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28 Apr – Everest Climbing Season

Some of you may wonder why you always seem to hear news from Everest around this same time every year.  There’s a very good reason for that:  the month of May affords by far the most favorable conditions for a summit attempt on Mt. Everest.

Most have you have seen the iconic photos of Everest, with the trademark plume of snow blowing from its summit.  Because the mountain rises to such a great height, 29,035’, the upper reaches of the mountain actually jut up into the jet stream.  That means for most of the year, the summit is raked by winds in excess of 100 mph.  But in May as the monsoon season approaches, the warmed air moving in from the Bay of Bengal pushes the jet stream to the north, affording climbers the opportunity to reach the summit without having to battle hurricane force winds.

View_of_Mt_Everest_from_Buddha_Air_Beech_1900_Hanuise

Ideally, climbing teams are looking for a four or five day window of stable weather with the jet stream pushed well to the north, when winds drop to a more hospitable 20-30 mph. Usually this window opens in early May, and the timing of most expeditions is designed to allow climbers to be fully acclimatized and ready for a summit attempt by then.  The temperature rises somewhat in Spring as well, although the summit of Everest is almost always below zero (F).  Late in May, the arrival of the monsoon season brings heavy snowfalls, which increase the avalanche hazard, and therefore the Everest climbing season is usually over by the first of June.

Since accurately forecasting “the window” is so crucial to success on Everest, large expeditions spend a considerable sum for dedicated meteorological support.  (Smaller groups without such support spend a lot of time wandering around base camp, hoping to glean as much information as they can from the others.)  The forecasts cover a four or five day period, and obviously they are more accurate in the near term than further out.  As the team gets closer to its summit attempt, discussing the weather becomes almost a full time obsession, and an integral part of overall risk management.  (Fortunately, several of our team members are pilots, for whom studying weather forecasts is a very familiar task!)

As you can see, a lot of things have to come together all at once for a successful climb:  a strong, healthy, and acclimatized team, ropes properly fixed on key sections of the route, high camps supplied, clear skies, and favorable winds.  Right now, the jet stream is still fairly close to the mountain.  As “the window” gets closer, keep your fingers crossed that all the stars align for our team!