What Makes Thunderstorms So Hazardous for Pilots?
Weather Hazard – Thunderstorms – Video Transcript
Today, as we get into the summertime, I wanted to talk a little bit about a specific weather hazard, and that is thunderstorms. Specifically, what I want to do is answer two different questions. The first is, why is a thunderstorm hazardous? So, what are the hazards of a thunderstorm, and then the second I want to talk a little bit about the life cycle of a thunderstorm. So, how they form and what ultimately allows them to continue on. That’s what we’re going to dive into, and hopefully we find this video of use. Let’s start with what is hazardous about a thunderstorm.
What’s Hazardous about a Thunderstorm?
Some of the hazards associated with a thunderstorm, I think the most common that we would probably describe are extreme or very severe turbulence and extreme or very severe icing conditions that would affect us if we were trying to fly through a thunderstorm. This is why in the case of this kind of turbulence, that it’s the kind of turbulence that could do enough damage to the aircraft that we could be structurally unsound. Also, a big result of thunderstorms is hail. Hail are large pieces of ice that can cause significant damage to the skin of our aircraft as well. Lightning, another result of thunderstorms. Lightning can also cause disruption with electrical interference and can also potentially spark fires. The last two may be less common with all thunderstorms, but certainly significant factors of thunderstorms are these things like a microburst or a tornado. Both of those are maybe a little less likely than these others to occur in every thunderstorm but they certainly have dramatic effects on us flying. Next what I want to do is talk a little bit about how a thunderstorm forms, and then how it ultimately carries out the rest of its life cycle.
What’s the Life Cycle of a Thunderstorm?
Typically, when we talk about the lifecycle of a thunderstorm, we break it into three different stages or phases of its life. We have the cumulus stage, the mature stage, and the dissipating stage. What I want to do is dive into each of those and talk a little bit more about what’s happening as we transition from the beginning to the end.
In the cumulus stage, we can think of that as like the birth of a thunderstorm, and what’s happening here is the culmination of a bunch of ingredients coming together to form this thunderstorm. First and foremost, we have to have moist, unstable air so we need a lot of moisture in the air, and we need the air to be unstable so the lapse rate is changing pretty dramatically and we have this instability in the air. The other major ingredient that we’re going to need is some kind of a lifting force. So commonly people might think of fronts for example, where we have air masses colliding and one is going to force the other up. Another example could be orographic lifting, as in the air mass moves over terrain like a mountain. It’s forced up by this terrain and the result is this lifting force. In either case, or whatever the lifting force is, we need something that causes this lifting force to occur and so when we start forcing this moist unstable air to rise, what’s going to happen? Well that lifting force is going to force that moist unstable air up into the air. That means the moisture is going to then condense. As it condenses, it forms this cumulus cloud and that cumulus cloud is just going to continue to grow bigger and bigger and bigger. So this cumulus stage is really the build out of these very large cumulus clouds, but the more the air is forced up, the greater the amount of condensation that’s happening. So the more and more moisture in the air that is condensing into liquid or turning it directly into a solid, and so that means then we have suddenly a bunch of either liquid or solid objects that are trying to be suspended in the air. That obviously has a lot more weight, and so eventually this lifting force can’t keep going indefinitely forever. As the air mass continues to move, eventually we don’t have enough lifting force to be able to hold all of that solid or liquid material up, and eventually it’s going to start coming out. When it starts coming out this is going to mark the beginning of this mature stage which is certainly the most severe part of a thunderstorm.
We can identify the beginning of the mature stage as when the precipitation begins, and this is where the reason why it’s going to be the most severe, as I trying to illustrate here, is we have areas where we have intense lifting force. We have this instability where the air is mostly rising and then areas where the air is being pushed down by all of this precipitation that’s falling out. So, we have maybe dramatic changes in temperature, and this creates huge amounts of instability in the air and massive amounts of turbulence and this is why we have more showery precipitation. We have areas where this precipitation is being forced out and other areas where lifting forces might be more prevalent and there’s not really any precipitation. So, this is where we tend to see most of the severe conditions, the hazards that we had talked about before. We have the greatest amount of turbulence, the greatest opportunities for icing, we have now the formation of something like hail. In that case, what’s happening here is we have moisture that condenses, it freezes into a ball of ice, it attempts to fall down, and somehow it gets recirculated, and it gets recirculated, and every time it gets recirculated, it grows a little bit bigger, a little bit bigger, a little bit bigger, until eventually it’s so large, it has so much mass, that it’s just sort of thrown out of the cloud or thrown out of this cycle. It has more mass than is necessary and it gets tossed out. This is also the reason why we say that thunderstorms aren’t just dangerous in the areas that we see the activity going on, but also even outside of that. Hail can be thrown for many miles outside of a thunderstorm as well, and then eventually what’s going to happen then is this. Eventually, that lifting force is going to fade for whatever reason either because the air masses are melding together or the orographic force, for example, that was lifting them has now passed, the air mass has moved beyond it. In either case, now we still have all of this moisture in this cloud that’s going to continue to come out.
This is then going to transition towards this dissipating stage where this thunderstorm is more or less dying and what I mean by that is, now we have mostly down forces happening. We have very little lifting force so now the lapse rate becomes more stabilized as all of this air is just sort of moving down equally. Temperatures start to flatten out across various altitudes so therefore the lapse rate stays relatively similar and all of this moisture is now falling out equally. So this dissipating stage would mark the end of the rest of this and really what we see typically as a result is we end up with an atmosphere that’s very stable. We have relatively standard pressures that we’ll experience, we see that the lapse rate is pretty much equal across a region, and therefore we would anticipate much more stable air. Usually it’s very smooth after that and this would mark for the end of this dying stage, this dissipating stage of the thunderstorm. So, I think this helps elaborate a little bit more on this in these three stages, this cumulus, mature, and dissipating stage. I hope this video has been helpful to you.