Crystal Ball Volume 26 - Winter 2015

Crystal Ball

Periodical of the New Zealand Avalanche Community * The latest information about research and resources * 2015 Southern Hemisphere Avalanche Conference

- Role of slabs and weak layers in fracture arrest

- Mechanisms for producing significant snow in New Zealand - Systematic probing after transceiver searching

* From Whakapapa to the Arctic Circle

Winter 2015 Volume 26 • Plan your trip • Tell someone • Be aware of the weather • Know your limits • Take sufficient supplies

www.mountainsafety.org.nz

Periodical of the New Zealand Avalanche Community.

COntents Welcome

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News

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Resources

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Research

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Sourthern Hemisphere Avalanche Conference 2015 (SHAC)

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SHAC material Karl Birkeland - The role of slabs and weak layers in fracture arrest Mads Naeraa-Spiers - Mechanisms for producing significant snow in New Zealand

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Christian Zammit - NIWA snow and ice network Arian Camm - Systematic probing after transceiver searching

General Dave McKinley - Summary of summer forecasting at Aoraki/Mount Cook

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Karyn Heald - Avalanche search dogs

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Mike Lundin - From Whakapapa to the Arctic Circle

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Crystal Ball - Volume 25, Winter 2015 Editors: Megan Heffield and Laura Adams Designer: Ros Wells Cover Photo: Nathan Watson Thank you to the contributors for giving permission to reproduce their material. Copyright Š New Zealand Mountain Safety Council 2015. All rights reserved.

The opinions expressed in this magazine are not necessarily those of the New Zealand Mountain Safety Council. While efforts are made to check facts are accurate, responsibility lies with the author.

Editorial and advertising enquiries Do you have something to say or show? We would like articles relating to the professional avalanche industry, public avalanche safety, teaching tips, research papers, accounts of avalanche events, book and gear reviews, event listings, interviews, letters to the editor, and humorous stories related to avalanches.

For more information please contact: Email: marketing@mountainsafety.org.nz or visit www.mountainsafety.org.nz

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An update on the MSC’s Backcountry Avalanche Advisory and Info-Ex exchange

Welcome to the winter 2015 edition of Crystal Ball It was great to see many of you at the Southern Hemisphere Avalanche Conference in Christchurch at the beginning of June.

The MSC has contracted Alpine Guides Aoraki Ltd to coordinate its avalanche forecasting programme for this season 2015, We had two great days of networking, workshops and ensuring coordination of the MSC’s regional forecasters and presentations from New Zealand and international speakers who the Info-Ex database/information exchange. In addition to this shared the latest knowledge and developments from around the coordination role, Alpine Guides Aoraki Ltd is also providing world. alpine-related communications support.

Our keynote speaker Karl Birkeland was incredibly well received.

It’s great to have the support of the hugely experienced team of Many of you will know or have met Karl during his last visit to New Zealand a few years ago, and many more will have read his Trev Streat, Laura Adams, Jamie Robertson and Kevin Boekholt impressive collection of published papers. Both his presentation coordinating the MSC avalanche advisory service. ’Knowing what we don’t know’ and his Saturday evening guest Trev and Laura are based in Aoraki/Mount Cook, and Kevin and speaker presentation were insightful and thought provoking. It Jamie are based in Methven. They will provide oversight of was great to have Karl join us all the way from the US. Thanks and mentoring for the wider Backcountry Avalanche Advisory Karl. forecasters and training/support to Info-Ex users as required.

Overall, the conference provided a fantastic opportunity for those in the avalanche sector to network and share challenges and ideas, and it was a pleasure to be a part of this.

Please direct your questions, comments or any technical issues to the team using the following contact details.

The snow season is now well and truly underway, with most alpine areas of the country having experienced multiple significant snowfall events. Unfortunately we’ve already seen a few examples of people getting caught out by avalanches – one on Ruapehu and one in the Southern Alps.

MSC Avalanche Forecasting Team NZ Info-Ex and Backcountry Avalanche Advisory Programme New Zealand Mountain Safety Council Email: avalanche@mountainsafety.org.nz Mobile: +64 21 857 609

In both cases, the people involved managed to escape unscathed but the outcomes could have been very different.

Sadly, we’ve seen the flip side of this as well, with two Canadian tourists dying after being caught in an avalanche on the Kepler Track in July and a heli-skier getting caught in an event in the Hector Mountains outside of Queenstown in August.

It is incidents like these that serve as a tragic reminder of why we’re all so committed to avalanche safety, and outdoor safety in general. They also show that locals and tourists alike can underestimate both the terrain and weather conditions that are typical of a New Zealand winter. The skier on Godley Glacier was experienced but hadn’t heeded the weather warnings, and carried a personal locator beacon but no avalanche transceiver.

On another note, some of you will be aware of recent changes to the New Zealand Mountain Safety Council’s (MSC) Alpine and Avalanche programme with the departures of Andrew Hobman and Gordie Smith.

The team at Alpine Guides Aoraki Ltd is currently providing overall coordination of the MSC’s Avalanche Advisory service and at the end of July the MSC began recruiting for a new role; Partnership Advisor – Alpine.

Lastly, this issue has been published later than normal so we apologise if you’ve been waiting for it! Because of this, we won’t be publishing a second issue of Crystal Ball this year. However, we’ll continue to be in touch and keep you all informed of plans for Crystal Ball and what’s going on with our Avalanche work into the future.

As always, we love hearing what you’ve been up to, and receiving your stories, articles and submissions, so keep sending these in and we’ll continue to showcase them as appropriate.

Mike Daisley CEO New Zealand Mountain Safety Council

Nathan WAtson Acting operations manager New Zealand Mountain Safety Council

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NEWS Product recall – ORTOVOX S1+ avalanche transceiver Outdoor equipment provider ORTOVOX, has issued a product recall for one of its avalanche transceivers.

Individual feedback after search training and intensive follow-up inspections have shown that in very rare cases, a disturbance can occur in the transmission function in the ORTOVOX S1+ avalanche transceiver.

The S1+ devices affected by the recall may no longer be used without the required component being replaced.

research Avalanche Awareness and Risk Perception in Backcountry Terrain // Jeremy BelL and Dr. Nicolas Cullen, University of otago

New Zealand has a relatively high proportion of avalanche terrain, with seasonal snow falling on steep slopes covering approximately 35% of the South Island and 5% of the North Island. An increase in avalanche fatalities can be attributed to the increase in popularity of alpine recreation from 1950-1990.

In recent years there has been a reduction in avalanche fatalities as the result of education and equipment advances.

This precautionary recall applies exclusively to the ORTOVOX S1+ model of avalanche transceiver. All other ORTOVOX avalanche Currently there are large data bases of avalanche fatality transceivers are unaffected. Its predecessor, the ORTOVOX S1, is statistics, however, less is known about the users of avalanche likewise unaffected. terrain. The aim of this research is to assess the behaviour and decision making of recreational users of avalanche terrain.

For further information, please visit: The research will be completed in two parts at Craigieburn http://www.ortovox.com/us/services/emergency-equipment/ Valley Ski Club (CVSC) during the winter of 2015. Firstly, the avalanche-transceivers/recall-s1/recall-s1/ decision-making and behaviour of avalanche terrain users will be investigated. Secondly, quantitative information regarding frequency and preparedness of skiers on the mountain will resources also be obtained. Qualitative data will be gathered using questionnaires and key informant interviews. This will allow ISSW searchable archive - including 2014 a demographic analysis to be carried out using defined presentation papers criteria such as education, as well as allowing an assessment http://arc.lib.montana.edu/snow-science/index.php of experience, decision making, risk management and risk perception.

Snow War Quantitative data will be gathered using a TRAFx Infrared http://issuu.com/revelstokemuseum/docs/snow_war_book_final Trail Counter to determine user number and group sizes. An A book illustrating the history of Rogers Pass in Glacier National avalanche beacon checkpoint will also be deployed to determine Park, British Columbia. the preparedness of these users. Additional data to be collected will include snow depth and stability of easily accessed Peter Schaerer Photo collection backcountry locations and on-ski field stability. Meteorological Swiss born avalanche researcher, Peter Schaerer, recorded data will also be collected onsite, including air temperature and avalanche activity in Roger’s Pass, Canada through reports and relative humidity, wind speed and direction. Importantly, this stunning photograpy in the late 50’s to 60’s. Check out the research will provide new information regarding skier decision history he has captured through the link to this exhibition making and risk perception by providing insights as to how of his work. people make decisions when they enter and take advantage of http://www.revelstokemuseum.ca/peter-schaerer-collection/ backcountry terrain.

Snow grain photo library Follow this link to the page on the Italian Avalanche site, then click on either the “Photo library” or the “Gallery” for a great learning resource for students to become familiar with what they might be looking at through their crystal loupes. http://www.snowcrystals.it/index.php?Lg=en FORECASTS Follow this link to check out a summary of NIWA forecasts for the season. https://www.niwa.co.nz/climate/sco Above: Beacon checker open and closed.

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SHAC Conference 12-14 June 2015 More than 100 people attended the MSC’s 2015 Southern Hemisphere Avalanche Conference held in Christchurch from 12-14 June.

The conference was a fantastic opportunity for participants to share knowledge and challenges, discuss opportunities and solutions, and network with other attendees from across the sector.

The conference kicked off with an optional Workshop Day on the Friday, covering everything from weather forecasting to explosive use in avalanche management.

The conference itself hosted a great range of New Zealand and international speakers who presented on the themes of planning and preparation, management and mitigation, and reaction and rescue response across the two days.

Keynote speaker Karl Birkeland, Director of the US Forest Service National Avalanche Centre, presented an overview of the scientific research being undertaken in the Northern Hemisphere - what is known, what is questioned, how it fits into the bigger picture and what it means for practitioners in the Southern Hemisphere. Karl also spoke at the Snowball Dinner, held on the Saturday evening.

Below are some photos from the conference – take a look and see if you can spot anyone you know!

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SHAC material THE ROLE OF SLABS AND WEAK LAYERS IN FRACTURE ARREST // karl birkeland, USDA Forest Service National Avalanche Center, Montana, USA Alec van Herwijnen WSL-SLF Swiss Institute for Snow and Avalanche Research, Davos, Switzerland Eric Knoff Gallatin National Forest Avalanche Center, Bozeman, Montana, USA Mark Staples Gallatin National Forest Avalanche Center, Bozeman, Montana, USA Edward Bair Earth Research Institute, University of California, Santa Barbara, CA USA Couer Alaska, Juneau, Alaska USA Ron Simenhois Couer Alaska, Juneau, Alaska USA

ABSTRACT: Though recent work on fracture has provided us with new stability tests and improved our knowledge of avalanche release, our understanding of fracture arrest is still limited. We studied fracture arrest by making modifications to weak layers and slabs in a series of propagation saw tests (PSTs). We conducted more than 100 tests at a single study plot over eight weeks during which cracks along a surface hoar weak layer consistently propagated. Slab characteristics changed dramatically over time, with increasing slab depth, density, and hardness. High speed videos of more than 70 tests allow the analysis of fracture arrest dynamics. Our results show that removing the weak layer had no effect on propagation. Fracture arrest only occurred when we replaced a 30cm long section of the weak layer with a non-collapsible structure. Modifying the slab by introducing slope normal cracks (either from the surface down or from the weak layer up) showed that sometimes small changes to soft (F hardness) parts of a slab were sufficient to arrest fractures through slab fracture, while other times only a strong thin portion of a thick slab was capable of communicating fracture farther down the beam. Our results suggest that the tensile strength of the upper layers of the slab is a key component for crack propagation. This work demonstrates the importance of the slab in slope stability, and it also suggests avenues for developing tests capable of assessing slab characteristics conducive to fracture propagation.

There are four criteria necessary for slab avalanche release: 1) crack initiation, 2) slow crack growth to a critical size, 3) rapid crack propagation (or fracture) along the weak layer, and 4) slab detachment. While past work and many snowpack tests looked at crack initiation, more recent practical work and stability tests have focused on the propagation part of the puzzle (e.g., Sigrist and Schweizer, 2007; Gauthier and Jamieson, 2008; Simenhois and Birkeland, 2009).

Slab avalanches require both a slab and a weak layer or interface. The combination of the slab and the weak layer is critically important for propagation. However, a great deal of past research focused on weak layers and paid little attention to slabs. Indeed, the widely used shear frame test requires the complete removal of the slab (Perla et al., 1982; Jamieson and Johnston, 2001).

The exact role that changes in slab and weak layer properties have on fracture arrest is unclear, but recent research is starting to address this topic. Gauthier and Jamieson (2010) discuss the role of the slab and weak layer, and the importance of the slab for “communicating” the fracture outward as part of propagation. In essence, they argue that fractures arrest where Crystal Ball - Periodical of the New Zealand Avalanche Community

Figure 1: Our experimental setup involved taking high-speed video of our tests for particle tracking velocimetry. This picture also shows the relatively uniform, gently sloping meadow where we conducted our experiments.

“the energy transfer required for propagation exceeds the energy transfer capacity of the slab” (Gauthier and Jamieson, 2010, p. 226). van Herwijnen (2005) discusses the importance of an intact slab for propagation and notes that cracks in the slab may effectively arrest fracture. Simenhois and Birkeland (2008) found that changes in slab thickness could arrest fractures in extended column tests, and Simenhois and Birkeland (2014) made measurements at slab boundaries to investigate possible fracture arrest mechanisms. Other recent work by Gaume et al. (2014) and Schweizer et al. (2014) discuss the importance of slab properties such as density and tensile strength for crack propagation and fracture arrest.

In terms of weak layers, we decided to test whether or not introducing voids to the weak layer could arrest fracture.

Though this seems counterintuitive since snow is porous and weak layers can be viewed as a series of voids, the fracture mechanics literature establishes that crack tips are “atomically sharp” and that voids effectively arrest classic fractures (eg, a hole arresting fracture in glass) (Lawn, 1993). For snow, Chiaia and Frigo (2010) use a modeling approach to show the effectiveness of voids in arrest fractures in homogeneous slab layers.

Another way to potentially arrest fractures is by eliminating weak layer collapse. The mixed-mode anticrack model presented

by Heierli et al. (2008) requires collapse to drive propagation, and Heierli (2005) suggests a large area of weak layer that is not “appropriately collapsible” can arrest fracture.

The purpose of this paper is to conduct field experiments to qualitatively test the effect of changes in slabs and weak layers on fracture arrest. We conducted long propagation saw tests (PSTs) during conditions favorable for crack propagation, and we modified slabs and weak layers to see the effect of those changes. Our results demonstrate the critical importance of an intact slab and a collapsible weak layer for propagation, and therefore for slope stability.

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THE ROLE OF SLABS AND WEAK LAYERS IN FRACTURE ARREST // karl birkeland, USDA Forest Service National Avalanche Center 2. FIELD AREA AND METHODS 2.1 Field area We conducted our fieldwork in southwest Montana’s Madison Range near Bacon Rind Creek (44º58’13”N, 111º5’50”W). The site is an open, wind-protected, easterly-facing meadow at 2700m (9000ft) that offers ample sampling terrain with slope angles ranging from 19º to 25º (Figure 1).

2.2 Field data We visited our field site eight times over a seven week period from 8 February to 1 April 2014. Each field day we collected a manual snow profile, including measuring density for each significant layer in the slab (Greene et al., 2010). Our targeted weak layer was a layer of surface hoar buried in late January.

Over the course of our sampling, slab thickness increased from 39 to 125cm, average slab density increased from 124 to 298kg/ m3, and the maximum density measured in the profile increased from 160 to 385kg/m3.

On each sampling day we conducted PSTs (Greene et al., 2010) with some slight modifications. First, in order to facilitate particle tracking, we cut the back and sides perpendicular to the slope rather than vertically. Second, we made the columns as long as possible while still ensuring that unmodified columns would consistently propagate to the end of the column. Our column length started at 1.0m, but increased to 2.5m by the end of our sampling. By that time we may have been able to utilize even longer columns, but conducting multiple tests > 2.5m was too time-consuming.

2.3 Slab and weak layer modifications On each field day the sampling team conducted a few PSTs to confirm consistent propagation to the end of the column. We then did additional tests after modifying either the weak layer or the slab. On all but the first sampling day, we placed plastic markers in the snowpack and filmed our tests with a high speed (120 frames per second at 640X480 resolution) video camera for particle tracking velocimetry (PTV) (Figure 1). Those results are the subject of another paper (Birkeland and van Herwijnen, In preparation) and are also being used to validate a propagation model (Gaume et al., 2014), while this paper focuses qualitatively on the effect of weak layer and slab modifications on fracture arrest.

Weak layer modifications included: 1) removing the weak layer to simulate crack-tip blunting using a 5.5cm diameter density tube (Figure 2a and 2b), 2) interrupting the weak layer by placing a piece of cardboard or a three-ring binder through the weak layer (Figure 2c), and 3) supporting the slab over a 30cm section of the weak layer to eliminate collapse (Figure 2e and 2f).

Slab modifications included making slope normal cuts from the surface down into the slab (Figure 2d), and making slope normal cuts from the weak layer up into the slab (not shown). Except for our last day, we made surface down cuts each field day and varied the cuts until we ascertained within about 5cm how much slab was necessary for continued propagation and how deep a cut caused fracture arrest. We cut up from the weak layer to compare how cuts up from the weak layer compared with cuts down from the surface.

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3. RESULTS AND DISCUSSION

3.1 Weak layer modifications 3.1.1 Removing the weak layer Using a 5.5cm diameter density tube we removed anywhere from 5.5 to 68.0cm of the weak layer (Figure 2a and 2b).

In every case the crack propagated through the gaps and continued to the end of the column. Fractures did not arrest in any of these cases.

Clearly, gaps at this scale are not sufficient to arrest fracture.

Indeed, they may have facilitated fracture since the PTV analysis shows that the fracture speeds were greater for these modified tests than in our unmodified tests (Birkeland and van Herwijnen, In preparation). The gaps may not arrest fracture due to the scale of the gaps in relation to the scale of the weak layer crystal size. Alternatively, this could be because cohesive slab above the weak layer caused all the stress to be immediately transferred across the gap and to the start of the weak layer on the other side, which is clearly an existing flaw in the material.

3.1.2 Interrupting the weak layer Interrupting 10 to 20cm of the weak layer with a three ring binder pushed about 5cm up into the slab did not affect propagation (Figure 2c). We did observe fracture arrest when the binder was pushed far into the slab, but this was due to modifications to the slab and not to the weak layer.

These results confirm that propagation does not proceed like dominoes through the weak layer: the slab drives the crack. In our experiments propagation continued even when the weak layer was interrupted for up to 30cm. Fractures did not arrest as long as the slab’s integrity was not compromised and there was sufficient collapse for the slab to bend and “communicate” the fracture.

a

D

b

E

C

F

Figure 2: Weak layer and slab modifications included: a) removing a portion of the weak layer , b) close up of (a), c) interrupting the weak layer with a three ring binder with the rings removed, d) slope normal cuts into the slab from the surface down (this particular case resulted in weak layer fracture arrest due to slab fracture) and from the weak layer up (not shown), e) supporting the slab over a 30cm distance using binder pieces placed up into the slab and down into the layer below the weak layer, and f) close up of (e) with weak layer visible through the middle of the structure.

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THE ROLE OF SLABS AND WEAK LAYERS IN FRACTURE ARREST // karl birkeland, USDA Forest Service National Avalanche Center

Figure 3: Snow profile from our first sampling day, nine days after weak layer burial. On this day a cut of only 7cm into the extremely soft slab (shown by the arrow) was sufficient to arrest fracture.

3.1.3 Supporting the slab In order to eliminate weak layer collapse, we constructed a structure with several pieces of cut up three ring binder (Figure 2e and 2f). This structure extended up into the slab, down into the snow underneath the weak layer, and across the entire beam. We found that lesser structures allowed a small amount of collapse and did not arrest fractures. However, this particular structure eliminated collapse over a 30cm length of the column, arresting the fracture at or close to the position of the support.

We confirmed the slab was well supported when we removed the structure after the test. During removal the undisturbed section of the weak layer collapsed, and the crack propagated to the end of the column.

Fracture arrest occurred when we eliminated collapse in our tests, consistent with Heierli’s (2005) contention that fractures will arrest when the weak layers are not “appropriately collapsible”.

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3.2 Slab modifications 3.2.1 C uts into the slab from the snow surface down On every sampling day besides our final field day we made cuts down into the slab and identified the cut length necessary to cause fracture arrest (Figure 2d). In all cases, disturbing a certain portion of the slab effectively arrested fracture, which is consistent with past work (Simenhois and Birkeland, 2008).

A few results were surprising. For example, our first sampling day had a 38cm thick soft slab. A cut of only 7cm into the soft (F- hardness) surface snow was sufficient to arrest the fracture (Figure 3). On other days we cut through significant layering, but the harder snow layers immediately above the weak layer provided enough integrity to communicate the fracture farther along the column, which propagated to the end (Figure 4).

Over the 45 day period that we made these cuts, the proportion of the existing slab necessary for propagation decreased sharply, from around 85% on our first sampling days, to between 50% and 60% by the end (Figure 5a). This change occurred as the average slab density increased from 135 to 325kg/m3 (Figure 5b). Thus, as the density (and associated tensile strength) of the slab increases, a smaller percentage of the original slab is necessary to continue weak layer crack propagation.

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THE ROLE OF SLABS AND WEAK LAYERS IN FRACTURE ARREST // karl birkeland, USDA Forest Service National Avalanche Center

Figure 4: Snow profile from March 20, 49 days after weak layer burial. The arrows show how far we could cut the slab from the surface down and from the weak layer up and still get propagation. The ice crust immediately above our upward cut from the weak layer was only 2cm thick, but it had sufficient tensile strength to keep the crack propagating along the weak layer.

This part of our work clearly showed the importance of the slab for propagation. If the integrity of the slab is compromised past a certain point, weak layer fractures will arrest. In some cases, disturbing a relatively small and soft portion of a soft slab is sufficient to arrest fracture.

3.2.2 Cuts from the weak layer up into the slab As with the cuts down from the surface, cuts up from the weak layer also affected the slab integrity and arrested fractures.

Since the lower part of the slab is in compression during the slab bending that accompanies fracture, we hypothesised that smaller cuts would be needed from the surface down than from the weak layer up to arrest fracture. Unfortunately, we could not adequately test this hypothesis because of the differing physical characteristics between the layers at the surface (generally softer and less dense) and those just above the weak layer (generally harder and denser).

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THE ROLE OF SLABS AND WEAK LAYERS IN FRACTURE ARREST // karl birkeland, USDA Forest Service National Avalanche Center

Figure 5: Over the sampling period, (a) the proportion of the slab necessary for propagation decreased, while (b) the average density of the minimum slab required to maintain propagation increased.

Still, cutting from the weak layer up provided some unexpected results. In one case with an 82cm deep slab, we could cut all but the top 13cm of the slab and still get propagation. In this case, the upper part of the slab consisted of a 2cm ice crust that was K hard, as well as softer snow and another slightly softer crust (Figure 4). Amazingly, all it took was the stiff and thin upper snowpack layer to communicate the fracture even when the thicker lower part of the slab (which was P hard and had a density of 330kg/m3) was disrupted.

This work emphasises the importance of both the slab and the weak layer in crack propagation. Though much past work focused only on the weak layer, our experiments demonstrate that both a collapsible layer and an intact cohesive slab are necessary for propagation and therefore for avalanche release.

Our work is consistent with other ongoing research emphasising the importance of slab tensile strength – which relates to both density and hardness – in crack propagation (Gaume et al., 2014; Schweizer et al., 2014). Future experimental and modelling work may help us to better understand the nature of the slab/ weak layer relationship that is so critical for understanding slope 4. CONCLUSIONS This paper qualitatively examines how changes in slabs and weak stability. layers affect fracture arrest. Our field experiments utilising long PSTs suggest the following: •

•

•

•

oids in the weak layer do not arrest fracture. This helps V explain why weak layer voids in talus fields, for example, do not arrest fracture.

Collapse is necessary for propagation. Eliminating collapse causes fractures to arrest. This result is consistent with past work on mixed-mode anticracks (Heierli, 2005; Heierli et al., 2008).

Since an intact slab is required for propagation, compromising the integrity of the slab will arrest fractures. Thus, when conducting propagation tests, especially with new soft slabs, keeping surface snow undisturbed is important.

Conversely, sometimes only a small part of slab is required to communicate the fracture. In these cases, if that part is intact then the fracture will not arrest.

Our results provide experimental evidence of mechanisms for fracture arrest. Since a great deal of variability of both slabs and weak layers are found on avalanche slopes (Schweizer et al., 2008), changes in their properties may explain slab boundaries.

Indeed, measurements by Simenhois and Birkeland (2014) on the crowns and flanks of avalanches suggested that many slab boundaries were associated either with decreases in weak layer collapse amplitude or decreases in slab depth.

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THE ROLE OF SLABS AND WEAK LAYERS IN FRACTURE ARREST // karl birkeland, USDA Forest Service National Avalanche Center ACKNOWLEDGEMENTS The Gallatin National Forest Avalanche Center provided logistical support for this work. Jordy Hendrikx and Packy Cronin helped with some of the data collection.

Simenhois, R. and Birkeland, K.W., 2008. The effect of changing slab thickness on fracture propagation, 2008 International Snow Science Workshop, Whistler, British Columbia.

REFERENCES Birkeland, K.W. and van Herwijnen, A., In preparation. The effect of changes in slabs and weak layers on snowpack weak layer fracturing.

Cold Regions Science and Technology.

Simenhois, R. and Birkeland, K.W., 2009. The Extended Column Test: Test effectiveness, spatial variability, and comparison with the Propagation Saw Test. Cold Regions Science and Technology, 59: 210216.

Chiaia, B.M. and Frigo, B., 2010. Numerical studies of fracture arrest on Simenhois, R. and Birkeland, K.W., 2014. Observations of fracture arrest snow cover. Frattura ed Integrita Strutturale, 14: 45-51. at slab avalanche boundaries. In: P. Haegeli (Editor), 2014 International Snow Science Workshop, Banff, Alberta.

Gaume, J., van Herwijnen, A., Schweizer, J., Chambon, G. and Birkeland, K.W., 2014. Discrete element modeling of crack propagation in weak van Herwijnen, A., 2005. Fractures in weak snowpack layers in relation snowpack layers. In: P. Haegeli (Editor), 2014 International Snow to slab avalanche release, University of Calgary, Calgary, 296 pp.

Science Workshop, Banff, Alberta.

Gauthier, D. and Jamieson, J.B., 2008. Fracture propagation propensity in relation to snow slab avalanche release: Validating the propagation saw test. Geophysical Research Letters, 35(L13501): doi: 10.1029/2008GL034245.

Gauthier, D. and Jamieson, J.B., 2010. On the sustainability and arrest of weak layer fracture in whumpfs and avalanches. In: R. Osterhuber (Editor), 2010 International Snow Science Workshop, Squaw Valley, California, pp. 224-231.

Greene, E.M., Atkins, D., Birkeland, K.W., Elder, K., Landry, C.C., Lazar, B., McCammon, I., Moore, M., Sharaf, D., Sterbenz, C., Tremper, B. and Williams, K., 2010. Snow, Weather and Avalanches: Observation guidelines for avalanche programs in the United States. American Avalanche Association, Pagosa Springs, Colorado, 150 pp.

Heierli, J., 2005. Solitary fracture waves in metastable snow stratifications. Journal of Geophysical Research, 110: doi: 10.1029/2004JF000178.

Heierli, J., Gumbsch, P. and Zaiser, M., 2008. Anticrack nucleation as triggering mechanism for snow slab avalanches. Science, 321: 240-243.

Jamieson, J.B. and Johnston, C.D., 2001. Evaluation of the shear frame test for weak snowpack layers. Annals of Glaciology, 32: 59-68.

Lawn, B., 1993. Fracture of Brittle Solids. Cambridge University Press, Cambridge, 378 pp.

Perla, R., Beck, T.M.H. and Cheng, T.T., 1982. The shear strength index of alpine snow. Cold Regions Science and Technology, 6(1): 11-20.

Schweizer, J., Kronholm, K., Jamieson, J.B. and Birkeland, K.W., 2008.

Review of spatial variability of snowpack properties and its importance for avalanche formation. Cold Regions Science and Technology, 51(2-3): 253-272.

Schweizer, J., Reuter, B., van Herwijnen, A. and Jamieson, J.B., 2014.

On how the tensile strength of the slab affects crack propagation propensity. In: P. Haegeli (Editor), 2014 International Snow Science Workshop, Banff, Alberta.

Sigrist, C. and Schweizer, J., 2007. Critical energy release rates of weak snowpack layers determined in field experiments. Geophysical Research Letters, 34(3): L03502.

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mechanisms for producing significant snow in new zealand // mads naeraa-spiers, Metservice Originally from Denmark, Mads now resides in Wellington and is a Severe Weather Forecaster for MetService. He is a keen backcountry skier and tells us he needs to secure more time to get into the field so he can verify his snow predictions.

Sitting proudly in the Roaring Forties, New Zealand certainly gets its fair share of weather. With nothing but the Southern Ocean between us and the Antarctic, tropical air only a strong northerly away, and with a large continent prone to producing hot air right across the Tasman, variety is the name of the game here. For forecasters, this brings never ending challenges, and as skiers we’ve come to accept that conditions change often and rapidly – sometimes for the better, sometimes for the worse.

Very rarely can we count on a consistent supply of snow producing storms, nor of extended periods of fine weather.

There are, of course, exceptions, with last year’s mid-winter drought a good example; the barometer barely moved from 1030hPa, and warm sunny days stretched on for over a month.

Unfortunately this came on the back of very low early winter snowfall.

This means that with a good grasp of meteorology, local knowledge, and a good attitude, you will be in a much better position to enjoy what our fabulous mountains have to offer.

In this article, we’ll take a closer look at the two main mechanisms for producing significant snow in New Zealand - warm advection, and polar air outbreak (vorticity advection) with a special focus on the most popular regions – the Southern Lakes, the Canterbury High Country/Arthurs Pass, and Tongariro National Park.

Figure 1: Model “Tephigram”, showing temperature and humidity through the atmosphere. Shown here is saturation (lines close together) through the Dendritic Zone (the light blue area on the left).

Mt Ruapehu. Our North Island volcanoes stick out like the proverbial sore thumb, and they are fickle places for fine weather and snow to coincide.

Often there is a westerly wind carrying moisture from the Tasman Sea onto the Central Plateau, and as this is lifted by the western slopes, freezing rain or tiny ice crystals are formed. The freezing rain will turn to ice the second it hits solid surfaces, hence the common build-up of rime ice on lifts, pylons, noses and ears, but no proper snow falls in these conditions.

Snow theory In simple terms, to produce snow you need: • • •

Moist air Lift Cold air at surface

Moist air is lifted, either on broad frontal surfaces, orographically (by going over a mountain), or via instability (convection). As it is lifted and cooled, the water vapour is gradually condensed into water droplets, which then fall to the ground as precipitation.

The temperature at which this condensation happens, and at which the precipitation hits the ground, determines whether we get rain, drizzle, freezing rain, graupel, snow, heavy snow etc.

To explain things we have to delve into the physics of ice crystal growth. Don’t worry – it won’t hurt.

Figures 2 and 3: Stellar dendritea

If the temperature in a cloud is above -10°C, it is likely to contain super cooled water droplets, and little or no ice. In this case, only freezing drizzle or very light snow will be produced. In order for proper snowflakes (stellar dendrites) to form, the atmosphere has to be saturated through the “dendritic zone”, i.e. -12°C to -18°C. In this temperature range, ice is present in the clouds, and crystal growth occurs by deposition of water vapour onto the crystal, forming the characteristic stellar dendrites.

It is not enough to take a moist air mass and lift to temperatures below freezing, and a good illustration of this is conditions at Crystal Ball - Periodical of the New Zealand Avalanche Community

Figure 4: Several stellar dendrites put to good use

Figure 5: An astounding number of stellar dendrites piled up

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mechanisms for producing significant snow in new zealand // mads naeraa-spiers, metservice If the air is saturated through a deeper layer of the atmosphere (the dendritic zone is typically at around 5km a.s.l.), stellar dendrites are formed. Whether they reach the ground or not of course depends on the temperature at the surface, and throughout the layer they fall through.

But be aware, heavy snow can fall many hundred meters below the freezing level (FZL), and heavy snow itself can lower the freezing level.

To melt snow takes energy - we know that from making drinking water on the mountain. As snowflakes fall below the FZL and melt, the energy required to melt them is taken from the ambient air, lowering the air temperature and the FZL in the process. Therefore, it might be 5°C and bucketing down with rain at first, but a few hours later this will turn to snow provided that it keeps snowing aloft.

A similar lowering of the FZL happens if snow is falling into dry air, as evaporation also takes energy/heat out of the ambient air.

Warm Advection Snow Most people probably associate heavy snowfall with bitterly cold southerlies but, as shown above, saturation through the middle of the atmosphere is necessary to produce significant snow, and moist subtropical air is actually an important factor in the heaviest snow events in New Zealand.

Figure 6 is a “model sounding” or a “tephigram”, ie, what a computer model thinks the temperature and dew point will look like at a certain point at a certain time. For forecasters, this is like the finger print of an air mass, and an invaluable tool in snow forecasting. Temperature is along the x-axis, height along the y-axis. Winds are shown on the far right, and the FZL is the red line on the right (intersecting the temp curve at about 600m a.s.l.).

What this sounding shows is a typical warm advection, heavy snow situation. The air is saturated (dew point and temperature lines close together) from the surface through the dendritic zone (the light blue lines towards the left). The “warm nose”,

Figure 6: Warm moist northwest airstream aloft – cold southerly below.

or temperature inversion, shows warm air streaming down from the northwest (see winds), while cold air from the south “undercuts” the warm air.

Warm advection events can often lead to low density snow, as large stellar dendrites fall through relatively light winds.

It may seem confusing or counterintuitive to have such different air masses - moist, warm northwest winds aloft, and cold southerlies near the surface – but in fact this is often the case.

A front travelling up the South Island is likely to have the surface front ahead of the upper trough, and hence the warm air aloft will over run the cold surface air. To illustrate this, see Figures 7, 8 and 9.

Figure 7. Surface analysis at noon 08/10/2013

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mechanisms for producing significant snow in new zealand // mads naeraa-spiers, Metservice

Figure 8: Surface chart on left – 500hPa (~5km) level on right at noon 08/10/2013. Northern boundary of cold surface air indicated by blue line – southern boundary of warm air aloft by red line.

Figure 9: Intensity of precipitation on right and Freezing level on left.

Note how the cold surface air corresponds to the position of the front across central New Zealand, and that the area of precipitation coincides with the overlap of the warm air aloft and the cold surface air.

In the above example, heavy snow is likely from the ranges of Nelson to about the Arrowsmiths.

Warm air advection snow characteristics: • • • •

Shallow cold air near surface Moisture through middle atmosphere from sub tropics Widespread heavy snowfall Often low density snow – 10% or less

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mechanisms for producing significant snow in new zealand // mads naeraa-spiers, METservice Polar air outbreaks At times the jet stream will move in giant loops, just like a river meandering through a rainforest.

Figures 12 and 13: Meandering river compared with with the movements of jet stream around the globe.

When a large high settles over the Tasman Sea or eastern Australia, and a broad trough lies over and just east of New Zealand, very cold air will stream directly from the Antarctic towards the South Island.

As this air mass travels northwards it is modified by the sea, warming and picking up moisture from below. Meanwhile, temperatures through the middle and higher parts of the atmosphere will remain very cold – often around -40°C.

This makes for cold and very unstable conditions, as the relatively warmer and lighter surface air bubbles up through the much colder and denser air aloft, creating wintry showers with snow to low levels. Aloft, short wave upper troughs (SWUTs) lower the temperature even further, bringing enhanced convection and bursts of heavy snow.

Figure 14: Significant polar outbreak, August 2011. It snowed at sea level in Wellington, and Christchurch City got more than a foot of snow.

The surface analysis above is from the major polar outbreak, which affected large parts of the country in 2011. With the ridge of high pressure sitting over the Tasman Sea, and extending all the way to the Antarctic ice edge, very cold air was streaming onto New Zealand from the south and southwest. In other events, the ridge or high lies farther west, and the flow is more westerly.

strongly into play, with ranges facing into the wind receiving the most snow, and downslope areas much more sheltered. This is, however, significantly modulated by stability factors; the more unstable the air mass, the farther downwind from a mountain barrier the snow will fall. For instance, the Craigieburn Range remains dry in most stable rainfall events, but can get lots of snow – and frequent thunder – in cold, unstable westerlies.

The direction of the flow can be crucial in determining which areas will see snowfall, as a lot of the moisture is at lower levels than with warm advection snow. Orographic effects come Crystal Ball - Periodical of the New Zealand Avalanche Community

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mechanisms for producing significant snow in new zealand // mads naeraa-spiers, Metservice

Figures 15 and 16: Two examples of polar air outbreaks: Unstable west to southwest flow on left (red shaded area shows convective (buoyant) energy).

On the right, colder south to southwest flow.

Polar air outbreak characteristics: • • • •

Bitterly cold, driving snow.

Often windy Often large variation in depth (orographic effects) Only exposed areas get snow; sheltered downstream from main ranges

Figures 17 and 18: Sheltering effect in very cold polar air outbreak. Wind is travelling in a southwest direction.

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mechanisms for producing significant snow in new zealand // mads naeraa-spiers, Metservice Other snow producing scenarios While warm advection and polar air outbreaks are the most common heavy snow producers, other typical synoptic situations will lead to significant snowfall.

A good example of this is when a high or ridge sits to the southwest of the country, while a low or trough lies over the North Island. The resulting southeasterly flow can bring lots of snow to exposed ranges from the Kaikouras to the Two Thumb Range, and in La Niña years this setup is common, sometimes lingering for days on end.

Snowfall in three main regions So let’s take a look at what synoptic situations favour snowfall in the Southern Lakes, Canterbury High Country (including Arthur’s Pass), and Tongariro.

The Southern Lakes With large mountains dropping straight into scenic lakes, and epic terrain everywhere, all that our most popular mountain area is missing is a little more snow. The massive ranges of Fiordland and Mt Aspiring National Park provide shelter from the prevailing westerly flow, and the closest neighbour to the east is the virtual desert of Central Otago – with MacKenzie Basin the driest region in New Zealand (less than 400mm annual precipitation in some places). Large east-west differences here see the Richardson Mountains get many times more snow than the Pisa Range. To the south lie the Garvie and Eyre Mountains, providing some sheltering from southerly snow.

Figure 19: Moist southeast flow over the South Island

Even with these barriers in place, the Southern Lakes area does get snow from both the west and the south. With a large trough over the Tasman Sea forcing moist, unstable west or northwest winds onto the lower South Island, substantial snowfall can happen. Look for the aforementioned large trough/low over the Tasman Sea on the weather chart, and bright, speckled looking cloud on the satellite image, indicating unstable conditions (Figure 26): http://www.metservice.com/maps-radar/maps/tasman-sea-nz http://www.metservice.com/maps-radar/satellite/tasman-seanz-infrared The more unstable, the heavier the snow is likely to be, and the farther downstream from blocking ranges it will fall. A large trough, like in the image on the right, can remain in place for several days, resulting in large snow accumulations, especially on (east and southeast) lee slopes.

Areas of very bright cloud indicate very cold cloud tops associated with upper short wave troughs, and heavy snow can fall from these.

Warm advection snow is a great snow producer for this area.

With the necessary moisture carried aloft on northwest winds, and cold, dense southerlies providing a solid wedge to lift this air, the surrounding ranges are not able to block the snow. This synoptic situation can produce the most intense snowfall, often with very large, light snowflakes making for high quality snow.

However, it is not likely to continue for several days.

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Figures 20 and 21: Two examples of a trough/low over the Tasman Sea producing snow over the Southern Lakes.

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mechanisms for producing significant snow in new zealand // mads naeraa-spiers, metservice

This scenario is reasonably easy to identify, and Figures 23 and 24 show a typical example: On the left, a low off eastern Australia is deepening, while cold fronts move out of the Southern Ocean towards the South Island. On the right - 24 hours later – the now deep low is forcing moist air southwards onto the South Island, while cold air at the surface has pushed northwards to the Kaikoura Coast.

The Canterbury High Country Like the Southern Lakes, this area is sheltered from westerly snow by the Main Divide. Precipitation drops off rapidly the farther east you go, with Arthur’s Pass receiving about three times more than Castle Hill; rainforest to dry tussock land in 25km. These characteristics mimic what’s seen in the Southern Lakes, but the difference is that the Canterbury High Country is exposed to the south and east, and significant polar air outbreaks can dump metres of snow in a day or two - as happened in June 2013.

Still, warm advection snow events produce the most, and best quality, snow, with unstable west and northwest flow a close second. As before, warm advection events will see widespread and intense snowfall, while unstable west and northwest flows dump much more snow at Arthur’s Pass and The Arrowsmiths than on the Craigieburn and Torlesse Ranges.

Conversely, the moist southeast flow (Figures 24 and 25) will bring much more snow to eastern ranges than to the Main Divide. With El Niño strengthening at the time of writing, westerlies are more likely over New Zealand this winter, but this does not exclude southerly or easterly events.

Figures 23 and 24: Warm advection snow setup

Figures 24 and 25: Southerly snow storm June 2013

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mechanisms for producing significant snow in new zealand // mads naeraa-spiers, metservice Tongariro National Park In sharp contrast to the ranges of Southern Lakes and Canterbury, the central volcanic plateau of the North Island stands alone – and stands out like a sore thumb, attracting lots of weather, often building up a deep snow pack. Shallow moisture will lead to ice crystals or freezing rain falling, while deep polar air outbreaks, especially with a large trough over the Tasman Sea, will bring bursts of heavy snow from the west.

In a southerly flow, the jet stream is typically farther east, and the moisture not quite as deep, often making for less intense snowfall.

If the flow is out of the southwest, the South Island ranges can block the snow, forming a large wedge of clear skies in their wake. Figures 17 and 18 are a good example of this effect.

So what happens then?

The snowfall itself is of course only part of the equation, and how it settles and is transformed makes a huge difference to how conditions turn out. Does it bond well with the existing snowpack? What wind loading takes place during and after the storm? Does the temperature change significantly? The snowpack can settle and stabilise beautifully, or it can turn into heavy glop and avalanches come down on all aspects.

Figure 26: Deep cold airmass and warming aloft.

There is always more to learn, and post storm weather could be the focus of a future article.

niwa snow and ice network // christian zammit, NIWA Zammit, C. Harper, A, Rutherford, J, Willsman, A, Mc Dermott, H, Newland, R, Hay, R. NIWA-National Institute of Water and Atmospheric Research Christchurch

Monitoring plays a pivotal role in determining sustainable strategy for efficient overall management of the water resource.

Though periodic monitoring provides some information, only long-term monitoring can provide data sufficient in quantity and quality to determine trends and develop predictive models.

These can support informed decisions about sustainable and efficient use of water resources in New Zealand. However, the development of such strategies is underpinned by our understanding and our ability to measure all inputs in headwaters catchments, where most of the precipitation is falling.

Historically, New Zealand has had little to no formal high elevation monitoring stations for all climate and snow related parameters outside of ski field climate and snow stations. This leads to sparse and incomplete archived datasets. Due to the importance of these catchments to the New Zealand economy (eg, irrigation, hydro-electricity generation, tourism), NIWA developed a climate-snow and ice monitoring network (SIN) in 2006. This network extends existing monitoring by Meridian Crystal Ball - Periodical of the New Zealand Avalanche Community

Energy and ski stations and is used by a number of stakeholders.

In 2014 the network comprises 13 stations located at elevation above 700masl.

As part of the WMO Solid Precipitation Intercomparison Experiment (SPICE), NIWA is carrying out an intercomparison of precipitation data over the period 2013-2015 at Mueller Hut. The site was commissioned on 11 July 2013, set up on the 17th September 2013 and comprises two Geonor weighing bucket raingauges, one shielded and the other un-shielded, in association with a conventional tipping bucket raingauge and conventional climate and snow measurements (temperature, wind, solar radiation, relative humidity, snow depth and snow pillow).

The presentation aims to outline the state of the current monitoring network, its use by NIWA and to present preliminary results obtained part of SPICE experiment over the period September 2013-March 2015.

Email: Christian.Zammit@niwa.co.nz 19

Systematic probing after Transceiver Searching // adrian Camm, Aspiring guides The impetus for this article came from my own experience of failing to find a deeply-buried target during a guides course transceiver test a few years ago then hearing other peoples’ experience in a similar situation during a subsequent Stage 2 Avalanche course. Afterwards we all said the same thing: “The transceiver search went fine but it all went wrong when it came to the probing”. Hopefully these notes can help with that part of the process.

Here’s an example. We’re looking vertically down on the probing area. Each blue blob is a probe hole arranged in a square grid.

Transceivers are expensive and electronic and make exciting noises. They’re fun to practice with, so they get lots of attention and a skilled searcher with a modern transceiver will usually get to within a couple of metres of a buried target very quickly.

Similarly, digging out a buried victim is the most time-consuming stage so shovelling has been the subject of research and articles and we now learn how to organise groups of shovellers. The poor old probe doesn’t have words like “digital”, “three antenna” or “strategic” associated with it. However, the basic technology was used in Hannibal’s time to locate soldiers buried by avalanches during an early traverse of the Alps, and this suggests an enduring usefulness.

It may only be a stick but it’s the probe that actually locates the victim and, for the purposes of the tests we do, allows us to shout “strike” and move on to the next step. Yet I can’t find much written about probing technique and, if what I’ve done, seen and heard is anything to go by, it is often the stage that causes problems during what we call transceiver searches.

The aim of this article is to raise some of the main points around probing and try to clarify some important steps. A couple of quick notes before we get going – this article is partly aimed at the transceiver tests that we all do during Avalanche 1 and 2 and the Ski Guide courses when we’re searching for targets that are about 45cm across and roughly square. There’s a discussion of how well these targets represent a real buried person and whether that might affect our search strategy later on. Secondly, this is all about probing for a target immediately following a transceiver search - it’s not about probe-line searching but some of it is relevant to spot-probing.

Figure 1: Nowhere to hide. If the largest gap in your grid is smaller than the target, then you must hit it provided you make an accurate grid of holes. If you do this the probability of discovery is 100%.

Can We Improve on this Grid Pattern?

The pattern below is an offset grid rather than a square one.

You can think of it as a series of adjacent triangles where you position each hole the same distance from two earlier ones, or you can look at it as concentric rings (although they’re actually hexagons.) This pattern has a couple of advantages over the square grid. Firstly, with the same hole spacing you make more holes per square metre so you’re more likely to hit a smaller target. Secondly, there’s a higher chance that at least two probe holes are “on-target”, so if your hole positioning isn’t perfect and you miss the target there’s usually a second or even a third chance for a strike later in the pattern. It’s more forgiving of inaccuracy and this is an important advantage over the square grid shown in Figure 1.

What’s the Idea?

The key feature of a probe search is that it can’t give you a false negative result. If you probe in the right place you must hit the target. If your probe goes all the way to ground then the target simply isn’t there – you can’t push through a solid target. When you probe in the right place you will get a strike so the aim is to organise your probing in a way that ensures you will sooner or later probe in the right spot. In other words, we want to probe in an efficient way that minimises the element of chance.

So, if shovelling gets the word “strategic”, what’s a good word to go with probing? Systematic. What does systematic probing mean? It means using the probe to make a grid of parallel holes in the snow, a fixed distance apart and all of the same depth. If you do that, and your grid spacing is the right size in relation to the target then you can’t fail to strike it. Right?

Figure 2: This pattern gives smaller average gaps between probe holes than the square grid.

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Systematic probing after transceiver searching // adrian Camm, aspiring guides Of course, there’s a time cost for using this pattern. It has about 15% more holes per square metre than the square grid so it’s going to take that much longer to cover an area.

What about Hole Spacing?

That depends on the size of the target! With a 30cm spacing and the concentric circles pattern a target that’s larger than 45x45cm can’t hide. But the target shown below can be missed with this pattern.

Figure 4: Target represents the torso of a person lying on one side.

Figure 3: This target could be missed. 29x52cm is a little larger than an A3 sheet of paper.

Is this a problem for us? With a 45cm square wooden target then it probably isn’t but now let’s look at a real burial.

Unfortunately, a buried person isn’t a convenient square shape so how should we go about probing in a real search?

According to the Architectural Record the dimensions of an “average” adult male human torso are apparently 63x34x26cm so an average male who is conveniently buried perfectly flat on either their back or their front is going to be found with the 30cm concentric circle pattern shown above – even if we ignore the possibility of striking a limb or their head. But of course many people are smaller than average male and there’s a good chance the victim won’t be buried in the ideal orientation to be a good probing target. Here the textbooks do have something to say and the consensus seems to be a 25cm spacing. Once again, there’s a time cost to using a 25cm spacing instead of 30cm – you’ll cover about 70% of the surface area in the same time but with the uncertainty of size and orientation of a human target the only way we can ensure we’re eventually going to probe the victim is to use a small enough grid. Figure 4 shows the 25cm grid with that “average” torso person lying on one side.

Should we use different tactics when we’re hunting for a training target from what we’d do in a real burial? In training and exam situations we’re developing successful habits that will kick in and help us through a genuine emergency. If we make the right behaviours automatic we’ll avoid wasting time thinking so it seems like a good idea always to use a pattern and spacing that’s tight enough to ensure you hit a small human target. If you do that it’ll definitely work fine on a 45cm square target or a large backpack.

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Spot Probing The probing patterns above are relevant for probing after a transceiver search when you have narrowed down the search to a relatively small area. What about spot probing? In this case you’re going to do what you can to identify likely burial areas. You’ll use last-seen points, visual clues like equipment on the surface and features such as terrain traps to improve your chance of probing in the right area, however your start point is unlikely to have anything like the accuracy a transceiver would give. It’s still important to be systematic but area coverage becomes more important, so a bigger grid spacing is worth considering. Planning your search by identifying the limits of the area you’re going to spot probe and where you’re going to start, then working over it systematically, is going to give a more thorough search than simply starting at the first spot that catches your eye.

Summary on pattern and spacing No doubt there are different ways to think of the hole pattern.

However, the key points with the pattern you use are:• • •

T he spacing is small enough to guarantee hitting whatever you know to be buried The pattern is easy for you to visualise and accurately follow as you move out from the start point The pattern should allow some room for error – ideally there should be more than one hole position that’s going to hit most targets.

Whether that’s something you see as a grid or a series of triangles or concentric circles is less important than being able to project it mentally onto the snow and follow it systematically with your probe.

A few things to build into your probing process…

1. Probe at 90 degrees to the snow surface Your transceiver will lead you to the place with the strongest signal, which will usually be where the buried transceiver is nearest. You can see on Figure 5 (over page) that if you’re on a slope and you go to this spot and probe vertically you’ll miss the target. This is even more likely with a deep burial. The probe needs to go in at 90 degrees (perpendicular) to the snow’s surface (remember this is for a transceiver search – not a probe line). This is much easier to achieve if you move your feet to beside the next hole position before inserting the probe.

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Systematic probing after transceiver searching // adrian Camm, aspiring guides In the heat of the moment it’s quite hard to keep probing exactly perpendicular to the surface. Even if you’re really trying to do it right, the natural tendency is to probe at an angle somewhere between vertical and perpendicular (ie, between the red (dashed) and green (solid) probes in the diagram above).

This means there’s a good chance your probe will miss on the downhill side of the target. The target is slightly further up the slope. So if you’re searching on a slope and you don’t hit anything with your first probe insertion, make your next probe hole uphill from the first and continue your grid from there.

2. Think systematically What’s going on in your mind when you’re probing? If you’re thinking “gotta find the target, gotta find the target…” then, paradoxically, you’re more likely to miss it. When your mind

two hands on the probe – the lower hand places and guides it while the upper one does the pushing and pulling. Secondly, it’s quite common to see people probe a few holes then, if they don’t hit anything, grab their transceiver and go through the pinpointing again. What does that achieve? Think about it.

You re-do the pin-pointing and let’s say your point of strongest signal has moved 25cm. So you re-probe an area starting 25cm from where you just began, making a new set of holes amongst your previous ones. But you know the target isn’t there! You just probed that area and you didn’t hit anything. If it was there you’d have hit it so what does repeating it achieve? It wastes precious time - nothing else. Unless you have a good reason to think that you messed up the probing first time round then there’s no point re-probing an area. Redoing the transceiver pinpointing is a sign that you don’t believe that systematic probing will find the target - or that you’ve forgotten where you started.

5. Mark your start-point It’s much easier to keep track of the spot where you found the strongest transceiver signal if you mark it with something like a spare glove. This gives you a great visual reference point around which to make your grid. It can be hard to remember where you began after the first few holes and the feeling of “now where did I start?” is an uncertainty you just don’t want in your mind.

Remember not to use a marker that’ll confuse other searchers, including dogs.

Figure 5: Probing at 90 degrees to the surface

is fixated on feeling the probe hit something then your search will subconsciously become less and less organised. You’ll tend towards poking holes in any old direction on irrational hunches about where the target might be. You might get lucky but you won’t be systematic.

On the other hand if you’re thinking “next hole, 90 degrees to the surface, 25cm from the previous one, parallel to it, 2.5m deep,” then you are focussed on making that perfect grid of parallel holes and at least one of them will be on target.

3. Stick with it Have another look at Figure 1. Imagine that you probed systematically in the order of the numbers next to each probe hole. You wouldn’t have hit the target until your ninth probe insertion even though the distance between the buried transceiver and hole number one (that’s the place that gave you the closest transceiver signal) was only about 20cm. In other words your transceiver pinpointing was pretty good but the probing pattern meant that you were never going to hit the target until your ninth attempt. However in this example, unless your ninth hole position was wildly inaccurate, you were guaranteed to hit it at the ninth attempt.

Probing Depth It’s useful to have a way to ensure consistent depth to your probing. You can put a brightly coloured piece of tape around your probe at whatever depth you’re going to probe to (eg, 2.5m) or, alternatively, push the probe all the way in until your hand on the end of it touches the snow (or you hit the ground) each time.

As Steve Achelis points out on Beaconreviews.com, your transceiver doesn’t provide a calibrated measurement of the target’s depth; your probe does. Noting the depth of a strike enables you to begin shovelling at the right spot as well as prioritising victims in a multiple burial situation. Digging out the victims will usually be the time and energy consuming part of the process so identifying the shallower burials that can be dug out fastest and with the fewest diggers is a key step in getting the best possible outcome.

Summary Probing shouldn’t be a breathless game of lucky dip that finally yields a strike accompanied by equal amounts of relief and surprise. It should be a calm, accurately executed process that’s carried out with the confidence of having developed and practiced a reliable system.

If you’d started losing faith in the process after five or six Key elements of that system are:attempts and become less systematic you might have got a lucky • Getting your transceiver out of the way – it has done its job hit but that’s not what we’re aiming for. Keeping to the grid for • Creating an accurate grid with appropriate hole spacing another three or four probe insertions would have resulted in a • Inserting the probe at 90 degrees to the snow surface strike.

4. Put your transceiver away When you start probing, put your transceiver away in a pocket and leave it there until you’ve found the target (don’t leave it dangling around your boots on its elastic cord). Firstly, you need Crystal Ball - Periodical of the New Zealand Avalanche Community

• •

Knowing exactly where you started probing Sticking with your probe search until you hit the target.

opefully the ideas in this article can help to make probe H searching a more systematic, successful and serene process.

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Summary of summer forecasting at aoraki/ mt cook // Dave MCKinley, alpine guides Dave is an International Federation of Mountain Guides Associations (IFMGA) Mountain & Ski Guide, and is the Guiding Director of Alpine Guides Ltd (AGL) at Mt Cook. He also leads the avalanche forecasting team for the region.

Following the “Winter of our discontent”, all was set for a relaxing summer season of hit the three days button, and repeat forecasting. Such was not to be the case. Whispers were on the wind, “winter is coming”.

And so it was. As operations wound down, staff laid off and all looked back at the season that was (or wasn’t), winter did indeed come.

We had skied a magic few days of corn in the spring at Mt Cook, but as it rolled into October and we started to look at “summer” activities, the first question we were asking our clients was “Can you ski?”. If not, here’s a pair of snowshoes.

By early October we had 140mm of rain in the village, translating to 1.5m new snow above 2000m and a ‘considerable’ danger rating. Shortly after we observed several wet loose releases in the Gammack Range. I wondered why is it that the worst stability = the best quality? Take it where you can, but pick that line with a LOT of care!

And so it continued in the early part of the month, with plenty of graupel and regular top ups. I’m still waiting for the appropriate computer geek or person with a direct line to divine powers to find out how to move these events to when we need them.

In mid-October after the briefest of interludes we were back to another 50cm of new snow near the Divide. Windy-as from the northwest, plenty of wet loose slides and a few small slabs avalanches were observed.

A note from the time was that there existed a potential of “step down” fractures from new to old snow surfaces. We then had a period of rain down to 1000m over this delicate multi-layered snowpack within the top 50cm-1m.

Guess what? Between October 20 and 27 there was a vigorous avalanche cycle with up to size three slabs on most aspects.

Then it got cold again and although not a massive amount of snow, there was enough wind transport lee to the northwest to cause concern.

Starting into November we had a really interesting sight at the Grand Plateau. Just about every aspect slid (about 20-30cm deep) on really low angles. Some slopes ran on angles as low as 15° to 20°, slopes which I’ve personally never seen run before.

Come 4 November there was a wind shift and a stabilising trend of rising freezing levels, but at upper elevations there was still considerable wind transportation going on lee to the south and southwest.

“ Whispers were on the wind, winter is coming.”

Everything settled out for a few days, but by the middle of the month there was both a return to strong south and southwest winds and, for those unfortunate to be in the higher huts of the National Park, a return to the “grey room” existence and 50cm+ new snow above 2000m.

On November 16 there was a huge avalanche observed by people on the Fox Glacier from off the Paschendale Ridge region. It was very large in size, ran to ground, probably a wet slab, and quite impressive by all accounts.

Fortunately there was a break in hazardous conditions, which it would only last a couple of days.

By 19 November we were back to a considerable danger for storm slab above 2000m with 50-150cm above 2000m by 21 November.Fun and games again!

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Summary of summer forecasting at aoraki/ mt cook // Dave MCKinley, alpine guides

Well, so much for November. Any hope for December?

The first words from the December reports were about a “still winter snowpack”. Plenty of graupel with a considerable hazard above 2000m lee to the south and southwest.

But by 6 December there was a hint of hope with reports from the hills that the recent storm snows were settling out quite rapidly and for the mid period of the month stability was good.

Loose wet avalanches in the heat of the day were the only main factors to note.

One curious event was that somewhere between 14 and 16 December, there was a large rock avalanche east of Rose Peak near the Mannering glacier. The dust was visible for several days.

Late in the month there was a significant rain event with plenty of loose wet avalanche activity and yet more new snow above 2000m. Reports were coming in of people still skiing the glaciers!

It was only by January that we saw a truly stable period where the snow and avalanche conditions became “normalised” for a summer snowpack, with the main danger being that of isolated wet loose events out of steep, solar affected terrain.

In the middle of the month we did have a period of 40-50cm of new snow, but it only resulted in a shallow windslab overlaying some old graupel and soon bonded well.

The most serious hazard came from slide for life on icy crusts combined with long runouts. This was created by more snow cover than normal at this time of year and the associated nasty outcomes from taking a ride. This remained the case for the remainder of the month.

February started with rain and more rain but by February 6 there was snow again making us wonder if winter had turned up early. But freezing levels rose and sorted it out.

For the remainder of February and March the main concern was solar affected slopes with the exception of a bizarre blizzard event early in the month. But what the winds didn’t remove, the return of the sun soon did. As March drew to a close, there were a few dustings of snow above 1900m. Enough to look pretty, but not enough to change the danger to travellers or get any sane person excited enough to break out the skis (unless they’re not yours)!

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Are you interested in becoming involved with avalanche search dogs? // Karyn Heald Robertson, Landsar search dogs NZ Land Search and Rescue (LandSAR) is the volunteer organisation that provides land search and rescue services to the Police. As a specialist group under LandSAR, they are the official search dog group in New Zealand.

NZ LandSAR search dogs are divided into avalanche and wilderness dog categories with some teams crossing over both disciplines.

Currently the avalanche search dogs are looking at succession planning as a number of our operational dogs are nearing retirement in the next few seasons.

We have identified that ski-field-based avalanche dog teams are desirable due to the response time. As the preferred skill base of the dog handler is suited (but not limited) to alpine professionals, the person needs to have a passion for dogs and the alpine environment.

Above: Ohau Training Camp

If you think there is anyone within your area or elsewhere in the ski industry who might be suitable - please let us know. There is an opportunity for interested people to attend our training camps. Our camps are most excellent fun and great learning opportunities.

Selecting the appropriate dog for search work is one of the most important aspects. If you are interested in training an avalanche dog, (in a perfect world) we would like interested people to please contact us before getting a dog, as the drive of the dog is one of those non-negotiables in terms of pre-requisites in order to progress through the training pathway. This is not to say that if you already have a dog that you need to be looking for another - but all dogs are tested prior to starting training to ensure they have what it takes.

Not all dogs will make great search dogs and the New Zealand Police Dog section assist us with dog selection.

Above: Ernie in action with handler Courtney Wiedel while Rob T. looks on

All the information including our standards and training information can be found on our website www.searchdogs.co.nz and we can also put anyone keen in touch with one of our operational handlers in their area for a casual coffee and chat.

Get in touch if you want to attend one of our training camps or for more information: Email: avalanche@searchdogs.co.nz Phone: Karyn 027 406 3604

Above: Four of our current operational handlers - Dan Kennedy and Courtney Wiedel from Canterbury and Matt Gunn & Andy Wardell from Southern Lakes.

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From Whakapapa To The Artic Circle // Mike Lundin Mike Lundin has been working within the New Zealand avalanche community for the past twelve years on a number of ski patrol crews from Queenstown, Porters and more recently Whakapapa where he has held the position of Assistant Snow Safety Supervisor for the past four winter seasons.

He has been involved with avalanche forecasting and education through the Mountain Safety Council for five years now and has worked in the mountains of Canada, Japan and now Norway. He has been lucky enough to ski in a number of amazing places over the years; this article talks about one of these places.

Narvikfjellet - The Magic Mountain.

For the past three months we have been based at latitude 68° north in the Norwegian industrial seaside town of Narvik.

We had secured work ski patrolling at Narvikfjellet. Here the mountains fall into the ocean with potential ski lines everywhere you look. On arrival the steep, dark, icy streets of Narvik made for a harsh introduction but we were to find that this place on the other side of the world had many similarities to our home.

A land of contrast and extremes, the ski area rises 1100m above the town and opens up some incredible ski lines adjacent to the ski area. The locals here more or less use the ski area to access the backcountry. It is not uncommon to have more uphill traffic than downhill. The season of 2014/15 was a mixed bag with a slow start, massive windstorms damaging lift shacks, and arctic ‘pow’ which will remain in our memories for years to come.

When it’s on it’s on, and when it’s stormy you can’t see your hand in front of your face.

Above: Ralphie making the most of one of the better days at Narvikfjellet

Gaining information on current conditions is getting easier with the Norwegian Avalanche Association publishing forecasts using information gathered by field staff on a regular basis. The system is young, but no doubt will gather momentum over time with many Norwegians and visitors venturing into the mountains.

Some say Norway is the birth pace of skiing and it easy to see why. I feel very fortunate to have been able to experience the Despite not speaking Norwegian, Ralphie and I managed to work alpine environment here, from meeting a herd of reindeer on a ski trip to eating boiled mashed potatoes filled with pork and while not understanding anything that was being discussed on lathered with butter and jam at a ski area cafe. Norway will be a the radio. The ski area is made up of three t-bars, one gondola stand out for many reasons for some time. and a chairlift. Norwegian ski area regulation means only the hazards on groomed trails and two metres off the ‘cord’ need Photos supplied by Kaj Sønnichsen to be managed by the ski patrol. Therefore avalanche control is For information on Norwegian avalanche conditions go to limited to two paths that provided a modest overhead hazard. http://varsom.no/en/Snow-avalanche Needless to say explosives are not required here.

In my short experience the mountains of Norway are quiet and peaceful. Drive an hour west over the border to Sweden and you will be greeted by the ear piercing groan of snowmobiles and helicopters ferrying cashed up Norwegians to local summits.

Recreational snowmobiling and heli-skiing are both prohibited in Norway.

We quickly discovered ski touring in this region often requires gaining considerable vertical before being able to enjoy the fruits of your labour. However, in saying this, the payback can be out of this world. Directly translated ‘Skamdalsrenne’ means Shame Valley Chute. A 30 minute drive up a neighboring fiord provided access to the most dramatic line I have been fortunate to ski. After being shut down on the first attempt I was stoked to get into the feature a few days later.

Above: Mike Lundin

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Over page: Mike dwarfed by the cliffs of Skamdalsrenne

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Brought to you by the New Zealand Mountain Safety Council.

Phone: 04 385 7162 Fax: 04 385 7366 Address: Ground Floor, 86 Customhouse Quay Wellington 6011 / PO Box 6027, Wellington 6141

www.mountainsafety.org.nz www.avalanche.net.nz www.incidentreport.org.nz www.adventuresmart.org.nz

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