Vertical wind shear (VWS) includes deep-layer shear and low-level shear. Deep-layer shear is the vector difference of the wind on 200 hPa and 850hPa isobaric.  Low-level shear is the vector difference of the wind on 850(or 700) hPa and 1000hPa isobaric. The former is more popular in research and operation. There is some statistical correlation between VWS and typhoon intensity change. In west north Pacific and South China sea, when VWS less than 10m/s typhoon has a better chance to intensify.