Wind patterns near the sea shore.
Land and the wind
Winds coming off the land will always be more unpredictable and difficult to handle than those coming to you over open water. You have to bear in mind that and always be on the alert for abrupt changes. The situation becomes even more difficult when there is a mountain near the shore. Then you need to study the winds with 24-h activity and those that are seasonal and on which the mountain has impact. River valleys also create conditions for specific winds, even though at a smaller scale. Another extremely important thing you have to reckon is that lake winds and sea (ocean) winds are very different, their nature is dissimilar; that explains why experienced ocean sailors sometimes get confused at lake sailing and vice-versa.
Of great significance to the good sailor are the small land peculiarities, that have inevitable effect on the wind. Even a small island, cape or inlet changes the straight-forward motion of the wind, and creates turbulences, areas with lower and higher pressure, funnels. Cliffs actually have almost negligible effect on the winds blowing along them, but have a seminal influence on winds coming toward or over them. Solid objects like buildings or even other vessels create wind shadows (places of lee) - it is calculated that they can extend 30 times the height of the object which creates them in downwind direction. Bridges and open barriers are more tricky - they make up wind flaws with baffling shifts, sometimes it is very difficult to foresee what will happen. The very passage of a gust or lull over or through something is enough to alter the shift.
Prevailing Windsurfers
The wind patterns are extremely complicated - they are influenced and related to many things, and they at their turn influence many things on the planet. The atmosphere is like a vivid and fully alive organism - it changes every second. Basically, prevailing winds are created by the difference in temperatures. You will say - so what, any wind can be resolved into 2 - difference in temperatures and difference in pressures. Here we have something larger in mind - the difference in temperatures at the Equator and at the Poles. The warm rises, it is then replaced by colder air. We should not forget to add a deflecting effect from the Earth's eastward rotation, the presence of relatively constant areas of high and low pressure.
From 30 to 50 degrees north and south latitude is the home of the Westerlies Just south of 30 degrees north is Florida. The narrow buffer zone between two major wind systems is an area of sedate and light not much variable winds, called the 'horse latitudes'. The name comes from something horrid which happened to the early explorers - they had to throw overboard their horses because the food was scarce and they were standing in the calms waiting patiently to reach the trade winds and ride them in westward direction to cross the Atlantic ocean.
The global wind patterns are sometimes faded by strong local influences.
Land & Sea Breezes
During the day, the land heats up. The heated land warms the air just above it. This air becomes warm thus lighter and rises. As the atmosphere is in the form of gas, no vacuum can exist, so immediately the place left by the warm air is taken by the nearest cold air. This movement is actually the wind. The cooler air is above the water, because water gets warm much more slowly than land. That is why during the day, the sea breeze is from water to land. It is strongest in the afternoon (can reach up to 15 mph), then it dies away at sunset. At night, the land cools down rapidly; water - once heated - remains warmer for a longer period, and it is stable, too. So during the night the process is reversed: the colder air is above the land and it goes to the water (the land breeze). It starts before midnight and it does not stop until the land is heated again (on the following day). Temperature differences are small- so the speed rarely exceeds 10 mph.
Interesting thing is that sea breezes can work with or against a prevailing wind.
Any big lake has lake breezes, working at the same principle like the sea ones. On smaller lakes, 24-h breezes are weaker and are only around the shore, in a small perimeter. Often times there is wind around the shoes, while at the same time the centre is flat and as calm as a mirror.
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