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

 

Q: Just why has April been so dry & sunny?

Q: Just why has it been so dry and sunny and dry this April?

Figure 1 – Data courtesy of NCEP/NOAA reanalysis

A: Because for the first 18 days of the month there has been a large (+11 hPa) positive MSLP anomaly sat just to the west of Ireland (fig 1). As I reported earlier this month (never thinking that the first half of April would turn out as anticyclonic as it has), 1938 was the most anticyclonic in records that started in 1871 (fig 2). The two April’s are indeed very similar, but the anomaly chart for 1938 was for the entire month, and not just the first 18 days, and were larger and even more pronounced. That’s not to say that the second half of April 2017 won’t continue to be just as anticyclonic as was the first.

Figure 2 – Data courtesy of NCEP/NOAA reanalysis

I’ve just put quite a lot of programming effort into the program that I use to download, parse and visualise reanalysis MSLP data from NOAA, so hopefully I’ve got things right. The LTA that I have used to calculate the anomalies for years 2012 or earlier is for the whole of the 20th Century i.e 1901-2000. For the years after 2012 the LTA is for the 66 year period 1948-2013. This is because the older reanalysis data uses a 2 x 2° grid, whilst the data after 2012 is from the 20th Century reanalysis on a 2.5 x 2.5° grid.

Jersey the sunny Channel Island

Figure 1 – Courtesy of vintagerailposters.co.uk

Jersey have taken over at the top of the sunshine league this April, with almost 9 hours of sunshine each day for the first 20 days of the month. Their total of 178.6 hours so far is I estimate 66.1% of the possible maximum total. It’s not been sunny everywhere across the British Isles, but without detailed climate statistics to produce anomaly values it’s impossible to be precise, but as usual, it seems to have been duller the further west and north that you are so far this month (fig 2).

Figure 2

The driest Aprils since 1910 by region

I’ve spent a bit of time today creating an infographic of driest April’s. I’ve used the free data set maintained by the Met Office, which started in 1910 and is produced from gridded data for ten regions across the country. Hopefully one day the Met Office will extend this series to cover all the rainfall data that they inherited from the British Rainfall Organization in 1919 and just sat on for the last 98 years. I knew about the very anticyclonic and dry April of 1938 from a previous article that I had written earlier this month, but hadn’t realised that it was only driest in three out of the ten regions, even though it was the driest April in the EWP monthly series that started in 1766. The 1.0 mm in East Anglia in 2007 tops the list of driest region by region, which is something else I missed. I’ve borrowed the regional map from the Met Office, I’m sure that they won’t mind, let me know if you spot any issues.

Data courtesy of the Met Office

Later….

What’s slightly puzzling about these figures for April is why the UK value is the highest April value for all regions at 14.1 mm, when it’s made up of the value for Wales 8.8 mm, and the value for England 6.7 mm. Both values are for the same year 1938, I would have thought that the combined UK value should be some kind of mean of the two, but obviously not. It must have something to do with the gridding I suppose.

April in pictures

Images courtesy of the Met Office and EUMETSAT

Here in Devon, we just about got away with five consecutive sunny days at the start of this April, but even today it’s still very pleasant, and unofficially the air temperature is around 17.5°C at 15 BST. A number of stations won’t be that far short of a 100 hours of sunshine in the first 11 days by close of play today I would have thought, Lyneham most certainly will have a ton up (fig 2).

Figure 2

Sunny start to April

It’s been a very sunny start to April 2017. In the first eight days Lyneham in Wiltshire is top of the sunshine league in this part of NW Europe with 78.3 hours of bright sunshine, which I make as 73.9% of what’s possible, and a daily average of almost 10 hours. Unfortunately the further west and north that you went the cloudier the month has been. The ‘Rx’ column by the way indicates the percentage of reports received, which is out of my control.

April 2011 – warmest on record*

Figure 1 – Image and data courtesy of the Met Office, CRU & Wetterzentrale

April 2011 – warmest on record*

*Or what you can do with a load of climate and weather data

Figure 2 – Data courtesy of the Met Office

It seems that we have incredibly short memories when it comes to weather across the country, well at least I know that I have, and that’s why I never noticed that April 2011 was, and still is the warmest April on record since at least 1659 in Central England (figs 2, 3 & 4). The mean CET temperature for the month was +3.91°C above the 1961-1990 long-term average, and 0.6°C warmer than the second warmest April in the list 2007. I’ve just put together a blog that consists of a number of tables, charts and graphs of climate data for the month that I’ve constructed from data or images that I’ve downloaded from the Internet.

Figure 3  – Data courtesy of the Met Office

Here’s a more detailed of daily temperatures, in what was a very mild Spring in Central England, particularly in March and April (fig 4).

Figure 4 – Data courtesy of the Met Office

The monthly mean 12 UTC temperature anomaly of +5°C sits across northeast France and dominates most of western Europe by its influence (fig 5).

Figure 5  – Data courtesy of NCEP/NOAA

The mean pressure field for the month of April was ideal for warm and dry weather with plenty of sunshine. An anomaly of +6 hPa over the North Sea enabled a cut-off anticyclonic cell over England and Wales, although the weather was more southwesterly in the northwest (figs 6 & 7).

Figure 6 & 7 – Data courtesy of NCEP/NOAA

Here’s a chart of daily rainfall from the EWP series (fig 8), apart from a wet start, the month was predominantly dry in all areas of the UK except the northwest of Scotland.

Figure  8 – Data courtesy of the Met Office

And here are the 12 UTC plotted SYNOP observations for Northolt  in London for each day of that April (fig 9).

Figure 9 – Images courtesy of OGIMET

And finally here are anomaly charts of rainfall, temperature and sunshine for the month courtesy of the Met Office (fig 10). The thing is I can produce maps, charts and graphs easier than I can write the text that glues them all altogether.

Figure 10 – Images courtesy of the Met Office