The local workers become redundant at their work-place and are soon retrenched,they lose their jobs
Despite Hong Kong historically being part of China and being inhabited by Chinese people, that drastically happened in the last century. Hong Kong got into the hands of the European colonial powers, and even after they left the area, they didn't left Hong Kong. The reason why the presence in Hong Kong was kept was because of its excellent strategic position.
The newly formed nation had excellent ports and excellent location. It was quickly industrialized. That led to rapid economic growth. The economic growth and the prosperity of the small nation made, as well as it deep connections with the Western World, attracted lot of people to move in it. The Chinese population is still dominant, but over time people from all over the world moved in, thus the ethnic structure of this nation changes significantly, to a point where now it has citizens from pretty much every corner of the world.
Weather is a complex phenomena. in order to solve engineering problems such as the prediction of weather, we utilize degrees of freedom (DoF)... weather is one of the many elements that need millions of DoF and still cannot accurately predict it. mainly it's a vector analysis much akin to finite element analysis where each micro degree of freedom or say molecule of air is represented as one point interconnected in a web of points and each point's properties are altered relatively (similar principles how autonomous mini drones coordinate synchoronously) to each other.
many factors are considered: pressure, temperature and density of the air for sure. friction factors. drag factors. rotation of the earth. and that's the natural phenomena. include the heat given off the land, the radiation from the sun, airplanes, people, etc... its highly complicated. having done a weather station project, it's fair to say that there isn't a simple answer to your simple question. we measured wind direction, wind current, temp and humidity, visibility, pressure, etc... and we couls measure these things, but can't really say why say the wind went east or west... except tell you that its because of millions of degrees of freedom interacting with each other simultaneously and some things like weather are just like that.