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Climax Post Control CE

Climax Post Control CE. Tuesday 2/27/07 Ned Bair. Video shot by guest 4/17/07 @ 1352 hrs. Weather Summary. 9” inches of new snow, 1.23” SWE, 13.7% water. Base depth 210” @ 1400 hrs on day of incident

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Climax Post Control CE

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  1. Climax Post Control CE Tuesday 2/27/07 Ned Bair

  2. Video shot by guest 4/17/07 @ 1352 hrs

  3. Weather Summary • 9” inches of new snow, 1.23” SWE, 13.7% water. • Base depth 210” @ 1400 hrs on day of incident • Temperature change from low of 12°F @ 0600hrs on 4/17 to 28° F @ 1400 hrs at Sesame Street Snow Plot (el 9000 ft.). • Time of accident 1352 hrs. • Temperature change from low of 6°F @ 0600 hrs on 4/17 to 11°F @ 1400hrs at the Top Weather Station (el. 11,052 ft.).

  4. Nearest Neighbors Forecast • Running a Nearest Neighbors forecast retroactively for 4/17/06 using Cornice 2.0 came up with 5/5 days that produced avalanches. • Maximum Class size from neighbors was 3. Maximum Crown size 12”.

  5. Nearest Neighbors Forecast • Climax produced avalanches in 1 of 4 neighbors (3 non-occurrences) • Climax slide in NN forecast : 4/19/1984 1229 hrs, Class 3, 12” crown, SS, 6 shots, AE, unknown path length. • Climax slide on 4/17/2006: 1352 hrs, Class 4, 28-48” crown, 755’ path width, 710’ path length.

  6. 4/17/2006

  7. 4/19/1984

  8. Weather Factors for4/17/06 vs. 4/19/1984 • Precipitation: same new snow (9”), same storm total (9”). Similar SWE (1.23” and 1.1”, respectively). Densities 13.7% and 12.2%. • Winds: Gusts and average at ML were also similar (14,41 mph) vs. (19,30 mph). Average winds from the SSW and S, respectively. • Temperatures: 4/19/84 warmer: 24 hr lo was 17°F, hi was 34°F. 4/17/06 colder: 24 hr low was 13°F, hi was 25°F.

  9. Weather Factors for4/17/06 vs. 4/19/1984 • Base depth: Approximately double for 2006 (103” vs 210”), 1983 could be considered a depth hoar year with it’s total SWE of 33.43” vs. 68.45” both respective dates. • Exact same barometric pressure readings are likely coincidence.

  10. 4/17/2006 • 32 other avalanches • Max. class size 4, max. crown size 60”. Dave’s Run. 400’ path width, 1000’ path length. • 5 avalanches that were class 3 and above with ≥ 30” crown sizes.

  11. Occurrences on 4/17/06 ranked by size

  12. Snowpack Analysis • Step down failure • Slab: 0.1-0.3mm wind slab, broken particles, mostly rounded forms. • Bed Surface: 1F MF clusters .5-1mm.

  13. Snowpack Analysis • The ability for bonds to form necks is inversely proportional to grain size(0.1 versus 1 mm). Substantial differences in grain size will result in lack of inter-layer bonding. • Possible mechanism for slab release may have been an initial failure @ 43cm caused by hand charges and ski cutting. Subsequent deeper failure @ 72cm may have been caused by additional weight of skiers.

  14. Snowpack Analysis • Flanks and/or shear surface may have already failed on one or both slabs before total failure of both slabs. • This is evidenced by shooting cracks and settlement. Brings up the classic question of whether a slope becomes more or less stable after collapse. Karl Birkeland has done research on this topic if you’re interested. I’ve got some of his papers in PDF format. • It’s possible that the crown may have been the only structure supporting the slabs.

  15. Snowpack Analysis • Slab failure and fracture mechanics in avalanches are poorly understood. • All we know is that the crown and sidewalls cannot fail prior to the shear failure since we can see the crown.

  16. How do we deal with Climax? • Not a viable gun target. Hand charges on that day did not seem to produce the results that were in Dave’s from the gun/hand charge combination. • Other possible strategies include: Lower shots placements, shots from gondola, Avalanche Tube, ANFO. • Sit on the top for a day? Ideally…but when you have people lined up at 6am for the gondola that’s difficult.

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