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

 

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

18 April – Sharp frost in north

 

Not a perfect radiation night across Scotland, there was always a little too much residual gradient left over from yesterday, even with a high pressure cell sat right slap bang over the country. Despite this Tulloch Bridge still recorded an overnight minimum of -5.7°C [06-06] which is not bad going for mid April (fig 2).

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.

The sun shines on the righteous and the unrighteous

Figure 1 – Courtesy of the Met Office and EUMETSAT

A lovely sunny morning down here in Devon after a sharp overnight frost, the 18-06 minimum at Exeter Airport was -3.4°C. But I notice that the edge of the SC sheet has just taken Yeovilton out, and a few bits of cloud have appeared on the eastern horizon as I type, so the sunshine might not last the morning out. The SC sheet itself looks very uniform across the country, with a base of 3,000 feet and tops of around 5,000 feet if the Herstmonceux midnight ascent is anything to go by.

Figure 2 – Data courtesy of OGIMET

Figure 3 – Data courtesy of OGIMET

 

More strong winds for France

Another low, not all that dissimilar to yesterday’s low, is now tracking into central France with some very strong winds on its southern flank. Yesterday’s low is now sitting over the Western Isles of Scotland, meanwhile a short-lived col over central southern England has allowed a touch of frost to develop.

Figure 1

 

Frost count so far this Winter

Figure 1

Because of the anticyclonic nature of this meteorological Winter with 58 days of it gone so far, the air frost count across the British isles is looking fairly respectable as you can see from figure 1. There is certainly a cold pole in central southern England due to the frosts of the last week, but there are still a number of stations holding out at zero air frosts so far this Winter.

Figure 2

An interesting chart plotting the total number of ice days (fig 2) across Europe so far this Winter, so if you think you that we’ve had a few hard frosts or even the odd ice day in the last week or so, have a look at further east and think again.

Of course, before someone points this out to me, ice days are when the temperature fails to rise above freezing over a 24 hour period, usually from 0900 to 0900. This chart is a count of days when the 06-18 maximum is less than 0°C, that’s because not all countries (including the UK & Ireland) report a 18-06 maximum along with their 18-06 minimum in their SYNOP reports, or an 06-18 minimum to accompany the 06-18 maximum come to that, so this will have to do. I won’t even bother trying to sort out the time zone issues a chart like this one (fig 2) that spans multiple time zones throws up.

Interestingly the French do report both a 12 hour maximum and a minimum in both their 06 and 18 UTC SYNOP observations, which is very sensible, they also report hourly rainfall totals which again I applaud them for, but I still won’t buy any French apples, not after they sank the Rainbow Warrior in 1985!

Ice day

The low stratus is finally clearing across the southwest of England as drier air is entrained across the Channel from France. There’s been a lovely wave-like ripple in the low cloud running downwind of Cornwall through the Celtic Sea, and along the eastern side of the Irish through today.


It looks like that they’ll be a number of stations reporting an ice day today, judging by the mid-afternoon temperatures across some parts of Eastern England at the moment. The temperature at Wattisham for instance at 14 UTC was -2.4°C, and -1.6°C and -2.1°C at Wittering and Andrewsfield respectively, this combined with the wind speed make it a fairly penetrating black frost.

Exeter catches the BBC out again in more ways than one…

The -5.2°C overnight minimum at Exeter airport last night caught out not only David Braine in the Spotlight SW weather forecast at 6.55 PM, but also John Hammond in the later national forecast at the BBC.

Figure 1

It’s always very difficult gleaning evidence after the event in any BBC forecast from the previous day, suffice it to say the -5.2°C (fig 1) was considerably lower than either presenter forecast.  Even the forecast temperatures for 08 UTC this morning left a lot to be desired (fig 2 & 3).

Figure 2 – Courtesy of the BBC

Figure 3

Fog all day at Exeter

What annoyed me with David Braine last night is the fact that even though Exeter Airport had been in fog all day on Tuesday, with visibilities of 100 or 200 metres and a maximum of 1.8°C (as had we in Bradninch), he never even bothered to mention it. The plot grid (fig 4) is especially for David as a reminder that it might be a very good idea to have a look at a handful of observations from across the southwest before going on air. Even Holly made a quick reference to the fog in ‘southeast Devon’ in the weather at 1.40 PM. As for the Spotlight news team, they were probably too busy having another go at the NHS to mention any travel disruptions at a distant airport, but I digress…

Figure 4

I can’t believe that hundreds of people weren’t inconvenienced by not being able to fly where they wanted to yesterday (and in the last week) from Exeter. Surely that’s newsworthy to the people of the southwest? When David did mention fog in his presentation, it was with a passing reference to Dorset and Somerset. Curiously the fog that had blighted the airport for days cleared by the early hours by drier air that had been advected up from France.

Minimum Temperatures

As for his stab at the minimum temperatures they were wildly on the high side, he was too busy going on about how cold it will feel on Thursday when the wind picks up, the increased wind chill in the strong SE’ly wind, and what a shock to the system it will be.  And I do know that Exeter Airport is a well-known cold spot, which doesn’t excuse the insertion of an extra low value on the chart to cover this possibility.

Plymouth Centric Spotlight

It may have been much milder in Plymouth, but for a number of mornings in the last week I’ve been scraping the ice of our car, so I know how cold it’s been in our part of Devon. All I can conclude is just how Plymouth centric both his, and the rest of the Spotlight news teams thinking really is.

At 08 UTC this part of mid-Devon was covered white in frost as the sun was rising and the sky was a gorgeous Mediterranean blue, the temperature at Exeter Airport was a full 12°C colder than it was at Plymouth, it’s as if we were in a different world, because of course geographically we are.