GordonFreeman 0 Posted December 3, 2008 Share Posted December 3, 2008 Can the Munter reduction method be used for off piste skiing in Japan. I understand the prevailing wind is Westerly so any wind slab would be deposited on eastern facing slopes rather than NE as in Europe. Just a theoretical question... Link to post Share on other sites
telehugh 0 Posted December 3, 2008 Share Posted December 3, 2008 Local wind patterns are less predictable than in Europe, slopes are less steep and in most locations we are skiing on marine snow pack. Personally I wouldn't use the Munter method in Europe or in Japan. I take a much simpler approach - watch the weather, talk to people more experienced than me, think about the route, dig a pit, maybe dig another pit, watch the terrain. Link to post Share on other sites
GordonFreeman 0 Posted December 4, 2008 Author Share Posted December 4, 2008 Originally Posted By: telehugh Local wind patterns are less predictable than in Europe, slopes are less steep and in most locations we are skiing on marine snow pack. Personally I wouldn't use the Munter method in Europe or in Japan. I take a much simpler approach - watch the weather, talk to people more experienced than me, think about the route, dig a pit, maybe dig another pit, watch the terrain. Marine snowpack as in hot air rising quickly and cooling on mountain ranges close to the sea? What's the difference in snow structure? Link to post Share on other sites
telehugh 0 Posted December 4, 2008 Share Posted December 4, 2008 Marine snow pack is denser and more cohesive - ie more stable but if it does slide typically more destructive. Whereas continental snowpack is drier, lighter and less well bonded. While carrying the rubbish up the hill this morning (cold with good view of the mountains) I thought a little more about this ... other reasons why the Munter method may not be appropriate include the terrain - skiing in the alpine zone is normally the exception in Japan. Tree skiing is more normal particularly if there is a heavy snow fall when viz is bad so the snowpack is well anchored - conversely if you are skiing in a valley where there are no big trees then watch out - this is a slide zone. This plus the typically gentler slopes (we are often skiing volcanic mountains) makes Munter unproven and arguably uncalibrated / applicable. I'll still be digging pits, jumping on blocks and playing in the trees Hugh Link to post Share on other sites
GordonFreeman 0 Posted December 5, 2008 Author Share Posted December 5, 2008 Munter works on angle of slop though. Are you saying because the snowpack is bonded better, then angle for an avalanche needs to be less or greater (I know there's lots of factors). Is there more moisture in the air in mountains next to marine environments? Link to post Share on other sites
SerreChe 2 Posted December 7, 2008 Share Posted December 7, 2008 "Munter is a statistical method which summarizes general wisdom about avalanche accidents but ignores detailed local conditions". Local knowledge is very important. Also, there is no avalanche bulletin scale in Japan like there is in France for example just in case you are trying to work out your reduction factors. So by paying attention to the usual risk factors without necessarily sticking them into an equation then you are kind of doing the same, it is just you will not end with a number at the end of it. As per my obs last season I thought E-NE were the most unstable throughout the season, not just going into spring, but this is again a generalized statement that does not take local specificities into account. So Hugh is in my mind doing the right things. I believe that in general maritime snowpacks such as Japan's are thicker (thereby reducing the steepness of the temperature gradient that can lead among other things to depth hoar) and denser and tend to have better bounding. But it also tends to have more layers impacted by rainy periods, etc... It is off the top of my head, but I think continental snowpacks tend to have the higher incidences of avie accidents/fatalities in the US. Anyway, have fun and be safe in Haks. Link to post Share on other sites
SerreChe 2 Posted December 7, 2008 Share Posted December 7, 2008 Originally Posted By: GordonFreeman Munter works on angle of slop though. Are you saying because the snowpack is bonded better, then angle for an avalanche needs to be less or greater (I know there's lots of factors). Is there more moisture in the air in mountains next to marine environments? I would tend to think so. Link to post Share on other sites
telehugh 0 Posted December 7, 2008 Share Posted December 7, 2008 SerreChe Temperature gradient - when I was first writing one of my replies I first wrote "maritime ..... less temperature gradient ..." but then realised that I didn't have anything to back this up. Intuitively I'd have thought that the temp grad in Japan snow pack's would typically be less (deeper snow pack, base at zero and surface not so different etc) but do we actually know if the typical JP gradient's are less? And while I'm asking questions .... why are we taught that the ground is at zero and not colder? Hugh Link to post Share on other sites
SerreChe 2 Posted December 9, 2008 Share Posted December 9, 2008 Hugh, fair (excellent actually) questions. I think the less steep temp gradient in thicker snowpack is what I would consider to be 'generaly accepted principle'. On the other hand to be perfectly honest I have never really compared data sets to actually be able to confirm/deny this. Some of the guys in Hakuba who dig pits often and have a wide data-set may be able to answer this question. Even then, I think very often people do not dig to the ground and do a full temp analysis. The types of layers within the pack should also impact how steep that gradient is, as the steepness is not constant across that pack. I think it would be an excellent question for some of the advanced guys in the field. Regarding the ground temp, I have also never dug to the ground under a thick pack and done a ground temp analysis nor read about samplings done on this. So I think that theoretically it could be both slightly colder or even warmer which would both impact the gradient. Japan with its many areas of geothermal activity could be a good example as to why the ground temps may not be necessarily zero. On average though, I assume it should be fairly close to zero. I'll try to ask those 2 questions to some of the gurus I know to see what they think. Link to post Share on other sites
GordonFreeman 0 Posted December 9, 2008 Author Share Posted December 9, 2008 Related question... How much surface hoar is considered bad? Sitting on the lift today, you could see the hoar over the snow that hadn't been skied on, ie the glistening stuff. Link to post Share on other sites
SerreChe 2 Posted December 9, 2008 Share Posted December 9, 2008 I would say that any surface hoar that does not get wiped out by either the sun and/or wind and gets buried under new layers of snow is a serious source of concern when going off-piste. On the other hand I do not know if there is an optimal crystal size per se. Buried surface hoar is tricky as it can be very localized. If you dig a pit in a wind-swept slope you might find a weak layer. You send start riding a shaded wind-protected gulley and may trigger a slide. I would think that the shape of the crystals in the new layer and their inter-locking properties with the hoar crystals would be a big factor as to how risky it is. Then over time, pressure/temps should impact the resilience of that weak layer as well as how long it takes for it to dissipate within the pack. I am no expert though, just rambling along... Are you in Haks or Niseko. I know some people in Haks have observed a lot of it recently and are currently staying away from the BC. Link to post Share on other sites
SerreChe 2 Posted December 10, 2008 Share Posted December 10, 2008 Hugh, I have asked one of the resident Gurus (he asked me to put a disclaimer on that title :-) )in Haks who confirmed that his observations there as well as his experience in Europe in more continental climates confirm the fact the thicker the pack, the less likely you are to get steep TG & resulting DH. Even within Japan, his data confirm the relation between snow-pack thickness & TG and the likelyhood to get DH. Link to post Share on other sites
telehugh 0 Posted December 10, 2008 Share Posted December 10, 2008 SerreChe Thanks for the comment - yours and the "guru's" (vvvvvv dangerous to be a nominated guru.....) The more I learn about any natural phenomena the less I know. When I get the chance I'll do a literature search and see if anything comes up - I'd guess that we'd find a bunch of inconclusive datasets. Reckon we get funding to do a 3-year study on comparative thermal gardients - Lake Louise, Hakuba, Whistler? Always fancied a PhD in Snow Science In the meantime I'll be talking to locals, (avoiding any self-styled gurus), digging some pits and doing the block dance Hugh Link to post Share on other sites
SerreChe 2 Posted December 12, 2008 Share Posted December 12, 2008 Telehugh, no worries man, your questions were interesting & got me thinking. I think next pit I will go the bottom & stick the thermometer in the ground just for the hell of it, just to check ! My guru refused to be called one as he is humble, but he's got Level 1, got international experience, is very dedicated and takes snow samples everyday around Hakuba and is always very happy to share info with people going into the BC. He is a real asset to the BC community. If you can get the funding for that study, let me know, ahah, I wanna join. Take it easy. Link to post Share on other sites
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