Just a few bones to pick with today’s BBC forecast brought to us by Helen Willets which I couldn’t help but get off my chest.
When are the UKMO and the BBC going to stop using wind speeds from the Needles Old Battery on the Isle of Wight whenever we get any coastal gales? I can see why the Daily Mail or the Daily Express would have no qualms in using them in their headlines, but not so called professional organisations such as them. There is a reason why wind speeds have been gusting to nearly 90 mph today at the Needles, and that’s because the anemometer sits at atop a 400 foot sheer cliff. And it’s the same reason why wind speeds from mountain stations are normally never mentioned and that’s because they are unrepresentative of low lying sites in open country.
So a land gale is when we get a gust of wind of 50 mph or more, well that’s a new one on me Helen, whatever happened to the good old Beaufort force 8 – a ten minute mean speed of 34 knots or more?
A WIND with a mean speed in the range 34-40 knots (force 8 on the BEAUFORT SCALE of wind force, where it was originally described as ‘fresh gale’) and/or gusts reaching 43-51 knots, at a free exposure 10 m (33 ft) above ground. In general, a mean speed over a period of 10 consecutive minutes, as reported in synoptic code, is implied by the term ‘gale’; where this is not intended, the specific threshold for the gusts is used. While the term ‘gale’ applies strictly to the speed limits given above, and higher winds are referred to in other terms, e.g. severe gale, storm, etc., statistics of gales refer to the attainment of mean speeds of 34 kn or over.Met Office Glossary 1993
I simply wouldn’t have displayed this graphic of wind gusts across the country like Helen did, it’s plainly wrong. I don’t know if the gusts have been grabbed from observational data or from NWP values. They certainly aren’t gusting 35 mph at the center of low Marco this afternoon, here’s a chart showing the reported gusts at 14 UTC, notice the absence of gusts above 25 knots across the north of Yorkshire.
I will certainly agree with Helen that it’s been a cold day for May across IONA, but I wouldn’t describe it as either a cool or a chilly day, I would describe it as being rather cold or just plain cold. When you are enduring anomalies as low as -6°C and negative wind chill values like we are today, it’s a bit of an insult to describe temperatures as rather chilly, just tell it like it is.
“Unseasonably deep low“
Finally the low that we have over the UK today with a minimum central pressure of around 986 hPa is deep, but not that unusual for May. Here’s one from as recently as May 2015 just to prove it.
If you look at this reanalysis data for extreme MSLP values in May across the central UK you’ll see that lows this deep are far from uncommon. Todays low may seem “unseasonable” but I think the real reason is that we just forget what came before.