Jonathan Hoffman, age 12, of Shreveport, Louisiana, for his question:
What exactly are anticyclones?
Cyclones and anticyclones are weather events and we all know that cyclones are associated with storms. A tornado is a fierce little cyclone; a hurricane is a large tropical one. As you might expect an anticyclone is something very different and opposite from a cyclone. And so it is. As a rule, weather reporters call it a high, or a high pressure cell and we prepare ourselves for a pleasant spell of clear, calm weather.
When you listen to the weather reports day after day, you get the impression that highs and lows are forever passing overhead. In the midst of a stormy low pressure cell chances are you hear that a high is farther west and soon expected in your locality. However, in a long range forecast you are likely to hear that another low is following hard on the heels of the expected high and so on. These highs and lows, are systems of high and low atmospheric pressure. At one time it was common to call the lows cyclones, and the highs anticyclones.
Cyclone and anticyclone are still good terms in meteorology because they give clues to their particular structures. Cycles and cyclones suggest circular motions and circular motions of air are involved in both of these weather events. North of the equator, cyclone winds spiral in a counterclockwise direction, while the gentle breezes of an anticyclone move clockwise in the opposite direction.
Cyclones and anticyclones are opposites in every way they are even born from opposite conditions in the atmosphere. The low pressure cell that gives birth to a cyclone is a pocket of light, rising air. The atmosphere acts somewhat like an ocean of water always striving to fill up its empty and partly empty pockets. Denser air surrounding a low pressure cell flows and blows in toward the center. The rotating earth deflects the inflowing winds and they swerve around in spirals. This low pressure system creates a spell of stormy weather with cloudy skies and usually rain.
The opposite high pressure cell is a mass of heavy air pressing down on the earth. It spreads out to mingle and mix with the lighter air around it. This creates winds blowing gently outward from the center. Because they are blowing in the opposite direction from cyclone winds, the rotating earth deflects them in a clockwise direction.
What exactly are anticyclones for Monday, April 20, 1970 An anticyclone is usually larger in area and lasts longer than a cyclone. And usually it brings a spell of balmy weather with clear skies and gentle breezes. Highs and lows are world wide weather events. However, the rotating earth changes the rules for them south of the equator. In the Southern Hemisphere, the stormy cyclones spiral in a clockwise direction, and the gentler anticyclones move in the opposite counterclockwise direction.
Alternating highs and lows do indeed chase each other around the globe. This is because they are merely small weather pockets in wide belts of prevailing winds. Most of our country lies within the path of the prevailing westerlies. As these winds circle around and around the globe, they carry the highs and lows with them. This is why most of our changing weather events approach us from the west and move overhead toward the east.