Classification of winds.
Winds may be calm, gentle, moderate, strong or gale. Some countries have slightly different names for each of them, and some even have more classifications between each. Let us look at these 5 basic classes.
These are generally felt as an airy condition. This class is not enough, even to fly a feather kite. It is also called light wind, and it has a speed of about 1km/hr. Calm air will be noticed by smoke rising vertically from a chimney. They have a Beaufort Number 0.
Gentle breezes have speeds of about 12-20km/hr. They are called Gentle-Moderate Winds in the USA. Leaves and small twigs would be constantly moving with gentle breezes. They have a Beaufort Number 3.
Moderate winds have speeds of about 20-38km/hr. They are enough to fly a kite and keep it going higher and higher. They can cause moderate waves with whitecaps on the sea and make trees whistle.
Strong winds are also called gale in the USA. They have speeds of about 62-74km/hr. They can cause high waves over the seas and break off twigs and small branches from trees. They have a Beaufort number of 8.
Gale winds have speeds of about 75km/hr and more. They can be very destructive and they carry lots of broken branches and twigs from trees. They cause high tidal waves and rolling seas. They can also rip off roofs of building.
Gale winds that progress end up as tornadoes and hurricanes, even though they are formed differently.