Item: SITE SPECIFIC WARNING POLLFJELLET AKA "THE AVALANCHE MACHINE", THE SIGNIFICANCE OF A METEOROLOGICAL ANALYSIS
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Title: SITE SPECIFIC WARNING POLLFJELLET AKA "THE AVALANCHE MACHINE", THE SIGNIFICANCE OF A METEOROLOGICAL ANALYSIS
Proceedings: International Snow Science Workshop 2024, Tromsø, Norway
Authors:
- Kristin Brandtsegg Lome [ Skred AS ]
- Hallvard Skaare Nordbrøden [ Skred AS ]
- Siiri Wickström [ Skred AS ]
- Nils Arne Kavli Walberg [ Skred AS ]
Date: 2024-09-23
Abstract: The mountain “Pollfjellet” in Lyngen municipality has several avalanche paths, and a radar is installed as a mitigation measure to detect avalanches. During three operative seasons, the radar has provided data from more than 400 avalanches from Pollfjellet. Pollfjellet has been called “the avalanche machine”, hence the avalanche history for the more frequent avalanche paths is plentiful. The avalanche path Geitlirenna threaten the road between Furuflaten and Lyngseidet. During the winter of 2023 there was ongoing construction work to finish avalanche sheds in the runout from this avalanche path. Skred AS provided the risk owner daily site-specific avalanche forecasts as a risk reduction measure to increase worker safety at the construction site during the winter of 2023. The prediction of snow avalanches is a complex problem. Snowpack instability and, hence, the risk of avalanches is dependent on past, current and future meteorological conditions. With Pollfjellet generating many avalanches and a radar to detect them, available meteorological data from close by and local knowledge, we were able to make a useful analysis of the meteorological conditions causing the release of dry slab avalanches in Geitlirenna. Past and current meteorological conditions were monitored using weather stations nearby, web cameras, on-site snow observations done by the construction workers and recorded in the avalanche database RegObs. Future meteorological conditions are forecasted by the Norwegian meteorological office, MET Norway, and are available for the public through their service “Yr”. We found that most dry slab avalanches release after a cycle of precipitation with little wind followed by wind veering from south to west. Southerly winds create cross loading in the release areas of Geitlirenna and with snow available for transport this eventually release avalanches. These weather conditions were often observed in association with a warm-front passage. This is contrary to the typical avalanche cycles in the region where wind and snow transport from west and north-west is dominant, which is often related to cold front passages. This result highlights the importance of knowledge on local meteorological conditions, analyzing available data and use local knowledge in site specific avalanche warning.
Object ID: ISSW2024_O1.1.pdf
Language of Article: English
Presenter(s): Kristin Brandtsegg Lome
Keywords: Site-specific, avalanche warning, meteorological condition
Page Number(s): 1 - 6
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