Friday, February 04, 2011

THEY TAUGHT US WELL

Seeing a plastic bag being blown down Barnard Avenue tonight, in the strong wind, I recalled geography master Geoff "Shoddy" Jarvis teaching us the benefits of the Beaufort Scale at Brigg Grammar. I'd reckon the current weather conditions are 6/7.
Now over to Ken Harrison for the finale...

4 comments:

Ken Harrison said...

I'm not certain what the winds been like around Brigg today...I've been around Leeds where there are a number of lorries overturned on both the M62 and M1......I was about 300 metres behind a high-sided artic just before Junction 30, the Rothwell turn-off, when the wind caught the lorry and sent it sloughing down the road on its side. North of Leeds, matures tree had been brought down and one found it difficult to walk against the wind.
The current weather forecast predicts winds 70mph + over northern England/Scotland tonight. 70 mph is often decribed as a Severe Storm, of a Baufort 10 scale.

At sea, a Baufort 10 is a Violent Storm. Indeed, when the Baufort scale was devised is was used to describe the cumulative affects of sea-swell, tide and wind speed. For example sea (tide) against wind can create extreme angry sea even tho' the relative wind speed is low.

For info: the wind direction of wind crossing an expanse of water will veer when it meets lands and the reciprocal when land wind meets sea. One can also see this affect on lakes and across wide rivers.

When I took my boat into the Humber and the coastal waters it was blinking rough with anything more than a Force 4 (slightly less than 20mph), but I've been dinghy sailing on lakes when its been Force 5, perhaps 6 (up to 30 mph)...although capsizing was a common occurrence.

As a rule of thumb wind at sea is usually greater than wind on land...For example, if its Force 3 about Brigg, expect Force 5 at the Humber Light-Ship.

Structural damage to houses/trees/property (relative to the inherent condition of such) is possible around Force 8 and above - 35/40 mph or 'Gale'.

Another rule of thumb....if you can hear overhead wires whistling, or howling noises in chimneys and similar place, the wind speed is around 30mph or the upper end of F6 - going to F7. I can hear such noises in my gas fire vent, so I guess the wind about Wrawby at this present time F6 - possibly greater.

Advance bit:
Your empirical observation of the plastic bag, Scribs also possibly brings into the equation, the vortex effect of buildings to both wind speed and direction. For example, moderate wind travelling between houses - ie down a street could be conditioned by the Vettori
effect - ie lower pressure/higher velocity......it can be especially severe in and around high-rise buildings. (If you re-call, the Venttori tube is an important component of a carburettor and the same principle occurs over an aeroplane's wing)

Anonymous said...

On the subject of plastic carrier bags blowing in the wind - we used to call them witches knickers when they get trapped in trees when I was a kid.

Ken Harrison said...

I like that, Gavin.

Alan Richardson said...

Well here at Ancholme Mews, the wind has finished off what the snow and ice started and firmly planted a length of guttering into the lawn. looked like a piece of modern art until it was safely removed and put to one side. We are now waiting for the insurance company to give the go ahead for the repairs.