Derecho

danm I think some CET records could be under threat if this warmth persists. Check out my post in the CET thread but the 06z GFS is similar to the 00z EC control, which has a CET of 14.9C up to the 16th. This is all clearly a fine line because if the low ends up sat over us it will be a very different story but the sinking of the low southwards keeps warm air entrenched. Also just a side note but EC00z ensemble member 10 is the most extreme I have seen for the UK. It constantly has the warm air to the south feeding in for the entire later stages of the run, elevating maxima to the high 20s widely with minima in the high teens. After the 16th there are consistently daily CET returns in the low to mid 20s. Won't come off but I had to point it out because it was extraordinary.

Yesterday's CET hasn't been updated yet but I'm looking at the model output with great interest at the moment because if the Scandi high remains stubborn after next weekend some very high CET returns look likely. The EC 00z control keeps warmth going up to the 17th and we get some daily CETs in the 18s for a brief time. If that verified, by the 16th we could have a CET of 14.9C. Cooler air comes in later but the 1833 record is not too far away. Also worth noting P10 is off the scale and keeps the heat going through the entire run... I think that has to be the most extreme ensemble run I have seen.

Certainly is, if we hold onto the warmth I think it could turn very wet and thundery indeed. I'm leaning towards the cooler Atlantic influence returning early next week though as you say.

Daniel* Do you think the Scandi high could complicate things? EC OP and the AIFS is quite bullish in bringing the cooler air after next weekend but UKMO and GFS operationals look a bit messy at this stage. Probably worth noting that the GFS ensemble mean is more bullish at bringing an Atlantic influence back compared to the OP but there's still quite a few members that extend the warmth past next Sunday.

CET returns from the 00z EC this morning. A very warm near term outlook with the high returns from the 7th to 12th not that far removed from the ensemble average. The 13th to 17th are cooler then the ensemble mean so scope for some high values here. I think mid to high 13s looks likely up to the 15th but anything could happen after the 12th really. EC brings back some Atlantic influence after this date. GFS 06z brings cooler air from the NE while the UKMO at T168 looks really warm. Interesting that both the GFS and UKMO are showing pressure rises over Scandi, it could very easily prolong the warmth that is currently expected to shift on the 12th.

CET returns from the 00z EC control, as expected it is a warm outlook. The control is definitely on the warm side from the 11th to 14th but I wouldn't call it an outlier. The result if it verified would be an impressive CET of 14.5C up to the 15th but as recent model output has shown, this output should be taken with a pinch of salt. Today for example looks likely to return a pretty average CET value.

Metwatch I think the challenge with such long series of temperature is the need for overlapping observations to homogenise the data. London is a lot more handy in this regard as there were many observers going back to the 18th century. Armagh has daily temperatures going back to 1796 (I think!) and Edinburgh has monthly means going back to 1764 I think but I'm not sure there are many other stations in the UK that have overlapping stations going back that far (Radcliffe Observatory in Oxford is another). Maybe a UK series based on Edinburgh, Armagh and London would be more handy though only London and Armagh have daily data going that far back for the duration.

B87 It's not the raw temperature used to calculate the CET mean, it's the anomaly from the average at the London station that is applied to the CET mean. It doesn't matter how much warmer London is compared to the CET mean when you are basing the CET mean off station anomalies unless you see regional variations in temperature anomalies associated with persistent weather patterns.

B87 The raw temperature was not used to calculate the CET but the anomaly from the station average. Here is a more detailed explanation from another thread I posted on: To follow my earlier post, the temperature anomaly in London will have equated to 3.9C above the 1961-90 average there, the raw value would not have been 15.1C that appears in the CET series. The CET value would have been 11.2C + 3.9C London anomaly = 15.1C. If the raw temperature for London was used you'd see a long sustained upwards spike in CET before it became 3 stations, outside of winter and especially for summer months as SE England is warmer. In order to beat the 1833 record, you'd need an average temperature anomaly of +3.9C at Rothamstad, Pershore College and Stonyhurst, rather then just a +3.9C temperature anomaly over the London area. That would be difficult even in todays climate, every once in a while you get a month of truly exceptional weather.

Sprites Indeed, it's a very unusual synoptic either way. Shame we can't see this kind of setup for storms more in the summer. It seems like anything thundery is heading further north of here though unfortunately.

reef Yup I've been saying that to others myself. I've never seen it here. Doesn't feel stormy here either. Just 11C, cloudy and calm. Bizarre.

To follow my earlier post, the temperature anomaly in London will have equated to 3.9C above the 1961-90 average there, the raw value would not have been 15.1C that appears in the CET series. The CET value would have been 11.2C + 3.9C London anomaly = 15.1C. If the raw temperature for London was used you'd see a long sustained upwards spike in CET before it became 3 stations, presumably, especially for summer months. In order to beat the 1833 record, you'd need an average temperature anomaly of +3.9C at Rothamstad, Pershore College and Stonyhurst, rather then just a +3.9C temperature anomaly over the London area. That would be difficult even in todays climate, every once in a while you get a month of truly exceptional weather.

I doubt this, they will have taken the temperature anomaly from that station to calculate the CET. The uncertainty comes in when you've got regional differences in anomalies. So for example. 1961-1990 May CET: 11.2C (I think) London station: Anomaly = 2C above 1961-1990 average. CET = 13.2C Now if you had Stonyhurst at the time and the anomaly there was only 1C above average, you'd have a CET of 12.7C (+2C anomaly in London, +1C at Stonyhurst equals an average of +1.5C assuming equal weightings). Over long time scales any discrepancies should even out generally but the uncertainty for an individual month in those earlier periods will be higher and there may be a higher standard deviation too.

raz.org.rain I guess the westerlies in 2015 were influential enough to keep the heat further SE. There is definitely evidence to support the theory that the cold blob encourages more heat to build over Europe. 2015 however was particularly unusual however in that the temperatures to the south of Greenland were record breakingly cold. This likely allowed for the cool air to influence the synoptics over a wider area. The brief period the westerlies relented was when we saw that 1 day plume at the start of July. Interestingly I recall a NAVGEM run going for 44C in Cambridgeshire in the lead up to that. GFS also had a few runs that saw temps above 40C. I remember it very well as it was the first time I saw 40C on a model run over the UK. Only other times after that were August 2018 and July 2019 before July 2022 of course came along. Some model runs indicated that plume would last several days but in the end the heat only moved across us on the 1st July before it waned.

Yeah 2015 had a reasonable June when I was in Southampton. First half of July was decent but the second half was awful, especially when I was in Norfolk. August I was back in Southampton again and that was a bit of a washout.