What does Gust mean?
Gust is a positive or negative deviation of wind speed from its average value within a specified period of time, lasting no more than 2 minutes. Negative gusts are also called dead winds.
Meteorological term, special air flow phenomenon, refers to wind speed that suddenly changes from large to small in a short period of time. Usually refers to "instantaneous maximum wind speed".
When winds are strong, meteorological stations often add "gusts" in their wind forecasts, such as winds of level 5-6 and gusts of level 7, or winds of level 7-8 and gusts of level 9. It means that the general (or average) wind force is level 5-6 (or level 7-8), the maximum wind force can reach level 7 (or level 9), and the gust can reach the maximum in a short time or instant.
In routine aviation weather forecasts, gust refers to the maximum value when the instantaneous wind speed is greater than or equal to the average wind speed of 5 meters/second within two minutes or ten minutes.
The reason why the wind force is usually relatively strong when gusts occur
The generation of gusts is the result of air disturbance. When a fluid is in motion and flows through a solid surface, it will encounter resistance from the solid surface, which slows down the flow rate of the fluid. Air is a type of fluid. When the air flows through the ground, due to the resistance of the ground to the air, the wind speed at the lower level decreases, while the upper level remains unchanged, which causes the air to be disturbed.
Not only does it advance, it also descends. Sometimes there are backflows in the direction of air flow due to obstructions such as hills, buildings, and forests, which can cause many irregular vortices, which can change the speed of the air flow.
When the flow direction of the vortex is consistent with the general air flow direction, the wind speed will be increased; on the contrary, the wind speed will be reduced, so the wind speed is sometimes high and sometimes small; when the vortex is in the same direction as the air flow When the wind speed is increased uniformly, an instantaneous maximum wind speed will be generated, which is called a gust.