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ExWeb series - Winter climbing: The BAD chart
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Dec 29, 2004 09: 29 EST
Previously pubished Dec 16, 2004

Lately we've run a series about winter climbing in Himalaya. In high mountaineering, there are two ways to define winter; “calendar” and “permit”. The Calendar winter starts December 21, whilst a winter climbing permit begins December 1.

The Calendar winter is considered a "classic winter" climb. All first winter accents of 8000ers were made by Polish climbers - in Calendar winter. The first ascent was on Everest in 1980 and the latest on Lhotse in 1988.

But still, what does the reality look like? Let's put calendars and permits aside for a while, and examine the weather only, in order to find the worst time to climb.

Very few people have climbed 8000ers in the winter, and no one has skied to the North Pole or the South Pole in the cold season. This series is divided in 4 parts:

1. Wind Force

2. Temperature, Wind-Chill

3. Humidity

4. The “Bad” Chart – Defining Seasons

Today, part 1 - The Windiest place on Earth

Extremely exposed and often hit directly by the Jet wind - the summit of Everest is the windiest place on Earth. The highest forecasted wind speed during our research period (2 latest years), was 78 m/s (175miles/hour) on Feb 6, 2004. This is well above the 156 miles/hour threshold for a Category 5 Hurricane.

Kick-ass winter

But it’s not the maximum wind speed that makes Everest summit extremely windy, it’s the consistency of high winds, especially during autumn and winter. From October 20 until end of March, there is an almost constant Category 1 Hurricane (32m/s - 74 miles/hour) pounding the summit of Everest. During this period 3 out of 4 days experience above 32 ms/74 mph.

Moving around in hurricane wind is hard but possible at sea-level. But add oxygen depravation and below -30C/-22F temperature to the wind and you'll find close to impossible climbing conditions - even for the absolute elite of climbers. In fact, on the latest wind chill charts, a combination of -12F/75mph gives a less than 5 minute frostbite time. Note that we are counting an average here, not extremes.

A winter Everest/8000+ expedition has to be lucky to stand even a slim chance of making the summit. To open new routes on 8000ers in such conditions - like the Polish have - is simply outstanding.

Monsoon brings calm summer weather

It is a well known fact that the Monsoons arrival in Nepal in the first week of June brings with it low winds all the way into October. It is still surprising though that the average wind forecasts for the four months, June through September goes all the way down to 5 m/s (11 mph), or virtually no wind at all.

Moody spring

While the wind suddenly shoots up from calm to hurricane in October, wind speeds fluctuate more in the spring. February and March have high winds but with increasing chances of calmer days. That pattern strengthens during April and May, until the Spring Weather Window opens end of May.

BaseCamp Winds

The wind patterns in Base Camp follow the Summit pattern, but variations are not so extreme. December to February is bad with average winds close to 10 m/s (22 mph) in base camp.

As we can see, the winds are pretty bad all the way from end October. Tomorrow we will examine the main difference of the true winter season - the temperatures.

Next: Temperature, Wind-Chill


Image 1 (ExplorersWeb): Average Monthly Wind at the Summit of Everest since 2002
Image 2 (ExplorersWeb): Percentage of hurricane days on the summit of Everest
Image 3 (ExplorersWeb): 110 mile/hour wind hit Everest summit in April 1998
Image 4 (ExplorersWeb): Average Monthly Wind at Everest BC since 2002


"BaseCamp" is at Pressure (hPa) 495 or app. 6100m of altitude

"Summit" is at Pressure (hPa) 346 or app. 8750m of altitude

The charts are based on forecasts delivered by SMHI and compiled by the super-computer at ECMWF. The information below is compiled from 868 forecasts from May 1 2002 to Nov 1 2004.

There is no weather station at the Summit of Everest which would have allowed exact readings, but the forecast should be fairly accurate - as it has been used by climbers for 10 Himalayan seasons and hundreds of high-altitude expeditions.

The AdventureWeather 8000 meter forecasting project is free of charge to climbers and sponsored by ExplorersWeb.com and its partners.
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