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Thunderstorms and Flying

To everyone’s amazement, especially considering the dire predictions of a long winter, summer-like weather is already upon us. Maybe it’s just a short-term glitch, but warm unseasonable weather is spawning a great deal of thunderstorms in rare locations. For pilots, airline operations, ATC, and passengers, thunderstorms are a frustrating reality of summer time flying. With the undue arrival of fowl weather, I’d like to shed some light on what makes these storms such a problem for all things aviation as well as how it directly affects you, the passenger.

Thunderstorms are an airplanes worst enemy. Meteorologically speaking, thunderstorms are a result of the lifting of warm, moist air. As the air rises, it cools condenses into a cloud. As the droplets of water collide with each other, they grow and eventually fall in the form of rain. This rainfall causes downdrafts of air that hit the ground and spread out laterally. Downdrafts pose a large threat to aircraft in the form of wind shear. Aircraft and airports have equipment that detects wind shear and warns pilots of its presence. If the aircraft equipment detects a wind shear situation, it directs the pilots with visual cues to avoid it.

The rising of air that results in a storm is the result of a lifting force. This force can be the result of a weather front or warm air rising on its own. A cool air mass often results in the most severe thunderstorms, named squall lines. As cool air overtakes a warm air mass, it forces the warm air to rise rapidly into the atmosphere, causing severe storms. Such storms typically grow on a massive scale and move laterally across a region with great speed. Air-mass thunderstorms on the other hand, are a result of rising warm air, typically on a hot summer afternoon. They don’t move laterally like squall lines, but instead form all over the place like popcorn. These storms build and dissipate quickly compared to squall lines. Both types of storms have the ability to grow vertically on a massive scale, often reaching more than 60,000 feet. The rapidly rising air that builds the storms causes severe turbulence, and often spews out hail near the storm. Lightning is another factor at play, and aircraft are frequently struck. The good news is that airplanes are designed to withstand lightning strikes and usually it’s a non-event when it happens.

Aircraft must avoid thunderstorms as well as the surface conditions they produce. In terms of wind shear, pilots avoid both taking off and landing during such conditions. Often the passage of a storm near or over an airport causes operations to grind to a halt. For aircraft attempting to take off, a tarmac delay can result until the storm passes. Returning to the gate is not usually possible either, as ground personnel are not allowed on the ramp when lightning is present. That means there’s nobody available to marshal an airplane into the gate, let alone to retrieve baggage. For aircraft attempting to land, an airport closure results in aircraft holding pattern assignments. Of course flights can only hold for so long with fuel endurance becoming an issue. When holding is no longer possible, and the destination airport is still closed, the pilots are forced to divert to an alternate airport to refuel and wait out the storm. If you have a connecting flight, chances are your connecting aircraft is in the same situation and therefore there’s still hope that you won’t be stranded.

Aside from threats to the airport directly, thunderstorms can also pose threats to aircraft en route to a destination. As mentioned in previous articles, a storm acts like a broken down car causing a freeway backup. As aircraft veer off course to avoid a storm, they may interfere with the path of other flights, causing aircraft spacing to be reduced. If spacing is reduced too much, ATC must slow the pace of traffic down to accommodate aircraft that are deviating around a storm. If you’re on the ground waiting to take off and your flight is slated to occupy one of those congested routes, ATC may hold you on the ground until there is room for your flight. This often results in a tarmac delay.

Storms tend to form in various places and/or move to a new location, and as such they create a very dynamic and frustrating situation for ATC. Long delays can result. A solid line of impenetrable storms, such as a squall line, will often force a flight to deviate significantly from its ideal routing. Airline dispatchers will plan flights to avoid these storms, and could result in an additional hour or more to the original planned flight time.

It’s hard to predict if you flight will be affected by such weather well in advance. My best advice for those travelers slated for flights during the summer months is to keep your eye on weather reports. The day before, or the morning of your afternoon flight, watching weather reports can be a good indicator of what airports will be facing weather delays. And remember, just because the weather at your departure and arrival airport looks good, doesn’t mean you’ll be on time. Weather nearby or in-between you and your destination can pose a threat. If getting to point ‘B’ is crucial, consider working with the airline to change your departure time or connection airport. Connecting through another city away from the forecasted storms could mean a longer trip and a change fee, but may result in a far less stressful trip. Although storms associated with weather fronts can form day or night, the more typical hot summer day storms tend to form in the afternoon. Knowing this, I always plan my personal travel during the summer months to take place early in the morning, long before storms begin to form. That’s my best advice.

As you approach the summer months with travel plans, although frustrations are inevitable, understand that your safety is paramount. That’s the bottom line and always will be. Plan accordingly and keep apprised of the situation across the country with the invaluable information provided right here on the FlightAware website. Thanks for reading and safe travels!

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Chuck Me 3
Another great article, Mr. Fahl. I enjoy reading your work.
andy streit 2
Take a look at some of the DFW arrivals tonight. A normal 40 min flight is taking over 3 hours. It's really quite amazing to see aircraft tracks tonight.
preacher1 2
Andy: just to drive home his point and your comment. Your post was around midninght last nite, and with the head end of the squall line coming into town, they ran a 2-3 hour delay most all night, BUT, the squall line itself has gone thru and just heavy bad rain right now a little after 6am and there are no delays, at least none posted on FA. That system stretches all the way out of Deep South Texas clear up into Southwestern Missouri. Not sure how tall it is but you can bet there ain't no way to easily go around it. As Daniel says, you'll either wait or be in for a rough ride if a pilot has to pick his way through that mess; more than likely a rough ride as you can't wait out one that
Cow Bert 2
I believe you meant "foul weather" not "chicken weather"
Mark Lansdell 1
Well thought out and articulated. Good article. Read and learn or at least be reminded.
Yesterday we flew through some weather, and it was quite bumpy. However, it was just a rainstorm. I take it these are not as much of a problem? The Pilot did sound a little frustrated when he came over the PA to announce that the ride was going to get bumpy, but nothing more really. Is there some sort of "line" for lack of better words, in deciding what weather can be flown through and what cannot?

Sorry for the newbie comments... lol! However, the science behind Aviation is quite fascinating. Thanks for taking the time to write this, as well!
houtxpilot 2
I have been an airline pilot for over 5 years. I fly the Airbus A320. I would say that for each pilot the "line" of what is acceptable weather to fly through and what is not acceptable is different. I am probably a little more on the conservative side. Up high, say at cruise altitude around FL390, 39,000 feet, I will avoid build ups and thunderstorms by 20-30 miles. Down lower, I will use the weather radar to determine where to fly. I will fly through green and yellow returns, but I will avoid any red or worse returns on the radar. You get pretty good at looking at a storm or build ups and determining what you should do. Each instance is completely different from the one before, so it has to be experience that drives your decisions. As far as the "bumpy" rides go, that's somewhat a different story
I just flew a trip that ended yesterday and we were in and out of Denver both days. It was completely clear, but Moderate to Severe turbulence below 20,000 feet. Then you have other days, where you can be flying in overhang near thunderstorms or fly through heavy rain and the ride be completely smooth. We classify the ride conditions into two main categories: CHOP and TURBULENCE. Chop is less significant than turbulence. We then can break down chop by calling it Light Chop or Moderate Chop. Most often on any given flight, even if it feels worse to the passengers, we will only encounter light chop. As far as turbulence goes, we classify it as Light, Moderate, Severe and Extreme. The difference is of course the intensity of the "bumps" and the upset that it causes to the aircraft. My personal minimums, as well as my companies procedures, all us to dispatch into any of the reported turbulence, except severe or extreme. Since the Airbus is a larger aircraft, our books do say we can disregard certain reports of severe turbulence. For example, if a regional jet or a turbo prob reports severe turbulence, we can safely disregard these reports since our aircraft is larger and heavier than the other aircraft, it is inherently more stable through these conditions. The most important thing when flying through any conditions worse than chop, I.E. light turbulence or greater, is controlling your airspeed. The Airbus makes this very simple because it has a fantastic autopilot with auto thrust as well. We do have to know the speeds which to fly during these conditions, they are considered limitations of the aircraft. Turbulent air penetration speeds for the A320 series is: Below FL200 - 250 knots, FL200 to FL310- 275 knots, above FL310-.76Mach.
DashTrash 2
Some of those RJ's probably have a higher wing loading than your A320 giving them a better ride in turbulence. CRJ-200s are fairly high. I wouldn't disregard those reports at all.
houtxpilot 1
I didn't say I disregarded them, I said we are allowed to disregard them. Anytime anyone reports Severe Turbulence, it gets my attention, because it is rare. I have 5000+ hours and have only been in severe turbulence once, and have never experienced nor met anyone who has experienced Extreme turbulence.
Robert Hepler 2
I have worked many that have. You can absolutely hear the fear in a pilot's voice at these moments.
DashTrash 1
I gotcha.
Sounds like most of the people who have encountered Extreme turbulence might be in the graveyard.
Bill Watson 1
A buddy of mine who is a FE in a C5 encountered "severe" turbulence for the first time over in the Afghanistan the other day. They did a 180 and all other military traffic was turned around due to both the size (!!?) and severity of the storm.
Notably, this was the first time in 10 years my buddy ever felt compelled to share any flying experiences. I had to laugh, "yes, that sounds like severe turbulence".
Thank you for the insight!! :)
Matt Hall 1
Good explanation. Thanks for taking the time to share.
smsatgnv 1
Thanks for the article. Please keep them coming.

During the summer, I book morning flights to avoid the afternoon thunderstorms.
crk112 1
Nicely done!

lol FOWL weather ;-)
Michael Reedy 1
Great article with good info for both business and personal travelers.
thank you.
Ralph Addison 1
Aircraft must avoid thunderstorms as well as the surface conditions they produce. In terms of wind shear, pilots avoid both taking off and landing during such conditions. Yet flying out of Miami to Dallas, the pilot made the decision to fly during a terrible thunderstorm. What a ride. I think the pilot took way to many risks with over a hundred passengers to take us into that storm. And when we got to Dallas, they had freezing rain, so we couldn't land.
Why are pilots given the authority to make such a critical decision?
Jackson Berry 1
Perhaps they had get-there-itis. If pilots shouldn't have the authority to make such decisions, then who should?
I sure don't know who else should make the call. That said, I watch the radar closely and if they decide to board and boogie I don't have to get on. Haven't not boarded yet but if I really didn't like what I saw I would just stay put. I'm not an airline pilot but I have been a pilot long enough to know my comfort level.
Thomas Berman 1
Wait, did you say something like "working with your airline to change your departure time"? Have you flown recently? Try doing that with United. It is to laugh (or cry).
Fred Jones 1
I fly often and I was surprised at the early onset of thunder bumpers. I just came through Dallas a few days ago, and you would have thought it was July. I was delayed seven hours, but American personnel were great, well there was the one! The old DCs are still comfortable !
Mike Petro 1
"fowl" weather? It's raining chickens?
Daniel Fahl Staff Writer 1
Mike, you're absolutely in the "right" correcting me. There are a few grammatical errors in this article and it's my fault for rushing to get this out to our valuable readers. I saw an opportunity to publish this during the FOUL weather that plagued the Midwest last week and as it was, flying and posting this article at the airport was a challenge! Going forward, this will not be a common theme. Thanks for your feedback.
Mike Petro 1
Thank you for your reply Daniel; it wasn't supposed to be a criticism, it was just too funny to pass up. I hope you also read my follow-up comment!
Mike Petro 1
All kidding aside (those spellcheckers are fallible), this is an excellent article. As a fairly frequent flyer I've been victimized by thunderstorms a number of times; one time in Baltimore the aircraft had left the gate and we were required to sit on the taxiway for about an hour waiting for one to pass. That was OK with me as the winds were so strong it felt like we were experiencing in-flight turbulence! I don't want to know what it would feel like trying to fly through that!
will Thornton 1
Great article, very good info, thanks!
Very informative,appreciate it.


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