JOHN NOLTON, post: 417703, member: 225 wrote: The above post by Larry Scott is correct but one thing must be added.
You cannot be that far from the weather station to convert back from sea level to station pressure.
The calculations are easy now (2017) because you can find many internet sites that will do the calculations for you.
Its a simple calculation to go from one to the other (sort of).
Before hand held calculators (HP, 1972) you used Logarithms and the Smithsonian Meteorological Table (I still have both).
Go to drkfs.net/correctiontosealevel.htm for some good information.JOHN NOLTON
Note: you can use a very easy conversion from sea level pressure to station pressure, if you know your elevation (you can
get it from a topo map) for each 30 meters difference in elevation there is 0.1 inch of Hg difference. Minus if station is above sea level.
So if you are at +300 meters elevation then 300m/30m = 10 and 10 times 0.1 = 1 inch; or 1 inch of Hg less that the reported sea level pressure.
Good enough for all but geodetic work.
I query 2-3 nearby airport (automated weather conditions are easy to get online with phone app). There's generally not a lot of difference. But that's east coast. In mountainous terrain, they do vary a lot over few miles when the elevation difference is big.