Bill Burton: It is 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's topic is something you could tip your hat to.
BB: Oh, I like that. I like where you went to, because we're going to be talking about a cap... not a baseball cap, not a salary cap, or any other sport caps you could come up with, but something that pertains to weather. Tell us about the cap for weather.
TA: So for weather, usually we're thinking of the cap as a layer of warm air in the atmosphere. Because in the troposphere, so where we have weather happening in our world, temperatures consistently decline as you increase in altitude. This is the critical process that allows warm surface air to ascend, cool and eventually lead to cloud formation. But sometimes you have that layer of warm air in the atmosphere, A.K.A. the cap, that actively inhibits cloud and thunderstorm development. So usually this is found below 10,000 feet, and where you have it in altitude can vary by location and time of year. For example, in Texas, it's around 2,000 to 5000 feet here... in Louisville, Kentucky, Indiana. It's usually closer to about 5,000 feet, depending on the time of the year. It will vary.
But within this layer, the temperatures remain stable. They remain warm, and they restrict the warm surface air from rising and generating clouds. Think the lid on a pot, as you have all that steam and water boiling. All of it's trapped when the lid is on, but if you release that lid, all the steam is going to violently shoot up into the air, and hopefully not your face.
BB: I'll remember that the next time I'm making pasta.
TA: Yeah, so when you're making pasta, think of weather, because it's the exact same type of dynamic that's happening in the sky. So without the cap, you have an atmospheric instability being released sometimes too quickly. So you end up with kind of a showery setup, because everything is being released before the necessary conditions for severe weather are in place.
However, if you have the presence of that cap below it, you have continued warming. The air becomes more saturated and becomes more and more unstable. A strong cap effectively limits the potential for severe thunderstorms, since that ascending air cannot overcome it. But as soon as that cap weakens or breaks, as we talked about with the lid on a pot, all that warm, unstable air can surge rapidly upward, and that is when you end up with, like that summer kind of situation where you have a thunderstorm popping very quickly becomes intense. You can have a lot of heavy rain, a lot of hail, and then it's gone. Think of a cap in that type of situation. But forecasting the breaking of the cap is probably one of the most stressful things you can do.
BB: What makes it so hard?
TA: So the thing that makes it so bad is that you it can be one to two degrees or even three degrees of temperature difference that could make or break whether or not you actually have a cap or a complete disintegrates. So that could be the distinction between severe thunderstorms or calm day. So that's why you should be a little bit kinder to meteorologists as we head into the late spring and early summer months, because forecasting gets a lot more difficult, all because of a simple cap.
BB: You should always be kind to your meteorologist, and now we have a much better understanding of the concept of the cap thanks to this edition of Science Behind the Forecast with WAVE 3 meteorologist, Tawana Andrew. Thanks for the knowledge, Tawana.
TA: Of course.
