UKH

I'm looking at yr.no, MWIS and mountain-forecast. They all seem to agree on precipitation and wind direction, but the wind speeds are not even close. Looking Cairngrorms/Ben Macdui for tomorrow.

MWIS for Eastern Highlands

South or southeasterly in the range 40 to 65mph. Generally strongest Cairngorms plateau, speeds varying considerably between tops; sudden gusts lower slopes (particularly north of Cairngorm plateau).

http://www.mwis.org.uk/pdf/weather-forecasts/EH-MWI-WM11772_2018-12-13_1238...

Mountain-forecast for Ben Macdui

70-75kph (about 45mph)

https://www.mountain-forecast.com/peaks/Ben-Macdui/forecasts/1309

yr.no for Ben Macdui

7-8m/s (about 18mph)

https://www.yr.no/place/United_Kingdom/Scotland/Ben_Macdui/long.html

MWIS and MF seem to be similar but yr.no is nowhere near. Am I reading the predicted speeds from yr/no incorrectly or missing something, or is this just a natural variation in forecasts? I've never found yr.no to be accurate, and am curious if it's me or them.

I have been caught out by believing YR's wind speeds and getting a total battering. Stick with met and MWIS!

Have you looked at windy.com? You can compare different weather forecast models.

YR's windspeeds are always hilariously underestimated. Anything more than 10m/s on there translates to seriously bad news in the real world.

YR's wind speed are utter rubbish. In fact I don't rate YR at all, there precipitation can be quite hard to work out as well. Mountain-forecast.com is my new favourite weather site

It's because the wind travelling over the Scottish Highlands has reduced in speed by the time it reaches Yr HQ in Norway. Hence the wind is measured as being less.

Yr shows the base speed, the minimum between gusts. Other sites like smhi(no good for scotland) show both, so you might get 4m/s(15m/s).

As said above if yr says anything over 10 or 12m/s then expect it to be pretty mental on the ground. 

You've beaten me to it, I was thinking about posting on that.

Their temperatures are often estimated lower too but by so much.

MWIS on the other hand often gives a higher windspeed than turns out to be the case but sometimes not by much.

It's not hard to see that yr.no is ignoring altitude. This is a bit strange since the temperatures in their forecasts seem to account for altitude effects but their wind speeds do not. A quick look at their 2m/s wind forecast for the summit of Mount Everest today provides all the evidence one needs.

+1 for Windy. DMI (the Danish met office) use it when they can't figure out the weather themselves...

FYI, for Cairngorm Mt as well as other locations you can get real time actual info (delayed by 1hr) Here, as you can see on Thursday  morning it was averaging over 100 mph needless to say I went home! 

http://www.weathercast.co.uk/world-weather/weather-stations/obsid/3065.html

Plus another for windy. It gives you the raw data out of the various forecast models to work out for yourself what it’s going to be like. I can spend hours looking through the patterns.

I gave up on YR last winter when predicted zero snow, in fact no precipitation at all for my locale. Couldn't have been more wrong as I enjoyed a couple of days off work due to heavy snow.

Thanks everyone, really useful.

In reply to pass and peak: Thanks for the link, I'd used Cairngorm AWS before. And it was a shame the Aonach Mor weather station went offline a few years ago. Seems to be back now:

http://www.weathercast.co.uk/world-weather/weather-stations/obsid/3041.html

Much as folk like to deride weather forecasters, it should not really be a surprise that mountain specific forecasts for the UK written by experienced humans are likely to be a lot better that machine generated generic forecasts coming from a different country. Having said that, even automated forecasts should be doing a much better job of extracting sensible wind speeds from the raw model output data. 

At the end of the day, any of the computer based forecasts are going to have inaccuracies in unpredictable hill areas, but I agree that the wind speed element on yr.no is poor. And most of us have to convert it to mph from m/s. 

I used to use yr.no quite a lot, and if in the wilds with a poor phone signal, I find its app loads faster than others, needing less signal, and useful it holds the data from the last time you connected it so you can remind yourself again later. I find its general trend forecasting pretty good, the detail less so.

I mostly use xcweather for wind speed (as an open canoeist you can get quite obsessed with wind!), balanced with the other obvious sites/apps and if in the hills, always check MWIS/Met Office Mountain weather too. 

Ironically, the time when I've found yr.no to be most inaccurate was, of course, in Norway. Luckily, this was good news, as the forecast rainy days simply never arrived.