What does gust mean?

Gust is the positive or negative deviation of the average duration of wind speed not exceeding 2 minutes in a specific time. Negative gusts are also called calm winds.

Meteorological term, a special airflow phenomenon, refers to the sudden change of wind speed in a short time. Usually refers to "instantaneous maximum wind speed".

When the wind is strong, meteorological stations often add "gust" to the wind forecast, such as wind level 5-6, gust level 7, or wind level 7-8, gust level 9. It means that the general (or average) wind force is 5-6 (or 7-8), and the maximum wind force can reach 7 (or 9), and the gust can reach its maximum in a short time or in an instant.

In the routine weather forecast of aviation flight meteorology, gust refers to the maximum value when the instantaneous wind speed is greater than or equal to the average wind speed of 5 meters per second in two minutes or ten minutes.

The reason why the wind is usually strong when the gust occurs:

1, gust is the result of air disturbance. When the fluid flows over the moving solid surface, it will encounter the resistance of the solid surface, which will slow down the fluid flow rate. Air is a fluid. When the air flows through the ground, due to the resistance of the ground to the air, the wind speed in the lower layer decreases and the upper layer remains unchanged, so that the air is disturbed.

It not only goes forward, but also goes down. Sometimes, in the direction of airflow, there are hills, buildings, forests and other obstacles to block the backflow, which will cause many irregular eddies and change the airflow speed.

3. When the vortex direction is consistent with the general airflow direction, the wind speed will increase; On the contrary, it will reduce the wind speed, so the wind speed is large and small; When the vortex is in the same direction as the airflow and the wind speed increases, the instantaneous maximum wind speed will be generated, which is the gust.