The weather is the state of the atmosphere with refference to wind, temperature, state of the sea, cloudiness, precipitation, atmospheric pressure, humidity, mist, fog, ice conditions.

It is important for seaman to understand all phenomena conected with the weather and to be able to read weather maps and listen to the weather forecast and report weather conditions at sea such as visibility and the direction of wind and its force according Beaufort Wind Scale.

Winds

Winds are mainly caused by a difference of temperature which in turn is sometimes responsible for the differences of barometric pressure. The strength and speed of wind at any given time depend on the gradient of atmospheric pressure that is the rate at which pressure changes with distance.


Speed of movement of pressure systems

Slowly: Moving at less than 15 knots
Steadily: Moving at 15 to 25 knots
Rather quickly: Moving at 25 to 35 knots
Rapidly: Moving at 35 to 45 knots
Very rapidly: Moving at more than 45 knots


Timing of gale warnings

Imminent: Within 6 hours of time of issue
Soon: Within 6 - 12 hours of time of issue
Later: More than 12 hours from time of issue

Terms referring to wind:

Backing - Indicates the changing of wind in the anticlockwise direction (i.e. from W to SW)

Becoming cyclonic - Indicates that there will be considerable changes in wind direction across the path of a depression within the forecast area.

Wind direction - Indicates the direction from which the wind is blowing.

Veering - Indicates the changing of the wind in a clockwise direction (i.e. from SW to W)

Variable - Indicates the wind constantly changing the direction from which it blows.