This interview first aired in 2019.
Bill Burton: It is time for us to take a look at the Science Behind the Forecast as I'm joined by WAVE 3 meteorologist Tawana Andrew. Good morning, Tawana.
Tawana Andrew: Good morning. Are you ready for some physics?
BB: Yes, I've got my chalkboard. I have multiple colored chalks. I'm ready to go.
TA: You're missing a calculator, but we'll get you one.
BB: I've got a pocket protector. How about that?
TA: That works. Okay, you look cool and you know that you're super excited. So today, we are learning about how the cold air and the winter air affects our vehicles. And to do this, especially for our tires, we have to bring in this equation called the ideal gas law.
BB: The ideal gas law.
TA: Or also known as the equation of state And it is PV equals nRT. I hope you're writing this down.
BB: PV equals nRT, okay, PV equals nRT.
TA: So P is pressure, V is volume, and T is temperature. The other two are basically types of constants. So this equation for our tires demonstrates that lower temperatures lead to a decrease in pressure. So your tire pressure will actually drop around a pound per square inch for every 10 degree drop in temperature. So that means that a fully inflated tire at 80 degrees Fahrenheit will be six psi under inflated at 20 degrees Fahrenheit. This is just what the temperature does to your tires. And that in itself, can cause issues. So when you see that tire, light come on. Actually check it. Don't be like me and ignore it.
BB: Don't put a little piece of tape over that part of the screen.
TA: Check it. It can be dangerous. Also, the cold air messes with your car batteries for a few reasons. First, it thickens the oil inside the battery, and it also reduces the amount of energy that the battery can produce. So a cold engine must work so much harder to push around, think oil that looks like molasses, so the oil is already thick, but then it just gets even thicker, and it makes it so much harder for the engine to start. That's why, in colder temperatures, synthetic oils are recommended. So that's when you're like in the Midwest, they always give you the synthetic oil when you get your oil changed. Also the chemical reactions inside of a car battery slow down at colder temperatures, which forces the battery to produce less energy. And then the starter motor. I knew that I was going to say that word wrong. The starter motor does not have enough energy to work with to start the engine. And then that's why you have your car like turnover a few times.
BB: Imitates a car engine not turning over
TA: You're really good at that sound effect, by the way.
BB: I heard it way too often.
TA: And just so you know, a conventional gas cars mileage will be 12% lower at 20 degrees Fahrenheit than it is at 77 degrees Fahrenheit.
BB: Just the temperature alone will do that.
TA: Exactly. But the US Department of Energy has a long list of other ways that the cold air and the winter weather can affect your fuel economy.
BB: A long, sad list.
TA: Oh yeah, it made me cry a little bit. So for those shorter trips, it takes longer for your engine to reach its most fuel efficient temperatures.
BB: Makes sense.
TA: So those shorter trips to Kroger to McDonald's when you don't feel like cooking, yeah, that's not helping your car. Your heated seats, for those of you lucky people who have them and are enjoying them right now...
BB: My hand is not going up.
TA: Mine either. Um, window defrosters and heated fans actually use more power.
BB: So winter is out to get you. That's that's essentially what this is.
TA: Yeah.
BB: So the cold has a definite effect on your car, and all of this put together, is why we need to spend the next three or four months down in the Florida Keys.
TA: I'm with you.
BB: All right. It's Science Behind the Forecast with WAVE 3 meteorologist Tawana Andrew. Thanks for the knowledge, Tawana.
TA: Of course.
This transcript was edited for clarity.
