140 mph gusts in Corsican storm

Figure 1

A fierce northwesterly storm is affecting the northwest of Corsica at the moment (fig 1), and there have been gusts in excess of 100 knots since 17 UTC at Cap Corse, with maximum gusts of 122 knots (140 mph) reported at 00,01 & 02 UTC earlier this morning. Mean speeds on the cape have been in excess of 50 knots for the last 24 hours.

From reading the Wikipedia article it appears that Cap Corse is the name for the whole peninsula at the top of Corsica, and that Capo Grosso (I wonder what that translates to?) is the proper location of the SYNOP station WMO #07785. Anyway at first glance the wind speeds look far too high, but they are supported partly by the pressure field, and surrounding observations – perhaps they’ve switched to reporting in knots and I’m still converting then from metres per second?! Here’s a map of Corsican SYNOP stations with Capo Grosso highlighted in yellow (fig 2).

Figure 2

Let’s take a little closer look at the SYNOP station at Capo Grosso with aid of Google maps (fig 3).

Figure 3 – Courtesy of Google Maps

Well, there you have it, Capo Grosso seems to be the French equivalent of what our old Needles battery is to us! It looks like the station is perched atop a 370 foot cliff which is open to anything that the Ligurian Sea can throw at it. The northwesterly gradient will no doubt be getting a hand from funneling off the Alps, and the Mistral that’s currently blowing across the south of France and the northwest of Italy (fig 4).

Figure 4 – Courtesy of Wikipedia

Why did the Met Office ever close Stornoway?

As you go through life you come up with questions that seem so obvious that you wonder why no one has asked them before. One of them is why did the Met Office choose to close the radiosonde station at Stornoway on the Isle of Lewis?

This is the 300 hPa chart for midnight last night across our part of the world, and as you can see Stornoway is conspicuous by its absence (fig 1).

Figure 1

Scotland did have three strategically placed upper air stations for many years, they where:

  • 03005 – Lerwick
  • 03026 – Stornoway
  • 03170 – Shanwell

All but one now remain. Germany on the other hand since unification, has maintained a good coverage of upper air stations which is second to none. You would have thought that the NWP models would have loved to have the latest information from the eastern edge of the North Atlantic Ocean, in fact since Stornoway closed, you could argue that the NWP model initial analysis is a little less accurate in that very important area.

Of course upper wind and temperature nowadays are being gathered by satellite sensors in space and commercial jets that criss-cross the Atlantic, and the requirement for observations made by radiosondes are no longer that important, but if that thought was shared by the rest of the other European weather services, why haven’t they closed many of their upper air stations too?

I can’t pinpoint the exact date when Stornoway did close, but I think the observations swapped to automatic sometime in 2002, which probably marked the end of the radiosondes, although it may well have been earlier.

Recently the weather radar has undergone a refit on Lewis at great expense to someone. It does rather beg the question that if weather radar data is so important in that part of the world why isn’t upper air data as well?

Another possible option that was open to the Met Office was to relocate to RAF Lossiemouth in Moray, and continue from there as they did for many years with the ad hoc launching of boundary layer sondes at Kinloss. This would have provided the military forecasters there with more observational data with which to forecast for military fast jets and helicopter movements to the rigs in that part of the Moray Firth and North Sea, but that didn’t happen either.

I suppose it’ll just have to remain another one of life’s mysteries why anyone in their right minds would ever close Stornoway, known only to the powers that be down here in Exeter.

BBC: Ben Nevis gets automatic weather station

The BBC news report that a temporary weather station has been installed on the summit of Ben Nevis this Autumn, this is 113 years after the original weather observatory which commenced observations in 1884 closed in 1904.

Figure 1 – Courtesy of the BBC and the National Centre for Atmospheric Science

The AWS looks suspiciously like a Vaisala Weatherhawk (Vaisala WXT536) something I’ve always wanted to replace my aging Vantage Pro with, but something we simply can’t afford my wife says. It stands just a few metres from the summit cairn on what looks like a six metre mast with two huge solar panels bolted on it to provide the power. It looks like the whole thing is a publicity stunt funded by the NCAS and Leeds University to help get a permanent weather station for Britain’s highest mountain. I’ve hunted around on their site, but can’t find any of the data that its reporting. In all honesty it will be little different from the readings that we see from the SIESAWS stations on nearby Aonach Mor (1130* M) or Cairngorm (1237* M) to the east, but then again 108 metres does equates to being 354 feet higher I suppose.

Powering the AWS

The big problem is getting mains power up to the top of the Ben would be very difficult. Even if they dug up the entire tourist route and paved it at the same time, burying the mains cable under it as they did it. No one would want to put pylons up it and scar the whole mountain, the objection let alone the cost would be enormous. Solar power from solar cells might be the best answer, but the Ben is so often cloud covered, and in winter the amount of sunlight those panel would receive would be very small indeed. I shouldn’t think that the transmitter or the sensors would require that much power, but the heating of the anemometer to keep it free of riming would be enormous, and this would be required for at least 75% of the year at a guess. That’s probably why the weather station is being removed in December, I doubt that the temporary structure they have in place at the moment is up to seeing a winter out at 1345 M, the force of wind on those two solar panels must be enormous, and I suspect that if they didn’t take it down it would be blown down anyway.

Possible Solution

I wrote an article earlier this week about the fact that there are two weather stations on Cairngorm, one owned and run by Heriot-Watt university and the other by the Met Office. Wouldn’t it be sensible if Heriot-Watt and NCAS collaborate with one another and move the existing one on Cairngorm (the one that pops up out of a protective can twice every hour) and relocate it to the old observatory ruins on top of Ben Nevis? Of course this doesn’t get round the crucial power problem, which short of installing some kind of small nuclear power cell might always be the problem. They must have power on Cairngorm to run both weather stations, but because it’s close by the ski slopes there is power to the Ptarmigan restaurant at the top of the funicular railway less than a kilometre away. It must have been a tough job but someone must have buried an armored power cable right to the rocky top of Cairngorm to provide power for those weather stations, and did a pretty good job of disguising it because I never saw any sign of them – that maybe the way to go on Ben Nevis?

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*Station height
Addendum:- After a little investigation the prices for the Weatherhawk don’t look as expensive as they were a just a few years ago.

Recent Cairngorm observations

Figure 1 – Courtesy of Heriot-Watt University & Facebook

There must be some weird kind of icing problem going on with the Cairngorm SIESAWS over the last 24 hours, because when things should have been cooling off yesterday the temperature sensor got stuck at around -0.7°C for much of the day and wouldn’t go any lower until 23 UTC last night when it suddenly fell to -3.2°C (fig 2). Equally, the wind sensor has now just stopped reporting at 05 UTC this morning, but oddly the station is still reporting a gust, but no mean speed or direction. The Aonach Mor SIESAWS is also out of action at the moment so it’s impossible to confirm what I suspect.

Figure 2

But then as I am writing this, I do remember that there is there is another way to verify those temperature readings, and that’s with the help of the Heriot-Watt University Physics Department! They have had an AWS on Cairngorm since 1977, that’s the one that pops up out of a big can every half hour to do an observation (fig 3) such a British solution to the icing problem!

Figure 3 – Courtesy of Heriot-Watt University & Facebook

The recent thermograph from the Heriot-Watt AWS (fig 4) confirms what I suspected about yesterday’s temperature readings from the it’s very close neighbour the Met Office SIESAWS:

Figure 4 – Courtesy of Heriot-Watt University

I hope they get the anemometer replaced in their AWS before much longer, they will certainly be hard pushed to replace it this late in the year I fear.

Overnight rain 3-4 November 2017

Figure 1

Wettest place overnight looks to have been Hurn in Dorset with 34 mm of rain between 18-06 UTC (fig 2). My estimates from the weather radar looks about 10% too low (fig 1), which at the resolution that you get from the Met Office images isn’t that bad.

Figure 2

15°C warmer than yesterday in places

Figure 1

It was 15.2°C warmer at Loch Glascarnoch at 06 UTC this morning than it was on Monday warming (fig 1), although there was little difference in the temperatures in the far south and southwest, where another widespread slight ground frost occurred (fig 2).

Figure 2

What they call Loch Glascarnoch is an AWS that sits midway between Loch Droma and Loch Glascarnoch (fig 3), on a featureless bit of moorland next to the A835 on the road to Ullapool. The only reason that I know a little bit about it is that it’s the starting place for a group of Munros called “The Fannaichs” that lie to the southwest, which my wife and I climbed on a summer’s day over 25 years ago now – how time flies! Don’t ask me why they don’t share the same spelling as Loch Fannich to their south, I have no idea. I recommend pulling into a lay by off that road on a clear evening in Winter to get the best view of the stars and milky way that you’re ever likely to see.

Figure 3 – Courtesy of Google Maps

A bit parky up the Brocken this morning

Figure 1 – Courtesy of harztourist.de

It looks a bit cold on top of the Brocken mountain in Germany this morning (fig 1). At 09 UTC the temperature was -1.3°C and the wind was still meaning 23 knots (Jag windchill -9.3°C). It’s not a particularly high mountain at 1142 M, and not that dissimilar to Cairngorm at 1245 M, although wind speeds never get quite as severe as they do in Scotland, the weather can still get pretty cold and stormy at times, as the plot grid for the last 24 hours shows (fig 2).

Figure 2