Do you know what dry bulb temperature is? In the latest "Science Behind the Forecast," WAVE 3 meteorologist Tawana Andrew explains.
Bill Burton: It's time for us to take a look at the Science Behind the Forecast as I am joined by WAVE 3 meteorologist Tawana Andrew. Good morning. Tawana.
Tawana Andrew: Good morning. Today we're talking about a more accurate way to tell the temperature.
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BB: Yeah, we have the standard temperature, of course, we have the heat index, which kind of gives you a better idea how things really feel when you're outside. But something that's even more accurate is the wet bulb temperature. Explain what that is, please.
TA: Yeah, so going into what I do on a daily basis, I'm, you know, standing on TV, pointing at a screen and telling people what the air temperature is. When you see me doing that, or any other meteorologist doing that, we're talking about the dry bulb temperature. So this is measured with a thermometer that it's in an area that's shielded from moisture and solar radiation, so it's pretty confined when we have that measurement.
But, the wet bulb temperature is more accurate because it is a good indication of how it feels outside in direct sunlight. So how you measure this is that you take a piece of wet cloth, you put it on a thermometer, and that cloth kind of acts like our skin when we're sweating. In drier air, that cloths moisture would dry out more quickly because it's able to that moisture is able to go easily into the atmosphere. But on a humid day, the cloth moisture takes a lot longer to evaporate. So for the wet bulb temperature, it accounts for the influence of temperature, humidity, sun angle, cloud cover and even wind speed, because it's easier for us to have that evaporation happening on a day where the wind is blowing a little bit more. So it takes all of that into account compared to the dry bulb temperature, which is just like if you're inside and there's no sunshine on you. So when you think about wet bulb temperature, some people are, oh, the heat index kind of covers that. Well, it doesn't, because the heat index is actually more of a formula. It's a calculation of what the combination of relative humidity and temperature feel like to the human body, and that's also calculated for the shade and not for direct sunlight. So even that isn't entirely accurate to what you're going to be fully experiencing when you are outside. The dry bulb temperature will almost always be lower than the wet bulb temperature unless the air is fully saturated, So basically at 100% humidity, and once you reach that 100% humidity, then those temperatures will actually be equal. And even though, yeah, we're going in the fall, and people are like, Oh, it's cooling down right now, it's super important to keep the wet bulb temperature in mind.
But you can actually get a forecast from of this, by the way, from the National Weather Service, because high wet bulb temperatures indicate dangerous heat, since it correlates, as I mentioned, to how our sweat evaporates on a hot, more humid day, and our bodies are working harder to cool down in those higher wet bulb temperatures. In fact, there was a 2010 study that uncovered that a 95 degree wet bulb temperature could lead to our bodies overheating within six hours. But Penn State, some of their researchers were working in 2022 and they found for a healthy young body, that even a wet bulb temperature of 87 degrees could lead to heat related illnesses when the humidity or is at or above 50% so that that kind of correlates to temperatures of 100 degrees at 60% humidity, or you're going to be down into those 70s with like 100% humidity. So it's just super important to make sure you're taking your care of yourself, no matter the actual temperature, whether it's wet bulb or dry bulb or heat index. Just when you're outside, just make sure you're paying attention and drinking lots of water, be alert.
