Station Pressure from 'Weather Forecast Pressure' - quick mental maths solution

[brown dog]

Just learnt this SWAG (metres and millibars/Hpa) for altitudes below a few hundred metres:

 

 

Station pressure = Forecast (ie Barometric) Pressure - (Altitude / 9.2)

 

 

 

I'm at 127 metres map altitude.

 

The weather forecast says 1020mb

 

Station Pressure SWAG = 1020 - (127 / 9.2)

 

Station Pressure SWAG = 1006mb

 

Close enough for government work!

[Roe]

It's more than good enough for most shooting when you examine what it does.

 

9.2 will work better for high elevations.

8 is bettter down to sealevel. I think 8.6 was the standard number.

Roughly 10 hpa for 80-90 meters elevation.

 

ALL of the above numbers is good enough for shooting, you don't reach a significant enough deviation to see it other than on paper (and not the paper target)

[Jagged 77]

That works out pretty close - my Kestrel is reading 987 hPa - your formula is working out at 988 based on my current altitude.