On Monday, February 8, 2016 at 12:09:40 PM UTC, wrote:
"xmetman" wrote in message
...
On Monday, 8 February 2016 11:35:50 UTC, Norman Lynagh wrote:
On Mon, 8 Feb 2016 02:24:07 -0800 (PST), 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.


Bruce,

The Vantage Pro console receives a wind measurement from the anemometer
sensorevery 2.5 seconds. That is the ever-changing figure that is
displayed on
the console. It calculates a rolling 10-min mean from those figures which
can be
displayed in the text bar on the bottom of the console screen. There are
other
options for that text bar.

A random 1-min mean wind speed may be higher or lower than a corresponding
10-min mean within which it is embedded.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
http://peakdistrictweather.org

Norman

Yes, of course you're right it could be. But what if the PC software people
use in conjunction with their AWS (to publish it on a website) has been
coded to select the highest 1 minute speed rather than the mean of the last
10 minutes?

All I'm trying to do is to compare like for like, i.e. mean wind speed
reported by people's AWS with those in UK SYNOPs, and it's not that easy!

Bruce.
========

In the real world it's gusts that do damage. And gusts can last for less
than a minute, so I'd say that peak 1 minute gusts will be most
representative of real life. Another issue is that we measure wind speeds at
10 metres above ground, so means speeds experienced by Joe Public will be
lower but 1 minute gusts will not be very different of course.

Will
--
" Some sects believe that the world was created 5000 years ago. Another sect
believes that it was created in 1910 "
http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------

Yes, ignoring Norman's 'minefield' surrounding mean speeds for the moment, many of the peak gusts reported have been pretty exceptional. The 100mph on St Martin's may seem very high, but bearing in mid it's been up to 79mph at Culdrose & 86mph at Land's End (I call it Land's End because Trebehor is basically just as exposed and people know where Land's End is) it's certainly not out of the question.

Rather worrying for the next high tide is the sea state, swell now in the 35' to 40' range at Sevenstone. In fact 38' at 10:00. Given that I don't recall seeing it that big in 2014, and a 11.5mm swell has a 10 year return period (thanks Norman!) that is seriously big. These are significant wave heights, not maximum, the biggest waves will be a good deal bigger.

One huge sea along the north coast.

I'm one of the people in west Cornwall with electricity. Several schools are shut as there is no power. Cape Cornwall school was evacuated due to storm damage.

I have to admit, it is exciting. If I can get to Sennen OK, pics later

Graham
Penzance

In message ,
Graham Easterling writes
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



Ho hum, welcome to winter 2015/16.

We've been having this sort of thing since November.


--
Cheers

Jim

On Wednesday, February 10, 2016 at 3:46:24 AM UTC, Jim Kewley wrote:
In message ,
Graham Easterling writes
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



Ho hum, welcome to winter 2015/16.

We've been having this sort of thing since November.


--
Cheers

Jim

Well, not quite, the peak swell height reached 19m! at the wave hub yesterday, with a significant wave height near 35'

You don't 'often' get that sort of thing anywhere.

Graham
Penzance

On Wednesday, February 10, 2016 at 11:17:27 AM UTC, Graham Easterling wrote:
On Wednesday, February 10, 2016 at 3:46:24 AM UTC, Jim Kewley wrote:
In message ,
Graham Easterling writes
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



Ho hum, welcome to winter 2015/16.

We've been having this sort of thing since November.


--
Cheers

Jim

Well, not quite, the peak swell height reached 19m! at the wave hub yesterday, with a significant wave height near 35'

You don't 'often' get that sort of thing anywhere.

Graham
Penzance

Sorry, not yesterday, Monday. Time goes so quick when you're having fun.

Graham

On Monday, 8 February 2016 08:51:24 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?

Lands End CYR?

"xmetman" wrote in message
...

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).
====================

Is it a VP you have (aka VP1 nowadays) or a VP2? If so, it might explain the
apparent default to small cups - that's not the been the default for a long
time. (Not that it makes a huge difference, it's just a different
second-order LUT that's applied for correcting speed vs direction AIUI to
account for effects of the anemometer arm geometry.

But why would you suppose that it collects 1-min means rather than averaging
out the full set of 2.5 sec gust values that are the values actually
measured?

In message ,
Graham Easterling writes


Ho hum, welcome to winter 2015/16.

We've been having this sort of thing since November.


--
Cheers

Jim

Well, not quite, the peak swell height reached 19m! at the wave hub
yesterday, with a significant wave height near 35'

You don't 'often' get that sort of thing anywhere.

Graham
Penzance

No not round the Isle of Man, there's not enough fetch on the sea for
the waves like that to build up.

We've certainly had similar wind speeds on several occasions though, not
to mention rainfall. In this SE/SW centric group it's never noticed,
reading this place you'd think the world revolves round SE London, Devon
and Cornwall. Hence my impatience with people calling this winter
boring.

--


Jim

On Wednesday, 10 February 2016 15:04:08 UTC, JohnD wrote:
"xmetman" wrote in message
...

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).
====================

Is it a VP you have (aka VP1 nowadays) or a VP2? If so, it might explain the
apparent default to small cups - that's not the been the default for a long
time. (Not that it makes a huge difference, it's just a different
second-order LUT that's applied for correcting speed vs direction AIUI to
account for effects of the anemometer arm geometry.

But why would you suppose that it collects 1-min means rather than averaging
out the full set of 2.5 sec gust values that are the values actually
measured?

Hi John

I know in the electronics it must collect data and average it out somehow, but as a programmer as far as I can see, the minimum resolution of the raw data it stores is 1 minute and not 2.5 seconds. All the data logger is collecting for wind speed I imagine is the number of revolutions that the anemometer cups make in 2.5 secs, and it would be a good idea if these values were accessible (even if was just for the last 10 minutes) before they were thrown away.

I realise that my Vantage Pro is coming up for 12 years old this April but I would like to think that with technology such as the Raspberry Pi, that either Davis or someone else would be able to put together a cheaper weather station that I could replace it with.

Personally I've always thought that the anemometer has always under read, that's probably because for twenty years of my life I was used to watching the trace from a Munro anemograph on an RAF airfield where there few obstructions. My anemometer for the last 10 years has been 35 ft of the ground on the top of our chimney and we aren't really in open country. The 8th was one of the windiest days I've seen in this part of Devon and I think the gust of 45 kts was the highest gust (max mean speed for the day was 22.6 kts) I've ever seen it register. A hundred yards away in the corner of our meadow a very large tree (~30 ft tall) was blown right over. The roots looked very shallow and in recent years other trees that were giving it shelter had been felled. But if you used the Beaufort scale to estimate the mean wind speed that lunch time you would have said it was force 10. So is it possible that a 45 knot gust can uproot a tree?.

I look at the cups spinning in a 20 knot mean, as it was on Tuesday and I wonder just how much faster they would have to spin to record a full gale, let alone a 103 knots. I think it's some kind of mercury switch that does the counting, how many revolutions a second would those cups be spinning at to measure 34 knot mean? And that's why I would like to see that kind of raw 2.5 second data. I suppose that you could strap the whole thing to your roof rack on a calm day and drive around in your car to see what it recorded!

Bruce.

Ho hum, welcome to winter 2015/16.

We've been having this sort of thing since November.

Cheers

Jim

Well, not quite, the peak swell height reached 19m! at the wave hub
yesterday, with a significant wave height near 35'

You don't 'often' get that sort of thing anywhere.

Graham
Penzance

No not round the Isle of Man, there's not enough fetch on the sea for
the waves like that to build up.

We've certainly had similar wind speeds on several occasions though, not
to mention rainfall. In this SE/SW centric group it's never noticed,
reading this place you'd think the world revolves round SE London, Devon
and Cornwall. Hence my impatience with people calling this winter
boring.


Jim

I thought I'd said rather the reverse!

Graham

On Thursday, 11 February 2016 10:31:53 UTC, Freddie wrote:
xmetman Wrote in message:
On Wednesday, 10 February 2016 15:04:08 UTC, JohnD wrote:
"xmetman" wrote in message
...

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).
====================

Is it a VP you have (aka VP1 nowadays) or a VP2? If so, it might explain the
apparent default to small cups - that's not the been the default for a long
time. (Not that it makes a huge difference, it's just a different
second-order LUT that's applied for correcting speed vs direction AIUI to
account for effects of the anemometer arm geometry.

But why would you suppose that it collects 1-min means rather than averaging
out the full set of 2.5 sec gust values that are the values actually
measured?

Hi John

I know in the electronics it must collect data and average it out somehow, but as a programmer as far as I can see, the minimum resolution of the raw data it stores is 1 minute and not 2.5 seconds. All the data logger is collecting for wind speed I imagine is the number of revolutions that the anemometer cups make in 2.5 secs, and it would be a good idea if these values were accessible (even if was just for the last 10 minutes) before they were thrown away.
snip

that's why I would like to see that kind of raw 2.5 second data
It is available, Bruce. Davis publish details of their serial
protocol, and there is software available (Cumulus for example)
that uses it. Now there's a programming challenge for
you!

--
Freddie
Pontesbury
Shropshire
102m AMSL
http://www.hosiene.co.uk/weather/
http://twitter.com/PontesburyWx for hourly reports


----Android NewsGroup Reader----
http://usenet.sinaapp.com/

Hi Freddie

I've already written it!

That was one of the main reasons to buy the VP back in 2004.

I don't tend to use the applications that I have developed to download, parse and display the VP data as much as I should do, and I've only written one or two blogs about it:

https://xmetman.wordpress.com/2015/1...it-rains-from/

I've been meaning to write an application to analyse temperature data and calculate the hours of frosts in a day, or the amount of time a temperature is above 25°C in a day, which would give me another way of visualising the almost 12 years of 1 minute data that I have.

As far as I know, even using the Davis API you can only access minute data, and most of the time this is fine, but as I said in my reply, sometimes it would be good to get at the 2.5 second data that the 1 minute wind speeds are derived from.

Bruce.