When checking the weather what does the pressure tell you?
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Change in the atmospheric pressure leads to changing weather (cloudy vs clear). IIRC pressure drop mains rain clouds coming and pressure increase means clear(ing) skies. It can predict heavy rains and to some degree even drizzles, but it’s tricky and we use better tools for meteorology nowadays.
To be clear observing the pressure alone won’t help with prediction: it is the pressure change that actually helps, so that’s why some old school barometers need some light tapping or knocking to check which way the barometer arm swings (increase- clearing skies, decrease- incoming rain) and how much.
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Pressure alone does not do much, but pilots need it for their altitude measurement.
Changes in pressure over time can indicate special weather patterns like so called “fronts” which, depending on the type, bring along some special weather types. Pressure maps can give you wind direction of strength, because wind flows along lines of equal pressure and the closer those lines are, the higher the wind speed.
Pressure change = weather change. Tap to check. Old school, but helpful. Meteorology uses better tools now.
Simplifying a lot: Winds generally blow from higher air pressure to lower air pressure. The winds blow the clouds along, and clouds cause rain.
So if there’s an area of low pressure, it’s probably going to be cloudy and rainy there, because the winds will gather all the clouds there. If there’s an area of high pressure, it’s probably going to be sunny there, because the winds will take all the clouds away.
Many years ago, just having a measurement of the air pressure where you are would let you do basic weather forecasting: If the pressure is high it’s mostly sunny. If the pressure is low it’s mostly cloudy and rainy. If the pressure is going up, the weather is getting sunnier. If the pressure is going down, the weather is getting rainier.
Nowadays, computer weather forecasting uses the air pressure as one of the many inputs into their very complicated models. It’s become much less relevant to people who are not weather experts, because we can just use the weather forecast without worrying about how that forecast was generated.
Higher pressure pushes bad weather away, meaning clear skies.
Low pressure is like a vacuum. It’s windy and blows clouds and bad weather around
Who knew tapping a barometer was the key to predicting weather? I guess we just need to give it a little love tap!
Atmospheric pressure isn’t the same everywhere and isn’t constant for any given location. It might be helpful to think of it like a hilly landscape and poor weather is like water running down hill. If you have high pressure or it looks like a high pressure zone is moving your way, clear weather is likely; that’s like standing on top of a hill. If pressure is dropping, that’s like walking down from the hill into a valley where the water is pooling. The lower you go the more likely you are to encounter precipitation
Think of low pressure like valleys and high pressure like mountains. Rain clouds flow down the mountains and sit in the valleys. Low pressure means rain.
Growing up in cold Canada, there’s a trick to telling the air pressure and what kind of weather you might be heading out into in winter. High pressure means clear skies and crisp cold temps. Low pressure means cloudy and chance of snow, or rain in the summer, as well as ‘warmer’ temps.
So, here’s the trick. If you see the smoke from someone’s chimney rising up into the air, that means high pressure, clear skies and colder temperatures. If the smoke from the chimney goes to side when it comes out, it’s lower pressure outside, likely less frigid and higher chance for potential snowfall.
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