Welcome to my autumn weather forecast for 2023.
First thing to note, as always, is that seasonal forecasting remains experimental. Whilst my forecast for June was good, and for August was respectable – for July I predicted a hot month. Aha. Though at least I thought there would be some rain, albeit of a thundery variety rather than Atlantic systems.
So, some of this forecast will be wrong – due to events, it is impossible to give accurate long-range forecasts, but you can give a general guide based on current weather patterns, background signals, etc.
I’m not sure what went wrong in July – did I misread the models? Perhaps but so did every other forecaster who I take notice of, in that case. I know there were unusual plunges of cold air into North America late June, which fired up the jetstream – and then there was some really anomalously warm waters off the coast of North America, which likely gave low pressure systems their oomph this summer.
That’s my working theory on what went wrong anyway.
So whatever I say here, take with a huge pinch of salt.
Thanks to Sarah for the superb photograph, and to all those that sent in – there were a few particularly excellent ones to choose from.
El Niño is still developing and is probably going to be a strong event. I’m not sure that it has too much effect on the UK weather patterns in autumn, perhaps a slightly increased chance of westerly flows later on.
Sea surface temperatures are still warmer than normal around the UK, which increase the chance of warmer than normal temperatures over the UK.
The Quasi-Biennial Oscillation is now in easterly mode – I’ve seen some people on weather forums blame that for our summer weather, but I’m not buying it. Though perhaps it can increase the chance of blocking highs or easterly flows during autumn.
As always, hurricanes/tropical storms and their remnants can affect our weather and add extra uncertainty, especially in September.
Speaking of hurricanes, Franklin is the major cause of our hot start to September, pushing high pressure east and allowing us to tap into continental warmth/heat.
So an increasingly hot and sunny start to September, very possible that the highest temperature of the year is recording during September, though I think we’ll stay short of the UK all-time September maximum – which is 35.6’C. Some warm nights too, though some early morning mist/fog/low cloud in places.
Towards the middle third, there will be (small) chances of thundery showers before the heat gradually faces, and by around mid-month or just after, we should be in something more changeable – perhaps briefly unsettled.
In the latter part of the month, probably some variation with some showers, but a return to warm and dry looks more likely overall. Bear in mind that hurricanes/tropical storms far to our west add uncertainty to this.
Overall I expect well above-average temperatures, above-average sunshine, and below-average rainfall – unless you catch a particularly heavy downpour during mid-month.
Confidence level of 85%.
Signals are weaker for October though there is a fairly notable signal for high pressure close to the east of the UK.
A dry start may give way to a spell of more unsettled weather into the first half of October, perhaps some very heavy, showery rain at times, and quite windy. Likely mild and occasionally warm.
In the latter half of October, it seems more likely that the high to our east will push west somewhat, meaning rain stays to our west most of the time, and it should generally be dry, mild with some overnight mist/fog.
Overall I expect above-average temperatures, around average sunshine and around or slightly below-average rainfall.
Confidence level of 60%. The main risk is that the high pressure block is further east and low pressure systems get stuck over the UK – bringing a wetter month than I expect.
November I think will more likely start dry with high pressure close by. Overnight frosts with some morning mist/fog patches possible. Some sunny days, some cloudy days, temperatures around normal for the time of year.
During the latter part of November, the jetstream should pick up and we’ll have a more westerly flow – some rain at times from weather fronts though I suspect the bulk of the heavy rain and strong winds will be towards Scotland. Generally mild/very mild under such a set-up. Uncertain on cloud/sunshine amounts.
Overall I expect slightly above-average temperatures, around average sunshine, below-average rainfall.
Confidence level of 50%.
Overall and Early Winter Thoughts:
So drier and warmer than normal for autumn, is what I expect. We shall see!
Early thoughts for winter are mostly for a mild and dry winter with a strong signal for higher than normal pressure over Europe.
I wouldn’t preclude a cold spell, and there will be some rain at some point, but overall drier and milder than normal seems the most likely outcome – albeit it’s 3 months away!