Mild air waiting in the wings

Figure 1

It might take the whole weekend before it gets across the whole country, but mild Atlantic air, which has already extended into the southwest of Ireland and England overnight, is waiting in the wings (fig 1). Temperatures of 11°C are already being reported in the southwest, in stark contrast to the -8.4°C over the snow fields of Scotland at the moment (fig 2).

Figure 2

The tendency in the GFS model over the next 16 days is for a gradual rise in pressure across the British Isles, and for an intense anticyclone to become established across the country by the start of February.

Figure 3 – Images courtesy of www.wxcharts.eu

Autopsy on a TV weather forecast

Figure 1 – Courtesy of the BBC (~20 secs of weather watcher pictures)
Figure 2 – Courtesy of the BBC  (~60 secs tomorrow’s weather)
Figure 3 – Courtesy of the BBC  (~20 secs the day after’s weather)
Figure 4 – Courtesy of the BBC  (~10 secs for warnings)

I thought that I’d perform a kind of ‘autopsy’ on what constitutes a typical weather forecast the follows the early evening news at 6.30 PM on BBC 1. It’s all over in just over in just a minute and fifty seconds, which is a ridiculously short length of time to cover the entire UK with a forecast for the next two days, especially in autumn and winter, when so much can be going on.

Overall, I think the weather presenters at the BBC do an admirable job of working under these severe time constraints, I certainly wouldn’t swap them their job.

The weather watchers slide show at the beginning when they highlight some severe weather event or contrast the difference between places across the UK is such a natural fit that you wonder how they ever managed without them before, although its usually at the expense of including a synoptic chart with isobars, which are omitted more and more these days. I wonder what changes are in store when the Meteogroup ‘The global weather authority“, finally unveils their new way of doing things in the spring?

Latest snow depths and avalanche risk in Scotland

Figure 1

There’s 38 cm (15″) of snow at Tulloch Bridge as of 16 UTC this afternoon with some more to come. The AWS at Tulloch Bridge is not particularly high at 249 metres above sea level (816 feet) lying as it does at the top of Glen Treig above the loch, but much more snow will have fallen on the higher slopes of the mountains on each side of the glen, and not just there, but across all the high ground of Scotland, Northern Ireland and northern England as you can see from the map of the latest reported snow depths across the country (fig 1).

Figure 2 – Courtesy of Bing maps and Ordnance Survey

It’s set to turn much milder from the start of next week over the whole country, and it maybe that the rapid thaw brought on by a lot of ‘warm’ rain will wash the snow of the tops, as it did on Mount Washington last week, and reduce the current avalanche risk, which is classed as ‘considerable’ for the mountains of Scotland at the moment (fig 3).

Figure 3 – Scottish Avalanche Information Service

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.

Gusts to 89 mph as Friederike batters the Netherlands

Figure 1

The northwesterly behind low Friederike is still producing storm force winds as she continues to track eastward, deepening a little in the process, to the north of the Netherlands at 09 UTC.  The 56 knot mean wind speed (violent storm force 11) and gust of 78 knots (89 mph) at the Hook of Holland stands out (fig 1).

Figure 2

Gusts belie the truth about Friederike

The worst is just about past now from low Friederike as she shoots off towards Germany to wreak more havoc no doubt. Yesterday mornings yellow warning of strong winds for gusts of 50-60 and a “small chance” of 70 mph issued by the Met Office didn’t last too long, because it was updated at around 03 UTC with a more cautiously worded one that upped the maximum gusts to 75 mph* (fig 1).

Figure 1 – Courtesy of the Met Office*

I don’t know what prompted the update at 03 UTC, but I don’t think it was the gust of 93 mph at Capel Curig, which happened at 2350 UTC and even before the warning had come into force (I did question why the start time had been 0005 UTC and not much earlier at 21 UTC). I think it was more likely that the Chief had just seen the T+3 forecast wind for eastern England from the 00 UTC mesoscale model, because let’s face it these days, and for many years past if truth be told, computers do all of the forecasting.

As always the media, and the Met Office to a large extent, seem to be completely fixated with gusts, and totally forget that storm force 10 – the basic definition of what constitutes a storm – is defined in the Beaufort scale as a 10 minute mean wind speed of 48 knots or higher. At Wittering this morning a true storm did occur, not many people noticed it, but I did, as did a lot of people in that part of Cambridgeshire as it rattled their windows. The winds were meaning at gale force 8 for around three hours between 03-06 UTC, with a maximum gust of 64 knots (~74 mph) at 05 UTC. The Met Office never mention the highest mean wind speed in any of their warnings, either for coasts, hills or inland, it would be just another thing that would require verification, and more often or not they would get it wrong anyway. Here’s a plotted grid of the last 24 hours observations from Wittering (fig 2).

Figure 2

Overall the updated warning just about covered it as far as maximum gusts were concerned (fig 3), that’s if you ignore the gusts at Capel Curig (93 mph), Aberdaron (78 mph) and Lake Vyrnwy (76 mph).

The last couple of days have been totally confusing since Met Éireann decided to call a tightening of the W’NW flow storm Fionn on Wednesday, especially when a potential and much better candidate for being named a storm arrived the very next day. I know that storm force winds can and do occur when the centre of the low is more than 800 miles away as it was on Wednesday on the west coast of Ireland. My idea for what it’s worth is that a truly memorable storm, and one that should be named, is a storm that’s associated with an intense vortex like the Braer Storm of January 1993 or the Burns’ day storm of 1990 were.

Figure 3

The final chart is the number of hourly observations when the mean speed was 34 knots or more – a gale to you and me (fig 4).

Figure 4

*I know I’m being even more picky than usual but if we have a ‘widely 50-60′ and a ’65-75 in some places’ what about gusts of 61-64?