a significant warm spell in October and back to cool and unsettled in November though turning settled but frosty towards the end.

But please take these autumn thoughts with a bigger pinch of salt than the council has left over from the winter.

Dare I mention winter?!

Last winter I said that the winter of 2014/15 would see more snow than the winter of 2013/14. Which will take one snowflake to be accurate.

My hunch is that we will see an early onset of cold weather in late November/December, but then turning milder and more unsettled as winter goes on.

Enjoy the summer.