Item: Thresholds in Wind Speed, Air Temperature and Relative Humidity Controlling Slab Formation
-
-
Title: Thresholds in Wind Speed, Air Temperature and Relative Humidity Controlling Slab Formation
Proceedings: International Snow Science Workshop Proceedings 2018, Innsbruck, Austria
Authors:
- Patrick J. Wright [ Inversion Labs, LLC, Wilson, WY, USA ]
- Bob Comey [ Bridger-Teton National Forest Avalanche Center, Teton Village, WY, USA ]
- Morgan Comey [ Bridger-Teton National Forest Avalanche Center, Teton Village, WY, USA ]
Date: 2018-10-07
Abstract: Weather variables including wind speed, air temperature and relative humidity have important controls on slab formation, influencing the dynamics of snow formation in the atmosphere, snow transport, and deposition. In this study we examine statistical thresholds in these variables that lead to formation of dry loose, soft slab, and hard slab avalanche events recorded by the Bridger-Teton Avalanche Center (Wyoming, USA). Using 43 seasons of historical 24-hr data from the Summit wind station at Jackson Hole Mountain Resort we quantify daily wind totals necessary to support slab formation. We then examine the distribution of hourly average wind speeds and max gusts during slab deposition by selecting wind data only during precipitation periods directly preceding slab avalanche events. To investigate potential thresholds between dry loose, soft slab, and shallow hard slab, we examine 15-minute weather data from ten case study periods between 1999 and 2017. Using five periods dominated by dry loose / very soft slab events, and five periods dominated by shallow hard slab events, we find characteristic weather conditions associated with these end-member types. In particular, these results show a distinct threshold in relative humidity associated with hard slab formation. Supporting previous work, we show that these weather variables have important controls on slab formation.
Object ID: ISSW2018_P10.27.pdf
Language of Article: English
Presenter(s):
Keywords: avalanche forecasting, slab formation, weather
Page Number(s): 987-991
-