Situazione meteorologica ed eventi valanghivi del Febbraio 1999 nelle Alpi Occidentali

Meteorologic situation, elevation of the isotherm 0 °C and the avalanches in the Western Alps during February 1999

Abstract

Between February 9th and the 23rd 1999, an exceptionally high number of large avalanches occurred in all the Alps. A number of big avalanches, and in particular almost all those which reached the bottom of the valley, were «cloud-shaped», characterised by a very high sliding speed and by the consequent phenomenon of aerosol with strong destructive power. The analysis of the daily variations of the 0°C isotherm elevation in the month of February calculated on the basis of the temperatures recorded by the meteorological stations of Morgex, La Thuile, Courmayeur, Chamonix, Aiguille du Midi, Colle del Gran San Bernardo, together with the other meteorological parameters (snowfalls, directions and speed of winds) shows that the frequent big avalanches of February 1999 depended on anomalous meteorological conditions which characterised not only the local area but all the Western Alps and probably also the entire Alps.