Q:My wife was officiating a game in Belleville one afternoon. The officials take PIAA and your words that “thunder is lightning’s alarm clock” to heart. Even though it seemed like the weather was moving up the valley on the State College side, and not in our valley, the match was delayed. You could hear the thunder but it didn’t have the immediacy condition. Visible lightning was also seen on the State College side of the ridges. My question is: Can there be a combination of mountain profiles combined with atmospheric conditions that could acoustically bounce sound waves into a neighboring valley and create the “appearance” of impending severe weather, but in actuality those threatening conditions are relatively far off? The locals also say that when they hear the train whistles in the next valley over (McVeytown side) they can expect to have rain or snow within a short time.
A:Before I get to your answer, I do have to say that as the crow flies, the lightning was well within 10 miles at the time of this question. So therefore, the risk of getting struck was present. The referees did the right thing and weren’t overcautious. Sometimes it just appears truly farther. The answer to your question is, yes, under certain conditions, sound will travel farther, though the mountains may have less to do with it than you think. In fact, in some cases, they help to inhibit sound waves from other valleys. And even if the sound was coming down the same valley, I’m thinking the vegetation on either side of the valley may also tend to dampen the sound waves a bit. With all of that being said, I do believe what the locals are talking about in regards to rain and snow holds true. I know I may have contradicted myself, but let me explain. A lot of our steadier rain and snow comes from a warm advection situation. In these cases, warmer air rides up over cool air trapped near the surface. This inversion where temperatures
increase with height actually creates a situation that is known to enhance sound and radio waves at a farther distance, though the enhancement of sound is not as great as with the radio waves. In addition, during these warm advection situations, the ground layer is colder and stable, which then helps to keep down the ambient noise from the breeze rustling things and allows for sound to travel farther until the actual rain or snow starts.
Now back to the severe weather and thunderstorms. These events occur with an unstable situation where the temperature decreases with height. In these cases, we wouldn’t have the lid of a stable layer to help promote the sound to go farther. Also, convective situations create their own breeze and ambient sound ahead of rain. That’s where the old saying about leaves turning before rain came about.
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