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By, Greg Brown

Enter a new electronic gizmo called the Brunton Sherpa. Don't think that because this device is named "Sherpa" that this device is limited to high altitude hikers (Sherpas are the Nepalese natives who serve as the backbone of Himalayan expeditions). The Brunton Sherpa is well suited for any type of amateur weather forecasting.

One of the best things about the Brunton Sherpa is that it displays an easy to read sixteen hour history of the barometric pressure in a column graph so it is easy to see the current pressure and determine if the pressure is rising or falling.

The image tells us quite a bit about what kind of weather we can expect. First, let's look at the historical graph. The historical graph is a column graph and we can see that there are five entries along the X axis. The five entries along the X axis represent measurements taken over the course of 16 hours. The graph is read left (oldest) to right (newest) measurement. The graphs on the X axis represent the hours 16, 8, 4, 2, and 0.

So, we can see that between 16 and eight hours ago we saw a rise in pressure. After the rise in pressure seen over eight hours ago the pressure has held steady. The longer the pressure has held steady, the longer we can expect the existing weather to remain the same. On the flip side, if we see a rapid rise or fall of pressure we can say that the current weather state will probably not be around that long.

How is this useful? If I arrive at the trailhead campground the night before under clear skies and pressure slowly drops through the night and continues on that trend in the early morning, I would expect the weather to change to rain and I would also expect the rain to hang around for a good part of the day. Not a good day to take off the top and doors or forget the rain gear.

If I arrived at the trail campground during the evening in the rain and the pressure remained the same all night long I would expect the rain to hang around for quite a while. Again, not a good day to leave the top and doors at home.

If the pressure is steady and remains the same and the weather was clear when I arrived at the trail the night before the ride I would expect good weather during the ride and I wouldn't bother with the rain gear.

The current conditions (when the picture was taken) was sunny without a cloud in the sky. The pressure is holding steady over the last eight hours and it rose between 16 and 8 hours ago, so I would expect the same sunny skies overhead for the remainder of the day.

Now, one thing to keep in mind is that changes in altitude will affect the readings of a barometer, so if you're traveling from Ocracoke, NC at sea level to Tellico, in the mountains of Western North Carolina, you will encounter the rise in elevation that will affect pressure and therefore possibly give you a false reading. One way to overcome this is to clear the historical graph when you arrive at the campsite or trail head, or just remember the time that you arrived so you can discount any portion of the historical graph that was recorded during a rapid ride of elevation.

Top down, baby!
Get the top and the doors on!
Find a palce to store the top and the doors.
Looks like it's going to clear up.

If your travels do not take you through a rapid rise in elevation the historical graph should still be valid. Keep in mind, though, that if your travels take you toward an approaching weather system you will see a faster rise in pressure than if you are staying in the same place and the weather system is slowly advancing toward you.

The Brunton Sherpa can do quite a bit more than just display a historical graph and current barometric pressure, but they are beyond the scope of this article.


I don't own a Sherpa, so what about me?


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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.