One of my favorite things to do as a meteorologist is to visit schools and talk about how the weather works. Growing up, I was always one of those nerdy, science-loving kids, and I’m so thankful that I have a job that lets me geek out every day.
When I visit schools, the students and I talk about everything from weather safety to how meteorologists predict tomorrow’s weather. I explain that in order to figure out what is going to happen tomorrow, meteorologists need to find out what happened in the recent past as well as what is happening right now. We do so by using various tools and instruments like thermometers, barometers, anemometers, etc. But my favorite tools by far are satellite and radar.
As a kid, whenever thunderstorms developed in my town, I’d park myself in front of the television set and watch the radar loop. Back then, there was no widespread internet (it was still 5 to 10 years away from becoming a household utility), so the only way my family and I got weather information was from the weather radio and the TV. One particular channel had the local radar loop every 10 minutes… I’m sure you know which one I’m talking about… They also had interesting “smooth jazz” music that I would hear so often I would hum along to it, prompting my mother to say “Christina, you have a problem…”
Needless to say, radar has been my favorite weather tool for a long, long time. I always enjoyed watching pop up storms bubble up and figuring out where they were going to go before they fizzled out.
During severe weather, I was glued to my seat, watching and tracking squall lines as they moved into my viewing area and calculating their approximate arrival to my house based on their current motion. I was stoked to take the radar class in college because I loved learning about how radars worked and discovering what tornadoes and straight-line winds looked like on the radar imagery.
But it was in college when I developed my greater appreciation for satellite imagery. When you watch a weather report on television, a meteorologist may only have a few seconds to point out a feature on a satellite image.
However, if you really take the time to study the various satellite imagery that is available (visible, infrared, and water vapor, among others), you can pin point features that a radar cannot show you.
For example, a radar is only able to detect hydrometeors (a fancy word for water particles, like raindrops, snowflakes, hailstones, etc) if they are falling within the radar’s beam, and if they are of a particular size that the radar can detect.
Radar beams propagate outward in a linear fashion, and the beams become wider the further out they travel. In contrast, the surface of the Earth curves, and there becomes a point at which it curves away from the radar beam (see image, below).
As a result, if a radar is too far away from a particular thunderstorm, then the radar won’t pick up its precipitation. Similarly, if a thunderstorm is too close to the radar, it will be above the radar’s beam, and “radar silence” is also the result.
During the summer, thunderstorms often build and produce dangerous lightning well before they produce their first raindrops, and the water drops within the cloud are often too small for the radar to detect. Satellite imagery became very, very useful in these situations, because it would show the building cloud tops which would let me know that a thunderstorm was brewing, well before the first rumble of thunder and the first plops of rain. This information came in handy when I was a lifeguard: Often times, I noticed cumulonimbus clouds building in the distance and faint rumbles of thunder, yet the radar checked out “clear”.
It’s my goal in future posts to more thoroughly flesh out the many uses of satellite and radar imagery, as well as key thunderstorm features that show up both on satellite and on radar. In the meantime, feel free to send me your questions about the weather!
– Christina Edwards
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