There is a simple key to understanding wind: Variations in pressure from place to place create wind, because air tends to flow from high pressure to low, as water flows from high ground to low. This phenomenon has led to the creation of a model to explain worldwide air circulation. Because cooler air is denser than warmer air, its pressure is higher. As air at the equator warms and rises, the pressure in the area lowers. Heavier, cooler air tends to flow toward the low, and as it does, it causes the warmer air to flow upward and poleward, where it cools and develops higher pressure. This air, in turn, will then tend to flow back toward the equator. The same principle of circulation--from areas of high pressure to areas of low--also governs the circulation around the high- and low-pressure areas that move across our country.

Isobars are lines drawn on a map to link points of equal atmospheric pressu

The proximity of water to land can cause wind. Sea breezes develop and flow from water to land during the day as the land warms. Cumulus clouds are likely to form over land, and the air beneath them will be bumpy even though the air over the adjacent water is smooth. In the evening, the flow will be likely to reverse itself and move from land to water. This is an example of just basic circulation.

The strength of wind flow is governed by how much the barometric pressure changes within a given distance. As they tell you in basic meteorology, the closer the isobars are to each other, the stronger the wind. Strong winds mean the highs are very high and the lows are very low.

Even the time of day does things to wind, and this is at least in part related to friction effects. As previously mentioned, heating on a summer day often causes cumulus clouds and an increase in surface wind. After sunset, however, the cooling of the surface results in increased stability at the lower levels; the clouds dissipate and the wind dies. Radiational cooling maximizes the effect of friction, so that even if pressure systems are the cause of a daytime wind, the surface wind can become calm at night.

If you stand with your back to the wind, low pressure will be to your left. If there's a strong crosswind component aloft, worse weather is ahead if the wind is from your left and better weather if the wind is from your right. Knowing these basics of wind flow will never take the place of a good weather map and the information we get from the National Weather Service, but it can be helpful when the forecasts are all going sour.

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