Barometer

On my RA Perth trip, there was this day we went out to sea on a boat to see sea lions. Although I wasn't interested in the swimming part, I was intrigued by the boat itself. I even drove it, you know. And the GPS was cool too. I remember asking our captain how it worked, and he was telling me how the depth meter was screwed up. But what really caught my eye was a little circular dial at the top of the cockpit. Yep, it was a barometer!


I remember asking the captain why the barometer, why there were two needles on it. Gosh, I actually didn't know why. Before that I always thought that barometers just needed one, to see the pressure. Well, the answer was, the second needle is one that you move around to mark the pressure at a point in time, so that when you check back later, you can see how it's changed. Bah, why didn't I think of that? To forecast with a barometer, of course you need to know the change, not just the absolute value. 

An example, if the pressure is 092mB now and changes to 988 in an hour, I would be wrong to say 'The pressure is really low. It's going to rain.' Since the pressure is actually rising in this case, I highly doubt that it would rain. Of course, nothing is impossible... Now that I think of it, that is Cat 5 hurricane pressure. It would be raining like you couldn't imagine already... But this is just an illustrative example. 


To forecast the upcoming weather from the barometer, in the most simplified way, you just take the pressure (mark it with the extra needle if your barometer has one) and check back later. If it has dropped, there's a higher chance of it going to rain, and vice-versa.

Now, in case this all seems to simple to be true, it actually is quite simple. Cloud formation is linked to pressure, because the convection that is the cause of cloud formation lowers the pressure pressure, and the subsiding air that inhibits cloud formation raises the pressure. Ding! You understood that. I made it very elementary.


Ooh, back to barometers. I just love them. What better complement to identification of clouds to forecast the weather than a indicator of pressure? And what more fitting time to get it than during the pressure module?


Ah, I so wish I had a barometer.


Oh yes, note that this post is all about analogue barometers.

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In the meantime, do await the next post in the weathers series!