AIR MOTIONS IN THE KHUMBU HIMAL AND POSSIBLE SOARING FLIGHTS

Abstract

Soaring flights have occurred in the Khumbu Himal, but not with a sailplane. Wick soared a single-engine, turbo-Porter aircraft up the face of Lhotse, the peak adjacent to Mt. Everest to above the summit of Everest and glided back to Kathmandu. Also, Simon Baker soared a Guppie Raven ultralight to 24,000 ft in the West Cwm in the fall of 1986 but could not continue the ascent because of a lack of oxygen. From these flights and the numerous photos of the banner clouds generated by Everest and Lhotse, it appears the strong westerly winds which impinge on the Everest massif are funneled up the West Cwm and over the summits causing an enorrnous eddy in which the banner clouds form. A path to the summit of Mt. Everest for a sailplane has been proposed by Hindman (1985). Meteorological observations and measurements made during the authors' treks into the Khumbu Himal region indicate that the proposed path appears feasible. We report the meteorological features relevant to soaring flights: the number of "soarable" days, dry-thermals rising up the valley slopes, the diumal behavior of the Everest/Lhotse banner clouds which we suggest are linked to the up and down-valley winds; up-valley winds blow with a maximum in the afternoon while down-valley blow with a maximum often iust before sunrise. Based on these findings, a plan is presented for soaring flights coordinated with ground observations in the Khumbu Himal to explore the soaring path to the summit of Everest.