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Old 12-21-2010, 02:40 PM   #334 (permalink)
3-Wheeler
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Quote:
Originally Posted by aerohead View Post
....As soon as I get the 1-mile to the house,I turn on the National Weather Service TV broadcast to record air temp,% relative humidity,barometric pressure,wind velocity,and direction....
Hi AeroHead,

I know that I have mentioned this before, but the broadcast barometric pressure is not "the real barometric pressure".

The local TV stations and such always correct the "real" barometric pressure to sea-level, which makes the baro higher than it really is.

There is hope however.

Knowing your elevation, you can subtract the elevation above sea-level to get the "real" baro.

In Wisconsin where I live, the "standardized baro" is 30.00 inches or so on any given day, but the real baro is actually 1.00 inch Hg less than this, since our "average" elevation is 1000 feet above sea level, which lowers the baro by 1.00 inch Hg.

If you don't correct for this, your air density readings will be off by about 3.5%.

Jim.
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