Summer 2017 failed on the 20th of July

Figure 1

Temperatures in the summer of 2017 in the UK crashed on the 20th of July and have never recovered in the almost three weeks since it’s been since then. You can see clearly how the temperature has almost flat lined in the NCEP reanalysis data for the grid point 52.5° north and 2.5° west (just to the west of Birmingham), with almost all the 6 hour anomalies negative since then, negative (fig 1). I remarked in a blog only yesterday about how unusually flat the daily CET values had been since the 20th of July. Its probably all tied up with that ‘ribbon of high wind speed high in the atmosphere‘ that we like to call the jet stream.

Meanwhile in stark contrast to the UK, just to the northeast of Rome in Italy, at the 42.5° north 12.5° east grid point, things have been slightly different. A part from three short cold spells, the temperature anomalies there have all been well above average since early June (and before), with the recent heatwave this month clearly evident.

Figure 2

 

Coldest start to an August in 30 years

Figure 1

I notice that the latest provisional mean maximum daily temperature for the first eight days of August in Central England of 18.89°C (-1.38°C) are the lowest for that period since 1987 (fig 2). The 10 year average mean temperature for this period, has been on a downturn since 2000, and even the linear trend shows only limited warming since 1772 (fig 1).

Figure 2

A cool start to August

Figure 1

A cool start to August in most places, but particularly so across southern areas, with daytime maximum temperature anomalies typically 2°C or more below the long-term average for the first eight days of the month. The chart is from the mean maximum temperatures [06-18] for the 1st to the 8th of August 2017 compared with the 1981-2010 daily averages than I’ve calculated from the SYNOP records that I have (fig 1). I think the low value for St Catherine’s point is probably due to missing data.

Cool out last night

Figure 1

Quite a cool night in places across the country last night under clearing skies and cool air for August (fig 2). Marked contrast between the coastal stations and the more rural inland stations as you would expect with SST around the coast of 16 or 17°C. Exeter with a min of 5.1°C and Portland 14.1°C is just one example (fig 1).

Figure 2

A cool night was well anticipated by the BBC, but it was a little colder than they thought in the south of Scotland, the west Midlands and Devon. They never can quite anticipate just how cold it can get at Exeter airport, with a grass minimum of just 2°C (fig 3), and the Met Office supercomputer just a couple of miles up the road.

Figure 3 – Courtesy of the BBC on the 5 August at 1pm

The crafty Met Office

Of course the Met Office and the BBC are very crafty, and since the demise of the magnetic weather charts, they now always quote a spot value for a particular time as the minimum temperature, rather than the true ‘minimum’ temperature for the whole night, which in my opinion is much more useful, and less misleading. It’s my belief that they don’t display a minimum or maximum temperature chart to hinder any verification of their forecasts, and prevent smart Alec’s like me from saying just how far their forecasts were out by.

A miserable cold July day…

A miserable cold July day here in our part of Devon, and also by the looks of it in a lot other places across the country. Cloudy with occasional outbreaks of light rain to go with it, and anomalies at 12 UTC around 3°C below the average for the 28th of July (fig 1). Tomorrow looks no better in this neck of the woods, although Sunday’s forecast does promise some brighter spells between occasional heavy and thundery showers.

Figure 1

Colder than Christmas!

I know it sounds incredible, but at 12 UTC today many places in Eastern England and Scotland, it was colder than it was at the same time last Christmas day (fig 1).

Figure 1

The temperatures at some places were more than 6°C below the long-term average for 12 UTC on this day (fig 2).

Figure 2


Late frost and egg on face

Figure 1

I knew that I was tempting fate by publishing a story the other day about the total number of frosts in the last year and saying that we wouldn’t be seeing anymore. Well last night there was a widespread ground frost (fig 3) and touch of air frost across the country (fig 2), and I’m still busy trying to get what’s left of the egg of my face as I type. I’m in good company though, because David Braine always seems to forget just how cold it can get at Exeter airport (-0.5°C). The 10th of May is not particularly late for an air frost in the UK, but I bet gardeners on chalky soils in Oxfordshire aren’t too pleased this morning, if the -2.8°C at Benson is anything to go by.

Figure 2

Figure 3

Frost over the British Isles during 2016-17

Figure 1

Now that May is with us and there can’t be many more frosts to come, I thought that I’d look back at the total number of frosts in the period from the 1st of July last year and see how the seasons panned out in regard to air frosts, ground frosts and the number of ice days (maximum temperatures below <0°C for 24 hours). As always with data like this it does depend on receiving 06 & 18 UTC SYNOP data from all stations, and which you can never entirely guarantee that you’ll get, so some of these figures may not be quite exact. I also apologise for the cluttered numbers at this zoom level, which only some fancy decluttering routine would fix. You’ll have to take my word for it, the application is much better than the screenshot.

Figure 2

I think the number of days with an air or ground frost were significantly boosted in the southeast of England as a result of the cold spell in January. It looks like St Mary’s on the Isles of Scilly even managed to escape a ground frost during this last winter, I’m not sure about the two sites on the coast of northern France though.

Figure 3

26/27 April – Sharp frost across the south

A mild night in the cloudier windier north, but inland and further south where winds fell light, a moderate frost in places.

Late April cold spells and the Easter Snowstorm of 1908

Figure 1 – Lymington High Street – April 25th 1908 (courtesy of lymington.org)

Easter in 1908 fell late, so the snow that fell over much of southern England must have come as a big surprise on the Easter Sunday on the 19th of April (fig 1). The following week was intensely cold for late April, and there were periods of heavy snow across much of southern England. In an article in the Met Mag of May 1908, Fred J Brodie said this about the snow at Oxford:

The conditions at Oxford are interesting in a special degree on account of the length of the meteorological records at the Radcliffe Observatory which run from 1853. The depth of snow there was 17 inches, and the only instance of a greater amount being recorded at any time of year was on February 13th and 14th, 1888, when 24 inches of undrifted snow was measured.

I love the comment that Fred went onto make a few lines further on…

The practice of comparing, for the purpose of record making, observations made in two different localities is not to
be commended…

He of course is completely right in what he says, but he must be spinning in his grave these days, on the goings on in the early 21st century with extreme temperature records I would have thought, because no one, and that includes myself seems to give a hoot these days about comparing extremes from weather stations without knowing thinking much about their actual location. You can find an article about the events of April 1908 on the Weather Outlook forum, which includes details of snow depths recorded at the time, plus a lot of other information and photographs about the blizzard. The Weather Magazine of December 1981 also had an article about April 1908 in which it linked it to the April of 1981 and said:

The marked similarity of the graphs for 1908 and 1981, especially in the second half of each, is confirmed by a correlation coefficient of 0.93 for the last 15 days of the month. For the full month the correlation coefficient is 0.65. The weather of late April was remarkably similar in these years.

Since 1981, the daily CET series may well have undergone some slight modifications, but there is most definitely a cold spell that occurred during at the second half of each month, the minimum CET in 1908 was a couple of degrees colder than it was in 1981 though, and those on the 24th and 25th still hold the record for lowest minimums on those two days (blue stars). Personally I only see a broad similarity between the two, I’ll have to spend some time and write some code to generate a correlation coefficients between these two months and see what I come up with. If you look closely at the graph of CET (fig 2), you’ll notice that in just over a week, maximum anomalies rose from around -8°C to +8°C. The resultant rapid thawing of lying snow from the week-long cold spell lead to great flooding in places along rivers in the southeast especially the Thames, and the Great Ouse at Buckingham.

Figure 2

Synoptically, the 25th of April in both 1908 and 1981 were slightly similar in that they were both cyclonic in nature.

Figure 3 – Courtesy of NCEP/NOAA reanalysis

But up aloft in the atmosphere the cold air of 1908 was much deeper than it was in 1981 (figs 4 & 5).

It seems cold outbreaks towards the end of April are not at all uncommon, I’ve just picked on probably two of the more extreme events. Next week promises its own cold outbreak (fig 6), but synoptically, if the GFS model is correct, it will be more of a cold northerly rather than cyclonic as it was either in 1908 or 1981.

Figure 6 – Courtesy of OGIMET