There are two changing influences on the North Atlantic jet stream that are having opposite effects, but taken together may partly explain what is going on regarding increased summer rainfall in NW England and SW Scotland and reduced summer rainfall and higher temperatures in SE England:
1) Poleward expansion of Hadley cell ie tendency for Azores High to extend slightly further North than previously
2) Arctic amplification(*) causing the Jet Stream in the North Atlantic to be further South than previously in summer
I posted several weeks ago that 4 out of the last 5 Junes feature in the top 20 wettest Junes in the NW England rainfall series [length of record = 148 yrs]
It is possible that (1) + (2) taken together are causing summer low pressure systems to follow a narrowed path, providing other factors align - ie there will still be occasional variations from this such as June & July 2018.
* Arctic amplification is a term used referring to the fact that the arctic is warming faster than the rest of the world

There are two changing influences on the North Atlantic jet stream that are having opposite effects, but taken together may partly explain what is going on regarding increased summer rainfall in NW England and SW Scotland and reduced summer rainfall and higher temperatures in SE England:
1) Poleward expansion of Hadley cell ie tendency for Azores High to extend slightly further North than previously
2) Arctic amplification(*) causing the Jet Stream in the North Atlantic to be further South than previously in summer
I posted several weeks ago that 4 out of the last 5 Junes feature in the top 20 wettest Junes in the NW England rainfall series [length of record = 148 yrs]
It is possible that (1) + (2) taken together are causing summer low pressure systems to follow a narrowed path, providing other factors align - ie there will still be occasional variations from this such as June & July 2018.
* Arctic amplification is a term used referring to the fact that the arctic is warming faster than the rest of the world

I think this is indeed exactly what has been posited in some research papers - not so much the point about the jet going South (because that varies by longitude, it's been further North in other regions) but more that the subtropical highs are expanding North but the Northern edge of the polar front is not, so the Ferrel cell itself is becoming narrower.

The trends imply as much. It may not be the case that the NW / Scotland is getting more zonal weather than before, but just that it's getting the same as before, is too far from the Azores high to benefit from expansion, and the increased moisture content in the air through higher SSTs is enough to boost rainfall and cloudiness.

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There are two changing influences on the North Atlantic jet stream that are having opposite effects, but taken together may partly explain what is going on regarding increased summer rainfall in NW England and SW Scotland and reduced summer rainfall and higher temperatures in SE England:
1) Poleward expansion of Hadley cell ie tendency for Azores High to extend slightly further North than previously
2) Arctic amplification(*) causing the Jet Stream in the North Atlantic to be further South than previously in summer
I posted several weeks ago that 4 out of the last 5 Junes feature in the top 20 wettest Junes in the NW England rainfall series [length of record = 148 yrs]
It is possible that (1) + (2) taken together are causing summer low pressure systems to follow a narrowed path, providing other factors align - ie there will still be occasional variations from this such as June & July 2018.
* Arctic amplification is a term used referring to the fact that the arctic is warming faster than the rest of the world

 

Funny you should mention the Hadley Cell, I was just thinking of that as I read through this thread from the start. 

Last month caught my attention with respect to that. There was predominantly very low atmospheric angular momentum due to a developing La Nina event, which usually corresponds to more rainfall than usual right down into France (with temps varying around the average).

Yet, the southern reach of anomalously wet weather was southern Wales eastward and it was actually drier than usual in the far south (I saw about half the usual rainfall here).

An outcome that fits the notion of Hadley Cell expansion well.

 

Your suggestion regarding Arctic amplification, I'm less sure about. Arctic amplification is likely weakening the polar jet stream (on average, across the weeks and months), but that doesn't necessarily mean it moves southward. In fact, as amount of cold air the Arctic can support reduces, there ought to be an overall northward shift as the colder 'pool' shrinks in spatial coverage.

This, I believe, is where the North Atlantic sea surface temperatures are taking the wheel to steer things the other way. The central North Atlantic has been persistently cooler than its surroundings, often by several °C, for nearly all of the the past 5 years. This is likely to do with freshwater influx from Greenland ice melt interfering with the Atlantic Meridional Overturning Circulation (AMOC), of which the surface component is the Gulf Stream. 

This has shifted the warm/cool boundary southward in the North Atlantic.

 

The outlook for the next decade is likely to be one largely decided by the Hadley Cell expansion and Arctic amplification competing with that. There are striking possible outcomes of the battle - the southward-shifted North Atlantic polar jet may become more restricted to over the ocean, leading to an increased incidence of troughs west of Europe working in tandem with highs over Europe to bring high-end heatwaves.

Perhaps, the rapidly developed, yet intense hot spells of 2019 & 2020 are demonstrations of that starting to become a feature already.

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Just to illustrate the fact that we are at the edge of a significantly warmer continent, below shows the change in JJA 2m Temperature 1995-2019 minus 1970-1994.

  

The change in climate in the UK from 1961 to 2016 can be seen by looking at these trend maps for Annual Mean Temperature, Annual Rainfall and Annual Sunshine hours as total trends for the 56 years in the range

For Temperature and Rainfall there is quite clearly a change to warmer, drier conditions in the SE quarter of the UK to less warm(er) and wetter conditions moving west and north. This is within an overall increase in both temperature and rainfall in the UK as a whole

The trend for sunshine hours is much more confusing however. It would appear that the biggest gainers are the Midlands and North East of the UK presumably folkowing the trend for less heavy industry in those areas.

I am puzzled about the big increase in East Kent/South Essex whilst parts of the mid South od England in Hampshire, Dorset and Devon have shown a decrease. Anyone know why this should be

 

clickable maps below

 

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The trend for sunshine hours is much more confusing however. It would appear that the biggest gainers are the Midlands and North East of the UK presumably folkowing the trend for less heavy industry in those areas.

I am puzzled about the big increase in East Kent/South Essex whilst parts of the mid South od England in Hampshire, Dorset and Devon have shown a decrease. Anyone know why this should be

An increase in flows over the Downs, maybe, causing clouds to break up? Anything between WSW and ESE will do the trick for various parts of Kent.

Thank you for posting the charts, they confirm that it's become a fair bit warmer, a lot sunnier and drier down here since the 60s (and anecdotally since the 80s, too!)

 

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Great maps 

 

MBY has seen a slight increase in rainfall, slight increase in sunshine, moderate increase in temps

 

DOn't know what to make of that, really. Can understand the temps (in part due to milder winters) and rainfall (some prolonged wet periods, including most of the summers that fell 2007-2012), but more sunshine? That surprises me.

 

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Given that it's only going to get worse I wouldn't use the word 'interesting'.  I won't say much more because we will end up with a climate change thread but the implications are troubling with likely water shortages linked to population growth and climate change and population growth accentuated by climate refugees.

Even more scary is that the rate of change will accelerate because we're not cutting GHG emissions at anything like the rate required.

If you think Covid has been scary just wait for the waves of climate change to just keep rolling in.

And here’s the thing. While we clean the air, the earth is heating at a faster rate?

While we reduce the amount of gasses, we are reducing sulfate gasses which cool the earth. While these gasses only remain in the atmosphere for at best a few weeks, greenhouse gasses can remain for years, hundreds of years. With our cleaning, we are increasing the differential between the gasses causing a heating imbalance, a reason why we are warming faster.

I would prefer fossil fuels gone, but I don’t know what the answer is. It could be without thinking about the other side of the coin, the innocent intentions of cleaning the air is actually making things worse. How long will this go on for? We need something to keep the remaining greenhouse gasses in check.

 

 

And here’s the thing. While we clean the air, the earth is heating at a faster rate?

While we reduce the amount of gasses, we are reducing sulfate gasses which cool the earth. While these gasses only remain in the atmosphere for at best a few weeks, greenhouse gasses can remain for years, hundreds of years. With our cleaning, we are increasing the differential between the gasses causing a heating imbalance, a reason why we are warming faster.

I would prefer fossil fuels gone, but I don’t know what the answer is. It could be without thinking about the other side of the coin, the innocent intentions of cleaning the air is actually making things worse. How long will this go on for? We need something to keep the remaining greenhouse gasses in check.

Heating through global brightening with reduction in aerosols is a one time hit. Like cold turkey. Whereas CO2 warming is a long term, cumulative issue. So best get it dive with and at the same time save lungs across the developing world.

On the maps: I notice an increase in sunshine and summer index along the North Sea coast of Lincs and E Yorks which to me implies an increase in westerlies.

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Great maps 

 

MBY has seen a slight increase in rainfall, slight increase in sunshine, moderate increase in temps

 

DOn't know what to make of that, really. Can understand the temps (in part due to milder winters) and rainfall (some prolonged wet periods, including most of the summers that fell 2007-2012), but more sunshine? That surprises me.

 

Yes there was a lot in that sunshine chart that surprised me too.

I think the trend increases in many areas since 1961 has more to do with the closure of heavy industry than the weather.  Looking at the +400hrs/year improvements for the Midlands, NE and Parts of SW Wales it looks like the close down of the Coal and Steel industries more than the weather synoptics so perhaps this chart is more of general interest than climate change !

It still doesn't explain why Ramsgate in East Kent logged an improvement of +310 hrs/year (and I went back and hand checked this one !) whilst some other spots further west near the S Coast in Devon and Dorset showed negatives (reductions)

 

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Heating through global brightening with reduction in aerosols is a one time hit. Like cold turkey. Whereas CO2 warming is a long term, cumulative issue. So best get it dive with and at the same time save lungs across the developing world.

On the maps: I notice an increase in sunshine and summer index along the North Sea coast of Lincs and E Yorks which to me implies an increase in westerlies.

How long is this warming going to go on for though Tim? I’m all for getting things ‘sorted’, but when does the rate of increase start to subside? It could get worse! Over the last two decades the graphs don’t lie. If things carry on as they are we will reach the precipice quicker than we thought through the actions of Greta & co.

Has everything really been thought through here?

Love those maps. Remind me of the old teletext ones.

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How long is this warming going to go on for though Tim? I’m all for getting things ‘sorted’, but when does the rate of increase start to subside? It could get worse! Over the last two decades the graphs don’t lie. If things carry on as they are we will reach the precipice quicker than we thought through the actions of Greta & co.

Has everything really been thought through here?

To quote an old saying which I have seen used in this forum in the past more than once, "The road to hell is paved with good intentions".

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Looks like we might have even seen a decrease in rainfall here. A 1.5 to 2 degree temperature increase isn’t too shabby either.

I feel like sunshine has increased more outside of the summer months, particularly spring.

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We've lived in the SE since 1976 (and in my case also before 1960). Thunderstorms were a regular occurrence, either drifting up overnight from France or marking the end of a hot spell as a cold front swung in from the W. For the last 20 years, any thunderstorms seem to have been home-grown, i.e generated over the UK and drifting N from there. The weather expert used as a go-to by Radio Sussex, Ian Curry, was making the same point last weekend, along with the increasing frequency of summer drought S of London.

Hoping to  be proved wrong with a good storm on Monday!

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While people in the SE sweat this weekend, we'll have our jumpers on in Edinburgh. Still got my winter quilt on up here 😂

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Our maxes won't be as high as your min's 😲

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How long is this warming going to go on for though Tim? I’m all for getting things ‘sorted’, but when does the rate of increase start to subside? It could get worse! Over the last two decades the graphs don’t lie. If things carry on as they are we will reach the precipice quicker than we thought through the actions of Greta & co.

Has everything really been thought through here?

Sorry but you'll have to explain how the actions of people trying to raise the profile of the growing and serious threat from climate change are making it worse? That is just a bizarre suggestion.

It seems pretty bl**dy obvious to me that we are all responsible for our use of fossil fuels and causing the resulting CO2 emissions.

The rate of increase will not lessen: we have pushed the concentrations of GHGs to levels not seen for 3-5 million years and they're still climbing.

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We've lived in the SE since 1976 (and in my case also before 1960). Thunderstorms were a regular occurrence, either drifting up overnight from France or marking the end of a hot spell as a cold front swung in from the W. For the last 20 years, any thunderstorms seem to have been home-grown, i.e generated over the UK and drifting N from there. The weather expert used as a go-to by Radio Sussex, Ian Curry, was making the same point last weekend, along with the increasing frequency of summer drought S of London.

Hoping to  be proved wrong with a good storm on Monday!

I was only thinking today about the storms of years past. You’d go to bed only to be woken in the early hours by all hell let loose as a storm had trundled up from France on warm sultry nights. Nowadays, a lot of storms seem to be deflected to the east with only the Kent crew seeing some action.

 

Sorry but you'll have to explain how the actions of people trying to raise the profile of the growing and serious threat from climate change are making it worse? That is just a bizarre suggestion.

It seems pretty bl**dy obvious to me that we are all responsible for our use of fossil fuels and causing the resulting CO2 emissions.

The rate of increase will not lessen: we have pushed the concentrations of GHGs to levels not seen for 3-5 million years and they're still climbing.

Pretty easy really. If you are reducing gasses, both warming greenhouse and cooling sullfates, you, we are creating an imbalance because the gg’s are harder to get rid of and stay up in the atmosphere a lot lot longer, perhaps hundreds of years compared to just a few weeks from sulfates.

While we reduce gasses, the differential grows, the cooling gasses are less, the heat increases. What else explains the warming charts over the last two decades. They don’t lie.

As we clean the air, we are in fact making the earth warmer. I am not sure what the answer is, but where does this end? When the UK reaches 45c, maybe more, we don’t know.