I am looking at an illustration of a cyclone and anticyclone in the northern hemisphere and am having problems

Question

I dont understand how an anticlockwise wind system can propagete to a centre of low pressure when the Coriolis force would divert the winds to the right and therefore should create a high pressure centre. Likewise a clockwise anticyclone apparentlydissppates out, demanding more air at its centre and therefore develops a high pressure centre. To me this seems the wrong way round. Could someone please let me know why it is not! Thanks a lot.

Answer 1

For the cyclone, the three balancing forces of the wind are pressure gradient force (PGF), Coriolis, and friction. The friction (caused by the ground) will slow the wind compared to if it was balanced by PGF and Coriolis alone. This weakens the Coriolis force, which depends on wind speed. The PGF becomes more dominate, allowing the wind to flow more directly to the center of the low. There is still some Coriolis, hence the counterclockwise circulation.

For the anticyclone, the same thing applies, so the air flows away (PGF acts to move wind from high pressure to low pressure). Also, the high gets its supply of air from aloft, where winds are converging and air continues to move downward.

Answer 2

A cyclone is low pressure and an anticyclone is high pressure. Low pressure attracts airflow while high pressure expels it. Those are the basics, and you seem to have them in place. Now, in the Northern hemisphere, moving streams are deflected towards the right. In the Southern hemisphere, they are deflected towards the left. You appear to grasp this as well. Now, put it together. If air is flowing inwards (low pressure) and is deflected towards the right of the direction of movement (Northern hemisphere), the air will be diverted into an anticlockwise flow around the low pressure. If the air were flowing outwards (high pressure) and deflected to the right, it would instead flow in a clockwise fashion.

If you're not convinced, try drawing a series of radial arrows with arrowheads showing their direction of motion. Draw a second set of lines from the ends of those lines, showing rightwards deflection (always relative to the original direction of movement), and see what type of pattern you've created.