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Climax Post Control CE Tuesday 2/27/07 Ned Bair. Video shot by guest 1352 hrs.

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Presentation on theme: "Climax Post Control CE Tuesday 2/27/07 Ned Bair. Video shot by guest 1352 hrs."— Presentation transcript:

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

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

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9 Weather Summary 9” inches of new snow, 1.23” SWE, 13.7% water. 9” inches of new snow, 1.23” SWE, 13.7% water. Base depth 210” @ 1400 hrs on day of incident 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.). 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. 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.). 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.).

10 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. 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”. Maximum Class size from neighbors was 3. Maximum Crown size 12”.

11 Nearest Neighbors Forecast Climax produced avalanches in 1 of 4 neighbors (3 non-occurrences) 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 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. Climax slide on 4/17/2006: 1352 hrs, Class 4, 28-48” crown, 755’ path width, 710’ path length.

12 4/17/2006

13 4/19/1984

14 Weather Factors for 4/17/06 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%. 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. 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. 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.

15 Weather Factors for 4/17/06 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. 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. Exact same barometric pressure readings are likely coincidence.

16 4/17/2006 32 other avalanches 32 other avalanches Max. class size 4, max. crown size 60”. Dave’s Run. 400’ path width, 1000’ path length. 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. 5 avalanches that were class 3 and above with ≥ 30” crown sizes.

17 Occurrences on 4/17/06 ranked by size

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

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20 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. 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. 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.

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22 Snowpack Analysis Flanks and/or shear surface may have already failed on one or both slabs before total failure of both slabs. 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. 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. It’s possible that the crown may have been the only structure supporting the slabs.

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

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29 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. 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. 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. 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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