40kt wind with relatively low speed.

40kt wind speed is equivalent to 8 winds. Grade 8 wind refers to the wind with the wind speed of 17.2 to 20.4m/s, which is equivalent to 62-74km/h and the wind pressure of 184.9-267.8pa. Fishing boats take shelter from the wind in the harbor, and the waves gradually rise, the peaks are broken, the waves are obviously blown down with the wind, the dead branches are blown off, and it is difficult to move forward against the wind.

Wind power level:

Wind power refers to the strength of the wind blowing on an object. Generally speaking, according to various phenomena caused by wind blowing on objects on the ground or water surface, the magnitude of wind power is divided into 18, with the smallest being 0 and the largest being 17. Wind speed is the forward speed of the wind. The greater the air pressure difference between two adjacent places, the faster the air flow, the greater the wind speed and the greater the wind force. Therefore, the magnitude of wind is usually expressed by wind power. The unit of wind speed is meters per second or kilometers per hour. When the weather forecast is released, the wind level is mostly used.