Summer 2015

[reef]

I think this pattern was truly amazing! To record 36.7C this early in the summer, especially when the hot uppers weren't really sustained for that long, and on a fairly cloudy day is astounding. Imagine what this pattern would have done in late July/early August?

 

Of course it has been a good spell, the record wouldn't have fallen otherwise. What I mean is, if we had had the same uppers with a direct southerly, the cloud would have stayed out west and there would have been no sea breezes meaning we'd have probably threatened the 2003 record and more areas would have joined in. Synoptically it hasn't actually been the best, but due to the sheer warmth of the upper temps we still managed to beat the July record.

 

I imagine with these 22-23C 850hPa uppers and a synoptic setup like August 1990/2003 we'd have been pushing 40C somewhere today and 35C would certainly be much more widespread.

[audiotech]

Fantastic hot day. My thermometer hit 34.2 C mid afternoon and it certainly felt it out and about in it. A proper full day of heat as well, not the usual peaking at 30 C for half an hour at 4pm, this time it was 30 C + all the way from 11am until evening. The surprising thing was that even though there were some quite lengthy cloudy periods it didn't seem to really surpress the temperatures at all. Paying for it now though with sleeping very difficult; the bricks will take a while to radiate all that heat away.

[Relativistic]

To be honest, I'm surprised July has never recorded 37C+ before, given that the June and September records are pushing 36C, and that the height of Summer is in late July/ early August. The July record afterall is less than a degree hotter than the June and September records, and the August record is a full two degrees hotter. That just doesn't seem right!

[March Blizzard]

To be honest, I'm surprised July has never recorded 37C+ before, given that the June and September records are pushing 36C, and that the height of Summer is in late July/ early August. The July record afterall is less than a degree hotter than the June and September records, and the August record is a full two degrees hotter. That just doesn't seem right!

Perhaps the 36-38C range is around the upper limit for the UK, regardless of the time of year, with late June-early September the window for it.

Kinda like how we have recorded -27.2C in every winter month, with late December to mid February the window for that, but haven't managed to drop lower.

You get the impression it would take something extremely exceptional to reach either 40C or -30 here, with a "perfect storm" of factors all having to come together.

I always find it odd when places abroad can completely obliterate records, by 5-10C, or even more in cases, yet in the UK we usually stumble over the line by 0.1C or so.

[Relativistic]

Perhaps the 36-38C range is around the upper limit for the UK, regardless of the time of year, with late June-early September the window for it.

Kinda like how we have recorded -27.2C in every winter month, with late December to mid February the window for that, but haven't managed to drop lower.

You get the impression it would take something extremely exceptional to reach either 40C or -30 here, with a "perfect storm" of factors all having to come together.

I always find it odd when places abroad can completely obliterate records, by 5-10C, or even more in cases, yet in the UK we usually stumble over the line by 0.1C or so.

What such records are you referring to? I don't really know anything about weather records in other countries. Perhaps these places haven't been recording weather data for that long, and so records are more prone to being smashed rather than just nudging over?

[Milhouse]

Perhaps a little warmer here today than it was yesterday due to the absence of any onshore breeze. It really does feel very warm and humid outside.

[reef]

Perhaps a little warmer here today than it was yesterday due to the absence of any onshore breeze. It really does feel very warm and humid outside.

 

 

Yes, it makes a big difference. Ironically today could be warmer than the last two days for us and Saturday looks like our best chance at 30C as the wind turns westerly with warm uppers just hanging on.

[summer blizzard]

Was lovely this morning however humid now. Definitely getting showers looking at the radar though.

[hillbilly]

What an amazing 24 hours,watching the thermometer rise yesterday was great only to go to bed last night and miss out on once in a lifetime event.I heard the rain lashing on the windows and almost got up to look but the next thing I remember was morning.I went to my friends just a couple of miles up the road and he told me about a hailstorm just before midnight that were bigger than golfballs,he had a couple of dents in his car roof and the neighbours green house had a broken pane.I did not realise it could do that in this country ,amazing and I missed it ,am told it made the daily mail,will have a look!!

[sebastiaan1973]

38,2c Maastricht (in the far south of the Netherlands). 3rd place. Just 0,4c difference with the record (38,6, Warnsveld 1944).

[cheeky_monkey]

well yesterday temp of 36.7c although short of the UK record is still higher than the highest ever recorded in my old haunts of Calgary and Edmonton which are 36.1c and 35.1c respectively.

[Snowyowl9]

15.5c here with rain summer heatwave by back

[March Blizzard]

June 1st came in at 9.5C in the CET zone, it'll be interesting to see the difference between it and July 1st.

Substantial is an understatement...

July 1st came in at 24.5C, a full 15C warmer than June 1st!

There can't have been many instances in the CET history in which two dates within 30/31 days of each other have seen such a disparity in temperature.

[March Blizzard]

The temperature has fallen in London from 27 to 26. Still good though.

Another world here, I'm not kidding when I say it's cool enough to see my breath.

Seriously.

[cheese]

It was 25C here today - but now it's 14C thanks to the rain earlier. Brr - feels very cold.

[summer blizzard]

Feels lovely.

[I Cumbria Marra I]

It was 25C here today - but now it's 14C thanks to the rain earlier. Brr - feels very cold.

Got to agree, much less comfortable today having to wear a jacket and pants to keep warm.

[BornFromTheVoid]

July 1st came in at 24.5C, a full 15C warmer than June 1st!

There can't have been many instances in the CET history in which two dates within 30/31 days of each other have seen such a disparity in temperature.

 

No other year has even come close to the difference between June 1st and July 1st at least.

 

As for any 30/31 day period, I'll see if I can figure that one out...

[March Blizzard]

No other year has even come close to the difference between June 1st and July 1st at least.

As for any 30/31 day period, I'll see if I can figure that one out...

Good stuff, BFTV. Looking forward to it!

Off the top of my head I'm thinking maybe a date in mid Feb 1947, and then mid March when the thaw came. It was quite abrupt, apparently? Even so, that would take a CET average of around -5C to +10C, respectively.

Edited July 3, 2015 by March Blizzard

[Interitus]

Okay - but Heathrow doesn't have much of an urban heat island to begin with - it's on the edge of London. Northolt isn't central either - it's north London. Why would Heathrow be hotter than Kew Gardens or London City Airport despite the latter two being considerably more urban in nature? Ditto the old London Weather Centre which was often a couple of degrees down on Heathrow's values when it was open.

Well Heathrow is slightly south of west from the centre and Northolt slightly north of west and casual observation suggests that with winds from the south east as on the 1st they tend to be warmer than London City Airport which on the eastern side does better with a more westerly component. The focus of the overall UHI shifts downwind.

Looking at it in more detail however it might be important not to forget the nature of the immediate environment and not just the conurbation as a whole. With Heathrow in particular, many will have questioned how representative a thermometer is in the vicinity of a few hundred acres of runways, airport apron and car parks.

Using data from weathercast, here is a graph of temperatures and dew points for Heathrow and Northolt plus Hampton Water Works which is to the south east and upwind of Heathrow, and Kew Gardens to the east of Heathrow and closer to the centre of London, and also the Heathrow sunshine figures.

 

 

The temperature profiles all show two heating peaks so while the sunshine figures would not be identical they appear to be similar indicative of a period of cloudiness around 1pm. With the cloud there is little to separate the stations with temperatures within a degree of each other. However with clear skies closest to peak insolation either side of the cloud at local noon (1pm BST), Heathrow's temperature soars above the others.

 

With rising temperatures dew point tends to increase as long there is enough moisture from water bodies, soil and vegetation but this can be countered by convective mixing bringing drier air to the surface. This seems to affect all stations with the lowest average dew point at 3pm. Heathrow though is generally the driest station with an average dew point of 13.85°C and this combined with the response to strong sun giving enhanced temperatures may all be due to the local surface. The other average dew points in order were Kew 14.33 (more central but with plenty green space), Northolt 14.63 and Hampton 14.81.

 

Throughout the 12 hour period average temperature however, Kew was the warmest station at 32.82°C followed by Heathrow 32.7, Northolt 32.38 and Hampton 31.68. This might suggest that Kew exhibits more 'genuine' UHI.

 

[hillbilly]

Good stuff, BFTV. Looking forward to it!

Off the top of my head I'm thinking maybe a date in mid Feb 1947, and then mid March when the thaw came. It was quite abrupt, apparently? Even so, that would take a CET average of around -5C to +10C, respectively.

Talking about that year was not the 1st june 1947 one of the hottest recorded in excess of 30 deg,how does that compare to 1st May that year also

[summer blizzard]

In actual fact it's the first time since April of last year that the qbo has been of a westerly calibre.

 

Largely neutral. Doubt it will have much impact.

[h2005__uk__]

Now that we're into July, how is this summer comparing to previous summers in terms of what's going on in Europe, the amount of heat there to 'tap' into, the possibility of us tapping into it, etc.?

 

I only really started following models less than a year ago which is why I'm asking.

[BornFromTheVoid]

July 1st came in at 24.5C, a full 15C warmer than June 1st!

There can't have been many instances in the CET history in which two dates within 30/31 days of each other have seen such a disparity in temperature.

 

 

Good stuff, BFTV. Looking forward to it!

Off the top of my head I'm thinking maybe a date in mid Feb 1947, and then mid March when the thaw came. It was quite abrupt, apparently? Even so, that would take a CET average of around -5C to +10C, respectively.

 

I had a little free time yesterday and got an answer to the other question.

 

The change in February to March 1947 was relatively benign compared to some, the largest <31 day increase occurred between February 24th, -6.7C, and March 22nd, 9.0C, giving a change of 15.7C.

 

The biggest variance in the daily average CET over a 31 days period occurred during the winter of 1837/8, with a high CET of 8.9C on December 1837, and a low of -11.9C on January 20th, giving a change of 20.8C over 27 days.

More recently, 1981 had a high of 12.0C on November 23rd followed 19 days later by a low of -8.5C on December 12th, a difference of 20.5C.

 

The vast majority of these record high changes occur during the autumn and winter months. You have to drop back to a 17.5C change to find a high value in spring. This comes from 1808, when April 19th recorded an average CET of 2.5C, followed 27 days later by a 20.0C value on May 16th, a 17.5C increase (3 days later, the CET was back at 9.3C!).

 

The find the largest variance within the JJA summer period, we have to drop back to 14.2C, which occurred between June 17th, 9.8C, and July 13th, 24.0C, in 1923. That means that this years increase of 15.2C between June 1st and July 1st is, provisionally, the largest on record to have occurred entirely within summer!

[sebastiaan1973]

A new temperature record in Germany, 40,3c. Kitzingen, in the south of Germany,