What do isobars that are close together represent

The isobars are generated from mean sea level pressure reports and the pressure values are given in millibars. The diagram below depicts a pair of isobars. At every point along the top isobar, the pressure is mb and at every point along the bottom isobar the pressure is mb.

Any point in between these two isobars will have a pressure somewhere between mb and mb. The wind would be perpendicular to the isobar if the Earth wasn't spherical and rotating around its axis. But instead, all moving objects, including wind, are subject to the influence of the so-called Coriolis force.

It deflects wind from the normal line to a certain angle. In the Northern Hemisphere air is rotated clockwise to the right and in the Southern - counterclockwise to the left with reference to the movement direction. The friction between air and sea is lower, that's why it's deflected more there.

The higher the pressure difference between two areas is, the higher the wind speed is. That's why isobars that are close to one another mean high wind speed. L on the isobar map is a cyclone with a low-pressure area in the circle. A cyclone means cloudy and rainy weather. H is an anticyclone with a high-pressure area in the circle. Anticyclone means calm and sunny weather. How atmospheric pressure works. Occluded fronts bring changeable weather conditions. On a synoptic chart, occluded fronts are represented by semicircles and triangles positioned next to each other.

The triangles are in blue and the semicircles are in red, or both are purple mixing both red and blue colours together. Isobars and fronts Isobars are lines on a weather map joining together places of equal atmospheric pressure. Isobars on a weather map The numbers measure the atmospheric pressure in millibars.

Usually isobars are drawn at intervals of two or four millibars one thousandth of a bar. The closer the isobars are together, the windier it is. If the lowest number is in the middle circle, this is a low pressure or depression.

Often low pressures mean wet and windy weather. If the highest number is in the middle circle, this is a high pressure or anticyclone. Often high pressures mean dry, sunny weather. Air pressure tends to range from mb a hurricane to mb an anticyclone.