Yet another warm October in Central England. I make the mean for October 2017 to be 12.35°C, which was 1.74°C above the 1961-1990 long-term average for the month, and placed it 13th warmest in the record that started back in 1659 (fig 2). Seven of the warmest 13 October’s have now occurred in the 21st century, and October shows one of the strongest decadal increases of any month at +0.173°C per decade. I remember seeing the odd bit of snow in late October but those days have gone, and in this part of Devon, I know that I’ll be very unlucky if I see any snow this coming winter. The only thing that I can say in mitigation, is that the size of each anomaly looks a little less steep with each year since 2001!
The current warm spell of weather across Central England, and rather spookily ushered in by the start of the astronomical Autumn, seems to be running on and on, and there doesn’t seem to be any sign in the latest NWP forecast charts that it intends to stop! The above chart clearly shows the warmth of the last four weeks or so (fig 1). The maximum temperature on ‘Ophelia day’ (the 16th of October) of 19.5°C, broke a record that had stood since the great Autumn of 1959, no mean feat.
Autumn mild spell continues into start of November
The low pressure area that’s currently over the northeast of Russia; as forecast by the latest run of the GFS model; is set to be replaced by a large anticyclone with a central pressure of 1040 hPa or higher by this time next week. This will in effect stem the flow of cyclones from tracking from the Atlantic across Scandinavia and into Russia as they have been doing of late, as pressure rises over Scandinavia and a block forms. This in turn will back the flow across the eastern Atlantic as it becomes progressively more meridional. This in turn will ensure the continuation of the autumn warm spell, and if anything we could see even higher anomalies both by day and night as we move into Autumn.
There’s quite a bit of conjecture in that last paragraph, so take it with the pinch of salt it deserves, but remember that you read it here first.
I know that many of the last 16 postings I’ve made today have been concerning storm Ophelia – never fear – here’s an article about something totally different – Central England Temperatures. The Met Office have just fixed the server that generates the provisional CET daily values on their website, and let me tell you they haven’t done that since the 3rd of October, so I was chafing at the bit to see just how mild October 2017 had been till now. In actually fact not only is October 2017 currently the 12th mildest mean temperature since 1772, the year 2017 to date is also the joint sixth warmest as well.
Welcome to the whacky world of xmetman.
So why have temperatures in the first half of September 2017 been so cool across most of northwest Europe? One glance at the mean pressure chart for the first 16 days will give you the answer (fig 1). The Azores high has been +5 hPa stronger than average, and the Icelandic low has become elongated eastward, with pressure 10 hPa lower than average across the northern Isles. This has resulted in a strong west northwesterly flow across the central Atlantic across much of central Europe. I’m sure that the fast-moving ribbon of air which some people call the jet stream has something to do with it, I find that it usually does.
Here are the fine details of how the circulation has been behaving over the last couple of years with the help of some values from the objective LWT analysis (fig 2). I’ve highlighted September to show how strong and persistent the combined SW-W-NW theme has been this month.
It’s quite noticeable, that from the from the third week in July, maximum temperatures in the CET series have generally been rather flat and slightly below average (fig 3). If you look at the spells bar chart (the fifth chart down) there have been few if any prolonged warm or cold spells longer than 3 days or more with anomalies 2°C either above or below the long-term average, compared with previous summers.
Looking over a much larger area with the 12 UTC mean temperature anomalies for the first 16 days of September, you can see that the increased westerly flow has resulted in a large -3°C temperature anomalies across central Europe, and even higher +5°C warm anomalies over northeast Turkey (fig 4).
What about the coming Autumn and Winter?
What does all this portend for the coming Autumn and Winter? I have got absolutely no idea. But if this kind of strong anomalous west or northwesterly flow continue like it’s been doing, I would guess that it looks likely to be cold, windy and rather wintry at times.
The coldest September in the UK on record, well in the abridged 1910 temperature series from the Met Office that is, was that of 1952, with a mean anomaly of -2.79°C (fig 1), in fact the headline in the Monthly Weather Report for the month read – Unusually cold.
It was also the fourth coldest September in the CET series that started in 1659, and still holds three extreme minimum daily CET records from 1878, and also four extreme low maximum records as well (fig 2).
September 1952 was generally anticyclonic from the 7th to the 16th, which did allow some night frosts to occur, before turning very cyclonic from the 25th (fig 3). You may have noticed that September 1986 was the joint third coldest in the UK since 1910 (fig 1), but unlike 1952 this was mainly due to the anticyclonic nature of the weather (fig 4), in fact 1986 is the joint 10th most anticyclonic on record since 1871 in the Objective LWT series. So September 1952 was cold both by night and day, whilst 1986 was colder at night than day. In contrast to either of those two years, 2017 has so far turned out so far to be generally colder by day than by night.
If you use the 1981-2010 long-term averages, Summer 2017 in Central England was a little above average, a mean temperature of 16.14°C gave it an anomaly of +0.28°C, making it the joint 41st warmest summer since 1659 for what it’s worth (fig 1). As far as I can see, looking at the individual months that make up the ‘meteorological’ summer of 2017, June was 20th warmest, July the 54th warmest and August the 87th warmest since 1659, which more or less tells you how the summer went temperature wise.
August 2017 in Central England was rather a cool affair, which would have been even cooler, if it hadn’t been for some warmer values in the last 10 days of the month. I made the mean temperature 15.6°C which gave it an anomaly of -0.8°C using the 1981-2010 long-term average (fig 1). This was the first below average month in Central England since January, nine of the last thirteen August’s have been cooler than average (fig 2).
I have a book in my library entitled “Weatherwise – England’s weather through the past thirty years‘ by John H Willis and published in 1944. John Willis who died in 1962, kept faithful records of temperature, sunshine and rainfall for many years and took photographs of trees on the same day each year. Strangely his work on phenology, which has been largely forgotten these days, came to a similar conclusion as this joint study between the Met Office and Woodland Trust did. I don’t think somehow that these results will come as any great surprise to people who love the weather and the countryside.
This is a graph and table (figs 2 & 3) from a study that I did myself using daily CET data earlier this year, to see just how much earlier the first day of spring was occurring in 2017 than it was in 1772. I reckon that the first day of spring now occurs three weeks earlier than it did in 1772 in Central England.
I am surprised that some of the UK climate records used by the Met Office to calculate their global land temperatures for CRUTEM4 with, are from sites where the instrument enclosure, primarily the Stevenson screen, has been compromised over the years by the encroachment of buildings, car parks, and runways and the various ‘climate’ sites around the country, to such an extent that it must in some way be affecting the temperature sensors. Creeping urbanisation has been happening for years, and is not a new problem, it’s a bit like how politicians suddenly realised that life expectancy has been on the rise for the last 100 years.
Before I go any further these concerns have been voiced before, and a review of the observing sites of the UK has been done before, and much more thoroughly than I can do in this short article, most notably in the Surface Stations Survey by Tim Channon on the TallBloke blog.
The Surface Stations Survey work was done a few years ago now, and as far as I see wasn’t directly linked to the ‘raw’ monthly CRUTEM4 temperature data that you can freely download from the Met Office, and which is used to calculate a monthly estimate of global land temperature with. In recent years the Met Office, for some reason known only to themselves, have reduced the number of the UK sites from well over 100 twenty years ago (fig 1), to just 18 sites in 2017 (fig 2).
Here’s a graph (fig 3) of how the total number of UK sites that are currently used in the CRUTEM4 calculations has declined in recent years.
The irony of this 80% or more reduction in UK sites used, is that two of the three sites used to calculate the composite CET series, the longest instrumental record of temperature in the world, are now no longer used – Rothamsted (1872-2012) and Preston Moor Park (aka Stonyhurst 1960-2012).
Poor siting of instrument enclosures
But I digress, what I really wanted to
moan about bring to people’s attention was the precarious siting of the Stevenson Screen at some of the 18 sites that we still use to calculate a global temperature with. Generally the siting of the screen didn’t look too bad, but there are a number that are poor, and here are three of the worst sited Stevenson screens that I found using Google Maps. Of course guessing where the screen is an art that has become a bit of an obsession with me. The biggest offenders are all at airports, namely Aberdeen, Valley and the infamous Heathrow (figs 4, 5 & 6).
At this point I would like to say I wouldn’t be able to do this without Google maps, but I have noticed that the generally the quality of the highest zoomed images is inferior to those in the Google map images of the Surface Stations Survey. This might be just a Google maps issue, or it maybe a deliberate restriction on quality and zoom level requested by the MOD for RAF stations. The yellow circle is at a radius of 10 metres and the blue circle at a radius of 30 metres. I won’t go into detail of what I estimate the WMO classification for each site would be as regards temperature, I’ll just leave it your imagination.
What can the Met Office do about it?
When I was an observer every so often at an outstation, someone would come round and inspect the ‘met’ enclosure to see if it was being maintained correctly, I wish now that I had taken a keener interest in what the inspector was looking at other than if the bare patch had been weeded recently! I wonder if there was tick box to confirm that no jet engines were being run up within 30 metres of the screen? I can remember quite clearly being wafted by warm gusts of air from an F3 Lightning at Binbrook en route to the Stevenson screen across the pan to do the 09 UTC observation even in the middle of winter.
They could if they wanted to without much effort do the following with the climate records used from the UK in CRUTEM4:
- Reinstate the best of the climate stations that have been lost in recent years, but not the records from RAF Waddington or RAF Brize Norton please!
- Immediately reinstate the temperature climate records for Rothamsted and Stonyhurst, at the same time adding the one from Pershore, so that the three stations used for the renown CET series are included in the calculations, which to my mind would be only fitting!
- Remove Heathrow until the enclosure has been relocated possibly in the middle of Bushy Park!
This would be very easy for the Met Office to do, they wouldn’t have to go cap in hand to any other meteorological service to ask them to supply the data, as they already have those temperature records.
I know just how sensitive temperature sensors are in AWS these days, I have a Vantage Pro, and over the years I’ve relocated it a number of times in our garden, each location had its different weaknesses, too close to trees or the hedge, or too close to an area of paving, now it’s far too close to the garage. It certainly is a very difficult, if not impossible task to find a location on a modern airfield that’s totally unaffected by external influences on temperature. But in this day and age of advanced wireless communication, I just can’t believe it’s not possible to install AWS as far away as possible from any runway, car park, building or road, at any site, which invariably is at an airport, be it military or civilian. I’ve been doing it with my AWS without a problem for the last 13 years, albeit at a range of less than 10 metres! Inevitably this will have to be done as the demand for green space on airfield sites increases till the whole damn place is paved for a parking lot.
Even after a relatively cool August, 2017 so far is still the sixth warmest to date (24th of August) since 1772 in Central England. As you can see in the table (fig 2), the mean temperature for 2017 so far is 11.09°C, which is +1.41°C above the 1961-1990 long-term average. For quite a while 2017 was the second warmest year and then August happened. 2014 is the year to beat though, because even though it’s currently only third in the table, it’s the warmest year on record, and for 2017 to catch it, the next four months will have to have a combined mean anomaly in excess of +1.6°C. That sounds a steep challenge, but it’s perfectly possible, after all 2014 has already done just that.
The problem of calculating just exactly what the anomaly for the next four months should be if 2017 is to beat 2014 is quite a challenge. I reckon a bit of calculus is required to do it, but any memory of that subject has long since disappeared from my memory. I could do it by trial and error using some code but I’ll leave it for a rainy day before I have a go.