weather and engines...?

Ok sometimes I over analize stuff, but now this has been circling in my head for 20 minutes and I need help. :biggest:

We all know that cooler/denser air is better for engines as you get more oxygen to burn.

Now what is confusing me is the weather. When a high pressure system moves in, it is generally warmer and drier. The barometer reading goes up, there is more pressure.

When a low pressure system moves in, it is generally cooler thus denser, but wet. When a low moves in the barometer goes down. Less air pressure.

So would a high pressure system be better for an engine, since there would be more air pressure? But in a low pressure system, the air is cooler and denser. So maybe it all just evens out??? Damn you relativity!! Damn you!!!:nuetron:

Here's a snippet from how stuff works.com on pressure,

A barometer measures air pressure: A "rising" barometer indicates increasing air pressure; a "falling" barometer indicates decreasing air pressure.

In space, there is a nearly complete vacuum so the air pressure is zero. On Earth, because there are many miles of air molecules stacked up and exerting pressure due to the force of gravity, the pressure is about 14.7 pounds per square inch at sea level (see this page for a good explanation of atmospheric pressure).

The interesting thing about air pressure is that it is different at different points on the planet and it changes over time. Why might that be? If you've read How Hot Air Balloons Work, you know that hot air is less dense (lighter) than cooler air. Therefore, on any given day you would expect the air over a desert to have a lower pressure than the air over an ice cap. And that would be true. These same sort of pressure differences occur all over the planet for various reasons.

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