A Channel Bridge – don’t forget about the weather Boris!

Figure 1 – Courtesy of BBC News

There’s no doubt in these days of advanced materials and engineering techniques why a bridge can’t be built across the English Channel, but here are a few problems that they would have to overcome to make it a success:

Cost- but that shouldn't be a problem in these days of PFI2.

Security - stopping illegal immigrants from simply taking a twenty mile walk across it.

Maintenance - apart from who would choose the colour, painting it would be a nightmare, and what happens when you drop your brush?

Weather - this is one that I imagine didn't immediately spring to the mind of Boris Johnson.

I thought that I’d use SYNOP observational data from the AWS on the Sandettie lightship, which lies approximately 8 or 9 nautical miles to the northeast of where any bridge might be built to see the kind of wind speeds any bridge would have to cope with.

Figure 2 – Courtesy of Google Maps and Bracknell District Caving Club

Figure 3 is an anemograph of the hourly surface winds since the 1st of November 2017 from Sandettie, in what’s been more or less a fairly typical autumn and winter so far across the British Isles. As you can see the English Channel, especially the mid-channel, is a very windy place. The yellow outlined smoothed line in the top chart is a 24 hour moving average of mean wind speed in knots. The mean looks to be about 20 knots for the last 11 weeks or so, with windier spells when the mean varied between 25 and 35 knots. As you can see there were plenty of occasions when the gusts (darker red) were of storm force 10, and on three occasions at hurricane force 12 strength.

If the bridge is to stand clear of shipping it will need to be high and the anemometer on Sandettie can’t be much more than 10 metres above the sea surface, so if anything you might need to add an extra 10 or even 20% to these values to get an idea of what the bridge would have to tolerate. Cars and lorries would have to be almost boxed in to prevent them from being side-swiped by any gale, if they weren’t, I can imagine that the bridge would have to be closed for extended periods during any autumn or winter.

Figure 3

Apparently the longest bridge in the world at the moment is the 26.4 mile long Jiaozhou bay bridge on the southern coast of China’s Shandong Peninsula in northeastern China (fig 4). Chinese workers there toiled at marathon pace to build the bridge in just four years, starting at each side and meeting in the middle. The structure has 5,200 pillars and cost at least $2.3 billion. The bridge is apparently earthquake and typhoon proof, and designed to withstand the impact of a 300,000 ton vessel.  I wonder if that’s the team Boris is planning to get to build it?

Figure 4 – Courtesy of the Xinhua News Agency

What wind speed will bring down a tree?

Figure 1 – Courtesy of BBC News

I saw this BBC news item and thought that in the light of the recent strong winds it might be of interest. I’ll let you run the video clip and find out the answer to how strong the wind has to be, to suffice it to say, and being the old curmudgeon that I am and in my best Victor Meldrew voice, I don’t believe it. It would be interesting to see the research on this one, because there must be other mitigating reasons why a tree is blown down, such as exposure, whether it’s in leaf, the health of the tree, how deep the roots are to name just four.

BBC: New radar on Lewis can measure size of snowflakes

Figure 1 – Courtesy of BBC News

The Stornoway radar is now back in service after being upgraded earlier this year. The only thing the Met Office now need to do is install one on Shetland. It’s difficult to understand why there has been a hole left in the coverage of the weather radar in the northern North Sea, in an area that must contain some of the busiest helicopter low fly zones in the world. There was talk a few years ago of establishing one at RAF Saxa Vord but it never came about. Recently it’s been announced that the radar station on Unst, which was mothballed in 2006, is to be reopened because of the need to monitor the increased Russian military threat. Why they need to measure the exact size of the snowflakes, when we already know that they’re pretty small beats me. They should be able to test that measuring out on Thursday of this week, all being well.

Figure 2

BBC: Yesterday’s flooding

Figure 1 – Courtesy of the BBC
Figure 2 – Courtesy of the BBC

It’s no surprise that there was such widespread flooding across the northwest in England and Wales yesterday with these kind of accumulations (fig 3).

Figure 3

BBC: Extreme flash flooding in Greece

Figure 1 – Courtesy of BBC weather

You can trace back the low that ended up being the root cause of the flash flooding in Greece in recent days as originating from the remains of what was tropical storm Rina that crossed the UK on Saturday. The Meteorological Institute of Berlin quickly renamed it Numa, but I did think that it would cause problems as it deepened over southern Germany on Sunday. I can’t add much to the fancy graphics and smart suit of Stav Danaos (fig 1), so this animation of 06 UTC MSLP charts for this week over that part of the world will suffice (fig 2). Hopefully the plotted values are the 24 hour rainfall totals might give you an idea of how wet it’s been over parts of Greece.

Figure 2

BBC: Antarctica’s warm underbelly revealed

News article courtesy of the BBC