MOUNT EVEREST'S WEATHER IN 1933

L. R. WAGER

In its winter condition Mount Everest, as seen from the Base Camp, shows a dark rock-face, and even the less steep slabs where scree has accumulated are largely free from snow. This appearance persists until May or June. Apparently in winter what little snow falls is soon evaporated or blown away by the powerful and almost continuous west wind.

The change to summer conditions takes place at no very definite time, but when it occurs the North Face of the mountain becomes dead-white with snow and only a few bands of rock, probably only those which are actually vertical, still stand out in black. This change, which is so significant to the climber, is not associated with any obvious change in the weather of the Mount Everest neighbourhood. There is no sudden increase in temperature; cloudiness, or precipitation, and the prevailing wind remains from the west. The snowing up of Mount Everest is due to gradual readjustments in the amount of the snow falling and the amount removed by the winds. With the coming of summer the winds on the average are less powerful, and precipitation gradually increases, so that a state is eventually reached when the accumulation of snow exceeds removal. When and how the mountain regains its winter appearance is not known, because the latest that any party has remained in the region was in 1921, when the reconnaissance party stayed until early September; when they left, the upper part of the North Face was still deep under snow.

Towards the end of April and in May 1933, while we were establishing the glacier camps and working out the way up to the North Col, the weather conditions resembled those during the same period in 1922 and 1924. We had our share of blizzard and snow, and if it had not been for the double-walled arctic tents, and for the greater acclimatization due to our slower advance, it is likely that we should have been forced to retire more than once.

In May at the Base Camp, 16,500 feet, the average minimum temperature was + 17⁰ F. At Camp II, about 19,500 feet, for the middle of May (7th to 17th), the average minimum was —8° F. and here on the nth May we experienced — 21° F., the lowest temperature recorded on the expedition. At this time, however, during the day the sun often felt pleasantly warm, if we were out of the wind, but the difficulty was of course to find shelter. The wind was not so regular in its rise and fall as during the march across Tibet. Usually, the nights were calm and the wind arose between 10 a.m. and noon, reaching at least force 4 on the Beaufort scale in the afternoon; high up on Mount Everest the winds appeared to be more continuous and much more powerful.

During May on the East Rongbuk glacier snow fell on 14 days, but the amount was usually small; on the night of the 2nd May about 5 inches fell and during the nights of both the 9th and 10th May, at Camp III0, there were falls of about 6 inches; these snowfalls were, however, the greatest that we recorded until monsoon conditions were established. It is probable that about the same amount of precipitation occurred on the North Face of Mount Everest, and snow would certainly have been accumulating there if it had not been for the wind. It would be interesting to know to what extent extreme dryness of the air high on the mountain is also a contributory factor in causing the disappearance of the snow. The hygro- metric measurements made this year were not sufficient to give any answer to the question.

On the 8th May, when I first saw the upper basin of the East Rongbuk glacier immediately below North Col, the surface of the glacier was wind-polished ice, but after the snow-fall of the 9th and 10th May we never saw bare ice again here. On several subsequent days at Camp Ilia there was violent wind; on the night of the 17th May this was sufficient to break one of the ash ribs of the arctic tent. Despite the winds, however, summer snowing-up began at 21,000 feet on this by no means sheltered glacier before the middle of May.

Camp V, 26,500 feet, was established on the 22nd May. The day was sunny and the wind, as we climbed the exposed North Arete, was probably never more than 1 o miles an hour. Scrambling over scree and rocks of low general gradient I never once remember the difficulties increased by snow. But in this early period days which were calm enough for climbing were rare, and it will be remembered that on the 23rd and 24th May the wind prevented an advance to Camp VI.

On the night of 28th May the minimum temperature at Camp V was — 4⁰ F. and at 8 a.m. on the following day, when we set off with the porters for Camp VI in a wind of about 10-15 miles an hour, the temperature was +4⁰ F. Unfortunately these are the only records of the temperature taken above the North Col. During the climb to Camp VI we worked out across the face to the right and then up, a way which proved less satisfactory than the usual ridge route, and we had to negotiate a fairly steep barrier of rock. On the sheltered side of this I remember soft powder-snow, which must be regarded as the beginning of the summer accumulation. While Longland was taking the porters down the mountain after the establishment of Camp VI, there was a fall of snow which came without much wind, from gently drifting cumulus clouds. This small amount of snow was sufficient to hinder our movements next day on the 'Yellow Slabs'. On that day, the 30th May, probably only half of the 'Yellow Slab⁵ area was covered by the fine powder of single-crystal snow, but this occupied the flatter parts, which if free from snow would have been chosen for foothold. Only a sprinkling of snow, covering the cracks and roughnesses on the overlapping roof-like slabs which form the upper part of Mount Everest, is sufficient to hinder a party seriously. The steeper rock-band from the 'First' and 'Second Steps' with the same sprinkling of snow was in a condition that must always render its traverse difficult or impossible. Ship ton and Smythe, on the 1st June, encountered conditions which were worse than those of the first party, owing to a day of intermittent snow-fall. Thus in 1933, by the 30th May there was sufficient snow, although actually only a sprinkling, to prevent, or at any rate make exceedingly difficult, the traverse of the rock-band which overlies the 'Yellow Slabs'.

Telephotograph of Mount Everest from Base Camp, under Monsoon Conditions

During June we watched Mount Everest from the Base Camp or the glacier camps. The wind remained from the west, and judging by the speed with which the clouds raced across the face of the mountain, it was still powerful, but precipitation continuously exceeded removal; by the 1oth June it was no longer possible, with the help of the astronomical telescope at the Base Camp, to make out the small tent at Camp VI. The mornings during June were usually clear and the wind low. At about 8 or 9 p.m. cumulus clouds began to struggle over the low cols of the main range and were caught in the west wind, which at the Base Camp at about this time was becoming strong. The clouds increased in depth and between 10 a.m. and 4 p.m. blotted out the view of the summit. It was from these clouds, above which there was often handsome false cirrus, that the snow fell.

There is some degree of correlation between the weather in Bengal and the weather on Mount Everest, and the chief value of careful weather observation at the Base Camp is to determine the extent of the correlation. For example, on the 29th May the height of the monsoon current over the Eastern Himalaya was reported as 18,000 feet. On the 31st the monsoon was very active from Darjeeling to Mus- soorie. Although on these days the monsoon did not actually reach the north side of Mount Everest, the slightly increased precipitation and cloudiness which was experienced during the high climbing on the mountain was no doubt the result of the monsoon to the south.

Cumulus clouds bringing considerable snow blew up from the south-east from the 19th to the 22 nd June. This was apparently the actual Bay of Bengal monsoon current reaching as far as the north side of the Mount Everest range. At this time the basin at the head of the East Rongbuk glacier was alive with avalanches, due no doubt to the new snow and perhaps to a somewhat higher temperature. These were the only days in June when south-east winds predominated over the usual westerly winds. Because it is only rarely that the actual low level monsoon current reaches the northern side of the Mount Everest group, it is desirable to use the term 'monsoon conditions' for the sort of weather which began this year on the 30th May. Information about the state of the monsoon, such as was sent to the Base Camp this year by Dr. Sen of the Indian Meteorological Department, should undoubtedly help future expeditions to decide the time for the final attack on the summit.

As a result of the 1933 expedition more is known of the climbing difficulties and the route to be followed, and much more is known of the processes of acclimatization and deterioration. We have also one more year's weather data on which to base the timing of any future expedition. I have written elsewhere a general account of the weather experienced during the course of the whole expedition,¹¹ and I believe that it would be no hardship for either Europeans or porters to make the journey through Tibet a month earlier than this year. The glacier camps and Camp IV on the North Col could then be occupied a fortnight earlier, and those who acclimatize quickly might attempt the mountain on any days of relatively calm weather which might happen in the last half of May. At this early time climbers would be liable to more severe winds and cold than in June, but they would almost certainly find the mountain free from snow. The slower acclimatizers, kept definitely in reserve at low glacier camps, would make their attack on the mountain if, as happened in 1924, but unfortunately not in 1933, there should be good weather in the first ten days of June.

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