Reading Everest Weather

More teams have made the decision for a summit bid this weekend. The latest include the Malta Everest team, half of Peak Freaks and a two person team from First Ascent. They are now at camp 2. Why are these climbers going to the top in marginal weather? Well maybe the weather will not be marginal – at least according to some weather forecasts.

Before looking at the weather, an quick update on the teams. There is movement on the north with a large Chinese team leaving base camp. Perhaps to fix the rope to the summit. And Jordan Romero latest post suggest they may go for their summit bid soon. On the south, the vast majority of the teams have chosen to wait for a longer weather window and the teams at C2 are resting up and waiting for the winds to calm before going higher.

Patrick Hollingworth posted this update on his climb from BC to C2:

These are some of the strongest winds I have experienced in the mountains – there is a massive and constant roar coming from Everest – the jetstream winds are in full flight! The winds were blowing snow UP the north face of Nuptse (like a reverse avalanche), and a few tents were destroyed here in C2 last night. C3 is uninhabitable at the moment because of the winds, as is C4 on the South Col. The winds are however forecast to drop in the coming days, and for now we’re still looking at Sunday 16th for our summit attempt.

Everyone in the world makes the same joke about their local weather. “If you don’t like the weather, just wait a day.” And on Everest it is the same. The key factor for a summit bid is the wind speed, most teams look for under 30 mph (48 km/h). This is mostly influenced by the position of the jet stream which is positioned on top of, or near, Everest almost all year. Historically, the jet moves away for a week or so in mid May as monsoons and typhoons build in the Bay of Bengal, thus the annual opportunity for summits each spring.

Most top teams pay for a professional weather forecast. Two primary sources are US based and Swiss service Meteotest. These are teams of meteorologists who not only look at the data but also interpret it and then communicate the forecast and recommendations to their members.

Climbers pay for these services and keep them private since it is a value to their team members and a safety issue. If you have watched the Discovery Everest series you have seen Russell Brice pour over his data to make an informed decision for his members.

Every model has a bias built in, or a base set of assumptions, used to calculate the end result. Knowing how the models are created allows an informed decision as to how to use the data. Simply reading the data is necessary but not sufficient to make a good decision. Experience is a major factor in the final decision. The professional services utilize multiple models before making a single conclusion.

However, accessible to any team with an internet connection, which is virtually all of them, teams can see a forecast from various websites. publishes a well known forecast that is posted on multiple expedition sites based on computer models according to their site:

We do not have a magic ball and we do not sell snake oil. Scientific knowledge of the weather systems and the behaviour of the atmosphere is still poor. Be very critical if anybody tells you something different! Even the most powerful supercomputers can not cope with the shear amount of data and number crunching that a detailed high resolution model requires

Yet, climate modellers are doing a pretty good job. And we make the most of it, by putting together state of the art modelling tools with our personal knowledge of weather behaviour, and a long term experience on mountain terrain.

This is meteoexploration’s current forecast for Everest and the weekend window teams are considering:

Weather by meteoexploration

From this chart, you can see a dip in the winds on Sunday then picking back up on Monday in 12 hour increments. From the same service, you can easily see from the graph to the right why teams including Adventure Consultants, AAI, Himex, IMG and others are waiting for the May 23rd window (click to enlarge).

However, some models disagree with this weekend’s window duration, thus the opportunity for human intervention. What if the forecast is off by 24 hours? Michael Fagin of put it this way in an interview I posted earlier this season:

Q: Some forecasts are posted on the web, the so called grid forecasts. What are these and how accurate are they?
A: These grid forecasts take what the weather conditions will be for an exact latitude longitude coordinate. So the grid forecast will give you the exact wind speed for the coordinates for Everest. I have found that the problem with these forecasts is if the forecast is off say 200 miles or so that this can make for an extremely inaccurate forecast. For example. Let us say that  the grid forecasts  says Everest summit winds will be 30 knots and the grid forecasts 70 knot winds several hundred miles to the north of Everest. It is not uncommon for the actual forecast to be off by several hundred miles and the real time winds can easily be at 70 knots over Everest. So the forecast of 30 knot wind over Everest vs. real time winds of 70 knots is a big problem. Thus, it is important to get some weather professional analyzing the forecast models and explaining to expedition groups what can happen

Dan Mazzur of Summit Climb posted yesterday that he is looking at 7 different forecast to make their decision.

The big topic for all Everest climbers is the weather. Well, the 7 websites all agree that around the 15th of May the wind is going to drop for a few hours, hopefully allowing the Tibetans to move up and work above 8300 metres and fix the rope. However, the seven websites say that on the 22nd of may the wind is going to drop for a few days, perhaps for, as long as, up to the 25th of May.

Dan goes on to graphically explain why this is important

Everyone is excited about the weather. As we are camped under Everest, we can see what the weather is doing up there every second of every day. And; Please let me inform you, it is not a pretty site. There is a two kilometre wind plume blowing from the top and according to several of the seven “Everest Weather” websites we are currently watching, the wind is cooking along up there at 138 kilometres/ hour. Exposed flesh would probably freeze solid in a minute or less up there right now, and you would not be able to stand up, just crawl along on your hands and knees.

So given all this data, what do you do? Well the worse case is for a team to cherry pick the forecast that tells them what they want to read, the case is to take the data combined with experience and current observations to make the decision possible taking into account safety as the primary factor.

Leaders will consult with the Sherpas. Then they must take into account the skills of their team, their experience, their self sufficiency in case a leader or Sherpa becomes impaired, rescue resources, availability of emergency oxygen and the ability to get it to climbers in need, access to medical consultation via reliable radios or sat phones and many other factors. But one of the key considerations is ability to move fast, speed, in case of problems.

Obviously no sane climber puts themselves knowingly into danger; but summit fever is powerful and can skew decision making. I am often asked what is the difference between one Everest expedition company and another. This is a perfect example. Access to information, experience to understand that information and judgment to make a safe decision.

So full circle to this weekend and the decision to go up. It appears most of the teams have access to multiple weather forecasts, many of the leaders are experienced; some with multiple Everest expeditions. They are making their decisions based on the information that can get. This is what mountaineering is all about, judgment. Some teams have chosen to wait, others to go.

The to all the climbers now at camp 2. We are all pulling for you and for the winds to lull as predicted.

Climb On!


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3 thoughts on “Reading Everest Weather

  1. I can see that some climbers narrow the window of error as they try for a summit.With the forcast being what it is the window is small with big winds on either side.Do you think they are wanting to walk the gauntlet just to higher the stackes and for more challenge or to get away from the crowds of climbers?Or a combo of the three or more?It would be personal for me to take a chance on a forcast window.For my family,I would wait for the best conditions.At this level in the game I’m sure its life or death and very little in between!

    It does seem that some know what thay want and that a combo of reasons may play a part.I can see that the young Jordan is looking at the window this week end,but I’m sure they are looking at the weather in real time.It sounds like it may be a good time if nothing goes wrong.
    Alan,you rock!

  2. Hi Alan,

    I click into your top-notch Everest reportage two or three times a day for the latest updates. Great writing, very informative and always reliable. Outstanding.

    I’ve been thinking alot about the Chinese team of Tibetan rope fixers currently to the North. Talk about epic. They and the Sherpas are the unsung heroes of Everest. When the circus comes to town, they make it all happen.

    Write on, Alan! The silly season usually gets good right about now! I just hope no one else is lost.


    Thomas Noy
    Maurice Wilson Researcher
    Solo Tibet Investigations 1985, 2007

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