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scenic The Summit Day
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Everest and the Jet Stream
Dramatic forces of nature are at play on the slopes of Everest with the jet stream blowing directly overhead. The jet stream is a fast-moving wind current that blows west to east around Earth between the altitudes of 25,000 to 45,000 feet. The speed of the average wind at the jet core is about 80 knots, or 120 mph, but can reach upwards of 200 mph in the winter. During the spring in the Himalaya, the jet stream typically blows on an oscillating trajectory between the 70th and 90th latitudes. Its position fluctuates during this season, sometimes blowing to the south of Everest, sometimes to the north, and often directly onto Everest's slopes. Ideally, low pressure systems will push the jet stream northward into Tibet just before the monsoon season hits the Everest region, creating a small window of opportunity for Everest's climbers. This is what David and his team are holding out for.

camp 2 The climbers have once again departed Base Camp and are waiting at Camp 2 at 21,500 feet for the right configuration of high and low pressures which will push the jet stream to the north. If this happens, the weather on the mountain should remain calm for a brief period just before the onset of the monsoon. High pressure last week is what pushed the jet stream south and brought on deceptively mild conditions. According to Bob Rice, a jet stream specialist and meteorologist out of Lancaster, MA: "When the jet stream moves south it becomes extremely unstable and could snap back north very quickly, catching climbers on Everest unaware." David Breashears is well aware of the deceptive weather patterns on Everest: "Several seasons of good weather have led people to think of Everest as benevolent. But there were three consecutive seasons in the mid eighties when no one climbed Everest because of wind."

scenic Martin Harris, a U.K. meteorologist and Everest upper air specialist agrees that this year has been fraught with unreliable conditions: "As a presumed result of global warming, the winter airflow pattern was disrupted as early as February this year, but it became re-established later, and is now undergoing a period of significant oscillations between the winter and pre-monsoonal patterns." As a result of this instability in the jet stream, last Friday's storm blew up without warning, leaving 21 climbers stranded at night on the exposed southeast ridge. Temperatures dropped to 40 degrees below zero and wind speeds reached 75 mph and higher.

Receiving weather reports from around the globe, David and his team wait it out at Camp 2 for a forecast of ideal conditions. "We hope and expect to get this period of calm," said David. "If we don't, our climbing permit expires on the first of June—though our motivation to stay may run out before then." David knows that to climb Everest one has only a brief moment of opportunity. If you wait too long for the right conditions you might not get your chance, as team members get progressively more exhausted from prolonged time spent at altitude.

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Photos: (1) courtesy Robert Schauer; (2) courtesy Ed Viesturs; (3) Liesl Clark.

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