Higher Ground

Snow falling over Lickey Hills near Birmingham yesterday:

Video of snow on the Lickey Hills yesterday...

You're actually making the same point as me with your first para. I don't think the Met Office would dispute research showing that both city-wide UHI and local heating effects can be very significant (e.g. up to 5C in extreme cases for UHI at night-time). We may be considering different questions here - perhaps I've misunderstood the history of the debate on these forums as I'm a rare visitor. My question would be, how much warmer are the recent record max temps at Heathrow than they would be if the site was in a location away from the airport with average levels of vegetation/trees around etc. There is a case to answer in this context, and it is nothing to do with whether Heathrow site meets official guidelines. I don't believe I've accused the Met Office of anything. I won't post any more on this, as I know how annoying it can be when the model discussion is derailed. Please don't think I'm trying to stir things up; the opposite is the case. I think dispassionate analyis of UHI and hyper-local warming effects is really useful, and I'm very receptive to anyone who engages in this, whatever their findings.

Well there's a couple of extreme views which are common: (1) Runways etc cause all the excess heat, end of story; (2) We can essentially ignore such factors as tarmac. Expressing one of these views will tend to bring out people with the opposite view. But hyper-localised heating effects are real, and often bigger than city UHI effects. For example in the Feb mini-heatwave last year, the thermometer in my back yard recorded 26C in the shade near to sunlit fence and decking, even though the temp at local wx stations only got up to the high teens. So there seems to be at least a case to answer here. As Daniel (I think it was?) suggested, I'd like to see a further breakdown of observed temps between Kew and Heathrow, and for more recent years. Adjusting for how sunny it is around typical time of max temperature, wind speed/direction etc.

Ah yes - in my defence I thought looking at the title of the bar chart: "Average monthly temperature" and the closeness of the Kew and Heathrow temps was enough to extract the vital information.... Glad you corrected me, and useful info in your post, thanks

Tarmac at Heathrow causing higher max on sunny days would also likely cause lower min on clear nights - especially as Kew more surrounded by city (UHI more pronounced at night-time as I understand it). Hence similar mean temps but Heathrow breaks the max temp records?

Yes I was considering that possibility quite seriously, especially if my hunch is correct that relatively cool minima seem to result in a bigger correction sometimes. However, the last few model runs have increasingly seemed to suggest that chances will be scuppered at the final hurdle - even if the night of 30/31st is average under high pressure, a hot sunny day on 31st would be likely to tip the balance away from a more notably low CET.

Interesting comparisons thanks! I've just been on a trip down memory lane to a time when I used to follow these things a little more closely. Specifically I found the July CET thread for 2007! Makes for fascinating reading. A couple of points caught my attention: Firstly, CET was 15.5c to the 21st July in 2007, so we are actually 0.2c cooler at the same point in July 2020. I'm guessing it will be tough though not impossible to remain cooler for a few days longer... https://www.netweather.tv/forum/topic/39130-july-cet/page/12 Secondly, people seemed almost more surprised by the cool temperatures then, e.g. a comment in the 2007 thread mentioned that "Philip Eden in today's telegraph was saying that it will be the coldest July for England and Wales since 1993, for some parts it could even be the coldest since 1988, quite some feat in these times of rising temperatures..." https://www.netweather.tv/forum/topic/39130-july-cet/page/15/ Oh and thirdly there was still talk of a possible plume or 'much warmer southerly draw' in the comments up to 19th July 2007! https://www.netweather.tv/forum/topic/39130-july-cet/page/11 (Similar this year in the model thread - significantly warmer weather to end the month still possible, but has been becoming less likely...)

This is something I had been looking at myself - noticed a similarity to 2007 with both CET and arctic sea ice area: CET June and July 2007: 15.1c and 15.2c CET June and July 2020: 15.3c and 15.3c (provisional to 21st) Arctic sea ice area June 2007: 8.2 million sq km Arctic sea ice area June 2020: 8.4 million sq km https://nsidc.org/data/seaice_index/bist ('Sea Ice Conc' gives area) - Note that sea ice more concentrated this year hence higher area but lower extent in June. Probably both lower now due to big July losses. - CET averages for first half of year were 9.7c for January-June 2007 and 9.6c for January-June 2020 https://www.metoffice.gov.uk/hadobs/hadcet/cetml1659on.dat

Well let's just wait and see what happens in a few weeks time... or less!?

Snow falling on top of the Lickey Hills this afternoon (close to 1000 feet / 300m). Very close to settling for a while. Video

https://www.metoffice.gov.uk/hadobs/hadcet/data/download.html

Re: whether summers are getting hotter - by my calculations: For the past 10 years (2009-2018) Mean annual max CET = 29.0C Mean summer CET = 15.9C Previous 10 years (1999-2008) Mean annual max CET = 29.3C Mean summer CET = 16.1C Decade before that (1989-1998) Mean annual max CET = 28.9C Mean summer CET = 16.0C

Even the biggest drifts didn't quite make it until the second Beast From The East here - though it was a close call, just a couple of days. But then again you had the Pest From The West to help tide you over, from what I remember...

Still good drifts here as well. Amazing isn't it how they've almost replicated the drifts (in the same places) from the last Beast From The East - such similar events