Welcome to my Autumn Weather Forecast 2020.
I always have mixed feelings about autumn. A relief that heatwaves are unlikely. An excitement about the potential for proper rain and wind! Sadness for the diminishing amount of daylight. And I enjoy the colour of the changing leaves – it can be such a photographic season.
First the admin. If you appreciate my forecasts, I ask you to share occasionally, use the “invite friends” button on Facebook, post on social media, send to your family/friends. It is all I ask.
Next, thank you to Ros for the photograph. There were 3 or 4 really strong contenders, but I was really keen on the fact that it offers both sunshine, and threat of rain – at least clouds, a bit like the autumn I’m expecting. A £10 donation to The British Heart Foundation has been made as a thank you.
Finally a reminder that seasonal forecasting is really rather difficult. There are some background signals to assist but it is quite speculative. Some of what I forecast will be incorrect, do not take it as gospel. The hope is to get more right than wrong, and the general picture.
Feel free to check my summer forecast – I thought that it went really well and am happier with it than most seasonal forecasts in the last couple of years.
So the main background signal that informs my forecast is that of La Niña, which is developing in the Pacific Ocean. Likely to be a fairly weak affair, I still expect this to increase the general westerly flow over the UK, increasing the chance of strong winds and rain overall.
However I expect the mean jetstream flow to be a little north of Scotland, on average through autumn, so for those of us in the south of the UK, this will mean high pressure loosely in control – often a similar pattern to July, where we swapped short spells of high pressure though often cloudy, for short unsettled spells – the westerly flow in July meant that temperatures were not hot, bar the last day of July.
September is always a tricky month to forecast as Atlantic hurricanes can change previously expected weather patterns, or sometimes exaggerate current patterns. It has been a busy hurricane season so far, though we’ve only had the remnants of one ex-tropical storm and that had no effect on our weather patterns, at least that I could ascertain.
So there is always that bit more uncertainty for September.
The first two weeks of September I expect to be broadly fair. Some sunny days, some occasional showers or fairly weak bands of rain. Some warm days, some with more average temperatures.
Around the middle of September, it looks like cooler air with spread down from the north-west, with rain, showers and strong winds.
Then the last week, maybe 10 days, seeing something more settled, though still fairly mixed with the odd weather front – but more dry days than not, some decent sunshine and some warm, perhaps very warm days.
Overall I expect around average sunshine amounts, below average rainfall and somewhat above average temperatures.
Confidence level around 65%.
At the moment I expect October to start with some decent spells of settled weather, likely rather warm with high pressure close to our east allowing for a more southerly or south-westerly flow – though chance of fog overnight.
During the middle portion of the month, we should see more in the way of weather fronts bringing wind and rain at times, but still some fine and dry weather mixed in. Temperatures around normal.
Suggestions that the month may end more deeply unsettled, but this is probably the most uncertain part of the forecast.
Overall I expect slightly above average sunshine, slightly below average rainfall and somewhat above average temperatures.
Confidence level around 60%.
No particular weather type expected to dominate in early November. I do expect the jetstream to be bringing wet and windy weather to Scotland – and some of this will drip down our way with some weather fronts, some windy days, mixed in with fine days and temperatures generally around average, though perhaps a tad chilly in any lengthy settled spells where frost and fog will be possible.
For the latter part of November, the general mixed theme remains though with more of a south-westerly flow, and something milder – though rain and wind that bit more often than early November.
Overall I expect slightly below average sunshine, around average rainfall and slightly above average temperatures.
Confidence level around 65%.
Well, December is a long way ahead. With La Niña I’d expect a wetter winter than normal and with the jetstream further south, so we’ll get more of the brunt of weather systems than during autumn, where Scotland should get the brunt.
That said there are plenty of background signals that suggest a good chance of cold spells. Then again, there were a few last season and look what happened!
So I’m fairly confident of a wetter winter than normal. For chances of cold spells and snow you’ll have to wait until nearer the time.