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

 

Ne’er cast a clout till May be out

Figure 1

Another touch of frost in places overnight, with air temperatures down to -1.8°C across the southeast of England this morning (fig 2). There has been a more general and sharp ground frost across most of the southern and eastern England too (fig 1), which won’t have please a lot of gardeners.

Figure 2

In fact the cold air at the moment is quite widespread across much of northern Europe and eastern Russia (fig 3), nothing exceptional, but because it comes after another relatively mild Winter and Spring so far, it’s come as a bit of a shock to some. And remember – ne’er cast a clout till May be out.

Figure 3

Another beautiful spring day across the south

Figure 1 – courtesy of the Met Office

Another lovely sunny morning down here in Devon again this morning – the third in a row (fig 1). Not wishing to rub it in at all after David Braine’s warnings of a cloudier Thursday down here for yesterday, I noticed that Exeter airport was the sunniest spot in the whole country with 12.6 hours of sunshine, ~94.6% of the maximum (fig 2). We must be in top gear making up for the dull March we had.

Figure 2

Last night was clear and starry, and led to a very cold night with a minimum of 0.0°C at the airport (fig 3), I wonder if he forecast that?

Figure 3

I suppose this is not at all surprising when you’re sat under a large anticyclone like we are at present, and as it pulls away later today we will find warmer air pushing up from France for the weekend. So we could end up with a run of five sunny days before it’s all swept away early next week.

How long will this high pressure stay?

How long will this high pressure stay around? Well the short answer to that – according to the latest NWP data from America – is not that long.

Image 1 – Courtesy of www.netweather.tv

The latest forecast run from the GFS courtesy of NetWeather has the high persisting till Monday of next week before pulling away to the northeast. We are then set for a cyclonic interlude for around a week, before high pressure returns in early April, and persists right through to the end of the forecast period (9th of April). If this forecast is anywhere near correct, the first few weeks of Spring may not be overly warm, but the dry anticyclonic theme looks likely to keep recurring as it’s done since last Autumn.

 

Equinoctial gale

The vernal equinox in 2017 is at precisely 1029 UTC on the 20th of March, and heralds the start of Spring proper, and none of these meteorological seasons malarkey. It just so happens, that the very next day, the GFS model produces a vigorous low across the country (fig 1). It’s true that the term ‘equinoctial gales’ is derived from the popular misconception that gales are more frequent at periods close to the equinoxes, but it would be very apt if the storm was named Fleur, especially as its arrival coincides with the start of Spring.

Figure 1 – Courtesy of OGIMET

Spring has sprung

Spring has sprung in Central England, to be precise it did it last Saturday (4th of March), but not a lot of people know that!  I almost missed it, but as I was tidying up some code in the immediate vicinity, and as the weather was rather quiet at the moment, I thought that I would mark the event.

Figure 1

The Spring of 2017 is 17 days earlier that the average date of the Spring vernal equinox, which this year occurs on the 20th of March, but not as early as it was last year (fig 2), when I estimate it occurred around 31 days earlier than average.

Figure 2

The weather is reasonably mild at the moment across the south of the country, but it’s set to get a wee bit milder than this in the next couple of days. Take a look at the 850 hPa forecast chart for tomorrow night, these are temperatures at 850 hPa (around 5,000 feet) (fig 3), the blue line represents the freezing level at that height, but as you can see that there is a tongue of warmer air, with temperature of 8°C or higher and strong southwesterly winds across western areas. If we get some sunshine with this then it really will feel like spring has finally arrived.

Figure 3 – Courtesy of OGIMET

I noticed that maximum temperatures yesterday were already getting into the low 80’s °F on the Costa del Sol (fig 4), although Scandinavia was still sub-zero.

Figure 4

Lovely day – shame about tomorrow

Figure 1

Exeter airport is top of the shop in the 14 UTC SYNOP reports with 12.2°C – and not “somewhere in the southeast” thank you very much Darren Bett (fig 1). My Vantage pro recorded a max of 13.2°C in a sunny spell around lunchtime here in mid-Devon, in what has been a lovely spring like day. It’s a shame it won’t last though, as I notice pressure has already start to fall ahead of another low that’s forecast to swing into the southwest of the country tomorrow (fig 2).

Figure 2 – Courtesy of OGIMET

 

Met Office long range forecast for Spring 2017

The Met Office have just released their 3 month outlook for March to May 2017, why for goodness sake don’t they just call it the Spring 2017 outlook? Hopefully, it will be more accurate than the last one for the meteorological winter that is just ending (a blog about that to follow in the next week or so). If you want to read the full report with all the detailed reasoning behind it you can find it here, but for the purposes of this blog these are the two headlines from it:

Temperature

For March and March-April-May, above-average temperatures are more probable than below-average. Overall, the probability that the UK-average temperature for March-April-May will fall into the coldest of our five categories is 5% and the probability that it will fall into the warmest of our five categories is around 40% (the 1981-2010 probability for each of these categories is 20%).

So basically, the chances of a very cold quintile 1 are around 5% and the chances of a very mild/warm quintile 5 are at around 40%. So if we remove all the gobbledygook, it looks to me like a pretty strong signal for a very mild/warm Spring in 2017.

On the face of it this strong signal looks rather exceptional, but if you look back at how Spring temperatures have been behaving in recent years with the help of the CET series (fig 1), then you will see that very mild Springs are far from uncommon, and indeed they are fast becoming the norm. The warmest Spring since 1659 occurred in 2011, and four of the warmest Springs on record have occurred in this century (2003, 2014, 2007 & 2011).

Figure 1 – Data courtesy of the Met Office

Precipitation

During March, above and below-average precipitation are almost equally probable. For March-April-May as a whole, above-average precipitation is slightly more probable than below-average. The probability that UK-average precipitation for March-April-May will fall into the driest of our five categories is 15% and the probability that it will fall into the wettest of our five categories is between 20% and 25% (the 1981-2010 probability for each of these categories is 20%).

There is less ‘useful’ guidance for precipitation than there is for temperature, and its rather bland, but I think it’s basically saying that precipitation will be near average for Spring 2017.

I always feel that precipitation is always going to be a lot more tricky to forecast than temperature. Looking back at some recent values with the help of the EWP series you can see that spring 2011 was very dry, and the third driest since 1766, but there is quite a spread usually between +/- 20% of average though.

Figure 2 – Data courtesy of the Met Office

Expect Spring a little early again this year

With my tried and trusted ‘First day of Spring’ algorithm, I estimate that Spring 2017 will be around eight days early in 2017, probably occurring on the 13th of March in Central England (fig 1). As usual I estimate it by calculating the degree days from the Winter solstice, and fix the first day of Spring when that count exceeds the mean number of degrees days between Winter Solstice and the Vernal equinox (December 21st and March 20th). And yes, I do know the time of both these can vary by day or so each year. The estimate is based on using the long-term average temperature for future temperatures, so if it’s warmer than usual in the next couple of weeks it may come even sooner, or later if the next six weeks or so are colder than average. That makes this Spring just over three weeks later than it was last year.

Figure 1

Cold Winters mean cold springs, so the Spring of 1963, the third latest since 1772, didn’t happen till the 4th of May that year, likewise a very mild Winter means a very early Spring as in 1989 , the earliest Spring since 1772, which occurred on St Hilary’s day of that year (fig 1). Of course, Central England has warmed since 1772, and the first day of Spring is occurring much earlier, in fact I estimate that Spring is now 20 days earlier than it was in 1772.

Figure 2

Spring has sprung…

Image 1 – Courtesy of the Met Office and EUMETSAT

Figure 2

Despite some quite strong easterly winds across the whole of the British Isles (fig 2), temperatures in the southwest were around 10°C warmer at 15 UTC today than they were yesterday at the same time (fig 3). At Exeter and Chivenor temperatures this afternoon have been close to the 14°C mark, and it really did feel like spring had suddenly arrived today, in what has been a lovely sunny day down here in darkest Devon (fig 1). I see the same can’t be said for eastern districts, where temperatures this afternoon seem to be closer to 4 or 5°C.

Figure 3