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A dropsonde is vital for forecasting. What is it?

A weather instrument called a dropsonde parachutes down from the sky.
Here's this week's Science Behind the Forecast.

Every week WAVE 3 meteorologist Tawana Andrew breaks down what we know and what we don't about the climate and weather here in Louisville.

Bill Burton: It's time for us to take a look at the Science Behind the Forecast as I am talking with WAVE 3 meteorologist Tawana Andrew. Good morning, Tawana.

Tawana Andrew: Good morning, we're talking about a specific package of weather instruments that are super vital to weather forecasting that a lot of people don't know about.

BB: Yeah, I kind of feel like I'm in a spelling bee, because you hit me this word. And I thought, "I think I'm going to need this in a sentence. And I'm definitely going to need the definition." It's dropsonde or dropsondes plural, with an s, tell us what we need to know.

TA: So dropsondes are these packages of various weather instruments that are basically attached to a parachute that's about a foot wide. Now the dropsondes, kind of think of a Pringles can that's a little bit longer. That's basically what it looks like without, you know, the fun packaging. But they fall from research, or NOAA, hurricane hunter planes. And they're really cool, because as they're falling through the atmosphere, they're sending radio signals about the atmospheric conditions around them. And they're sending their location twice every second. So they're very communicative as they're falling. And while they are falling, they're measuring everything from atmospheric pressure, to wind speed, direction, to dew point, to temperature. And for anybody worried about things falling on their heads, you're OK. They weigh less than a pound.

BB: So I can put my hard hat away?

TA: Yeah, you'll be just fine, just fine. And the parachutes that are attached to them are actually very specifically designed to make sure that they fall as slowly as they can. Because for, let's say, a dropsonde falling from about 46,000 feet, it'll take about 15 minutes for it to reach the ground. From about 20,000 feet, it'll take about seven minutes to reach the ground. And depending on what research we're trying to do, whether it's in hurricanes or getting ready for severe weather, they may be dropped from higher or lower altitudes. They were first developed in the 1970s. And engineers are still refining them, improving them all the way through today. They're tested in wind tunnels to make sure that they're pretty aerodynamic as well. So that's very helpful, because if they fall too quickly, then they can't collect the data that they need to collect. But if they fall too slowly, they may drift off course. And that doesn't help anybody either if they're in the wrong location where they're getting different information than what we need. Very, very fine tuned, because all of this information is being pumped into what we're using as weather models every single day. So we need this information. And the same instruments in a dropsonde are used in a radiosonde, which is attached to a weather balloon. So you have hundreds of weather balloons being launched twice daily by National Weather Service offices all around the country. So you basically have one that's rising and another one that's falling, but they're doing the same thing. They're pulling in all this information for us. And we use them in everyday forecasts so we can make sure that we know what's going on right now so we can tell you what's going to be happening potentially in the future.

BB: OK, so now you have the word. It's dropsondes. You've heard it used in a sentence, you know its definition so we can all win the spelling bee now. And we know how incredibly important dropsondes are thanks to the latest edition of Science Behind the Forecast with WAVE 3 meteorologist Tawana Andrew. Thanks for the knowledge, Tawana.

TA: Of course.

This transcript was lightly edited for clarity.

Bill Burton is the Morning Edition host for LPM. Email Bill at bburton@lpm.org.

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