What does the term “knot” which is used in marine weather forecasts mean and how does it relate to wind?
The “knot” is the unit used to describe the speed of the wind in Canadian marine forecasts. It is a measure of the wind speed in nautical miles per hour. One nautical mile is equal in distance to 1.852 kilometres. The nautical mile is the traditional unit of marine navigation derived from the 360 degrees of latitude comprising the circumference of the earth, measured around the poles. There are 60 minutes of arc in one degree of latitude, and the nautical mile is defined as a distance equal to one minute of latitude, or one sixtieth of a degree, on the earth’s surface. Thus one degree of latitude equals 60 nautical miles. It then follows that the earth’s circumference in nautical miles is 360 degrees X 60 nautical miles, or approximately 21,600 nautical miles.
