Sunday, January 27, 2013

Why the weatherman is often wrong

Even if there were enough sensors to measure all the information needed there might not be enough computer power to analyze it in time to make a timely weather forecast.

http://news.byu.edu/archive13-jan-weather.aspx

Jan. 24, 2014
Todd Hollingshead
Brigham Young University

Have you ever woken up to a sunny forecast only to get soaked on your way to the office? On days like that it's easy to blame the weatherman.

But BYU mechanical engineering professor Julie Crockett doesn’t get mad at meteorologists. She understands something that very few people know: it’s not the weatherman’s fault he’s wrong so often.

According to Crockett, forecasters make mistakes because the models they use for predicting weather can’t accurately track highly influential elements called internal waves.

Atmospheric internal waves are waves that propagate between layers of low-density and high-density air. Although hard to describe, almost everyone has seen or felt these waves. Cloud patterns made up of repeating lines are the result of internal waves, and airplane turbulence happens when internal waves run into each other and break.

“Internal waves are difficult to capture and quantify as they propagate, deposit energy and move energy around,” Crockett said. “When forecasters don’t account for them on a small scale, then the large scale picture becomes a little bit off, and sometimes being just a bit off is enough to be completely wrong about the weather.”

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Internal waves also exist in oceans between layers of low-density and high-density water. These waves, often visible from space, affect the general circulation of the ocean and phenomena like the Gulf Stream and Jet Stream.

Both oceanic and atmospheric internal waves carry a significant amount of energy that can alter climates.

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