In a previous post I talked about 
the danger of flying on a constant indicated altitude (caused by not updating the altimeters pressure setting).
Buys Ballot Law is a means by which you can work out if you’re flying into high or low pressure, from effects that will be felt on the airplane performance & direction. Hopefully setting off the mental spark of “I’m not updating my altimeter!!”
In the Northern hemisphere, if you stand with your back to the wind, the low pressure is on your left.
This is because in the northern hemisphere air flows clockwise around high pressure areas and anti-clockwise around low pressure areas. Thus no matter which area you’re in, if you have your back to the flow of air (wind), to the left will be low pressure.
In the southern hemisphere the inverse is true.
Practical Use
So if an aircraft is getting blown/drifting to the right (the wind is coming from the left of the aircraft). If you were to turn your back to the wind, your left would be in the direction the plane was flying……thus the plane is flying into low pressure (and the altimeter, if not updated, will begin to over-read).
The reverse is also true, if the wind is coming from the right and pushing the plane left. Then the plane is flying into High Pressure and the altimeter will begin to under read if not corrected.