Wind can tell us many things about weather conditions. A person knowledgeable about local weather can take the temperature and dew point, wind data and altimeter setting and make a pretty good estimate of what the present weather is. He can throw away all but the wind and still give you an approximate weather outlook.
             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 pressure. The textbook rule says that wind flows parallel to the isobars, but this appears to conflict with the basic principle of flow. If air flows from high pressure to low, shouldn't its movement be perpendicular to the isobars? The answer is that the rotation of the earth deflects the wind flow about 90 degrees, causing the air to circulate around the pressure systems instead of directly from one system to another. In the Northern Hemisphere, the flow is clockwise around high-pressure areas and counterclockwise around lows. This fact gives us a start on wind-based weather information.
             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...