The warmest place in the UK this afternoon is Hawarden in Flintshire with a temperature of 15.3°C at 13 UTC, contrast that with the 1.4°C at Aboyne in Aberdeenshire (fig 1). Temperatures across England and Wales to the lee of high ground are around 5°C or 6°C above average for 12 UTC (fig 2). The record warmest temperature for the 20th of November in the UK according to the TORRO website is 17.2°C held jointly by Dunoon in Renfrewshire and Hawarden Bridge in 1947. If the sun continues to shine downwind of Snowdonia as it’s currently doing, that record could be in jeopardy. Cold weather in the north and milder weather in the south looks likely to be the theme this week by the look of things, how I do detest this kind of setup.
It’s coming to things when you have to write a story about a couple of nights with a touch of frost (fig 1), but it might be something I’ll have to do in the future as the seasons continue to warm as they have since 1772 (fig 2). The last lying snow in our part of Devon was over the Christmas period of 2010 if I remember correctly, and the last few Winters have only produced a few fleeting flakes of snow before it quickly turned to rain. I see that the GFS have already backed off with the two cold northerly outbreaks that they were hinting at earlier in the week, it’s quite obvious already that it will take a miracle to produce any snow in this part of the world.
Autumn seems to have turned much colder in northern Scandinavia in the last week (fig 3), I can remember plotting the upper air ascent for Sodankyla in Finland a few times in my time at Strike in the 1970’s, it just show’s you what a good snow cover and a long clear night can do at this time of the year.
I wrote an article the other day that included a temperature anomaly chart for 12 UTC on Sunday for parts of the UK. But I thought I would look at back at what was the coldest spell of weather in my lifetime, and luckily for me I can include the winter of 1962-63 in that lifetime (even if I was just playing at being a snow plough!) and that was on Monday the 12th of January 1987. Don’t forget that the plotted values in the chart above (fig 1) are anomalies and not actual values for 12 UTC.
As you can see North Hessary Tor, sadly no longer with us as an observing site, had the lowest anomaly of -16.7°C, but many places across England and Wales had anomalies in the range -12°C to -15°C as you can see. 1000-500 hPa thicknesses in the midday ascents were 506 dam at Aughton, and 500 dam at Hemsby. I wrote a more detailed article about this spell of exceptionally cold weather which may well have been the coldest day in 20th century in the UK, and it was absolutely wonderful!
Just a quick paragraph about how I calculated six hourly mean temperatures for 237 observing sites from 1981 to 2010. It took a lot of file IO, parsing SYNOPs from 43,830 files takes some time even on a fast PC. I then plotted individual annual graphs for the 06-18 maximum, the 18-06 minimum, and for the main synoptic hours 00, 06, 12 and 18 UTC. Then, if there was enough data, I then ran a curve fitting algorithm on the results that gave me a formula that allows me to calculate a daily value for any day of the year. This is exactly the kind of work the Met Office should be doing on our behalf, but which sadly you will never see.
I know I’ve gone on about the simplicity of anomaly charts in the past, but I believe they are of far more use that just sticking a map with the highest and lowest temperatures on. Perhaps someone at Meteogroup is reading this particular blog (who am I kidding), I would urge them to be innovative, and make more use of anomaly charts in weather forecasts on TV when they finally take up the BBC contract. I doubt if we’ll ever see anomaly charts in regular use by the Met Office in their ‘Visual Cortex’ system, just a continuation of ‘shrunken’ Scotland in their maps, and ridiculous looking fronts overlaid on MSLP charts.
In my reworking of the old nursery rhyme, Jack is of course synonymous with the Met Office, if you’ve not already guessed! What I’m trying to say I suppose is this:
You may have the fastest and the most accurate forecast model in the world, but if you can’t visualise what the model is telling you, then you may be just wasting your time.
These NWP models generate so much highly detailed forecast data, a lot of which forecasters can’t possibly assimilate, and getting the salient facts about the weather across to the public, such as the overnight minimum temperatures seems to elude them. Compare the forecast temperatures in the graphic from the BBC with the actual temperatures at 04 UTC this morning, and you will notice that they are around 3°C too high in most of Devon. It makes no difference that the Cray XC40 supercomputer is located just 2.26 km to the west of the airport, and even though the mesoscale output from the model may have correctly forecast the temperature at 04 UTC, the BBC graphics are still wrong.
Some may argue that the temperature that the BBC show are for “towns and cities”, but that to me is just a clever get out on their part. There is a problem forecasting extreme temperatures, especially overnight minimum temperatures which has never successfully been resolved, in fact I would say that little effort has ever been expended either by the Met Office, or the company that provides the BBC graphics in doing so. Let’s hope that Meteogroup, in these days of 4K television, come up with an improved way of displaying extreme temperatures which more accurately reflects what the model is forecasting when they finally take over the service next March.
Here are the 12 UTC temperature anomalies for 12 UTC on the 12th of November (fig 1) and it’s a cold day everywhere, especially the further east and north that you are. Temperature anomalies are generally in the range 2 to 4°C below the 1981-2010 long-term average for 12 UTC on the 12th of November. But the weather is bright enough away from the east coast and the far southwest, where showers have continued in the fresh or strong N’NW wind.
Meanwhile low Numa continues to track SE and deepen across the south of Germany (fig 2). There’s quite an area of snow developed now in the cold air to the north of the low, I should imagine the Alps are in for a pasting in the next 12 hours.
There’s the usual ring of abnormally high positive temperature anomalies around the Arctic at the start of November (fig 1). I had a theory that the largest anomalies were located in areas of open water where no sea ice had formed, but this theory doesn’t look too plausible judging by the latest sea ice extent chart (fig 2). I notice that the recent cold weather in Canada has encouraged early ice formation around the coast of the Hudson Bay, but the area to the north of the Chukchi sea look severely depleted of any sea ice again for this time of the year.
There are still a good many places that haven’t seen an air frost this Autumn (fig 1), but only a few who have escaped a ground frost (fig 2). I notice that there is a spurious -9.8°C in those SYNOP figures from Cork so ignore that. Tibbenham in Norfolk is also an incomplete record which I haven’t filtered out. I’m a little suspicious of the two ground frosts for Jersey airport, but they do in fact check out. How an island can have ground frosts, and stations on the mainland can’t, looks very suspicious, all that I can think is not all of the French stations report minimum temperatures at 06 UTC.
The earliest air frost I see was reported by Redesdale Camp on the 19th of September, I don’t seem to collate the earliest ground frost for some reason, perhaps I was having a bad day when I wrote this app.
The -5.7°C in the Borders overnight Sunday, must be the coldest night of the year so far I would have thought, it’s a shame this ridge of high pressure isn’t going to last as frontal cloud is already piling in from the west.
It was 15.2°C warmer at Loch Glascarnoch at 06 UTC this morning than it was on Monday warming (fig 1), although there was little difference in the temperatures in the far south and southwest, where another widespread slight ground frost occurred (fig 2).
What they call Loch Glascarnoch is an AWS that sits midway between Loch Droma and Loch Glascarnoch (fig 3), on a featureless bit of moorland next to the A835 on the road to Ullapool. The only reason that I know a little bit about it is that it’s the starting place for a group of Munros called “The Fannaichs” that lie to the southwest, which my wife and I climbed on a summer’s day over 25 years ago now – how time flies! Don’t ask me why they don’t share the same spelling as Loch Fannich to their south, I have no idea. I recommend pulling into a lay by off that road on a clear evening in Winter to get the best view of the stars and milky way that you’re ever likely to see.