<http://schema.org/articleBody>
"  In the 1990s, pilots trying to fly into Juneau, Alaska, experienced several different episodes of severe turbulence. During one, a gust of wind lifted the wing of a Boeing 737 airliner and swung it past vertical. The pilot was able to get his passengers safely back on the ground, but it was obvious that the next flight might not be so lucky. Pilots flying in and around Alaska are used to dealing with sudden swings in Mother Nature&amp;#039;s temperament. But some skies are so rough that they convince you to come up with an inventive new solution. In this case, the violent but invisible demon of air turbulence inspired the Federal Aviation Administration to create a turbulence predictor. And this month, after years of development, it&amp;#039;s finally becoming a reality in Alaska, and could someday travel to airports beyond, perhaps in the lower 48 states. After those extreme turbulence incidents in the 1990s, every major carrier except Alaska Airlines cancelled its service to Juneau, a tough blow for the city given that it&amp;#039;s the only state capital in the U.S. that isn&amp;#039;t accessible by land. Pressed to find a solution, the FAA called upon the National Center for Atmospheric Research, a nonprofit organization geared to develop technology that can be transferred to private industry for commercialization. Its scientists recognized a problem that was simple in principle, but woefully complex to model: Strong winds were rushing over the steep mountains lining the channel in which Juneau is situated, creating what&amp;#039;s called &amp;quot;mechanical turbulence.&amp;quot;  If you&amp;#039;ve ever seen a shallow stream rushing over pebbles and creating turbulence downstream, you&amp;#039;re familiar with the hydrological equivalent of mechanical turbulence. This is a different beast from the &amp;quot;clear air turbulence&amp;quot; that&amp;#039;s familiar to any frequent air traveler; that&amp;#039;s caused by high-altitude wind shear, and by the thermal bumps experienced at low altitudes on a sunny day. Both of these can cause discomfort, and even injuries, in serious cases, to passengers who aren&amp;#039;t buckled in. But they can&amp;#039;t upend a full-size airliner the way the treacherous turbulence outside Juneau can. At the time, the only way for pilots to play it safe was to avoid Juneau whenever winds were above a certain speed\u2014say 35 knots or more. But that strategy was crude, and it left the city uncomfortably isolated. Not only that, it failed to protect planes, because zones of dangerous turbulence can develop from merely moderate winds. The solution, NCAR scientists knew, would be to gather detailed data about what winds caused how much turbulence, and where, so they could produce a detailed forecast model.  Each year, NCAR researchers have relocated to Juneau during the stormiest winter months. Anemometers and Doppler wind-measurement radar units collected wind-speed data from the ground, while a pair of aircraft flew patterns up and down the marine channel near. NCAR&amp;#039;s pilots faced the same unpredictable weather that commercial airline pilots faced. &amp;quot;We had one full year up there where the weather was benign,&amp;quot; project manager Al Yates says. During another season, the pilots encountered such intense turbulence that the pilots refused to repeat the pattern. &amp;quot;They said, &amp;#039;Uh-uh, we&amp;#039;re not going back there again.&amp;#039;&amp;quot; After five years, NCAR had collected enough data to create a model of the turbulence around the Juneau airport and how it changes over time. Hooking this model into real-time meteorological data, they created a prediction-and-alert program called the Juneau Airport Wind System (JAWS). During a trial run, the system was able to predict severe turbulence with 95 percent accuracy.   However, the hoped-for technology transfer to private enterprise never took place. Not enough airports faced enough severe turbulence to support a commercialization of the technology. Finally, the FAA stepped in and funded JAWS itself. The system became fully operational this month, providing pilots with an electronic representation of expected turbulence on a cockpit display.  &amp;quot;There are some instances we found where the old rules said, &amp;#039;Yeah, you can fly,&amp;#039; but our system said, &amp;#039;Uh-uh, don&amp;#039;t do that, you&amp;#039;ve got some severe turbulence out there,&amp;#039;&amp;quot; Yates says. Thanks to the JAWS prediction engine, Alaska Airlines will be able to schedule flights with much greater confidence. &amp;quot;They&amp;#039;ll fly as much as 50 percent more flights in and out of Juneau Airport, and do it more safely,&amp;quot; he says. Although the FAA has no current plans to implement a similar system elsewhere, there are about a dozen airports in the Lower 48 that could benefit from the technology, including such notoriously gusty airfields as Las Vegas, Colorado Springs, and Reno. The one Yates would really like to work on? Maui. &amp;quot;After five winters in Juneau,&amp;quot; he says, &amp;quot;that would be a nice change of pace.&amp;quot; "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/flight/a8282/how-to-build-a-turbulence-detector-13574935/?click=pm_latest>