Monsoon Onset and Everest Expeditions

Abstract

The paper presents the results of a study of the daily precipitation, temperature at 6 km and winds between 6 and 9 km a.s.l. Over the Everest area during the months of May and June for the period 1952 to 1962. The indications are that there is no well marked 'monsoon lull' or a 'monsoon onset' over the Everest. The transition from the strong and steady westerlies between 6 and 9 km a.s.1. of ,the pre-monsoon season to the steady easterlies of the monsoon season occurs over a period highly variable in duration and can occasionally extend over the whole of May and June. Winds over Everest during this period can be moderate or weak westerlies or weak easterlies. With weak westerlies precipitation can occur practically every day and in most of the years it is not possible to distinguish the onset of the monsoon rains as distinct from the’pre-monsoon thundershower activity'. The temperature of the strong and steady westerlies at 6 km a.s.l. over Everest increases gradually from -10^oC in early May to about 0°C by the time the variable winds set in. From a consideration of the weather features that were obtained by the successful and uJ18uccessful expeditions to the Mount Everest since 1952 it is considered more profitable for future expeditions to get to the high reaches of the Everest by early May instead of late May.