Wind charts show the wind speed and direction for a
given altitude. Be careful to check the altitude your wind chart applies
to - for fishing, you want surface-level winds. To get
around surface friction problems, surface-level wind speeds are normally
given for 10 metres above ground level.
Wind speed and direction. Wind speed may be in knots
(20kts is 23mph or 37kmph), miles per hour or kilometres per hour. On
met charts, wind speed is often represented by feathers on a wind arrow,
where one big feather = 10kts and one small one = 5kts. Wind direction
is represented by the direction the arrow is pointing towards.
Wave charts describe waves across the oceans.
But if you look at the sea surface in open ocean you see an almost
random pattern. With hundreds of waves, each with different heights and
Wave charts cannot show every wave and every ripple. They usually
show only one type of wave at a given position. The three main
types of waves are
- Swell (long-travelled waves)
- Windsea (short-travelled
- Significant waves (a mathematical average of swell and windsea).
To simplify things further, wave charts usually only display one or
two of the following three characteristics that are needed to fully
describe a wave -
- Wave height
- Wave direction
- Wave period
The first two are fairly obvious.
The latest Mid Atlantic significant wave height & direction, from
Wave period is the time (in seconds) between successive waves. Wave
period charts show either Swell period (long-travelled waves), Windsea
(short-travelled waves), or Peak period (a mathematical average of swell
and windsea wave periods).
On Peak period charts, waves that have been marching along for days
(swell waves), may suddenly all but disappear. Remember - The long swell
waves are still there, but the chart has masked them with
locally-generated (windsea) waves.