Weather & Barometers
How Weather Affects Air Pressure
The difference between a good or a bad day of fishing can be determined by the barometer. For years, anglers have watched the rising or falling barometric pressures to predict fish movement and feeding patterns in the hopes of increasing their chances of success. Anglers often debate which barometric reading indicates better fishing conditions. Both pressure changes are ideal times to fish; your reaction to those changes affects your overall success.
One of things you see most frequently in weather forecasts is big “H” and “L” signs moving across a map. These are large swaths usually many hundreds of miles across of high or low pressure. There’s no number which indicates high or low, it is merely a relative term an area of high pressure is higher than what is around it.
Rising Barometer - When the barometer is rising, weather conditions are relatively clear or improving. Fish movement becomes slightly more active.
High Pressure - After the rising barometer hits a high point, the skies are clear with overall bright light conditions. During this time, fish activity is generally slower, as the fish find cover or swim into deeper water.
Falling Barometer - When the barometer falls, weather conditions are generally getting worse, with the potential for storms. Fish react to the falling barometer with increased movement and feeding activity.
Low Pressure - When the falling barometer is at its lowest point, weather conditions are rainy and stormy. Fish patterns become less active and continue to decrease as the storm continues.
An area of high pressure - i.e. more downward force - pushes air down. As the air descends, it warms, which inhibits the formation of clouds and storm systems. So high pressure is almost always a sign of good or fair weather.
Air, however, wants to rise. So once it hits an area of low pressure where downward force isn’t as great it will have that chance. As the air rises, it cools which condenses and forms precipitation. Hence, low pressure is associated with poor weather (“poor” is of course a relative term some folks really like storms and rain!).
So you can imagine a patchwork of high and low pressure swaths across a map. These are created by wind, the rotation of the planet, the sun and all kinds of factors that are completely outside of human control or prediction. But what we do know is the type of weather that these differences in air pressure portend.
A barometer that has a high reading meaning high pressure and is stable indicating good weather. You’re in the midst of a high pressure system. A barometer that is falling indicates that a low pressure system is moving in, and you can expect poorer weather. How bad that weather becomes is the result of how great the difference is between the high pressure and low pressure system. The bigger the difference, the more volatility there is in the atmosphere and the stronger the storm. The smaller the difference, the less likely you are to see rain or storms.