Pressure Charts

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The isobars (lines with 1032, 1028, 1024, 1020...) join points of equal pressure, measured in mb (millibars).

Anticyclones are areas of high pressure (marked H), often associated with settled weather, while 
Depressions are area of low pressure (marked L), associated with unsettles, wet and windy weather.

Warm fronts (red lines) are where warm air is rising over cooler air - usually this means cloud and rain,
Cold fronts (blue lines) are where cold air is pushing underneath warmer air - often giving cloud, rain followed by showers.

Air would like to travel from area with high pressure to areas with low pressure, but like water running away down your bath or sink plughole, it has to spiral its way around rather than going directly from high to low! This is an effect of the earth's rotation (the Coriolis force).  

Consequently air travel roughly along the line of the isobars, but veering slightly towards the low and away from the high pressure areas.

The closer the isobars, the stronger the wind will be, the further away they are, the lighter the wind will be.

Generally, isobars are tightly wrapped around low pressure (so it is windy there as well as wet and cloudy), but well apart around high pressure (so winds there are light breezes or calm).

 

 
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