If the Earth was stationary...
air from an area of high pressure (Anticyclone - Near Right)
would flow towards an area of low pressure (Depression - Far
Right), like a stream flowing down a mountain side.
The Evolution of a Depression
The waters around the British Isles lie in a unique position. We are
the first land mass Atlantic weather reaches; to the North there is
the cold dry Polar air mass and to the South and West is the warm,
moist maritime air mass. With Europe lying to the East we sit at the
crossroads of Europe's weather.
Somewhere on the line separating a cold air mass and a warm air mass,
an undulation forms which then becomes a centre of low pressure. In
two or three days the depression deepens, and grows during the following
four to six days.
As the depression follows its path from west to east, the cold front
overtakes the warm front and turns into a spiral around the centre
of the depression.
...But the Earth does rotate!!
Owing to the effect of the earths rotation, the air is deviated
and flows in a spiral (clockwise in the northern hemisphere)
images show effect on an Anticyclone or a Depression.
When a cold front mixes with a warm front, an occlusion
Subsequently the depression fills and dissipates.