JulianUK
Topic Author
Posts: 105
Joined: Sat Apr 29, 2006 6:00 am

### Heights Of Thunderstorms And Flying Over Them

As an airline pilot if you are approaching a thunderstorm on the weather radar and you can visually see it, can you actually fly over it safely or are you not meant to judge the height of it and have to turn around it whatever? I just wonder whether pilots are allowed to guestimate the height of it and go over it?

joness0154
Posts: 650
Joined: Sat Nov 19, 2005 12:56 am

### RE: Heights Of Thunderstorms And Flying Over Them

You can pan the weather radar up and down to find the height of the cells. You can also check visually. Although with all the rising convection I don't know if I'd want to fly on top of them, some of the cells go up to 60,000+ feet. I'd rather fly around them.
I don't have an attitude problem. You have a perception problem

Goldenshield
Posts: 5017
Joined: Sun Jan 14, 2001 3:45 pm

### RE: Heights Of Thunderstorms And Flying Over Them

The general rule is 100 feet per 10 knots of wind, but with some storms, it doesn't leave much room, and going around is a better option.
Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.

JulianUK
Topic Author
Posts: 105
Joined: Sat Apr 29, 2006 6:00 am

### RE: Heights Of Thunderstorms And Flying Over Them

 Quoting Goldenshield (Reply 2):The general rule is 100 feet per 10 knots of wind, but with some storms, it doesn't leave much room, and going around is a better option.

So excuse me trying to understand but that is wind at your level and is this 100 feet horizontal outwards but not up?

LawrenceMck
Posts: 301
Joined: Sun Nov 27, 2005 3:45 am

### RE: Heights Of Thunderstorms And Flying Over Them

 Quoting Joness0154 (Reply 1):I'd rather fly around them.

I think thats what pilot's generally do. As on several occasions I have encountered thunderstorms and the Captain always announces that we are going to fly around it, I think it's much safer.

Lawrence
Love It To Live It

SlamClick
Posts: 9576
Joined: Sun Nov 23, 2003 7:09 am

### RE: Heights Of Thunderstorms And Flying Over Them

 Quoting Goldenshield (Reply 2):The general rule is 100 feet per 10 knots of wind

Didn't you want another zero in that altitude? You really think it is okay to overfly a towering cu at five hundred feet above it with a fifty knot wind?

I recall that a bizjet had its radome shattered by flying into a hailshaft in clear air a couple thousand feet above a TCU a few years back.

Highest I've ever actually seen was on the Gulf coast, near Mobile - Biloxi a few years back. Must have been fifty miles of red and purple returns and tops reported at seventy two thousand feet.

(he shudders)
Happiness is not seeing another trite Ste. Maarten photo all week long.

Posts: 415
Joined: Thu Jul 15, 2004 3:07 am

### RE: Heights Of Thunderstorms And Flying Over Them

I have been on airliners flying at ~35k going around cells that just stretched up into the atmosphere and didn't seem to stop...so yes, flying over is not really an option.

LH463
Posts: 68
Joined: Sun Apr 02, 2006 6:51 am

### RE: Heights Of Thunderstorms And Flying Over Them

I have actually flown over some nasty stuff over Kansas/ Oklahoma, en-route DEN STL, it wasn't an individual CB, but there were embedded thunderstorms. When they are visible I've never flown over one, only around or right through. On approach to San Jose, Costa Rica about 10 years ago in an AA 727 we flew right through hell, it was the worst aviation experience I've ever had.
For the most part pilots flying IFR just ask for a weather deviation wherever they can, so that they are able to weave in and out of these things. I think the AIM also says that pilots should avoid CB's by 20nm or more to avoid it's effects, such as wind shear etc. Please correct me if I'm wrong...

Regards,
LH463
Turning final...

meister808
Posts: 924
Joined: Sat Jan 01, 2000 11:45 am

### RE: Heights Of Thunderstorms And Flying Over Them

 Quoting SlamClick (Reply 5):tops reported at seventy two thousand feet

Jesus... I know that the tropopause gets significantly higher as you go south, but that is nuts. Updraft velocities in the core there were probably upwards of 20,000 feet/minute to get that kind of height, since anything that goes up into the stratosphere is pretty much carried there by momentum.

I can't imagine what the size of the hail that was coming out the bottom of that was... updrafts like that could keep something the size of a small car suspended for a while. Of course, I'm assuming the system was sheared, so there's a little less opportunity for hail development before things get blown out the side.

-Meister
Twin Cessna 812 Victor, Minneapolis Center, we observe your operation in the immediate vicinity of extreme precipitation

Goldenshield
Posts: 5017
Joined: Sun Jan 14, 2001 3:45 pm

### RE: Heights Of Thunderstorms And Flying Over Them

Oops. Typo there. Yes, it is 1000.

 Quoting SlamClick (Reply 5):Didn't you want another zero in that altitude?
Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.

mikkel777
Posts: 361
Joined: Thu Oct 03, 2002 1:15 am

### RE: Heights Of Thunderstorms And Flying Over Them

 Quoting Radelow (Reply 6):I have been on airliners flying at ~35k going around cells that just stretched up into the atmosphere and didn't seem to stop...so yes, flying over is not really an option.

This is taken one or two days after emily last year, EWR-MCO et FL380. Did a lot of S-turns to avoid TCU, so yes, airliners fly around the big cells

onetogo
Posts: 286
Joined: Thu Feb 02, 2006 1:40 pm

### RE: Heights Of Thunderstorms And Flying Over Them

Fantastic shot Mikkel777!

pilotpip
Posts: 2828
Joined: Fri Sep 19, 2003 3:26 pm

### RE: Heights Of Thunderstorms And Flying Over Them

Thunderstorms this time of year in the midwest regularly get over 30,000 feet. We had some today around STL that had echo tops on the radar of FL550, the summary on the WSI only goes to FL600. At that point, the only option is to fly around. If there's a line of them, that may not even be an option.

Let the diversions begin!!!
DMI

SlamClick
Posts: 9576
Joined: Sun Nov 23, 2003 7:09 am

### RE: Heights Of Thunderstorms And Flying Over Them

 Quoting Meister808 (Reply 8):Jesus... I know that the tropopause gets significantly higher as you go south, but that is nuts. Updraft velocities in the core there were probably upwards of 20,000 feet/minute to get that kind of height, since anything that goes up into the stratosphere is pretty much carried there by momentum.

Exactly. We tend to think of 'weather' as something that happens in the troposphere - the layer closest to the surface. But I think towering cu are so powerful and so 'well organized' that they kind of create their own atmosphere. You might have a 20000 foot per minute updraft carrying tons of hot, humid, unstable air and it will just punch right through the trop. The Gulf Coast and Florida thunderstorms are impressive for sure, but I prefer them, most days, to the lines you get in the midwest. There are days when there are only a couple of holes through the line from southwest Texas all the way to the great lakes. I love looking at them and that is something best done from a little distance back.

Coming up the east coast a few years ago at 370 and only about two thirds of the way up a cell near Savannah, we saw an MD-80 from another company fly past it, four thousand feet below us and only a mile or so outside the cloud wall. Right behind him it spit out a hailshaft at about our level. Maybe a hundred and twenty seconds or so difference and he would have flown right through it, and he never even knew it happened.

I could picture that MD captain smugly congratulating himself for making the bare minimum deviation for that cell while we swung twenty miles outside it. Personally I like to fly as smart as I can and save my 'luck' for when I really can't avoid using it.
Happiness is not seeing another trite Ste. Maarten photo all week long.

JulianUK
Topic Author
Posts: 105
Joined: Sat Apr 29, 2006 6:00 am

### RE: Heights Of Thunderstorms And Flying Over Them

Is there ever a time you might have to fly through something red on the weather radar? and if you did what can the passengers expect?

SlamClick
Posts: 9576
Joined: Sun Nov 23, 2003 7:09 am

### RE: Heights Of Thunderstorms And Flying Over Them

 Quoting Julianuk (Reply 14):Is there ever a time you might have to fly through something red on the weather radar?

Perhaps if you'd already violated basic safety rules and got yourself boxed-in somewhere. In all seriousness in that situation I might consider and emergency landing on an interstate highway as being an option of comparable merit to flying through a nasty thunderstorm.

 Quoting Julianuk (Reply 14):and if you did what can the passengers expect?

Well, here's one example of what they might expect:
http://www.airdisaster.com/cgi-bin/v...21980®=N6505&airline=Air+Wisconsin

Here's another:
http://www.airdisaster.com/cgi-bin/v...7®=N1335U&airline=Southern+Airways

Vertical currents (up AND down) even in a puny little CB that tops out in the mid-twenties can easily exceed the climb rate for any airliner you can think of. Rain can flame out engines and cause compressor stalls that will destroy them (Read Southern 242 above) hail can FOD-out engines, shatter windshields (1)

Turbulence is going to be 'severe' and may be 'extreme.' Now I've experienced severe turbulence which damaged my airplanes. We get broken bones and even the occasional fatality from just severe. I've never experienced 'extreme' and do not care to.

So, unless there was some extraordinary circumstance that put you in the red returns, expect to be disciplined by the airline, maybe violated by the FAA just as a minimum. Oh, and the flight attendants aren't going to like you anymore and they will remember your name forever! You'll have to get your own coffee just for starters.

(1) Also Southern 242. I have a DC-9 first officer's windshield out in my garage. It is about 1.5 inches thick, somthing like five layers of tempered, semi-tempered and acrylic and I don't remember what else. I'd bet that you could not make a hole in it big enough for you to crawl through if I gave you a hammer and an hour to bang away at it. And the hail blew it in!
Happiness is not seeing another trite Ste. Maarten photo all week long.

JulianUK
Topic Author
Posts: 105
Joined: Sat Apr 29, 2006 6:00 am

### RE: Heights Of Thunderstorms And Flying Over Them

Very impressive thanks for the answers - I have been on flights where the pilots says "erm things are going to get bumpy for a while so we will have to strap you in" - if they are not going near thunderstorms what else is causing it and how do they know....

SlamClick
Posts: 9576
Joined: Sun Nov 23, 2003 7:09 am

### RE: Heights Of Thunderstorms And Flying Over Them

 Quoting JulianUK (Reply 16): what else is causing it and how do they know....

Thunderstorms form in 'unstable' atmospheric conditions. That is, when hot humid air is lifted, it tends to accelerate upward. So if conditions are favorable for the development of thunderstorms, then the air is just generally bumpy. So you don't have to fly very near them to get at least a taste of this. Just about anywhere over the Florida peninsula on a summer day should do.
Happiness is not seeing another trite Ste. Maarten photo all week long.

Mir
Posts: 19271
Joined: Mon Jan 05, 2004 3:55 am

### RE: Heights Of Thunderstorms And Flying Over Them

 Quoting JulianUK (Reply 16):if they are not going near thunderstorms what else is causing it and how do they know....

In addition to what SlamClick said, there are weather reports and pilot reports that pilots get prior to flight. You could also ask ATC - they will occasionally query pilots as to how smooth the air is where they are, and thus build a good picture for the planes that are following, telling them where to expect turbulence, and how to avoid it if possible.

-Mir
7 billion, one nation, imagination...it's a beautiful day

JulianUK
Topic Author
Posts: 105
Joined: Sat Apr 29, 2006 6:00 am

### RE: Heights Of Thunderstorms And Flying Over Them

I have seen ACARS reports with turbulence reports on them, is this automatically done by in flight systems measuring turbulence or does the pilots have to put in what the turbulence is they perceive?

pelican
Posts: 2430
Joined: Mon Apr 05, 2004 9:51 pm

### RE: Heights Of Thunderstorms And Flying Over Them

On most occassions we flew right above them.

Signed,
ex-Blackbird pilot

pelican

waterpolodan
Posts: 1609
Joined: Sun Feb 13, 2005 3:46 pm

### RE: Heights Of Thunderstorms And Flying Over Them

I don't know much about cloud formation, but are there any clouds that top out at 85,000+ Ft, which the blackbird is capable of? Also, I'd imagine anyone looking to get a first hand account of severe and probably extreme turbulence should go talk with the crews of the P-3's that fly into the hurricanes each year... I've seen footage as they fly around inside the eye, but I've always wondered just how rough it can get when they fly through the eye wall. Those planes are also relatively old and slow, they must have some extraordinary matinence crews to repair them after the beatings I assume they take.

fr8tdog
Posts: 120
Joined: Wed Feb 16, 2000 4:25 pm

### RE: Heights Of Thunderstorms And Flying Over Them

Thunderstorms are nothing that you want to play with. If you can avoid them, do it. A buddy of mine who was flying a F-16 in the midwest one day encountered a line of thunderstorms blocking his route of flight, thought that he could out climb and go over... Much to his surprise the line out climbed him by the time he reached Fl 500.

Avoidance or penetration depends on a number of factors,

1. what phase of flight are you in?
3. what does the radar signature look like?
4. what is the surrounding weather doing?
5. What is the speed and movement?
6. What are other aircraft reporting and doing?

#1- Altitude is a large factor on what you can expect with ride conditions, aircraft performance and type of precip.

Downdrafts are the strongest near the base of the storm. The greatest shearing activity is near the middle of the storm and widens vertically and horizontally as the storm grows in size. near the top at the base of the outflow is where the updrafts reach their greatest velocities.

Turbulence is a change in velocity and or direction in the motion of parcels of air. (the more radical the change is, over a given distance and/or altitude is an indicator of progressively stronger turbulence)

One factor of aircraft performance is ISA deviation. I have had it where running parallel to a front on the warm side and had a steady decrease of IAS due to rapidly rising ISA, only option is to go down in order to maintain performance on the aircraft.

#2. Experience- comes from the collaboration of knowledge and hands on participation. (A fighter pilot does not become a fighter pilot on reading alone.)

#3. Thunderstorms come in a multitude of shapes and sizes, is it long and narrow, round, oblong, or does it have multifaceted sides. How close are the contours on the radar? are they symmetrical? These are just some of the questions you are trying to answer while thinking what your plan of action is going to be.

#4. speed and movement has effects on how big and aggressive a thunderstorm will be.

#5. This is part of situational awareness. What is going on in the environment around you............. this will help you in determining what your actions are going to be.

My role as an airline Capt. is #1 operate as safely as possible.
Tied with #1 is to try and give the best ride to the passengers as possible.
(they pay my wage  )

Fr8tdog

spudsmac
Posts: 253
Joined: Tue Feb 19, 2008 10:36 pm

### RE: Heights Of Thunderstorms And Flying Over Them

 Quoting Goldenshield (Reply 2):The general rule is 100 feet per 10 knots of wind, but with some storms, it doesn't leave much room, and going around is a better option.

I know it is really 1000ft/10kt of wind, but I started working on my CFI and as I'm teaching this, I start to question the reasoning behind it.

In AC00-24 section 2.e, it discusses overflight of a cell, but I still don't understand the relationship between the wind at the top and turbulence.

glen
Posts: 296
Joined: Thu Jun 30, 2005 4:43 pm

### RE: Heights Of Thunderstorms And Flying Over Them

 Quoting Spudsmac (Reply 23):I still don't understand the relationship between the wind at the top and turbulence.

A CB acts like an obstacle in the normal flow of the wind - thus generating turbulence like e.g. mountains. The higher the windspeed the bigger the turbulence caused by the cell.

However it's not wise to overfly an active cell to close, even with no or few wind. If the CB is still building up, its top is continuously rising and you could get trapped when flying over it.
"The horizon of many people is a circle with zero radius which they call their point of view." - Albert Einstein

Lexy
Posts: 1282
Joined: Wed Jun 07, 2006 10:05 am

### RE: Heights Of Thunderstorms And Flying Over Them

 Quoting Julianuk (Reply 14):Is there ever a time you might have to fly through something red on the weather radar? and if you did what can the passengers expect?

My wife and I flew from BNA to MDW back in May and we passed through a line of very severe thunderstorms over northern Indiana. They had produced some pretty bad hail in Illinois earlier that evening and did some major damage in Kansas hours earlier. We were on WN and were at the very back of the plane. She and I knew it would be a rough ride and we were ready, the crew was as well. When we got into the storm itself (we were flying at night), it became alot like daylight outside due to the lightning. Bumpy ride, VERY BUMPY ride, and lots of rain. Pax were a little nervous, crew was even showing signs of tension as well beacause their communication with the pilots was showing no way around it but to go through. We had a rought ride and finally broke out about 60 miles southeast of MDW and made a nice landing at the airport around midnight. I was obviously not in the cockpit, but I can promise you that what we flew through, was red, very red. It was intresting to hear what the crew was saying to eachother while flying through that nastiness.
Nashville, Tennessee KBNA

ngr
Posts: 172
Joined: Fri Apr 13, 2001 6:38 am

### RE: Heights Of Thunderstorms And Flying Over Them

I've experienced some really bad weather twice as a passenger. When I was younger (probably 12 or so) I recall flying in an MD-88 from ATL to CAE, and we were in or near thunderstorms the entire flight. Due to the short duration, we were at a maximum altitude of probably 20,000 feet. We were really being thrown around, and in hindsight, I'm not really sure why the flight wasn't delayed or cancelled.

More recently, I was on a flight that flew around the remains of a tropical storm. Most of the flight was uneventful, but during cruise we hit some rough turbulence. At the worst of it we "plummeted" for 3-5 seconds.

hodyoaten
Posts: 8
Joined: Sat Jul 04, 2009 1:37 am

### RE: Heights Of Thunderstorms And Flying Over Them

 Quote:A CB acts like an obstacle in the normal flow of the wind - thus generating turbulence like e.g. mountains. The higher the windspeed the bigger the turbulence caused by the cell.

That's not correct; barrier effects play only a very small part and strictly speaking would only occur around the fringes of the cumulonimbus tower. Turbulence can be quite severe within a storm that has weak winds throughout the entire troposphere, which is quite common in the summertime, particularly near DL's home turf.

The rising updraft is not anchored to the ground in any way. As it rises it encounters different wind fields, -usually- increasing, which causes it to move downwind. This results in a sheared updraft that looks tilted in a cross section.

Turbulence within the storm is caused by (1) direct contact of the plane with a buoyant, rising updraft, and (2) passage of the plane through areas where downdraft formation is occurring. The latter occurs through a combination of evaporation of air originating from the updraft, which increases the density of air where it occurs, and from loading as precip particles collide and coalesce and mechanically cause downward motion as they fall. All of this causes downward motion. Especially at the top of the storm this can be very uneven and can subject the plane to a pretty good range of vertical velocities in a small distance. It might be argued that very low relative humidity aloft is a better indicator of turbulence since this amplifies the formation of very dense, negatively buoyant air.

With regard to barrier flow effects, the assumptions with a mountain is that it is a solid object and it is unmoving. The rising updraft is has nearly the same density as the air around it and it indeed moves almost as quickly as the air around it (goes back to what I mention about tilted/sheared storms). The only "barrier flow concept" I've read about is rooted in a 1970s conceptual model of a thunderstorm, and it is largely dated. It's important to remember that strong winds aloft are strictly a ground-relative frame of reference. A layer with vertical shear (difference in winds with height) does have greater potential for chaotic motion, but this is a red herring -- any environment with strong winds aloft is more conducive to unstable, strong thunderstorms and this just amplifies the buoyant updraft and evaporational downdraft fields.

josekmlb
Posts: 195
Joined: Thu May 29, 2008 7:34 am

### RE: Heights Of Thunderstorms And Flying Over Them

http://flightaware.com/live/flight/DAL2021
This is the normal path from ATL-MLB.

Early today we had some strong storms and they flew around it.
http://flightaware.com/live/flight/ASQ5587

They do this alot during this time of year by floying around the storms here in Florida.

spudsmac
Posts: 253
Joined: Tue Feb 19, 2008 10:36 pm

### RE: Heights Of Thunderstorms And Flying Over Them

 Quoting HodyOaten (Reply 27):any environment with strong winds aloft is more conducive to unstable, strong thunderstorms and this just amplifies the buoyant updraft and evaporational downdraft fields.

Thank you!

ThirtyEcho
Posts: 1409
Joined: Tue Jan 01, 2002 1:21 am

### RE: Heights Of Thunderstorms And Flying Over Them

One of the surprises from the manned spacecraft program, and other very high altitude research, was that lightning not only strikes down and sideways but also strikes straight UP.

Better carry a solid rubber seat cushion for that.

wilco737
Posts: 7275
Joined: Sun Jun 20, 2004 12:21 am

### RE: Heights Of Thunderstorms And Flying Over Them

 Quoting ThirtyEcho (Reply 30):ightning not only strikes down and sideways but also strikes straight UP.

That's why we should circumnavigate the CB and not overfly it. Most of the times you cannot really fly above it anyway. Don't get too close to a CB, it can get nasty in there.

wilco737

murchmo
Posts: 101
Joined: Sun Sep 11, 2005 2:59 pm

### RE: Heights Of Thunderstorms And Flying Over Them

I have a different story...maybe this is rare so someone chime in if they've had similar experience. Coming back from a trip to DeltaConnection Academy I was flying ATL - LAX late at night. Over Texas there were thunderstorms but never a problem with the flight. I am aware the storms can reach 80000 feet but they can also be smaller. This was not only the best flight but also one of the best experiences of my life. Looking out the window with stars above and the rapid fire glows of the lightning in the clouds. It was so beautiful, and the smoothest flight. I think they were mostly north of us but I do remember looking downwards at them out the window.

I hope all of you get to experience this.
to strive to seek to find and not to yield

wilco737
Posts: 7275
Joined: Sun Jun 20, 2004 12:21 am

### RE: Heights Of Thunderstorms And Flying Over Them

 Quoting Murchmo (Reply 32): Looking out the window with stars above and the rapid fire glows of the lightning in the clouds.

I know what you are talknig about. That is incredible. It looks great. It is a great experience. The cloud can be seen completly during the lightning. It is just awesome.

wilco737

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