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Just to be clear, I wasn't dissing euro guides (if that's how my post came off. I can see how it might have.). I was just pointing out that what may be an unusual snowpack in one place may be the norm in another. Guides do exchanges all the time- perhaps that should be increased as that will spread knowledge of "unusual snowpacks".Quote:
Originally Posted by klar
To make sure I understand http://www.oocities.org/yosemite/tra.../1996/3x3.html <- this resource:Quote:
Originally Posted by klar
On a day with what the US would call a "Moderate" deep slab problem (avalanche report 2, danger 4), skiing a 38 degree (RF2) north facing (RF2) slope w/1 partner (RF2) would always be
Risk 4 / (2*2*2 = 8) = 0.5 = always safe?
I ask because that is not how I would interpret an avy report that had a moderate risk of persistent slab avalanche on N-facing slopes in eg January here in UT. Bear in mind I am in the US and am also wholly unfamiliar with Munter, just piecing it together from these links you posted. I'm also very conservative in this respect.
No, that part is misleading in that link. You are supposed to avoid the Northern aspects, not seek them out. You can apply the reduction factors if you are NOT on Northern sector/half sector slopes. (There are some special rules for wet snow.)
Is there a Bayesian problem with the statistical methods in use? If you're trying to reduce the risk of a specific choice how do you do so without knowing the historical rate? All you know is the absolute historical count of a positive result.
uhhh. I don't think I understand what you mean. Bayesian problem as in a logical cause and effect issue? "Statistical" is perhaps the wrong word for the methods in question, maybe "empirical" would be better?Quote:
Originally Posted by cmor
If X% of skier triggered avalanches occur in steep slopes with a northerly aspect, avoiding steep slopes with a northerly aspect will decrease your chances of triggering an avalanche to Y%, compared to a chance of Z% (Z>Y) when you select a slope at random from slopes of all aspects and angles. What do you mean by historical rate in this context?
Should the posterior distribution be reevaluated as more information becomes available (perhaps to incorporate additional "causal" variables), with the result then serving as the basis for a new model? yes.
Experienced based intuition isn't the complete mechanism by any means. I do think is an essential part, particularly when it feels wrong to ski something.Quote:
Originally Posted by klar
Great thread and discussion Klar, thanks for starting it. My $0.25 as a non-professional (CAA level 1 in '96; 1 week advanced refresher in '06) 25 yr back country skier. Nope, don't use the Munter method. Known about it for lots of years as I've done some touring in Europe with a German buddy who uses it as a tool in his decision making process. It was interesting that when touring with Andreas we'd come to the same conclusion (agreement) utilizing different means to come to that conclusion (and through discussion). At the end of the discussion there becomes a "go/no go" decision point whatever method you use (IMHO).
Agree with Neckbear's comment regarding the avaluator:
"Keep in mind these are entry-level tools to remind inexperienced people of what should be naturally churning through their head while trip planning, and then all day on the snow."
I really appreciate all the input. This has been interesting, especially in contrast with discussions at home .
That may have been the developer's intention and how the tools are perceived in North America. However, they are more than that here, hence much of the discussion. In practice, yes, inexperienced people tend to rely on the formalized decision aids to a greater extent than very experienced people. But here the public perception, particularly among people who do not have an intimate understanding of backcountry skiing, is not that these are just entry-level tools. They are considered the standard that separates negligence from bad luck. Notably, the courts tend to agree. That 1 in the Munter calculation has very much become the limit of what is generally considered a socially acceptable level of risk, from armchair QB discussions on the internet, to the media, to legal settings.Quote:
Originally Posted by garyfromterrace
I find the legal part of this most interesting and something that I was not aware of.
Thanks all for the great discussion. I like learning on TGR and this thread delivers.
Excellent thread.Quote:
Originally Posted by klar
I agree that it's not possible to claim that climate change as such is the driver of the changes we have seen the last few years, but I'd say that in Norway the last few years have been very different from when I started skiing and freeskiing/touring as such became normal in Norway. The last 5-ish years have had more extreme weather; as in longer dry spells, bigger storms when they come, colder and warmer periods during the winter etc. This leads to more complex layering in the snow, more scarcity and bigger local variations. When this is added to the already somewhat funky geography of Norway, where you can go from a costal climate to a more "continental" climate within an hour, I'm surprised we haven't seen the same tendency as in the Alps regarding avy deaths.
Anyhow, the norwegian forecasting site varsom.no has tried to put more information in the headline section this year. http://www.varsom.no/snoskredvarslin...7-03-25http://Quote:
Originally Posted by davidof
On the left it lists the regions with links to the region forecasts. It then lists the avalanche problems in the regions before the actual danger ratings (In the Indre Sogn region in actually lists a deep persistent weak layer). On some of the ratings you can see an exclamation mark suggestion that there is something specific to be aware of in addition to the normal hazards for a given rating.
I like the concepts above ^^ that sf describes.
Since the munter method is based on statistics, wouldn't statistics need to drive a change to the risk reduction methodology? are the statistics being updated with a goal of updating the method? (apologies if this has already been discussed upthread) Is there quality data from 2 more decades of touring and avi incidents in the sample region that could allow for a meaningful update? Some of the data may be skewed because of the use of the munter method during that timeframe, but I would think that could be accounted for in the number crunching.
the very recent incident in japan with those kids (RIP :( ) made me wonder if there's a similar risk reduction tool in japan; however, i think it would have been mentioned here if that was the case.
dunno
Nothing at all. Which is a shame as Japanese culture and character lends itself very well to rule based decision making.Quote:
Originally Posted by bodywhomper
That really is surprising! Thanks for starting this thread, klar.Quote:
Originally Posted by neck beard
... Thom
I mean the stats are not based on "selecting a slope at random", but they are applied that way. I was defining historical rate as incidents/# of tests, and we don't know the # of tests. For example it's likely there are more tests on northern exposures than southern exposures.Quote:
Originally Posted by klar
Big slide in the Hautes-Alpes in France on Sunday, one ski tourer seriously injured, again due to the PWL that has been there since the start of the winter. The frontier area has been the scene of a number of big slides this season, such as this one in the Ecrins: http://www.data-avalanche.org/listAv.../1492276335389 - a "stable" snowpack that went on a PWL that was possibly reactivated with the spring weather - the area is in the shadow during the winter months.