Cooler for some, warmer for others

Figure 1

It maybe a lot cooler for some first thing this morning in comparison with yesterday morning, more notably in the west and southwest of the country, but for other places, particularly in the east it’s much warmer than it was this time yesterday. The chart above (fig 1) is the 24 hour temperature difference, the chart below (fig 2) is the 24 hour differences in humidity.

It’s a lot more difficult to see whats going on with these humidity changes, the North Sea, Denmark, and much of Scandinavia are a lot more humid than yesterday, but lower humidities are evident in the southwest of Ireland, the far southwest and central parts of England.

Figure 2

The use of ‘fresher’ is obviously subjective, and is often bandied about by weather presenters without too much thought, other than to overly dramatise changes. The one big thing that I know is missing this morning in our part of Devon, is the sunshine of the last week (fig 3), it’s rather cloudy, temperature wise it’s certainly cooler than yesterday, but still fairly warm with temperatures around 18°C.

Figure 3

Unusual medium level shower activity…

Figure 1

I’m probably going to shoot myself in the foot with this one, but it looks to me, and I could be wrong, like much of the precipitation that’s been showing up on this afternoon’s weather radar, especially the belt that stretches across central England is from medium level unstable castellanus cloud, and is producing nothing more than the odd shower. There are some brighter echoes within, and the observing network is pretty thin so it could be falling between the gaps, but I see very few reports of any significant rain or thunderstorms from it.

Figure 2

Here’s the latest visible image (fig 3) that shows the band very well.

Figure 3

The rainfall over western Scotland looks even more dramatic, and this is thundery in nature (fig 4), although the rainfall indicated in the weather radar image looks very intense, it also seems to have escaped the observing network so far.

Figure 4 – Courtesy of Blitzortung

Interestingly, the current Met Office warning that is in force for heavy thundery rain this afternoon, completely omits the west and north of Scotland (fig 5)!

Figure 5 – Courtesy of the Met Office

 

Apparently, it’s the hottest June day since 1976 in the UK

Figure 1 – Courtesy of the Met Office and Twitter

Not a lot of people know this, but according to Twitter (fig 1) apparently this afternoons maximum of 34.5°C at Heathrow, make today the warmest June day since 1976 in the UK. All the weather presenters are very excited about all this, so I thought I would get in on the act, and take a wander down memory lane to see what the charts looked like back then. According to the TORRO website the three days with temperatures above 35°C in June 1976 were:

  • June 26  35.4  North Heath (W Sussex), East Dereham (Norfolk) 1976
  • June 27  35.5  Southampton-Mayflower Park 1976
  • June 28  35.6  Southampton-Mayflower Park 1976

I have SYNOP reports for main synoptic hours back to 1973, but unfortunately, in the older SYNOP format temperatures were reported in whole degrees, so it’s not possible to pinpoint the exact maximum at any SYNOP station on these days (figs 2, 3 & 4).

  • I can’t corroborate the reports at North Heath and East Dereham on the 26th, because neither are SYNOP stations, although both Heathrow and Southampton reported 35°C on that day.
  • The Southampton temperature of 35°C on the 27th fits with the TORRO maximum temperature of 35.5°C because the value would have been thrown to the odd.
  • The highest maximum on the 28th at Southampton was reported as 34 in the SYNOPs that I have so I don’t know what’s going on there.

Both the 26th and 27th were very similar days synoptically (figs 5 & 6), with a large anticyclone over Ireland (~1028 hPa) and a ridge eastward extending across the north of England and the North Sea, with a light or moderate E’NE flow over southern England. No real weather to speak of although there was a thunderstorm reported at Exeter on the 18 UTC chart on the Sunday (27th) with a pressure of 1027.6 hpa which is pretty good going (fig 6).

Figure 5

Figure 6

Here’s this afternoons chart for 14 UTC on June the 21st (fig 7), synoptically quite different from June 1976, with high pressure in the German bight (~1020 hPa), low pressure to the NW and trough and cold fronts coming into western Ireland, there is a light to moderate SE’ly flow over southern England this afternoon.

Figure 7

I wonder just how many more hectares of buildings, concrete and tarmac there are surrounding the Stevenson screen at Heathrow compared with 40 odd years ago. I personally think that climate stations and busy aerodromes aren’t a good fit, but historically that’s how the observing network the Met Office now manages evolved.

Figure 8

-80°C at Concordia Station

The summer solstice apparently occurred at 0424 UTC this morning, and of course ushers in the first day of summer in the northern hemisphere, which is a shame because the current heatwave is due to end tomorrow, so we’d better make the most of today.

With all this talk of hot weather, I thought that I’d have a scout round and find the coldest place in the world at the moment, and that of course is in Antarctica, at the Concordia research station to be precise, which sits 3,233 metres up on top of the Antarctic plateau. The temperature there at the moment (06 UTC on the 21st of June) is -80.1°C (-112°F), which is considerably colder than the -68.5°C at Vostok. I never realised that the Concordia research station existed till I found it listed in the SYNOP reports, and it wasn’t till I read the Wiki article about the French-Italian run concern that opened in 2005 did I realise that in sat right in the middle of a disputed area, apparently Australia hold claim to all that ice, the ridiculousness of this situation nicely sums up the stupidity of man in a nutshell. Below is the thermograph trace from Concordia for the last three months (fig 1). Let’s hope that they’re main purpose there isn’t to drill through the ice cap and release some alien life form like in the film ‘The Thing‘.

Figure 1

 

Maximum temperature of 49.7°C Nuevo León in Mexico

Figure 1

I heard Eddie Mair going on about the temperature in Phoenix Arizona in yesterday evening’s PM program on BBC Radio 4, so I thought I’d keep an eye out on the maximum temperatures and see what turned up. Well to trump Phoenix (no pun intended) the maximum temperature reported at 00 UTC from Nuevo León in Mexico was 49.7°C (121.4°F), and a shade (I can’t help it) higher than the 48.3°C in Arizona. Excuse the contouring of temperatures is far too smooth and not accurate.

36.8°C at Le Mans

Figure 1

Jersey airport ended up being the warmest place in WMO block #03 as suspected with 32.4°C, but Le Mans was the hottest place in France with 36.8°C this afternoon. That air over France will start to feed up across the channel as the gradient starts to veer overnight and possibly produce an even hotter day tomorrow across the south.

Figure 2

Warmest June day here since at least 2004

Jersey looks like taking the crown today as the warmest SYNOP station in WMO block #03, with a temperature just over 90°F at 14 UTC (fig 1).

Figure 1

Here in Bradninch mid-Devon, the temperature has been hovering around 30 or 31°C for much of the afternoon, so to escape the sun that I’d string some code together and look at a couple of thermographs since Saturday for Exeter (fig 2) and Heathrow (fig 3).

Figure 2

Not bad going for Devon, when you consider that Exeter is always starting several degrees cooler than Heathrow each day. I think the sea breeze just kicked in time to prevent the temperature at Exeter airport possibly exceeding 31°C at 14 UTC, as it did here in Bradninch. My Vantage Pro has been recording temperature since September 2004 and this afternoon’s max of 31.3°C makes it the warmest June day in that time.

Figure 3

Is a mean of 24°C a good heatwave threshold for the UK?

There seems to be no exact definition of what constitutes a heatwave, either how long the spell should last, or how hot it should be to be classified as one, either here in the UK or anywhere else come to that from the different rules adopted by different countries. Looking at the daily CET series and the reported temperature observations of the current ‘heatwave’, I reckon a mean 24 hour temperature of 24°C  or above might be a good threshold to use here in the UK.

Figure 1

The above graph (fig 1) are the hourly temperatures from Heathrow Airport since the start of June. The yellow outlined series is the 24 hour centred moving average, and the red line is 24°C, that would mean that we are in day four of the current one.

Of course you could use the daily anomalies for a station, which would make it more flexible, but that would be more difficult to compute if you did it hourly, because you would also need hourly anomalies, although it could be done if you could access the data from the AWS.

That 24°C threshold wouldn’t do for the summers in the south of Spain though, because the entire month of June so far has been more or less one continuous heatwave, so perhaps 28°C or even higher might be more appropriate here (fig 2).

Figure 2

 

Hot spell not going to go quietly…

The latest 06 UTC model run must be showing signs that the breakdown of the current hot spell is not going to be a quiet one.

Figure 1

It looks like the Met Office are still having problems with this new warnings web page of theirs. The map is a great improvement on the old one, but some of the locations plotted on it are blatantly in the wrong place. I reported this to them a couple of weeks ago, and it really should have been fixed by now. At worst its misleading to the general public, at best it just doesn’t look professional, I am amazed that it wasn’t picked up at testing.

Topsy turvy weather

By this time next week this may current heat wave may be just a distant memory, that’s according to the latest GFS forecast, as the British summer monsoon gets into full gear.