We have all felt it before. A windless sunny day, with large storms on the horizon. The winds start to pick up slowly, the leaves rustling around. The familiar scent of the soil tickles the nose. Soon, the sun is blocked behind thick large grey clouds. And just as you make sense of what is to come, you see lightning in the clouds. The last fleeting moments of calmness are quickly replaced with a sudden and very loud boom that echoes through the clouds. Down come a few drops. Then some more. Those few drops quickly turn into an army of large drops hitting the ground with immense force. No matter where on Earth we happen to be, mother nature always reminds us of her fury. Today I get to write about thunderstorms, how they form, what they mean for pilots, and what we do to avoid them! Early on in our careers, we are taught to avoid them, but as we gain experience, we learn to handle them and most importantly, respect them. Read along, and gain a unique perspective!
How they form
To understand thunderstorms, we must first understand that the air we breathe is not as uniform as it seems to the naked eye. Air acts like a fluid, in that it moves around. Different masses of air have different characteristics. Think of us living in air the way fish live underwater. To the fish, the water is an element. But as we know, water has different characteristics and it flows! It is this core principle that gives rise to the weather we see around us. Thunderstorms generally form in three stages: development, maturity and dissipation. This knowledge is taught to pilots very early on, and we never forget it!
During the development stage, warm moist air starts to move upward. As it gains altitude, it also starts to slowly cool and eventually forms what we commonly call cumulus clouds. This cloud will continue to grow as long as there is this “fuel” of warm air below it to help it rise.
As the large cumulus cloud continues to grow, so too does the water droplets inside (which are colliding with more water from the rising air below). Fun fact: the colour of the cloud is generally due to the amount of water it holds. So the greyer the cloud, the more water it holds. This is why most storms have an ominous dark grey colour to them. All this water adds weight, enough weight that the cloud can no longer hold onto all that water. Raindrops only have one place left to go, and gravity helps get that job done! This is where we enter the maturity stage. Rain starts to fall on the ground and a downdraft (fast moving air towards the ground) pulls water down further, while updrafts push air further into the cell. This mix of updrafts and downdrafts can be in excess of 100 mph, and is what we call a thunderstorm cell.
Eventually, the downdrafts will overcome the forces of the updrafts and all the rain falls out. At this point, the storm weakens and enters the dissipation stage. The updrafts come to an end, the rain reduces in intensity, and we are left with huge puddles of water for kids to jump over! While this explains the basics of the thunderstorm formation cycle, the next part dives into what they mean for pilots.
From our perspective
In the beginning of our careers, we are taught theory on climate science with a special focus on storms. We are also taught to avoid them at all costs. I can agree that this basic rule is good one to follow, but if we just ended there, no plane would ever fly on days with storms. You see, general aviation planes (small trainers and such) do not have the equipment onboard to detect and manage storms. Our experience is also less, and for the most part, the planes are limited at altitudes below storms. This is where the idea of avoiding them at all costs comes from.
But as we start flying more complex machines and gain experience, storms become a normal part of our jobs and we share the airspace alongside them. We learn to interpret the weather and create a mental picture, a skill all pilots share. After all, how well we can do this plays a big role in the safety of the flight and our passengers. So then, how do we manage storms?
Well, onboard the plane I fly now (and most commercial jets), there is a system called weather radar. Weather radar works by sending microwave emissions ahead of the aircraft’s path. This beam of emission hits a target (effectively rain drops) and reflects it back. On the A220, clever software is able to understand and analyze this information before feeding us a colourful picture on the radar display in the cockpit. The colours generally correlate with rainfall density, green being minimal and magenta being sure death, we jokingly say. Of course, we have controls to manage the radar and change its tilt or sensitivity but it almost always works better in auto mode. This information helps us understand where the storms are and we can correlate rainfall density to storm intensity.
One might say, well why not just fly above them? Isn’t the sky always clear way up in cruise? Well, even while cruising at 40000’, storms can develop above that altitude. I recall a recent red eye flight, coming back from Seattle cruising at 39000’, the first rays of the sunrise were highlighting storms above 45000’. When we checked other reports, some of the storms on our flight path exceeded 50000’! This is higher than what almost any commercial jet can fly, clearly not a good strategy then! Between our weather radar, experience flying around storms, and help from the ever-present ATC, we use all these tools to create a mental picture of the storms. These become even more important if we are in conditions where we cannot see outside. General avoidance techniques include deviations, but in critical cases we may elect to divert to a safer airport.
The dangers of flying inside of, or too close to storms are very real. Plenty of crashes have occurred and to this day continue to claim the lives of passengers. Here are some of the critical dangers:
Powerful large storms create anvil like tops which extend horizontally. Getting caught too close to these can put the aircraft into severe clear air turbulence; the kind we cannot detect or see!
The mix of drafts inside the thunderstorm can reach speeds of up to 100 mph, and sometimes exceed them! Thus, trying to fly inside of one to get to the other side will almost certainly put the aircraft out of control.
At higher altitudes, storms contain hail which can physically damage the aircraft. And at the speeds we fly, even seemingly small pieces of hail can be detrimental.
I’ll spare an exhaustive list but as you can see, thunderstorms are nothing to scoff at! One important point I’d like to mention: Storms are at their greatest danger to us on approach, where we are low to the ground and slow. We don’t have the speed to quickly overcome changes in the air, and we don’t have the protection of altitude. At times, we only have seconds to react. In these moments, a strong adherence to our knowledge and skill helps mitigate thunderstorm threats. We may elect to hold somewhere in a racetrack pattern until the storm passes, and if caught in an unstable situation, we commit to a go-around.
Conclusion
Some of the best pilots in the world have lost their lives, aircraft, and cost passenger lives because of storms. And while we may not have had the best technology in the pioneer years of aviation, the current landscape puts multiple tools at our disposal. Training, for one, has gotten better. We learn from incidents around the world, and integrate it into simulator training every few months. Technology in the aircraft has also improved. The first commercial flying job I had, the aircraft had a pretty basic radar. It could paint what it saw but with limited accuracy, whereas the aircraft I fly now computes what it sees and creates a model free of errors, in real time! And as AI finds a way into the cockpit, safety margins will certainly improve.
In this post, we learned about how thunderstorms form. We also got to understand how pilots see storms, and their associated dangers. The next time there are delays due to weather, you now can appreciate why! When you’re enjoying snacks in cruise and the seat belt sign comes on, it’s happening for a good reason. Next time you look up and see a storm, you’ll have gained a new view of, and respect for mother nature’s fury!
Nice article, Sunny! Very informative.