Inside The Cyclone: What is Low-pressure?

Low-pressure means exactly what it implies. Pressure values within a given area are lower than in the surrounding area.

Look at these two examples:

Notice that Jefferson City has the lowest value of pressure on the map. Also notice in this figure, there is a large difference between the pressure values. Large pressure differences can mean strong wind and possibly strong storms.

When an area has lower pressure it means that there is less air "stacked" over it than surrounding areas, so to speak. Because the atmosphere is fluid like water, it has taller areas just as waves in a lake have high and low points. The points that are taller have more weight and exert more pressure on the ground below. Also, just as water tends to seek a level status so does air. Air, and as a result wind, will flow from high pressure to low pressure.

Regions which have a surface pressure pattern like figure #1 will tend to have the following characteristics.
1. Cloudy/Rainy
2. Rising air
3. Counterclockwise wind flow around the lowest central pressure