Tuesday, November 29, 2005

The way the wind blows

Those of you with eagle eyes will have noticed that the picture below came and went in the time it takes for a tropical squall to come and go.

The reason for the wobble was a sudden worry - was the arrow going the wrong way? For surely, surely winds rotate clockwise round a high pressure system, don't they? And if thats the case then surely the arrow should point the other way round.

Yes the wind does rotate clockwise around a high - if you're in the northern hemisphere as of course London is. Here it is simple:
High pressure = anticyclone = winds rotate clockwise
Low pressure = depression = winds rotate anti-clockwise.

However southern hemisphere all is reversed, so that:
High pressure = anticyclone = winds rotate anti-clockwise
Low pressure = depression = winds rotate clockwise.

So the picture above of the south Atlantic, with the high to the north of the low would result in winds being funnelled between them, blowing a good westerly wind that the Volvo fleet have been enjoying for the last few days.

Few! Got it right after all!

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