The wind is created by differences in air pressure and temperature —winds blow from areas of high pressure to those of low pressure. Rising warm air creates a low-pressure area, and the gap created is filled by high pressure produced by cooler air. The greater the difference in pressure, the stronger the wind.
Bob Dylan says, “You don’t need to be a weatherman to know which way the wind blows”. I say to Bob, “But, it doesn’t hurt!”
Wind is a rather elusive meteorological variable, especially since we can’t really see it, like we can clouds or precipitation. Wind, during a storm, is something we expect. Wind can be an unpleasant nuisance though, especially on a bluebird day, to cyclists, sailors, paragliders, climbers, etc.
The atmosphere is constantly adjusting itself, trying to balance the changes in temperature and humidity from one part of the planet to the other. This leads to different areas of high and low pressure that encircle the globe, and the bigger the difference in temperature, and/or humidity, from one area to another, the bigger the difference in pressure, and the faster the wind blows.
That’s what gets it started in motion, always moving from high pressure towards lower pressure. Friction at the surface, mountains, buildings, etc. can slow the wind down and alter its direction. In the upper levels of the atmosphere, the wind starts moving from high to low, but it gets re-routed, and turned to the right in the northern hemisphere, because the earth is rotating. This is known as the Coriolis Effect.
When we observe stronger winds, it means that there is a big difference in pressure across the region, or sometimes across the entire country. A big low-pressure center over the mid-western U.S. and a big area of high-pressure along the West Coast, for instance, could result in strong winds in-between, over the Rockies.
That difference in pressure from Point-A to Point-B is known as a pressure-gradient. A strong pressure-gradient equals strong winds. You can track that each day by looking at a surface weather map, and look for big highs and big lows, and lots of pressure contour lines in-between, as well.
The other thing that can cause strong winds at the surface is when the jet stream is directly overhead.
Example: The air pressure is higher in an inflated balloon than outside it. If a hole is made in the balloon, the air streams out, creating a wind that blows from the greater pressure in the direction of the lower. The wind settles when the pressure is the same inside the balloon as outside.In the atmosphere the pressure at the earth’s surface reflects the weight of air above it, which in turn is determined mostly by its temperature, and as people generally know from everyday life, hot air is lighter than cold. This fits with the fact that depressions (low pressure systems) usually bring warm air.
Picture Credit : Google