mountain-forecast.com accuracy

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mountain-forecast.com accuracy

Postby Drew » Wed 10 May, 2017 5:03 pm

Does anyone have much experience of using mountain-forecast.com for pre-trip weather forecasts? Any thoughts on its accuracy?

For those who don't know it, it provides forecasts for specific mountains all around the world, even giving separate forecasts for certain altitudes on the mountain. I think it's aimed at climbers. Given I'm now under 3 weeks from doing a hike in Peru (Ausangate Circuit - relevant forecast at https://www.mountain-forecast.com/peaks ... casts/4500), I've started having a look at the forecast. My research for this hike has led me to expect daytime temps anywhere between single figures and high teens and nighttime temps regularly down to -5 or even -10. The temps in the forecast at 4500m (I'll be around that altitude a lot of the time) are a bit colder in the day than that but much milder overnight.

The mountain-forecast.com forecast for Mt Hotham (at 1861m) is quite different to BOM. A little cooler in daytime and a few degrees warmer overnight.

Thanks.
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Re: mountain-forecast.com accuracy

Postby neilmny » Wed 10 May, 2017 6:17 pm

`I use it Drew but who knows with weather.
The BOM has a generic forecast for the entire region with temperature adjustment.
What I like about Mountain Forecast is it is specific to the actual location.

In terms of preperation I take the pessimistic view.....prepare for which ever is the worst forecast. Thay way your covered.
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Re: mountain-forecast.com accuracy

Postby Mark F » Wed 10 May, 2017 7:02 pm

I am not claiming the weather sites are necessarily bad and they are useful when going to unknown areas and places with poor met services. They are useful when trying to get weather forecasts where the alternative is an impenetrable web service in a foreign language - just how refugees and migrants must find it in Australia. However all the weather sites try to pretend they have accurate predictions for a very precise locations - they don't and they can't. They are using data from satellites and in Australia, bom ground stations (who also uses that satellite data) and cast then some general forecasting algorithms over it. They serve it up with the some adiabatic lapse rates similar to those used by bom. Most people don't check the weather at those locations so they never know how good or bad they are. Personally I just use bom for Australia.
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Re: mountain-forecast.com accuracy

Postby newhue » Thu 11 May, 2017 7:23 am

Sounds exciting Drew, I wish you well. For me the web site will be trying its best to be accurate, otherwise it will get no hits and become useless or worthless to its owner. Sites like BOM can be as sloppy as they like because they are government owned, though they will claim accuracy as people depend on them. Maybe just work on the macro; check for any big ugly fronts coming in the next week and make a call. Otherwise as you should be geared for all seasons, just look up now and then and enjoy the walk.
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Re: mountain-forecast.com accuracy

Postby Drew » Thu 11 May, 2017 9:23 am

Thanks for the replies.

Of course we'll be packing for the worst likely conditions and keeping an eye out for nasty fronts. And I'll ask around once in Cusco to get local knowledge and hopefully reports from people who've just done the hike. It would be great to know though if those overnight temperatures are remotely accurate, as 0 degrees is very different to -10! It might be the difference between renting CCF mats to boost our mats' warmth (which are R 4.4), renting warmer sleeping bags (likely to weigh a tonne) or taking our own etc.

The forecast for the next week for Cusco (which is at 3400m, 100km away from Ausangate) from a normal weather website is around 17-18 degrees max, 2-4 degrees min. mountain-forecast's lowest Ausangate forecast (3500m) is around 10-15 degrees max, 8-13 min. This makes me think that mountain-forecast's max temps might be around the mark but their minimums are a long way off!
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Re: mountain-forecast.com accuracy

Postby wayno » Thu 11 May, 2017 12:47 pm

its a rough indicator of what might happen, the temperatures i find are not too bad, its all computer generated forecasts aking into account average conditions for the time of year...
do not treat it as the gospel, but don't ignore it if its forecasting bad weather, as always be prepared for worse weather than forecast and plan accordingly
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Re: mountain-forecast.com accuracy

Postby newhue » Thu 11 May, 2017 5:48 pm

Drew you will be 1000m higher won't you, 10 deg variation would be possible. Still I see your point. Maybe pack a space blanket. Though painfully noisy, might be just the light weight thing to wrap yourself in if its that cold.

wayno, I wish the computer generated forecast were as accurate here in Aus as the NZ ones. Seems you guys can almost predict it to the hour, in the mountains, in my experience. We just hedge bets each way over here, chance of everything.
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Re: mountain-forecast.com accuracy

Postby wayno » Sat 13 May, 2017 7:14 am

forecasting is still hit and miss in NZ, maybe its more accurate than Oz but its a far smaller island. I never trust a forecast completely, its just an indicator of what has a moderate chance of happening and i prepare for a range of conditions around what is forecast... with forecasts being updated so often now, it pays to check regularly, I encountered a thunderstorm once and it wasnt put in the forecast until it was already happening..... we can get heavy rain forecasts and it can be hit and miss where it actually rains. some places the rain can be very localised from one mile to the next... the weather has deteriorated in recent years , tropical cyclones are having a much bigger influence in our weather, we're getting a month of rain in a couple of days, repeatedly... the tasman sea temp has gone up 4 degrees. although in general things are warmer, it actually brings more snow at times, because theres more humidity in the air and we're getting bigger dumps, then it melts and the rivers flood after the storm has gone...
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Re: mountain-forecast.com accuracy

Postby Drew » Mon 15 May, 2017 10:50 pm

I just found a trip report on Tripadvisor from an Ausangate trip just a few weeks ago. It doesn't sound like they do much hiking and I'll take what they say with a grain of salt, but regarding temperature they said: "Layers, layers, layers! It can be really warm and sunny (75-80F) then 30-40 within a few minutes based on weather, so be prepared with layers"

It's a bit hard to believe it was that warm (23-26 celsius), but even if they're exaggerating that's a lot warmer than the forecast temps. I might comment on their post and see if I can learn more.
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Re: mountain-forecast.com accuracy

Postby Swifty » Tue 16 May, 2017 5:26 pm

Hi Drew,
I was in the Puna in NW Argentina in late March. We used that mountain forecast website, really just to see if there are any approaching storm systems or not, their wind predictions were pretty useful for us.
Regarding temperature, we were at 4,000m and had balmy days (low to mid twenties), and clear, cool nights with windless dawns and temperatures down to -12 C. That's in March, probably a bit cooler now. Wind picks up in the afternoon and settles back down again around 10 pm. Snow line was at around 5,000m.
Local variations can be significant. One small town 100km to the east at 3,850m was having very mild nights - around zero or slightly above, we were getting -5 to -12 in the mornings.
So prepare for the cold, it's not much fun shivering.

Cheers
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Re: mountain-forecast.com accuracy

Postby Drew » Wed 17 May, 2017 4:20 pm

Thanks for the reply Swifty. That's a massive temperature range you had! What were you doing in that part of the world? I've only driven around up there but the landscapes are amazing. Not very hospitable though!

It's hard to imagine it will be that warm at Ausangate if it's only 16-18 in Cusco, but who knows.
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