In Part 3, we learned about pseudo forces. This discussion will put all the forces we have studied up to now into a comprehensive whole. It is the combination of forces that turn normal weather patterns into a hurricane.
Observe the figure above; however, remember that a package of air travels from high (H) to low pressure (L), and that the air travels in a straight line regardless of the spinning earth – just like on a merry-go-round. On the left side of the figure, the air package is launched and travels towards the low pressure. As it travels, the rotating earth rotates the low pressure to the other side of the globe, as is shown on the right side of the figure. From the reference point of the low, the air appears to veer to the right. That veering pattern as seen from the low is attributed to the Coriolis force. The force is not really there, it just appears to be.
Let us look at it from another point of view by referring to the above figure. As the pressure force pushes the air package towards the low, the Coriolis force is pushing the package to the right. In fact, the air packages coming from all directions appear to veer to the right. This is shown in the figure below.
However, the package is experiencing two forces: the force from pressure and the Coriolis force. The Coriolis force is pushing the air package away from the low; but, the pressure force is pulling the package into the low. In a sense, the Coriolis force acts as a centrifugal force; while the pressure force acts like the centripetal – the air goes into a form of an orbit. Granted the forces are not balanced, but a cyclonic pattern is generated.
My understanding is that the circulating air creates a vacuum and makes the low even lower. Thus, the difference between high and low pressure is made larger and the wind speeds increase. A hurricane is formed. The hurricane is maintained so long as the water temperature is 79F or above. It is the water temperature that provides plenty of hot air that rises and keeps the low pressure alive.
I hope you have enjoyed this series of articles. Any comments are welcome.
