A few bones to pick with today’s BBC forecast…

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.

Courtesy BBC

The Needles

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.

Courtesy BBC

Land Gale

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?

GALE

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

Graphics

Courtesy BBC

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.

Temperatures

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.

8 thoughts on “A few bones to pick with today’s BBC forecast…”

  1. I’m a little confused by the criticism in the Land Gale section. The inference is that 50 mph gusts doesn’t constitute a gale and only the mean counts but the glossary quoted below it contradicts the point being made saying a mean or gust satisfies the definition. Current definition remains unchanged from the 1993 version https://www.metoffice.gov.uk/weather/guides/coast-and-sea/glossary

    1. Don’t be confused.
      Forget gusts.
      The definition of a gale is a mean speed of 34 knots and has nothing to do with gusts.
      And a mean speed is a period of 10 minutes, and not just the one or two minute means used by the NHC for tropical cyclones.
      I speak not only as an xmetman, but also an ex-observer.

      1. Hang on, it says right there in the Met Office definition “or gusts reaching 43-51 knots”, which a quick Google tells me is 49.5-58.7 mph. 50 mph is a gale then, or perhaps as an observer you knew better than the Met Office?

      2. Whilst NCMs are still coded with definition of gale under the original definition, marine forecasts in the UK (and observations used to verify them) now use the definitions contained in the link. That is, it can be mean or gust criteria that can satisfied to define F8 through F11.

        1. That may have to do with the observations they get from the anemometer on the buoy.
          it could be that they only report a 1 or 2 minute mean and not a ten minute mean like an AWS on land would so they have to compromise.

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