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By, Greg Brown

Should I leave the top and doors home today? This is a question that a lot of 4x4 owners ask themselves before a nice day of trail riding. Wouldn't it be nice to know what weather is expected during the day without having to carry around a mobile digital satellite system in the Jeep with you?

Sure, NOAA weather radios are great things to have on the trail, but in some cases you need more information - especially when your trail ride is taking place somewhere that is not near a major metropolitan center, such as Tellico. Wouldn't it be nice if you had the tools with to you accurately forecast the weather to see if your information concurs with The Weather Channel or the NOAA?

Most of this information is available around you but you do need to know where to look. For instance, did you know that you can forecast the weather by looking at the smoke from a campfire or looking into a cup of hot java? It's true! For those of us who are addicted to electronic gizmos, there is a great miniature portable weather station that weights only ounces and measures just a few inches. We'll get to that later.

In order to make an accurate forecast of the weather you need to understand some of the very basic principals of weather and weather systems. We'll keep the details limited to just what you'll need in this article. For a more detailed explanation of weather systems and how to make a more accurate forecast, I suggest reading Weather Forecasting by Michael Hodgson (isbn 0-7627-0478-0).

Before we get into where wet and dry weather comes from and how you can forecast them, we'll need to understand the difference between warm and cold air masses and high and low pressure systems.

In the Northern hemisphere cold weather air masses generally travel from North to South. Cold air warms as it travels over the land and this causes the air system to become unstable. With cold air systems the weather can change very quickly. Warm air masses are more stable than cold air masses and the weather that is created from the warm air masses is more likely to stay around longer than weather created by cold weather systems. Warm air masses are generally swept into the country from South to North.

High pressure systems are associated with cold air masses while low pressure systems are associated with warm air masses. "High" and "low" pressure systems are so named because of the amount of pressure that each system puts on the ground that can actually be measured. As a rule heat rises and cold sinks. Since cold air is heavier than warm air, cold air will place greater pressure on the land below it. The amount of pressure that is placed on the ground is measured with a barometer.

By watching the change of barometric pressure one can determine what kind of weather you can expect during the day. Simply seeing what the current pressure is may not help that much. You need to watch the pressure change over time in order to properly forecast the weather. Having to write down the pressure of analog barometers is somewhat of a pain. You always need to have a pen and paper around to compare pressures and if you lose the scrap of paper you were writing on, you are out of luck. You could always write the pressure, date, and time in permanent marker on the side of your 4x4, but I think most people wouldn't go this route and you'd probably misplace the permanent marker anyway!


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Greg Brown is not a licensed metereologist. The information containted in this article is accurate, to the best of our knowledge.