Friday, August 20, 2010

Attention Pilots

I have written several times recently about thunderstorm turbulence. I thought it might be useful to take a look at a thunderstorm that was likely causing moderate or severe turbulence when I photographed it earlier this evening.

This rapidly intensifying thunderstorm can produce significant turbulence anywhere in its anvil. During the day, the anvil is easily avoided. At night, infrared satellite imagery can be used by flight dispatchers to route planes around the anvils and the updraft. Compare this image (taken this evening) with the image in this posting of the storms that caused a 777 to make an emergency warning. The isolated westernmost cell is the one depicted above.

The yellow/orange/red/pink colors represent vigorous thunderstorms and updrafts and potential significant turbulence.

If you don't have a dispatcher to assist, you have to rely on your onboard weather radar. The storm's
updrafts (reddish colors) are clearly visible. However, the greenish shades depict the anvil where significant turbulence may occur.

The "20-mile rule" (avoid thunderstorms by 20 miles) should be amended to "avoid the updraft by at least 20 miles" combined with "avoid the anvil."

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