Are winters becoming milder and wetter?

Figure 1

Q: Are winters becoming milder and wetter?

A: The short answer is yes they are. The Central England temperature series [CET] reveals that winters [DJF] are now on average 1°C warmer that they were 140 years ago back in 1878 (fig 1), and the England Wales Precipitation [EWP] series indicate that they’re also 18.6% wetter (fig 2).

Figure 2

Retrospective on the last cold spell from the Met Office

Figure 1 – Courtesy of the Met Office

The climate team at the Met Office have been working overtime and have produced a report detailing the events of the recent cold spell which as you know started on Sunday the 25th of February and lasted to following Saturday the 3rd of March 2018.

Figure 2 – Courtesy of the Met Office
Figure 3 – Courtesy of the Met Office

I’m not certain if the snow depths in this chart (fig 3) are particularly accurate from what I saw locally here in our part of Devon – 0 cm really? They would have been better using the snow depths reported from their WOW network, which for some reason known unto themselves you can’t plot on a chart.

Second sunniest Winter and February since 1929

Figure 1 – Courtesy of the Met Office

A sunny February (fig 1) ended what was a sunnier than average winter across the UK. I noticed the second sunniest February in the UK as it unfolded, but the second sunniest winter caught me out.

February 2018

February was the second sunniest since 1929, and the sunniest in the UK since 2008 with 136.8% of the 1981-2010 long-term average. The sunniest regions were generally further west, with parts of Devon, Dorset, Somerset, and south Wales receiving over 170% of the long-term average. February’s are over 10 hours sunnier than they were back in 1929 (fig 2).

Figure 2 – Courtesy of the Met Office
Winter 2017-18

Winter sunshine for December, January and February was 122.8% above the long-term average, and was the second sunniest winter since 1929, the furthest that the Met Office can currently be bothered to take the series back to, even if extensive sunshine records exist well back into the Victorian era, thanks to the Campbell–Stokes sunshine recorder, which was invented in 1853. Winters are now over 20 hours sunnier that they were in the age of the Charleston in the UK (fig 3).

Figure 3 – Courtesy of the Met Office

The contrast between some of the sunniest areas and the duller spots in western Scotland and Snowdonia is quite striking (fig 4).

Figure 4 – Courtesy of the Met Office (that should of course read 2017-18)

January 2018 climate statistics on Spotlight southwest

Figure 1 – Courtesy of the BBC

I wonder where David Braine gets his climate statistics from? I would have thought it was just up the road from the Met Office in Exeter. Last night David looked back at the weather for January 2018, and he displayed a table for Cornwall that showed a total of 115 mm precipitation fell in January and that the average for the month was just 70 mm (fig 1).

What’s the Average?

Take a look at the 1971-2000 rainfall averages (fig 1), and you’ll see that the whole of Cornwall is covered by at least light brown coloured contours, indicating a total of at least 100-140 mm, and over higher ground this increases to as high as 220-340 mm, so an average of 70 mm is woefully low.

Figure 2 – Courtesy of the Met Office

Luckily you can download the monthly climate data for Camborne from the Met Office for free. Here are the January totals there since 1978 (fig 3). I reckon the average rainfall total for January at a coastal site like Camborne is just over 131 mm.

Figure 3 – Data courtesy of the Met office
How much rain actually fell?

Here is my best estimate of precipitation accumulations for January that I’ve derived from the SYNOP reports, I miss the occasional report but the totals should be quite accurate (fig 4). As you can see the three Cornish mainland stations are reporting totals of 183.5, 188.9 and 206.8 mm, much more than the 115 mm in the table (fig 1). Perhaps he was using the total from St Mary’s of 104.9 mm? (ToDo: find out if the Scilly Isles are part of Cornwall).

Figure 4
Was it that wet?

The Met Office rainfall anomaly chart shows that January 2018 was indeed a wet month in Cornwall, and as you can see by the purple coloured contours indicating rainfall anomalies of between 125 and 150% of average (fig 5). I make the approximate anomaly for Camborne 140% (a total  of 183.5 mm with an average of 131 mm) which fits in nicely with the anomaly chart.

Figure 5 – Courtesy of the Met Office
So what should the graphic have looked like?

At a guess these values might be closer to the mark than the 115 and 70 mm shown in his original table (fig 6).

Image 6 – Courtesy of xmetman with data supplied by the Met Office and OGIMET

Regional correlation of temperature, precipitation and sunshine – January 2018

Figure 1 – click to enlarge

I’ve put a bit of development work into creating a panel of three scatter graphs that show the correlation between:

  • Mean temperature and precipitation.
  • Mean temperature and sunshine.
  • Precipitation and sunshine.

I’m using what I call the Met Office 1910 regional monthly data to display how the correlation looked for January 2018. I think these correlation scatter graphs are a quick and easy way to visualise climate for either a selected region since 1910, or as in this case for all regions for a particular, year, season or month as I’ve done with January 2018 (fig 1).

As you can see if you examine each graph in detail (fig 1) it’s easy to pick out the outliers which indicate regions that have seen the more extreme weather that occurred during the month. The temperature-rainfall scatter graph on the left for instance shows how much colder and drier Scotland was than other parts of the UK.

It’s not a new idea, but I personally think it’s a very useful visualisation tool for anyone that’s interested in climate, and shows much more that a line or bar chart could.

Bitterly cold – what happens when we run out of superlatives?

Just as a reminder a superlative is described by the dictionary in Google as:-

Figure 1 – Courtesy of Google

I’ve heard so many reports across social media describing just how cold, very cold, bitter or raw this weekend will be across the country as colder northeasterly air spreads southwestward across the country, that I thought I’d take a look. Here are the forecast temperatures across the country for Sunday (fig 2).

Figure 2 – Courtesy of Twitter and the BBC

And here are what the mean maximum temperatures for January look like across the UK (fig 3).

Figure 3 background map courtesy of BBC and Twitter

So all this incessant hype I’ve heard in social media about the coming change of weather type, and talk of just how cold this weekend will be, should be taken with a pinch of salt, because although it’s turned colder, in reality and for a variety of reasons it’s not that cold at all.

No doubt, the ‘feel like’ or ‘wind-chill’ temperature figures will be brought into play as winds strengthen across southern areas on Sunday, but let’s not get carried away with the fact that these temperature are nothing out of the ordinary for January and put them into perspective.

That’s not a knife –  that’s a knife!

Here’s a look back at the 12th of January 1987 (fig 4) to see a situation that does merit the superlative ‘bitter’, to describe the coldest and snowiest days spells of weather that I can remember in my lifetime in the British Isles.

Figure 4
Figure 5

Chances of a really cold winter 11.4% less than in 1960

I’ve just read a recent article in the weather and climate forum about severe winters and the enigmatic and elusive Scandinavian anticyclone. I could have used reanalysis data from NOAA, but decided instead to analyse the frequency of this particular weather feature with the help of the daily objective Lamb Weather Types from the UEA. It’s quite simple really, all you have to do is add up the occurrence of all days of a certain LWT, in this case these twelve types which I thought were the best associated with a blocked circulation and Scandinavian or Siberian anticyclone:

  1. ANE
  2. AE
  3. ASE
  4. AN
  5. NE
  6. E
  7. SE
  8. N
  9. CNE
  10. CE
  11. CSE
  12. CN

Then examine the LWT of each day in a Winter [DJF] and if it matches any of the types listed above add it to a total. At the end of each Winter, calculate the frequency by dividing the total by the number of days in the season and multiplying by a 100, then repeat the process for each Winter since 1871, before plotting the results as a scatter graph, with a 10 year centred average and linear trends (fig 1), and adding the results to a table of ranked frequencies in descending order (fig 2).

Figure 1 – Data courtesy of the UEA/CRU

No big surprises really, all the old favourites are showing frequencies of 30% or more. 1962-63, 1946-47, 1978-79, 2009-10 & 1985-86. The interesting thing is the steady decrease in frequency of these combined types since 1871, they are down 4.3%. Even more striking is the decline of 11.4% since 1960! It’s no wonder that people of a certain age feel like someone’s shut the fridge door since their school days in the 1960’s.

Figure 2 – Data courtesy of the UEA/CRU