On Mon, 8 Feb 2016 03:08:31 -0800 (PST), xmetman wrote:
On Monday, 8 February 2016 10:39:50 UTC, Graham Easterling wrote:
On Monday, February 8, 2016 at 10:24:08 AM UTC, xmetman wrote:
On Monday, 8 February 2016 09:21:57 UTC, Graham Easterling wrote:
On Monday, February 8, 2016 at 8:51:24 AM UTC, xmetman wrote:
On Monday, 8 February 2016 08:41:23 UTC, Graham Easterling wrote:
Gust of 86mph at Land's End. Mean speed reached 67mph!
Wind WNW offshore here, but still a gust of 59mph, the strongest in a W-NW wind since November 2009.
Given the time of high tides, I think 6pm is a strange time to remove the warning. Significant (not maximum!) swell height now 30' at Sevenstones. Easily the biggest since 2014.
Graham
Penzance
Graham
Where do you get that observation for Lands End from?
Bruce.
It's here http://www.landsendweather.info/met/mainframe.htm . It's actually the Porthgwarra side of Land's End, near Gwennap Head. It's run by John Chappell
I see from your list Culdrose reached 79mph. I think most of the the west Penwith peninsula has seen gust well 70mph (ways from sheltered Newlyn/Penzance). 76mph gust at St Ives.
Under these conditions the webcams are useless, covered in salt http://magicseaweed.com/Live-Sennen-Webcam/65/ vut I hope to get to Sennen this afternoon and hopefully post some pics lately.
I think the real flooding issues will be on this afternoons high tide, the swell was smaller on the last one, and the period is getting longer now.
Graham
Penzance
Graham
I can see the site and the anemometer and vane using Google street view. Mean speeds as high as 67 and gust to 86 mph will cause damage and look a tad high to me.
It got me to thinking about cup size of my Vantage Pro. I've just checked mine and realised that I've had it on 'small' cups for many years (oops!), I had thought it would default to 'large' (wrong!). I don't know how much difference that will make to the speed, probably not a lot.
The upper air station at Camborne (81 M amsl) was meaning (at 09 UTC) 44 mph with gusts to 65 mph, that still can't match the latest live mean wind speeds from Trebehor (270' ASL).
I suppose the Vantage Pro just collects 1 minute mean speeds and graphs those values in its own LCD display, and it's down to the display software on the PC to take the average of 10 of those one-minute values to produce a 10 minute mean. A one minute mean of 67 mph would be significantly higher than a 10 minute mean (~x1.2 or more higher). The length of that mean should be a user setting I would have thought and I bet it's not 10.
Bruce.
You can't really compare Camborne with Land's End, it's like comparing the centre of Torquay with Berry Head. John is quite careful with his setup, I suspect he's following this thread.
Remember, the area near Land's End is used to gusts in the 80-90mph range, (I think Gwennap Head holds the record for a lowland site on mainland England & Wales, 106mph?). There are no real trees or wooden fences etc, mainly granite buildings and stone walls (Cornish hedges) so the damage is far less than in an area not susceptible to severe gales.
Graham
Penzance
Graham
I just commented that it looked a tad high. And the reason that I compared it to Camborne is that it's the nearest land station, and we are not exactly comparing it to Lands End, but Trebehor which is 1.5 miles inland. All I was saying is that if the software is pushing out a 1 or 2 minute mean, this is not the same as a 10 minute mean, and the mean speed will be much higher.
I notice that the weather buoy 62107 is reporting 280° 48/82 (55/94 mph) at 10 UTC but that's ~30km offshore.
Bruce.
This really can be a bit of a minefield. Reported mean wind speeds are
'snapshot' winds. They are not the maximum that occurs. The convention in the UK
is that reported mean wind speeds reported in SYNOPs are the 10-min means
between HH-20 and HH-10. Almost certainly, in any hour there will be a 10-min
mean speed that is higher than any that is reported in the hourly SYNOPs. If any
10-min mean is assumed to be made up of 10 consecutive 1-min means then
approximately half of those 1-min means will be higher than the 10-min mean and
half will be lower than the 10-min mean. This means, for example, that the mean
speed during the last minute of a 10-minute period has an equal chance of being
higher or lower than the 10-minute mean. The highest 1-minute mean within a
10-min period will always be higher than the 10-min mean but that is not what is
reported by stations that report 1-min means. It is the figure that is used in
hurricane forecasts, for example, but the conventions used in forecasting are
different to those used in observing. As I said, it's a bit of a minefield.
--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
http://peakdistrictweather.org