Barometers Are Underrated Tech for DIY Weather Forecasting [CNET]

A barometer is one of the best ways to get a quick weather forecast before stepping outside.

I first learned about atmospheric pressure’s effect on the weather as a kid while doing a summer science project. It involved making an aneroid barometer with a balloon, pencil and an empty jar. As the season shifted into fall, I obsessed over the pencil’s reactions to daily weather patterns and learned little by little how to forecast impending inclement weather.

Eventually, my haphazard barometer broke, and I couldn’t be bothered to make a new one. Still, the experience of forecasting my weather conditions stuck with me. A dial barometer from a local thrift store has been among my favorite gadgets for years, even if it’s worse for wear.

Let’s dig into barometers and why you might want one.

What is a barometer?

A barometer is a simple sensor that measures atmospheric pressure. If you want to get more technical, retail barometers and weather apps in the US typically show atmospheric pressure using inches of mercury.

Meteorology-focused organizations like the National Weather Service also list a metric measurement in millibars or hectopascals. Hectopascals are equivalent to millibars — no unit conversion is required — my Unni weather station shows both.

Any of these units will work for everyday use. Still, I suggest using the option that aligns with your preferred weather app.

According to the National Oceanic and Atmospheric Administration, the numbers shown on a barometer come from the standard air pressure at sea level:

• 29.92 inches of mercury
• 1013.25 millibars/hectopascals

Readings below standard air pressure typically coincide with stormy weather, while sunshine comes as the pressure rises.

How to read a barometer

By watching for noticeable swings in the barometric pressure, you can often tell what the weather will be like in the next few hours — this is why most barometers allow you to see past measurements. You can expect more clouds and possibly stormy weather with low pressure. In contrast, high pressure means more sunshine and drier air.

If you hear the wind howling, it’s a great time to check your barometric reading. Wind usually accompanies pressure changes as a low pressure system makes way for high pressure, and vice versa.

Once you have a basic understanding of this scientific instrument, it’s a simple matter of making mental or written notes about changes in the weather. You’ll start to recognize patterns and the weather conditions they create.

It’s a good idea to check the barometer reading before you leave home so you know whether to throw an umbrella in your backpack. You can also get a portable unit to help you decide if those dark clouds will ruin your next hike or day on the lake. Consider checking your phone’s specs to see if there’s a built-in barometer you can try with a barometer app on iOS or Android.

Calibrating your barometer

Barometers require calibration during setup to match your local weather station. This is because air pressure changes based on your altitude relative to sea level. Since there’s less atmosphere at higher altitudes, they experience lower barometric pressure. Calibration compensates for the elevation difference and aligns your barometer with the station pressure.

The easiest way to find this info is by entering your ZIP code on weather.gov. Alternatively, most weather apps list the pressure. Weather station user manuals should have setup instructions, but an online calibration guide is also handy.

• Analog barometers have an adjustment screw on the back that turns with a small screwdriver.
• Digital barometers typically offer automatic calibration but have buttons on the back of the unit for quick corrections.
• Some internet-connected barometers require an offset setting to match the local weather station pressure. You can calculate the offset by subtracting your barometer’s current reading from the online station pressure. 

What type of barometer should you buy?

Regardless of the type, get a barometer or weather station that tracks at least one previous air pressure measurement. For analog barometers, look for a tendency needle you can rotate. Digital barometers should show a bar graph or arrow indicating recent pressure changes. Otherwise, you’ll need to write down or remember past readings.

Analog weather stations, like the Ambient Weather YG315 and Mavori, are great for beginners because they’re easy to read, and the traditional design looks great in most homes. They also provide temperature and humidity readings.

Still, you might need to wade through a sea of aneroid barometer product pages to find your preferred unit of measure. Some even show millimeters of mercury, which are more useful for blood pressure monitors than weather stations.

While analog barometers work well enough for everyday weather observations, electronic barometers are more reliable, and the precise measurements are perfect for amateur meteorologists. Choosing a digital weather station depends on your screen preference and the conditions you want to measure.

Light, monochrome LCDs are great for visibility, as found on the Unni UN0585, with or without a backlight. Still, you might want a full-color, backlit screen to see the barometric reading from farther away, like the La Crosse Technology S84107-INT.

Beyond the screen type, you can upgrade to a digital barometer model with more outdoor sensors for precipitation, wind speed, wind direction, dew point and solar radiation. Wind measurements can provide more context for your barometer since drastic pressure changes and high winds are the same. Keep in mind that extra sensors can drive up the price.

There are also options with Wi-Fi connections, mobile apps and the ability to share weather data with services like Weather Underground. I recently set up an Ecowitt GW1200 that I’m working to integrate with my home automation system — I plan to add more sensors as my needs change.

A barometer’s ability to show atmospheric pressure trends makes it a great addition to any home weather station. It helps you learn the weather patterns in your area and gives you insight into what to expect when clouds appear on the horizon. Best of all, it can spark a lifelong interest in meteorology as a hobby. That’s reason enough to pick one up.