John S2

In answer to the question about comparing July 2020 & July 2023, here in NW England there was a considerable difference between the two. July 2023 is one of the most vile summer months I have experienced. It is the wettest July in the NW England precipitation series [POR=151 years] with 174mm. July 2020 was nowhere near as bad with 110mm which comes in as 36th wettest.

I live in NW England. A good year is a dry one, and it is particularly important to me that March & September are good. So: best year of my lifetime - 1973. honourable mentions - 1997 & 2003, also liked 1969

CryoraptorA303 Regarding your reference to the 'cooling mechanism' of La Nina, my understanding is that it is El Nino that is the cooling mechanism in the sense that some of the excess heat brought to the surface during El Nino episodes is lost to space. The oceans absorb more heat during La Nina episodes. Interestingly the Medieval Warm Period is believed to have been dominated by La Nina episodes, although the MWP was a regional rather than global anomaly.

There appear to be regional differences in summer trends. In the NW England rainfall series [POR=151 years] 9 of the 24 summers this century feature amongst the top 25 wettest, but this trend is not present in the SE England series.

Hadley cell expansion, in isolation, would lead to drier summers particularly in the South - but there is more going on. There is a theory that Arctic Amplification - the fact that the Arctic is warming at a faster rate than the rest of the world - acts to send the jet stream further South. This is a battle between two conflicting influences. Since 2007 there has been an increased frequency in summers with negative NAO, indeed all 18 months in the awful cluster of summers 2007-2012 had negative NAO. It should be mentioned, however, that there are some good summer months with negative NAO so it is only part of the picture.

Could you enlighten us why 1973 is considered an anologue? It had a lovely dry and anticyclonic start to the year. E&W rainfall for 1973: Jan - 46mm, Feb - 45mm, Mar - 23mm

Both 1986 & 1988 had a good June, but as someone who likes my summers dry, there is no contest here for summer as a whole. 1986 is easily the best because it was the driest of the four by a big margin in my region [NW England]. Rainfall figures for NW England for the summers are 1986 - 214mm, 85/87/88 - 324/336/330 1985 was vile and was even worse in Southern Scotland where 1985 had the 2nd wettest July & 2nd wettest August on record contributing to a massive 513mm for wettest summer on record [even worse than 2012]

Rating of summers is controversial because the synoptics leading to a good summer month in areas such as North Lancashire, Cumbria and SW Scotland including Glasgow can be quite opposite to patterns more favourable to SE England & East Anglia. Also opinions vary about what makes a good summer. Personally I want dry weather and a sky that is a proper blue, not the depressing haze that comes with plumes from the South. So, with my bias declared, I nominate the following summers [from my lifetime] as underrated and give their rank in the NW England summer rainfall series [POR=150 years] as evidence. 1984 [7th driest], 2021 [15th driest]. 1996[20], 1969[21]

In answer to the question about causes of sea level rise, the main contributors appear to be: 1) Melting of land based ice 2) Thermal expansion of the oceans 3) Reduction in water held on land - eg reduction in size of lakes and soil moisture I have not been able to find a definitive answer on the percentages due to each of the above. Melting of arctic sea ice should have no immediate effect on sea level, but presumably if the summer trend is downwards then increased heat absorption will be a positive warming feedback.

Addicks Fan 1981 I am puzzled how some of these years are considered to be matches. 1964 is the driest winter in the Central England precipitation series [POR=150 years]. Winter 1973 was also very dry [26th driest]

Deniers have changed their tactics, and unfortunately they are winning in the sense that national politicians continue to make very bad policy decisions. Deniers haven't gone away, but rarely criticize the science these days. They focus instead on short term arguments about costs and jobs. 15 years ago I regularly posted counter arguments with evidence in response to deniers when they were criticizing the science in a Climate section that existed at the 'other place'. My own belief about deniers is that their main issue wasn't with the science even back then, but an irrational hatred of the type of collective action necessary to combat it.

I am not convinced that a significantly cold winter month is now 'long odds', even though the odds will have changed. There is a counter argument that we may see a colder winter at a similar point of the double sunspot cycle that 08/09, 09/10, and the famous Dec 2010 occurred. This would presumably be around 2030 ? Also it doesn't matter how warm the Atlantic is if the wind is blowing from the NE. Nevertheless, a warmer Atlantic and northward displacement of Azores high may help reduce the frequency of winter blocking in locations which bring cold conditions to the UK so it will be interesting to see if solar factors can outweigh this. I would remind members that there was a school of thought about 'modern winters' back around 2005, but only a few years later we had the above mentioned trio.

Agree. A good year countrywide - almost everywhere had above average sunshine, exceptionally so in many areas. Our best chance of something similar to 2003 would be if ENSO simply returned to neutral from the current Nino, but unfortunately a flip to La Nina appears to be statistically more likely. Given the unpredictability of ENSO states, however, it is possible.

For brevity I didn't make it clear what I meant by a 'bad' month. I live in NW England, where July 2023 was the wettest July on record and Sept 2023 had double the average rainfall in some places. Excluding periods of extreme cold, [lack of] rainfall is far more important than temperature in how usable a month is for outdoor activity. In my area [NW England] 2022 & 2023 have been generally poor, contrasting with several months during 2021 [including a controversial summer weatherwise] which were more usable. I trust this paragraph provides sufficient statistical support.

The main concern I have about 2024 is a likely flip from El Nino to La Nina. If a strong transition between these states coincides with summer then this could be bad news. The following is a guess based on the above, possible SSW early January, plus other factors: Significant cold mid-Jan to mid-Feb. Notable heatwaves second half of March plus mid-May. Pressure falls last week of May heralding an unsettled June. July & August nothing special but nowhere near as bad as July 2023, possible brief July 2022 type plume but less exceptional. Decent September - much more anticyclonic than the disappointing Septembers of 2022 & 2023.

Despite my previous post, I do agree with the quote from MP above. Pattern matching is only one indicator, and the current combination of 'drivers' is indeed unprecedented.

Pattern matching is definitely not 'useless'. For example, Septembers that can broadly be described as Anticyclonic Southwesterly - typically calm with temperatures either above average or close to average - are usually followed my mild winters. There have been a small number of exceptions, but they are rare. Sept 2023 was definitely not in the above category as it was stormy with widely above average rainfall.

Jules216 - what made you reject 2009 from your analogues? Just curious, not saying you're right or wrong to do so.

The first part of this sentence is correct, but the assertion about 'random' is quite simply wrong. The fact that correlations exist does not mean that a connection be considered as a rule, but as a useful indicator when considered with other factors.

September synoptic patterns are a good indicator for the following winter. Septembers where the main pattern can broadly be described as anticyclonic southwesterly, that are not wet and not cold, are usually followed by mild winters. Wet Septembers that follow unusually dry Augusts are usually followed by cold winters [I did a detailed post on this combination last year]. I don't know the reason why the October connection is different, but it is. The correlation between October NAO and the NAO for the following winter is inverse [but I wouldn't rely on this indicator in isolation] A particularly good example of this is Oct 1978, which had strongly positive NAO, and winter 78/79.

I suspect this is a little known fact, but July 1991 is the warmest July on record at Tiree. An interesting month synoptically.

My current thoughts on summer 2023 is that it will not be similar to any of the last 3 summers because I am expecting considerable variability of weather type. Conversely, the last 3 summers each had a persistent theme: 2020 - 3rd wettest on record [out of 150] here in NW England. All 3 months wet. 2021 - Quite special in NW England further North than Manchester, contrasting with poor summer in SE England 2022 - Consistently warm/hot with the good conditions expanding northwards as summer progressed The main reason to be positive about summer 2023 is that we will be transitioning from La Nina to El Nino, but I don't think it is guaranteed that the El Nino will be particularly strong. The years I have been looking at all had considerable variability of weather type from month to month, most having at least one very good month and one poor/abysmal. No common theme about which month will be best or worst. Hope to post more detail in due course. The Atlantic SST anomaly pattern is interesting.

Living in a fairly wet region - NW England - many of my favourite months tend to be the dry ones. When ranking months by rainfall, I have used the Hadley NW England series which has a period of record of 150 years. Jan 2022 - 13th driest, good for outdoor activity Feb 2019 - heatwave March 2017 Apr 2020 & May 2020 - lovely pair of months, wasted due to lockdown June 2021 - Exceptional month, warm dry & sunny. 7th driest in 150yr series. 2021 was a particularly good summer overall for areas in the NW further North than Manchester July 2018, Aug 2022, Sept 2014 Oct 2016 - a rarity. October is often a write off for outdoor activity here in the NW, but Oct 2016 was special with winds from NE quarter unusually frequent. 7th driest out of 150 Nov 2021 & Dec 2016 - least bad of a poor collection

Looking at Septembers from 1969 to present, most of the El Nino Septembers were quite dry. More variability for Oct & Nov with some years wet.

This statement is supported by the evidence, looking at ENSO indices since 1950. Two distinct groups that started the year with La Nina and finished the year with El Nino. Group (a) ENSO neutral during the summer (b) El Nino already arrived by summer: Group A - 1976, 2006, 2018 Group B - 1965, 1972, 2009