"Bob Gardner" writes:

According to "The Weather Book," by USA Today weather editor Jack Williams,
a one-half-pound pressure difference between places 500 miles apart will
accelerate still air to 80 mph in three hours. [...]

Does that refer to surface or upper winds?

[...] I think your .5 inch figure is overstated.

Well, today it's not hard to find two places on the continent with a
0.50 difference in altimeter settings: any place under the big storm
in the north east, and another place far enough, like KORD. That's
only a couple hours' flight in our bugsmashers.


- FChE