Traditional Culture Encyclopedia - Weather forecast - How to calculate the moving speed of the central weather system

How to calculate the moving speed of the central weather system

According to the material information "The weather system moves eastward at a speed of 2 km/day in the figure" and the line scale in the figure, the width of L is about 6 km. Under the control of the low-pressure center, there may be a rainstorm. In the figure, the weather system moves eastward at a speed of 2 km/day, and it is estimated that the duration of the rainstorm in A is about 7-9 hours.

Therefore, B.