03/12/2006 11:47:45
Ken Cook wrote in message
.com

Will Hand wrote:
0930

What a night.
Front came through at 0415 with a temperature drop of 3 degrees
and a massive
gust of 68 knots (81 mph) calculated at 10m agl, recorded 3 metre
gust was 41
knots (49 mph). I did say I expected the strongest wind to be on
the front. This
is my highest recorded gust so far. I am relieved to say that
there has been no
damage to the house as far as I can tell. That was higher than
expected as I am
fairly sheltered from the south. Rainfall 30 mm BTW.

Will.

Hi, Will,

I'm a bit confused with this. My Met O Observers Handbook states
that
only mean windspeed should be adjusted to an effective height of 10
metres. Gusts should be reported as read with no alteration.
Has this changed and am I living in the past yet again?
49mph gust at 9 metres agl here, so nothing special yet.

Ken
Copley, nr Barnard Castle, Teesdale, County Durham
http://copley.mysite.orange.co.uk
Several decades ago (pre full wind installation on 10 metre tower) I
was using a had-held anemo here on Fair Isle. Instructions were to
add 33% to mean readings but NOT gust values - to correct to the 10
metre value. This caused much confusion at times - especially with a
SE'ly gale (no obstructions and a smooth topographical profile so a
gust factor of just 1.2 or so) as corrected mean speed often exceeded
uncorrected gust!
Comments and suggestions to the MO elicited no (reasonable) response
back then. My main concern was the 33% correction required for the
mean value. In well exposed sites this was FAR to much. I have done
some subsequent research comparing hand-held readings to those from
the 10m anemo. This indicates that (in my situation) a 15-20%
correction should be applied and not the 33%.
Chosing the best site for a low-level anemometer is extremely
important. For example, in any wind situation, using a hand-held
(cica 2m) anemo, I can get a very wide range of values. As low as 1%
(stand in the lee of a building) to 60-80% above (look for funneling
effect) that of the 10m value when the correction for height is added.

Just a typical November day here in the far north.
F7 ESE'ly just veering SSE'ly at the moment. Max gst only 46kt (46 x
1.151=52.9 mph) earlier this morning with 38kt gst past hour. PPPP at
12z 964.2 hPa, ppp -4.8 last 3hr.
Not so good on the sea though with extremely rough conditions
persisting. Last time our boat managed it across to the Shetland
mainland was 12 days ago. Luckily we managed to get a few essential
supplies in by air last week - fresh fruit. Keep scurvy away? No -
included lemons for the G&Ts! Mind you ... were rapidly running out
of beer as well as other 'essential' (liquid) supplies!!
Dave
Fair Isle