22 July 2008

This article has two parts. First, it outlines the reported avalanche incidents across all of Japan for the 2007/08 season. Second, it focuses on the evolution of the Hakuba snowpack and details those incidents that occurred in Hakuba.

I am using avalanche incident data from the Japan Avalanche Network as the official source of data in Japan. I am a contributing member and attended their end of year meeting where the indecent summary was reviewed and discussed. Other incidents may have occurred yet remained un-reported.

The data and discussion on Hakuba’s snowpack and avalanche activity is based on my own weather station data, along with my own field observations and observations by guides in Hakuba recorded on the JAN public database.

PART 1: 2007/08 Avalanche Incidents in Japan

There were 15 reported avalanche incident in Japan from between 13 November 2007 and 12 April 2008. I do not have data available to compare to the previous season.

Of the 15 reported incidents:

41 people were caught in an avalanche
9 people sustained injury
15 people died.

Know the weather = know the snow pack = know the stability.  For previous weather and snow reports use the Diary link at the top of the page.

Steep Deep Japan Hakuba  weather data for the 24 hours to 7am for 860m asl. Max temp +11C, min temp -2C and  +4C at 7am. 0cm of new snow  in the last 24 hours.  Depth of snow 160cm after settlement.  Barometer is steady at 916mbar.  The sky has about 100% cloud cover and it is raining lightly, apparently as high as 1800m.

Field observations:  For the last two days we travelled in the backcountry to 2600m on mainly south and east aspects.  Solar radiation was intense.  Recorded temps at 2600m at midday were +1.5C.  Besides obvious wet snow sluffing on steeper aspects below cornices, we found very stable snow above 2200m.  Below that altitude is very unstable on steep solar terrain due to rapid melting and deep isothermal conditions:  there is no structure in the snowpack.

Know the weather = know the snow pack = know the stability.  For previous weather and snow reports use the Diary link at the top of the page.

I haven't had the chance to update the weather diary in a few days.  And it has been a dramatic few days as well.  Since Friday-Saturday last week we have plunged horribly fast into late spring conditions, with no gradual transition.  Constant winter storms followed by instant warm weather.  I don't like it at all.  The anticipated clear weather was welcome, but not to this extreme.

Steep Deep Japan Hakuba  weather data for the 24 hours to 7am for 860m. Max temp +13C, min temp -3C and  +3C at 7am. 0cm of new snow  in the last 24 hours.  Depth of snow 170cm after settlement.  Barometer 9121mbar.  The sky is has 100% cloud cover (fog), not snowing, no wind. 

Know the weather = know the snow pack = know the stability.  For previous weather and snow reports use the Diary link at the top of the page.

Steep Deep Japan Hakuba  weather data for the 24 hours to 7am for 860m. Max temp +6C, min temp -8C and  -0C at 7am.1cm of new snow  in the last 24 hours.  Depth of snow 190cm after settlement.  Barometer 919mbar.  The sky is has 25% cloud cover, not snowing, no wind.  It is the start of some very good mountain weather in Hakuba.