22 May 2017 – Mesoscale trough?

Figure 1

I know I shouldn’t have tempted fate going on as I did about how warm it had been today. I wasn’t paying attention to the visible satellite image sequence this afternoon, but finally noticed the increasing cirrus and cumulus bubbling up over northwest Devon (fig 2). From the observations there’s certainly evidence of some kind of trough pushing into western areas of Wales and the southwest at 15 UTC, with a band of thick cirrus strung out along it. The increased humidity must have been enough to cause the convection, and if you look closer you’ll see a wind veer and increase in dewpoint, behind some small falls of pressure over East Wales (fig 1). It could all simply be down to a southward extension to the first of two occlusions that the Met Office are showing in their 06 UTC analysis (fig 3), but it’s certainly put paid to what had been a lovely afternoon here in south Devon till then.

Figure 2

Figure 3 – Courtesy of the Met Office

Classic dumbbell lows

Some classic dumbbelling going on between these two lows in the latest forecast frames from the GFS model as they orbit around the British Isles during the next week. I would challenge any broadcast meteorologist to find anything good to say about the weather if these charts are accurate.

Courtesy of OGIMET

If this wasn’t a polar low the next one could be…

Figure 1

The small low pressure in the Moray Firth at the moment (fig 1) doesn’t quite fit the bill as a classic polar low according to my old copy of the Meteorological Glossary. It describes a polar-air depression as:

A SECONDARY DEPRESSION of a non-frontal character which forms, more especially in winter, within an apparently homogeneous polar AIR MASS; near the British Isles the development is usually within a northerly or north-westerly airstream. The chief characteristics of this type of depression, which seldom becomes intense, are a movement in accordance with the direction of the general current in which the depression forms, and the development of a belt of precipitation near the depression centre and along a trough line which often forms on the side farther from the parent depression where also the pressure gradient (and surface winds) is increased.

Meteorological Glossary (6th edition 1991) Courtesy of the Met Office ©Crown Copyright

In this morning’s visible satellite image (fig 2) the trough, which the Met Office have as a wrap round occlusion in their midnight analysis, would usually occur on the western side of the low in this situation, or so says the glossary, but not with this feature looking at the imagery and the weather radar (fig 3).

Figure 2

Figure 3

The precipitation is of snow across the north of Scotland down to quite low levels this morning, and warnings have been issued by the Met Office (fig 3). I hadn’t notice that the Met Office had finally updated the dreadful mapping that they use in their warnings, a lot smarter, but about time.

Figure 4 – Courtesy of the Met Office

Although this low might not be classed as a classic polar low, a proper one might be developing off the coast of eastern Iceland, because the latest pressure falls at Torshavn (fig 5), indicate either a trough or maybe even a proper polar low might be squeezing itself into the tight northerly flow and head southward later today (fig 6), so you never know.

Figure 5 (the wind directions maybe spurious at times)

Figure 6 – Courtesy of OGIMET

Sign of things to come at Baltasound

The cold air has dug back in behind the cold front at Baltasound, turning the rain to snow, as the low pressure whizzes across the Northern Isles.

I wish someone would sort out that anemometer at Torshavn, I’m sure that the wind direction is the exact reciprocal of what it should be, it’s happened before, you just can’t trust those AWS.


Extreme Easters since 1772 in Central England

Figure 1 – Data courtesy of NCEP/NOAA 20th Century Reanalysis

The Met Office beat me to a story about extreme Easters of the past, but undaunted, and without the masses of climate data they have at their disposal, I pressed on with a bit of research of my own.

Because Easter is not at a fixed time each year it’s difficult to compare one with another. Easter Sunday can fall as early as the 22nd of March or as late as the 25th of April. I’ve used the daily CET series from 1772 (now there’s a surprise), and calculated a five-day mean, from Maundy Thursday to Bank Holiday Monday to do my comparison with. Because of the time range that easter can fall, I have base it on mean temperature anomalies rather than the mean temperature. So from what I’ve found the coldest Easter period since 1772 occurred in 1892 (fig 3). The Easter Sunday that year fell on the 17th of April so it was by no means early.

Figure 2 – Data courtesy of the Met Office

The mean temperature for the five days between Maundy Thursday and the Bank Holiday Monday in 1892 was 2.1°C, which was -6.4°C below the long-term average for that period (fig 3). The weather chart for the Sunday (fig 1) shows just what a bleak and cold Easter that must have been in eastern parts.

Figure 3 – Data courtesy of the Met Office

I couldn’t resist including the Monthly Weather Report for April 1892 after using it to check out my story because I was taken with some of the phrases that were used by whoever wrote the report. I have highlighted some of them from the PDF that I accessed courtesy of the Met Office (fig 4). The remark about Vapour Tension exceeding 0.25 on the south coast of Ireland and England was a real charmer, I bet sixpence was a lot of money in 1892, and what happened to the Weekly Weather Report?

Figure 4 – Courtesy of the Met Office and ©Crown Copyright

Conversely, the warmest Easter using the same method, fell in 1926 in Central England at any rate.  Easter Sunday that year fell on April 4th, and the five-day mean was +6.5°C above today’s long-term average, and if you look at the synoptic situation (fig 5) you can understand why. I did look for any weather related news for Easter 1926, and mistakenly thought that this was the year of the Easter Rebellion in Ireland, but I was 10 years too late, that occurred in 1916.

Figure 5 – Good Friday 1926, data courtesy of NCEP/NOAA 20th Century Reanalysis

Storm Doris as it happened

1635 UTC

Final wash up, with gusts to 81 mph on the north Norfolk coast in the last couple of hours. All in all quite a windy day. Down here in Devon it’s been quite bright, and apart from a few spots of rain from the cold front, and an odd shower, no measurable rain either. The NWP from earlier in the week was pretty good all in all.

Figure 15

This chart (fig 14), although quite simple tells you where the real gale occurred today, even London had a proper gale for at least a while today.

Figure 14

1250 UTC

Doris is now away into the North Sea, leaving gales behind in her wake. The 44 knot mean gusting 58 at Cranwell makes it a force nine strong gale even inland.

Figure 13

The 94 mph from Capel Curig is looking like the headline maximum gust from Doris. Snow was well forecast, but it wasn’t really cold enough to present any real problems.

Figure 12

1002 UTC

All high ground in Scotland seems to be getting a good covering of snow as forecast. I can’t see it causing too much of a problem at the moment though.

Figure 11 – Courtesy of Traffic Scotland

0947 UTC

A gust to 94 mph at Capel Curig at 09 UTC. Storm Doris now over the Lake District, and bottomed out at around 975 hPa. 5 cm of snow at Aboyne, and rain turning to sleet at Edinburgh.

Figure 10

0840 UTC

Gust to 82 mph at Capel curig in last hour. Rain reluctant to turn to snow over southern Scotland…

Figure 9 – Highest gusts 00-08 UTC

Impressive visible satellite image.

Figure 8

0800 UTC

Figure 7 – Aberdaron observations

Having had a quick look at the map of the Aberdaron site and the terrain, it’s no wonder they had a 53 knot mean last hour. I just wonder how the wind speed will react as the gradient starts to vear.

Figure  6 – Courtesy of Bing Maps & Ordnance Survey

0742 UTC

Gust to 78 mph in last hour at Aberdaron…

Figure 5

Wet snow in the usual places…

Figure 4

0635 UTC

87 mph gust at 02 UTC at Mace Head is the highest gust I can see so far.

Figure 3

Doris is more or less on track and moving very quickly eastward at around 975 hPa.

Figure 2

Nice spiral of rain around the centre, cold front already through mid-Devon. Very heavy rain now moving through NW England. Snowing in parts of central Scotland, but Doris is moving so quickly I can’t see this being a big problem (famous last words) like the wind.

Figure 1

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


29 January 2017

Warm air has pushed well into Southwest England behind the warm front by 15 UTC today, with dewpoints of 11 and 12°C following on behind. I must say that the 12 UTC German analysis (fig 2) is more preferable to the complicated 06 UTC analysis from the Met Office (fig 1): a frontogenetic (?) warm front, followed by another warm front and warm sector, with yet another inner frontal system and warm sector pushing into Iberia.

Figure 1 – Courtesy of the Met Office

Figure 2 – Courtesy of the DWD

Figure 3

Figure 4 – Courtesy of the Met Office

Just guessing about the cold front, it may well be a lot further east than I’ve put it (fig 3), and the next frontal system is following along hard on its heels, judging from the 15 UTC visible satellite image (fig 4). The rainfall is certainly well ahead of the surface warm front as well (fig 5).

Figure 4 – Courtesy of the Met Office

Here are the accumulations across the south that I’ve estimated from the weather radar since 06 UTC this morning (fig 5). Looks like highest totals seem to be generally between 16 and 24 mm, but there are areas of 24-32 mm over the Mendips that I can see. We’ve had 14 mm today here in mid-Devon so it’s not that far out, a thoroughly nasty day down here but it looked lovely further north.

Figure 5 – Data courtesy of the Met Office

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.

Capracotta today

I thought I’d take a look at what the weather was doing in Capracotta in Italy today. The situation is not unlike the one that produced the record snowfall back in March 2015 except for one key difference, and that’s the airstream is very much colder. As you can see (fig 1) there was 65 cms of snow lying at 06 UTC this morning and the temperature was -8.8°C at Campobasso just to the southeast of Capracotta.

Figure 1

As you can see the visible satellite image (fig 2) the Bora winds is streaming showers from across the central Adriatic into the Apennine mountains in eastern Italy south of 42° north, in a similar way to the lake effect snow in North America, the big difference being that the SST in the central Adriatic at the moment is 15°C and much warmer than the SST in any of the Great lakes, although the air is still very dry thanks to the Bora.

Figure 2 courtesy of Sat24.com and EUMETSAT

Here’s a reminder of where Capracotta is:

Figure 3 courtesy of Bing Maps

Unfortunately there’s no SYNOP station closer to Capracotta than Campobasso, so here’s a late afternoon webcam shot from Capracotta that I found to illustrate the conditions there at the moment.

Figure 4 courtesy of the town of Capracotta

So a reasonably good covering of snow there, but not to the record depth of 2.56 metres of March 2015. This is probably because the airstream although very cold and reasonably unstable is still quite dry. The latest NWP indicates it will stay very cold in that part of the world till the middle of next week before turning milder.