October 19th, 2026
Hi All,
Firstly, my apologies for the lack of correspondence since late August, one of life's crappy curveballs came my partners way late summer and dealing with that is the focus of my efforts and my priority and will remain so for the foreseeable.
I have been working on my disease model in that time and of course watching the weather patterns. On that front I don't think I have ever seen them as they have been recently, with the Atlantic jet stream sitting north of the U.K (just south of Iceland actually) and so much heat out in The Atlantic. So strange for this time of year.
It is though this combination that has provided our unwelcome extension of summer into October from a lack of rainfall perspective.
Now we know we are heading towards a Super El Nino event and I can't help thinking that there is a connection here or maybe it is just because our oceans are that much warmer than they were when we had the last event back in 2015/16. Either way, I think that heat has been keeping the jet stream position further north and that means our normal Atlantic airflow that we experience in the autumn has been disrupted.
Yesterday and extending overnight into the early hours of this morning, the south east, east and Midlands received some very welcome rain. Not courtesy of the Atlantic, more so a 'Cut-Off Low' or COL as I call them that pushed westwards from Europe across the southern half of the U.K. Normally we get our rain from the west and it moves eastwards, this event was precisely the opposite.
Cut-Off low pressure systems are playing an increasingly important role in our weather because not only do they bring rainfall from the south and east sometimes, but they also tend to reconnect with the jet stream and cause it to shift position further southwards.
That in a nutshell is what's going to happen this week with that COL joining up with the jet stream and pulling it further south.
You can see this in the animated GIF above from tropicaltidbits.com.
With the jet stream moving further south, we 'reconnect' with the Atlantic flow of low pressure systems and that means this week we will see more familiar October weather with strong winds and heavy rainfall.
Beginning this week we will keep that easterly airflow courtesy of the COL rotating anti-clockwise as low pressure systems do in the Northern Hemisphere, but as we get to mid-week, those winds will shift round to the south west and gain intensity. So the first part of the week we will see continuing rain across the southern half of the U.K (yipee) but the main event is at the end of the week as an area of deep, low pressure arrives off the edge of Co. Kerry and then moves across Ireland and the U.K through Friday into Saturday. As is common when a low pressure moves across the U.K, its leading edge brings south westerly winds and its trailing edge, north westerly winds, dropping the temperature over the weekend. This will probably be the first named storm of the autumn / winter, 'Storm Austen' me thinks is first up. Hot on its heels is another low pressure system, this one sitting a bit further north so more in the way of rainfall for the weekend across all parts of the U.K for the weekend.
This event with a random COL pulling the Atlantic jet stream further south may ('may') be the catalyst to more consistent rainfall for the autumn / winter. Time will tell.
Owing to the late start to autumn rainfall, we have a problem and that is the time available to recover water levels in our aquafers, rivers and reservoirs before we go into next spring.
If I compare 2026 with 2025, you can see what I mean....
The annual reports for 2025 and 2026 y.t.d from our default location @ The Oxfordshire highlights this well.
Last year, July - October provided 221.2mm of rain, this year to date, that figure is 61.2mm, a good way down. For the same time period, in 2025 we lost 291.5mm through evapotranspiration and for 2026 (Oct to date), that figure is 362.7mm.
So in a nutshell, we are down 160mm of rainfall and up 70mm of E.T, just for this period.
The situation is clearer to see if we graph out the cumulative soil moisture surplus and deficit for the 2026 v. 2025.
So you can see in 2025, we actually reached the maximum soil moisture deficit for the year in August (-293.6mm), and then we started to head back towards a positive soil moisture situation ending the year around -100mm.
In 2026, the situation is very different, the soil moisture deficit is still increasing (albeit slowly now as daily E.T levels drop with cooler temperatures and shorter day length). Currently we are sitting at -420.2mm, which means we would need 320mm of rain to fall between now and the end of the year to recover to the same point as 2025.
That's a big ask meteorologically.
That said, the meteorologists are predicting a wet autumn before the potential of a cold, dry start to 2027. In my mind though, all the time that heat sits out in The Atlantic and keeps the jet stream position further north, we aren't going to get close to it rainfall-wise.
Let us hope for the southern half of the U.K at least that this week's re-engagement of the Atlantic air flow isn't a temporary one.
All the best.
Mark Hunt
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