Tuesday, March 16, 2010

Contrails and Weather

With all the warm weather lately, I've been noticing all the jets in the sky and their contrails.  

While I've used the term "contrails" before and I know what they look like, I didn't know the etymology.  So I went to my trusty Webster's to find the definition:  "white trail of condensed water vapor that sometimes forms in the wake of an aircraft."

When warm and humid jet exhaust hits cold air, water condenses.   Think of breathing on a cold winter day when your breath forms a visible cloud.

Why I don't notice contrails all the time?  (Am I not paying attention?) 

I went to "google" and hit the first link which took me to the Weather Service.  Hmmm.  There must be a "weather" connection here.  Sure enough, I found the connection towards the bottom of the page:

"... sailors have known for some time to look specifically at the patterns and persistence of jet contrails for weather forecasting. On days where the contrails disappear quickly or don't even form, they can expect continuing good weather, while on days where they persist, a change in the weather pattern may be expected."

If this is true, our weather is due to change.

What's the forecast?  Rain, slush and colder weather over the weekend.

Check out this website for more information.

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