Do gusts of over 50 mph require a yellow warning?

Figure 1

The Met Office issued a whole tranche of yellow warnings for heavy rain, snow and ice for the overnight period, as low Philine whizzed across the borders, but neglected to issue one for strong wind. This is getting a bit of habit with them now. I wonder just how high a gust has to reach before one is issued, obviously higher than the 79 mph at Capel Curig at 22 UTC yesterday evening (fig 1). They did go to town on snow and ice warnings, even one for ice down here in the southwest after the front cleared, although they never really amounted to a hill of beans. The warning for heavy rain was a horse of a different colour – but more of that later. As you can see my idiom output is set to maximum at the moment.

Just how windy was January 2018?

Figure 1 – Courtesy of the BBC

Last Monday night on BBC Spotlight, David Braine was looking back at January and saying about just how windy it had been in the UK particularly the southwest. David quoted some statistics for average wind speeds for the southwest (fig 1) which got me thinking about just how windy had it been.

Because I’ve been downloading hourly SYNOP observations for the UK for quite a while now I decided to find out how many UK stations had an average mean hourly speed of 15 knots or more during each of the last four January’s, and these are the four tables for each of those months (fig 2).

Figure 2

As you can see from this simple method 2018 was not particularly windy across the UK in general, being overshadowed by January 2015 and 2016. The mean wind from St Mary’s on the Scilly Isles is quite a good sentinel for wind speeds in the southwest. The mean there over the last four January’s has been 20.0, 20.4, 15.4 and 19.9 knots. So I would say that at least in this small survey January 2018 was no windier than usual.

Here’s a chart of the average mean wind speed this January for stations across the southwest (fig 3). What’s puzzling is that none of those stations have a mean speed of 17 knots as David showed in his graphic (fig 1). I’m not sure how he came up with that value, unless of course its some kind of  gridded regional mean wind speed from the Met Office.

Figure 3

The other thing I noticed that also looked a bit odd was the average gust of 27 knots that he quoted (fig 1). In a UK SYNOP report gusts are only reported if the wind speed in any hour has reached 25 knots or more. So the average would always be at least 25 knots, which would make it artificially high if it was made up of reported gusts – what about the hours when the gusts were below 25 knots? I would have thought the only meaningful statistics that you could extract would be the number of gusts that exceeded a specific threshold such as 34 knots, or the absolute highest gust for the month. Again I suppose it may be possible to derive a ‘average gust’ from a gridded dataset for a selected region. It would helpful in the future if the Meteogroup presenter on the BBC displayed a caption of where the climate statistics were for and the source of that information.

5 February 2018 – wind chill at 10 UTC

Figure 1

Lovely morning down here in the southwest, but the wind is adding a bit of a bite to it even so, with a-5.6°C wind chill at nearby Dunkeswell at 10 UTC (fig 1). The SC sheet that’s lying across northern England and Wales seems to be aligned with the lighter winds down the axis of the ridge (fig 2).

Figure 2

There’s talk of a SSW event later in the month, which may explain why the GFS model has been in a total quandary for a while now, with little consistency from run to run beyond T+120.

Winter in Africa

The cold air that’s currently affecting the North of Africa at the moment, is certainly producing some intense convection over the seas that’s resulted in this water-spout just off the coast of Tenerife yesterday. The video is courtesy of Twitter.

Figure 2 – Courtesy of Wikipedia

Up at Izaña on Tenerife at 2,390 metres (7,841 feet) above sea level, winter has the Observatory (fig 1) in its grips at the moment (fig 3).

Figure 3 – Courtesy of Twitter

Here are the observations from the last 24 hours from the Izaña observatory (fig 4).

Figure 4

And here are the temperatures for the last month at Izaña (fig 5).

Figure 5

So it’s no wonder that there was heavy snow in Ouarzazate, Morocco for the first time in 30 years on Sunday (28th January 2018). Thanks to Facebook for this particular video clip.

It certainly seems that there’s a lot greater chance of seeing some snow in North Africa than there is here in mid-Devon. It’s now over eight years since we have seen any snow lying here – what a place to retire to for a professed  snow lover!

24 January 2017 – line convection on cold front

Figure 1

One memorable thing that did come out of storm Georgina, was the line convection that ran southeastward across the country during the morning, it was associated with an active cold front that was aligned SW-NE, from Exeter in the southwest to Hull in the northeast at 09 UTC (fig 1). If you take a look at some of the times of the approximate peak gusts across the country, many of them occurred on the passage of the cold front (fig 2).

Figure 2 – Approximate hour of peak gusts

Georgina adds to the growing list of forgettable storms…

How many named storms can you remember? It’s a simple enough question and the scheme has been running for three years now so you should at least remember a couple. I can’t, but then again I’ve a dreadful memory, but you would have thought after writing an analysis on all twenty-three of them as I’ve done, I would have remembered  at least one.

Storm Georgina although it deepened explosively was just another failure in my opinion, another storm to forget, and again it was named by Met Éireann. Full marks to the Met Office for staying clear of this one. Met Éireann seem to be specialising in naming just about anything that comes their way at the moment, I suppose someone has to name them, and I’m sure if it hadn’t been them the French or maybe the Norwegians would have stepped in to do the honours.

Here’s an analysis of the top twenty or so peak gust from storm Georgina of Beaufort force 10 or higher, storm force gusts are an essential requirement of any reputable storm in my opinion, plus of course the obligatory vortex (fig 1).

Figure 1

The highest gust from a low-level land station was one to 85 mph at Benbecula on South Uist, the highest at all stations in WMO block #03 was the gust to 117 mph at the Bealach Na Ba on the road to Applecross in Wester Ross (fig 2). Interestingly the maximum gust across the Irish Republic was just 65 mph at Belmullet.

Figure 2
So much for storm naming – what about the warning?

I found it odd that there was just a single yellow warning issued for storm Georgina by the Met Office, and that covered just the Northwest of Scotland. Although the warning of gusts 50-60 occasionally 70-80 was very precise (as long as you weren’t driving to Applecross) the area of extent was far too limited. No warning were issued for the rest of Scotland, England or Wales, even though there have been gusts today of 83 mph at places such as Capel Curig and 70 mph on Emley Moor.

What difference is there for example, between the gust of 62 mph at Stornoway, in the yellow warning area, and the gust of 64 mph at Farnborough and not in the yellow warnings area? The chances of a slate being blown of a roof would be similar, but the difference in population would make the chances of it happening far greater at Farnborough.

In the table (fig 1) I’ve highlighted the stations that weren’t covered by the yellow warning, and as you can see they form the greater proportion of places that had storm force gusts. I don’t know, and can’t understand why a yellow warning wasn’t issued yesterday, when the GFS model correctly forecast peak gusts of 55 to 65 mph and occasionally higher for today. The Met Office needs to find some consistency in the thresholds they use in issuing warnings for strong wind, because I can’t see any logic in how they do it at the moment.

More explosive deepening and severe gales

Figure 1 – Courtesy of www.wxcharts.eu

The next Atlantic low is poised to run in later today and overnight and introduce gales across the whole country, with gusts to severe or even storm force across the northwest of Scotland. Low ‘Helene’, as the Institute of Meteorology at the Free University of Berlin have called it, will deepen according to the latest GFS model (o6 UTC) by around 29 hPa in 18 hours or so as it tracks across the Isle of Lewis and clips Caithness by 06 UTC tomorrow (fig 1).

The Met Office at the moment have issued a yellow warning for strong wind from 01 to 14 UTC tomorrow for gusts of 60-70 mph with some to 70-80 mph but it’s only for the northwest of Scotland (fig 2).

Figure 2 – Courtesy of the Met Office

The GFS model is forecasting severe gale force gusts ahead of the cold front across the whole of England and Wales later in the night (fig 3). There has been no word on any additional warnings for England and Wales from the Met Office, so I can only assume that the UKMO model is at odds with the GFS, or maybe that the fire at the Met Office this morning on a server, has been more serious than we thought and is somehow hampering them being issued?

Figure 3 – Courtesy of www.wxcharts.eu