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.

Snow in North Africa

Image 1 – Aïn Séfra (Algeria) on the 20th January 2017 –  Courtesy of MSN

I notice that a plunge of cold air has brought snow to the Atlas mountains of North Africa this morning. It’s quite usual for the Atlas to get snow at this time in winter, but snow lower down is a little rarer, and at places like Aïn Séfra in Algeria, which is at an altitude of 3,546 feet (image 1) it hasn’t happened since 1979 according to the Wikipedia article. A little further east in Algeria this morning, El-Bayadh are reporting 25 cm of lying snow in their 06 UTC observation. El-Bayadh is just a little higher than Aïn Séfra at 4,419 feet (just 8 feet higher than Ben Nevis).

Figure 1 – 06 UTC 23 January 2016

Looking at the observations since the New Year, El-Bayadh looks quite a hostile place to live either in summer or winter. If you examine the plot grid (fig 2) you will see that the snow fell heavily on the 20th and 21st of this month, with a snow depth of 35 cm on the morning of the 21st. This is a very good SYNOP report which puts observations from a lot of other countries to shame.

Figure 2 – El-Bayadh

Fog and frost in the south

It’s the coldest morning that we’ve had in our part of Devon in this recent ‘cold’ spell, on a night when it stayed cloud clear and the wind at last died out for a change. It looks like a layer of SC has saved stations north of London from also fogging out, which may stations south of the M4 seemed to have done this morning.

Colder and colder at Farnborough

Six air frosts in a row at Farnborough in Hampshire during the last week. Frosts on the 18th, 19th, 20th were moderate, but for the last two nights they’ve been severe. Still a reasonably dry January for this part of the world helped along by the anticyclonic weather.

How long does it take a front to die?

Figure 1 – Courtesy of the Met Office & EUMETSAT

Well the short answer to that one – with regards to the front that has been straddled across the British Isles for most of this week – is a very long time indeed, especially when it had nowhere to go. I think it could hold claim to have been the slowest moving cloud clearance that I’ve ever seen as well, because although its been responsible for some lovely visible satellite images of the British Isles this week (fig 1), the sheet of stratocumulus has proved more than a little reluctant to clear, and some poor souls (I was going to use another word there but that wouldn’t have been nice) in the North of England have been stuck under it since Sunday. This is all despite the fact that the British Isles has been sat under an anticyclonic ridge with the air pressure approaching 1040 hPa for most of that time.

Figure 2 – Courtesy of the Met Office

It must be getting wearing even for the Chief forecaster at the Met Office, because even he has now broken the link with the frontal system to the west in the midnight analysis (fig 2). So that’s a third morning with a moderate frost in the Southeast of England with Farnborough top of the coldest places in the 18-06 minimum temperatures (fig 3), but things are all set to warm up next week.

Figure 3 – Data courtesy of OGIMET

 

Moderate frost across the Southeast

For a change Gravesend, the site that’s so often the warmest in the whole of Britain and Ireland, last night for a change was the coldest. with a 18-06 minimum of -5.7°C. It does make me wonder though – is this what winter has come to in this country? Headlining the occasions when we get a sharp frost?

The curious case of the temperature at Topcliffe

After all this hype about blizzards and Arctic blasts of the last week, I was expecting Friday night to produce much lower temperatures than it did. In the end there was just too much wind to allow temperatures to fall that low. Our overnight minimum air temperature here in Bradninch was 2.0°C, but at Exeter airport which is 11 km to the south it was -1.8° C, interestingly our garden pond has a skin of ice on it despite this, and the only reason I can see is that the pond is just in the lee of our garage, which provides just enough shelter from the 5 knot northwesterly to allow ice to form. One value on the chart of overnight minimum temperatures (fig 1) did catch my eye though, I wonder if you can spot it.

Figure 1

Shelter from the wind is one of the key ingredients to a severe frost, and at most places that was just missing last night, but at Topcliffe in North Yorkshire for a couple of hours just after midnight the northwesterly wind fell light (fig 2), and as you can see from the thermograph (fig 3), that allowed the air temperature to fall from around zero to -5.5°C within an hour or so. At 04 UTC the gradient reasserted itself and the temperature shot up from -3.o to +2.5°C in the hour. Both Leeming to the north, and Linton-0n-Ouse to the south, had much higher minimums of -1.4°C in comparison.

Figure 2

Figure 3

What caused the wind to fall light and blow against the flow in this part of the Vale of York is another matter. It could have been a lee wave rotor effect off the Pennines to the west that caused both the wind to fall light, and to reverse direction against the flow. This could have been aided by a string of lively showers that were tracking NW-SW to the southwest of the station (fig 5).

Figure 4

Figure 5  – Courtesy of the Met Office

Who knows it could have been much more of a local effect – a bit like our garage providing the shelter for our pond to freeze over. Here’s a look at the airfield at Topcliffe in more detail just to see where the Met enclosure is probably situated.

Figure 6 – Courtesy of Google Maps

I have never been to Topcliffe, although I did work at Leeming and did do a shift ad Dishforth in 1971, but I would guess that the marker is where the Stevenson screen is located there (fig 6), and immediately to the west and northwest are three big hangers to provide some very good shelter from the northwesterly gradient. The question is though, why did they only provide shelter between 01 and 03 UTC? So was it a local effect or a much larger effect caused by the topography? Answers on a postcard please, because what the hell do I know.

Figure 7 – Courtesy of Google Maps

I remember that as an observer at Kinloss, we would see a rotor effect that would produce a light northerly, when the wind at 2,000 feet was a 40 knot southerly over the airfield, sometime the effect would get mixed up with a sea breeze and a dash of low stratus, which eventually would get pushed away by the southerly gradient. This happened on the 1st of May 1990 when Kinloss recorded a maximum of 27.2°C, which I’m sure must still hold the record as the warmest May Day in the UK. On that day Bracknell rang John Sutherland (the observer of the day shift, a great character, who is sadly no longer with us) and asked him to correct his observation because the temperature must be wrong. (todo: I must write a brief article about that day!).

Forget this cold spell – the next one might be better

For the snow lovers amongst us, especially down here in the south, I think this short one day ‘cold’ spell will certainly a big disappointment. Even if we do get some wet snow accumulations today or overnight, it’ll very soon be gone. There are changes ahead though, and towards Wednesday of next week (if the latest NWP is to be believed) we could see the start of a cold spell that lasts a lot longer, take a look at the latest T+186 from the GFS (fig 1).

Figure 1 – Courtesy of NetWeather

An anticyclonic easterly with a cold pool edging westward across the British Isles, it’s not particularly deep cold air, or well-connected connected cold air, but it’s cold air nonetheless, and for once the Southwest of the country looks at risk from snow. Of course as usual, it’s not long before the anticyclone over eastern Europe declines and slips southeastward, but the good news in the later frames of the GFS (fig 2) is that pressure builds to the northwest of the British Isles and extends the cold spell to at least five days, which is nothing short of miraculous in a British winter. Admittedly this is high pressure, so snowfall might be in short supply away from windward coasts, but there could be a good deal of frost and fog, spells of which seem to have been a recurring feature since November.

Figure 2 – Courtesy of NetWeather

Of course, as I’ve warned before on this blog, this is all science fiction, and may not happen. But I think a change to a more blocked anticyclonic type, and which has been anticipated since before Christmas, may well happen this time round.

 

Looking back at January 1987

Figure 1 – The garden of our old terrace house in Louth (which stood up to the Louth flood of 20 May 1920 by the way) sometime on the afternoon of January 12th 1987

It’s thirty years today that the cold spell of January 1987 started in earnest, so I thought that I’d put a piece together with my recollection of it scant as they are. It’s a shame that things like the Internet, WordPress and digital photography weren’t around back then otherwise I wouldn’t have needed to bother…

I remember Monday the 12th of January 1987 quite distinctly. I was due on a 12 hour day shift at RAF Binbrook that started at 8 am, so I usually left home around 7.30 AM to get there in the car. There maybe was 10 cm of snow on the roads in Louth where we lived when I left, but I managed to negotiate the road up and onto the Wolds, to a place called North Elkington which is at almost 400 feet above sea level. The wind, which had been quite light till then had started to pick up and was lifting all the snow of the fields and dropping it onto the road between the hedges. I did manage to get a small way up the road to Binbrook, before having to stop for a snow plough coming in the opposite direction. With the driver watching, I managed to get the car turned round and follow him back out. It was a brand new Fiat Uno and I had only recently passed my test, so driving on snow was a new experience to me.

The observer that I couldn’t relieve was on duty till the following Saturday, over 5 days, although I would have thought the Sergeants mess might have helped him out with meals through the week.

By the end of the afternoon back home in Louth, we had over a foot of the fluffiest lightest snow that I have ever seen in this country, falling from a succession of moderate snow showers that occasionally merged into longer periods of heavy snow. There are not many memorable weather memories that stick with me but that one did, bear with me as I make a quick of them!

  1. The Sheffield gale of February 1962
  2. Vague memories of the frost and snow of winter 1962/63.
  3. The glazed ice that brought down lots of branches from trees and the TV mast at nearby Emley Moor on the 19th March 1969
  4. The snow that stopped cricket at Buxton on the 2nd of June 1975
  5. The great summer of 1976 whilst working in Schleswig-Holstein, and coming back home in Autumn looking like a tanned Tarzan, and being stared at because I went into town wearing shorts.
  6. The snowstorms of January, February and March 1979 in Sheffield, in our flat above a green grocers shop.
  7. The intense cold of December 1981 and walking to and back from work at Tinsley Park, watching steam rising up from manhole covers just like in does in Chicago.
  8. The night shift at Binbrook on the 9th July 1984, and the high level thunderstorms that occurred over an airfield cover in shallow fog, and that would later set York Minster alight.
  9. The intense cold and snow of January 1987.
  10. Being caught in a cloud burst walking home from work and being absolutely drenched in less than 30 seconds (who knows when that happened).
  11. The Bracknell flood of 7th of May 2000, when I realised that you could still get flooded even though you live on a hill.
  12. The hot spell of August 2003, and particularly Monday the 11th  on the day we left Bracknell bound for Devon.
  13. The very cold December of 2010, and how for once Devon looked like with snow cover.

Only thirteen? Is the list so short because I have a bad memory, or maybe I’m hard to impress? Anyway I digress, back to January 1987 and a zoomed in chart for 06 UTC (fig 2).

Figure 2

The table of snow depths for 06 UTC snow depths on Monday morning (fig 3) show Jubilee Corner at the top with 37 cm. It’s difficult to question the 37 cm with all the snow fell overnight and the previous day, but I think it may have been closer to 27 or even 17 cm judging by the later reports from there.

Figure 3

As far as I’m concerned, there has never been a weather event in my memory that was as cold as the first few days of this week back in January 1987, and I’ve seen lots of observations and plotted charts from cold weather events of the past for the UK. This was just an intensely cold easterly air stream that blew in over across a comparatively warm North Sea, and yes December of 1981 did have lower temperatures, but that was under conditions of perfect radiative cooling on a deep cover of snow, and not directly comparable to this. Zooming out a little, this chart (fig 4) gives you a better way to visualise exactly what was going on across the North Sea and the near Continent.

Figure 4

Here’s the chart for 18 UTC on Monday (fig 5), the -16° at Cottesmore shows just how cold it was across the country that day. I generate these charts using observational data that I purchased from Weather Graphics. The SYNOPs are reconstituted in some way and occasionally omit climate and special groups, but overall the quality is good, and a lot better than trying to OCR data from the Daily Weather Report.

Figure 5

Here’s the zoomed in chart for 18 UTC (fig 6).

Figure 6

The coldest place that day in the 06-18 reports tabulated reports (fig 7) was Cottesmore with a maximum of -8.2°C but with a whole host of stations across the East of the country not far behind.

Figure 7

You might want to bookmark or even take a copy of the next chart (fig 8) because of the -6°C temperature at St Mary’s. It’s something the older ones amongst us like me are unlikely to see again in our lifetime.

Figure 8

To accompany that chart, here are the 18-06 UTC minima from Tuesday morning (fig 9). Before you ask – the reason why the actual temperature is -16°C in 18 UTC plotted chart for Cottesmore SYNOP (fig 6) and -15.5° in the 06 UTC tabulated list is because for some reason Weather Graphics omit the precision in the hourly temperatures but not in the extremes.

Figure 9

Here’s the chart for 18 UTC on the Tuesday (fig 10). By this time the cold pool had transferred across to Ireland but most, if not all of the country and nearby Europe had a good deep snow cover, and I see a -22° over what was West Germany even well before midnight.

Figure 10

Unfortunately the maximum temperature 06-18 (fig 11) from St Mary’s wasn’t reported, but I suspect it had been sub-zero all day.

Figure 11

These are the overnight minimums 18-06 UTC (fig 12) across the British Isles and the near Continent of Wednesday morning, with every station reporting a frost, even the Butt of Lewis.

Figure 12

I could go on till the weekend with more charts and stuff, but the sad inevitable thing about every cold spell be it cold or hot, is that they do have to come to an end sooner or later, and that was true of this event. This one gradually warmed up as an intense high pressure built over the country later the following week, and milder air spread in on the westerly flow around its northern flank. Having said that though the remainder of January did remain quite cold as this graph of daily CET for the winter of 1986-87 indicates (fig 13).

Figure 13

I did have to adjust the code to display a table of greatest snow depth (fig 14) from any of the main synoptic hours for that cold week, to list and rank the greatest snow depth, so there are duplicates, but they should be for a different day and time. Surprisingly to me the greatest depth was at Guernsey Airport, but with the amount of drifting and compaction as it slowly warmed during the week, you have to take these values with a pinch of salt (pardon the very bad pun).

Figure 14

The greatest snow depth is very dependent on their being a level depth of snow to measure without any significant drifting, which is not easy as most of my readers will probably only know too well. I for one know that there was significant amount of drifting over the Wolds in Lincolnshire (see fig 19), and when I finally returned to work at Binbrook on the Saturday to relieve the observer who had been on duty from the Monday, I remember having to climb an eight foot mountain of snow and ice that had been bulldozed to clear the pan where the Lightnings lined up to get to the Stevenson screen. The enclosure was around a ¼ of a mile or more from the office, It was the first time that I had ever to stoop down to take the readings.

Hopefully the following plotted 1000-500 hPa partial thickness and thermal wind charts (figs 15-17) will give you another idea of just how deep that cold air was. As you can see the cold pool drifted east west during the 12th and 13th of January 1987. I plotted and drew these charts up on the Saturday following the Monday if I remember correctly, and kept a copy of them for 30 years although they’re getting a bit indecipherable now though.

Figure 15

Figure 16

Figure 17

I never annotated this copy of a satellite fax chart that I made (fig 18), but by the look of it, it’s for sometime on the Monday.

Figure 18

Figure 19 (I can’t put an exact date to this photo)


I’ve added some additional information from The Met Office – I hope they don’t mind – which will bolster up some of the things I’ve said and add additional information that I couldn’t. Here’s an extract (fig 20) for the month of January from the The Snow Survey of Great Britain that you can access from the Met Office.

Figure 20 – Courtesy of the Met Office © Crown Copyright

Very luckily, the Daily Weather Summary [DWR] which started in 1981, has also has been digitised by the Met Office (thank you so much), and provides partial thickness charts for each day prepared by the old London Weather Centre [LWC]. It’s such a great shame that today’s version of the DWS contain no aerological charts whatsoever. So I’ve included a couple of LWC charts for the 12th and 13th  to compare with the three that I plotted and see the cold advection.

Figure 21 – Courtesy of the Met Office © Crown Copyright

Figure 22 – Courtesy of the Met Office © Crown Copyright

I did have a look in the Meteorological Magazine for the rest of 1987, and rather disappointedly found nothing about the cold spell, but then again it was always that kind of publication, which died not long after, but it was usually readable and interesting. The Weather magazine also had little coverage of the event as far I can see, although I did find an article by Roger Brugge in the May 1987 edition entitled ‘Low daytime temperatures over England and Wales on 12 January 1987‘ which was informative, but I think that the title was just a little understated, with temperatures of -6°C during the day at St Mary’s it could have been a little more catchy!

As a complete aside to all this January 1987 malarkey: It’s no wonder I lost interest in the Weather magazine during the 1980’s. Perhaps it was because they’re dependent on contributors to write articles about extreme weather events like this, or maybe they thought that one short article would cover it. To me the cold spell of January was just as remarkable a weather event as the October storm that occurred later in that year, but received very little coverage in comparison. I notice that recently the Weather magazine has become a lot more proactive, with a special article about the exceptional warmth and rainfall events of December 2015. If I’d have been the editor of Weather in 1987, I think I’d have made a little bit more effort to record the events of what was quite an exceptional cold spell for posterity.