It was already known in the last century that when the barometer showed a low air pressure bad weather could be expected and when the arrow pointed to a high pressure good weather was on the way. When all the air pressures of a region are known a map can be drawn up to show them. On these maps are drawn lines to join places which have the same air pressure: these lines are called isobars. When all these lines are drawn they reveal various systems of air pressures.
The anticyclones are areas of high pressure which usually bring good weather. Cyclones, or depressions, are low-pressure areas and usually bring rainy or stormy weather. Today meteorologists use equipment of great accuracy to probe the atmosphere around with a precision that would have seemed unbelievable not many years ago.
Picture Credit : Google
