Skew T - usefulness

[apilotb]

I've been dabbling with skew T for a few months. I know it is useful for cloud tops and for understanding the atmospheric thermodynamics, but other than those two aspects, what is useful that is not already available from aviationweather.gov? Cloud bases, winds & temperature aloft and convective & icing potential are already covered by other products. Are LCL, LFC and CAPE numbers really that useful for flying?

I guess my main question is, if it is so useful why is it not part of aviationweather.gov? It is not discussed in the FAA's aviation weather handbook, nor is it covered in any of the pilot training syllabi.

 

[Ted]

I guess my main question is, if it is so useful why is it not part of aviationweather.gov? It is not discussed in the FAA's aviation weather handbook, nor is it covered in any of the pilot training syllabi.

Because it's more complicated than most pilots, including instructors, understand.

My personal uses for it are to understand cloud tops, layers, and then also what the temperature profile is like (i.e. predicting icing in the cloud).

Kent has used it for predicting whether or not there will be icing in a cloud that's below freezing, which I don't think it's a good use of. My personal flow chart with my experience has always been:

Are you in a cloud? -> Yes -> Is it below freezing? -> Yes -> There will be ice

 

[apilotb]

I've been dabbling with skew T for a few months. I know it is useful for cloud tops and for understanding the atmospheric thermodynamics, but other than those two aspects, what is useful that is not already available from aviationweather.gov? Cloud bases, winds & temperature aloft and convective & icing potential are already covered by other products. Are LCL, LFC and CAPE numbers really that useful for flying?

I guess my main question is, if it is so useful why is it not part of aviationweather.gov? It is not discussed in the FAA's aviation weather handbook, nor is it covered in any of the pilot training syllabi.

Also, everything of interest to piston airplanes is scrunched up at the bottom right corner. More than two thirds of the plot is for FL 180 and above. I haven't figured out a way to scale the plots to only show below FL 180.

 

[kgruber]

It is of limited use because of its poor format. I'm a pilot, not a Phd atmospheric science person.

 

[Skyrys62]

Is it below freezing?

Probably a silly question...but other than OAT gauge, is there a way to tell?

 

[JC150]

Moisture content is important too. Plenty of times I’ve taken my arrow into IMC below freezing and got no icing

 

[apilotb]

Moisture content is important too. Plenty of times I’ve taken my arrow into IMC below freezing and got no icing

LWC (Liquid water content) is not used in ROAB or in any forecast models as far as I know.

 

[bobmrg]

I like the visual presentation of temperature vs dewpoint vs altitude as a guide to potential clouds. Also, if you click on "Get text" you will see a winds aloft presentation without the 3000-foot gaps in the FB. I also check out the CAPE as one of my sources relative to convective activity.

Bob Gardner

 

[Ted]

Probably a silly question...but other than OAT gauge, is there a way to tell?

That's where the Skew-T comes into play, is that it (in my experience quite accurately) predicts OAT. But I'm generally looking at the OAT, yes.

Moisture content is important too. Plenty of times I’ve taken my arrow into IMC below freezing and got no icing

I've heard plenty of similar reports and I almost never have it happen to me. I guess I'm just lucky.

 

[apilotb]

Another problem I've had with skew T plots is that there are no legends and no measurement units. Just lines and numbers. Seems like it is not really made for general consumption.

 

[AggieMike88]

Another problem I've had with skew T plots is that there are no legends and no measurement units. Just lines and numbers. Seems like it is not really made for general consumption.

No, it isn't. As most sheeple really don't care about this info. They just want to know current temp, the high temp of the day, and if they need their umbrella.

However, the way that it is (and works) is one of the best representations of ALL of the very useful information that the population it's designed for wants.

Where are your complaints coming from? Do you seek more instruction on how to read and interpret the info? Are you wanting more tips/tricks to make it useful as a route planning tool as well as a single point observation?

 

[flyingcheesehead]

My personal uses for it are to understand cloud tops, layers, and then also what the temperature profile is like (i.e. predicting icing in the cloud).

Kent has used it for predicting whether or not there will be icing in a cloud that's below freezing, which I don't think it's a good use of. My personal flow chart with my experience has always been:

Are you in a cloud? -> Yes -> Is it below freezing? -> Yes -> There will be ice

If I've given that impression, that is my mistake. That isn't even close to the primary thing I'm looking at with the Skew-T, and I think only @scottd knows enough to truly read them that way! I'm still very much learning those aspects.

But, the SkewT does tell me how thick that layer likely is, and like Ted I've found it to be very good when it comes to temps aloft. It's quite good for predicting layers/tops as well, and that's what I probably use it for the most, even in summer. I'd rather cruise on top or at least between layers, even if there isn't any icing, so even for summer flights with benign IMC I'll look at the Skew-T when choosing my cruising altitude.

I did launch on my flight the other day anyway, but it reminded me of flying 10+ years ago, trying to figure out where the tops were using PIREPs and other products, none of which are nearly as good at the Skew-Ts.

Moisture content is important too. Plenty of times I’ve taken my arrow into IMC below freezing and got no icing

Yup. I wish I was better at being able to determine moisture content. I ended up doing a slam dunk approach the other night due to the uncertainty over the atmospheric profile and it turned out that there were two layers instead of one thick one. I picked up some ice in the top layer, but not the bottom one. Both were below freezing.

 

[PaulS]

Skew ts are on my list of things to learn. Lot's of useful info, inversions, freezing temps, bases and tops and most importantly in my opinion, a graphical picture of instability for TS prediction. It's a fairly complicated presentation but I think learning to read certain information on it will be very useful. It is a log graph, so someone who hasn't been exposed to those may have a steeper learning curve, but should be able to learn it. Scott Dennstaedt has a pretty good presentation on how to use them, so I'm told. He's said in the past, that the Skew t is a useful piece in gathering weather information. I plan to take his course as soon as I finish up my IR.

 

[AggieMike88]

Skew ts are on my list of things to learn.

@scottd, Scott Deanstaedt, has a really good introductory video about the Skew-T diagram.

 

[Skepilot]

Rather than SkewT charts, I prefer the Vertical Weather Profile that Aerovie provides. It uses the same underlying sounding data upon which SkewT charts are based, but presents it in a format I find to be more intuitive for pilots. If you’re planning a trip, you would have to look up dozens of SkewT charts along the way to paint the same mental picture that Aerovie shows in one view. Great for finding cloud tops, freezing level, icing and turbulence along your route in one glance.

 

[AggieMike88]

Rather than SkewT charts, I prefer the Vertical Weather Profile that Aerovie provides.

For compare and contrast purposes.... Here is what WeatherSpork shows for same route. It too is using the underlying data from Skew-T.

 

[AggieMike88]

If you are already a subscriber to @scottd's WeatherSpork or www.avwxworkshops.com, be it known that he not only has some good intro material to the Skew-T, but many teaching modules that incorporate the Skew-T into the material. This way you get to see the diagram "in action". One such is this one...

 

[chartbundle]

I like Windy(.com) as a semi-friendly interface to Skew-T type data especially for visualizing larger areas. Then off to the actual Skew-T when needed for details.

 

[AggieMike88]

I like Windy(.com) as a semi-friendly interface to Skew-T type data especially for visualizing larger areas. Then off to the actual Skew-T when needed for details.

I'm also a fan of Windy.

It has been fun and interesting to see the development of useful weather products over the past 5-7 years. From items where you need to be an NWS expert to interpret to current offerings that quickly provide both the basic "surface level" stuff and easy access to the deeper level items when that's needed.

 

[Todd82]

It is of limited use because of its poor format. I'm a pilot, not a Phd atmospheric science person.

I'm only a BS atmospheric science person and I get it

And yeah I'm a BSer too but that's besides the fact.

 

[Ronnie Godfrey]

This is something I’d love to learn more about. Scott, do you have dates for that webinar yet?

 

[Ted]

If I've given that impression, that is my mistake. That isn't even close to the primary thing I'm looking at with the Skew-T, and I think only @scottd knows enough to truly read them that way! I'm still very much learning those aspects.

But, the SkewT does tell me how thick that layer likely is, and like Ted I've found it to be very good when it comes to temps aloft. It's quite good for predicting layers/tops as well, and that's what I probably use it for the most, even in summer. I'd rather cruise on top or at least between layers, even if there isn't any icing, so even for summer flights with benign IMC I'll look at the Skew-T when choosing my cruising altitude.

I did launch on my flight the other day anyway, but it reminded me of flying 10+ years ago, trying to figure out where the tops were using PIREPs and other products, none of which are nearly as good at the Skew-Ts.

I may have misunderstood what you had said, then. My recollection was you saying you had used Skew-Ts to try to figure out which clouds in the winter (and somehow there was an implication that those clouds would be below freezing) wouldn't have ice in them. Then you took off in the DA40, got ice in it, and were surprised. This was some time ago and I've had 3 kids since then, so my memory may be off a bit.

For practical purposes, my flow chart is what I think everyone should follow. Is there a cloud? Is that cloud below freezing? If yes to both, there will be ice.

Now, where I've used Skew-Ts very well is to find a temperature inversion where it's above freezing in a cloud at a particular altitude, and go along just fine ice-free. But it was +something C. As with anything where there may potentially be icing, having your outs figured out is important, and knowing the limitations and capabilities of your aircraft.

Funny thing about flying up in the flight levels now is that ice is basically an every flight occurrence. Now, it's typically not something that's concerning, but it does get to be an inconvenience because even a bit of ice can reduce your cruise speed pretty significantly. I find I put a lot more effort now into staying out of clouds for this reason.

 

[flyingcheesehead]

I may have misunderstood what you had said, then. My recollection was you saying you had used Skew-Ts to try to figure out which clouds in the winter (and somehow there was an implication that those clouds would be below freezing) wouldn't have ice in them. Then you took off in the DA40, got ice in it, and were surprised. This was some time ago and I've had 3 kids since then, so my memory may be off a bit.

I think the point I was making there must have been that clouds below freezing don't always mean ice, and that ice can be very localized - Because the only time I ever picked up any in the DA40 was descending through a layer where I picked up just a bit, where climbing through the same layer 15-20 minutes earlier was ice free.

Kids must do something to memory, because I can't even remember if I knew what a Skew-T was at that point.

 

[apilotb]

No, it isn't. As most sheeple really don't care about this info. They just want to know current temp, the high temp of the day, and if they need their umbrella.

However, the way that it is (and works) is one of the best representations of ALL of the very useful information that the population it's designed for wants.

Where are your complaints coming from? Do you seek more instruction on how to read and interpret the info? Are you wanting more tips/tricks to make it useful as a route planning tool as well as a single point observation?

I am quite familiar with the science behind skew-T. That was not my point. I am trying to understand the overwhelming connection to aeronautical decision making that is not already covered by other standard aviation products. I am also curious why it is not part of any flight briefing or in any FAA books if it is as useful for flight as it is being claimed to be.

Information also seems expensive to come by. The skewT workshops are the most expensive modules on avwxworkshops. Paying several hundreds dollars for a couple of videos when the connection to ADM is unclear to begin with seems a bit extreme to me, when the underlying data itself is largely paid for by the government.

 

[AggieMike88]

I am quite familiar with the science behind skew-T. That was not my point. I am trying to understand the overwhelming connection to aeronautical decision making that is not already covered by other standard aviation products. I am also curious why it is not part of any flight briefing or in any FAA books if it is as useful for flight as it is being claimed to be.

Information also seems expensive to come by. The skewT workshops are the most expensive modules on avwxworkshops. Paying several hundreds dollars for a couple of videos when the connection to ADM is unclear to begin with seems a bit extreme to me, when the underlying data itself is largely paid for by the government.

This all sounds like something that @scottd is best able to answer

 

[olasek]

Did you guy notice that SkewTLogPro stopped working very recently, it gives you error message that weather data is not loading ...
I just found out it is due to government shutdown - certain weather data that SkewTLogPro needs is no longer available from NOAA.

 

[Skepilot]

Did you guy notice that SkewTLogPro stopped working very recently, it gives you error message that weather data is not loading ...
I just found out it is due to government shutdown - certain weather data that SkewTLogPro needs is no longer available from NOAA.

Yep, and that's another reason why I like Aerovie's Vertical Weather Profile. It still works even during this government shutdown!

Someone else mentioned that it doesn't give you lapse rate, but that can be easily figured, and there are other ways to gauge stability.

 

[Skepilot]

Not sure why you'd want to do all that figurin' and gaugin' when the Skew-T gives it to you instantly. Would like to hear specifically how you'd do this figurin' and gaugin' to determine if the temperature profile has a mountain wave or stratocumulus cloud signature? Or nonconvective low level wind shear signature? How do you know if there's a risk of low-topped convection or the potential height of a cumulus cloud deck? Where's the haze layer top out? All of this is easy to see instantly on a Skew-T.

No need to get snarky or defensive. I understand, you have products and services to sell, I'm just saying there's more than one way to get the information necessary to safely plan a flight. In your example above you mention how you used Skew-T to determine a turbulence layer was thin. You could see the same thing using the turbulence overlay on any number of apps. Back in the day we could use Lifted Index / K-index to gauge stability. But newer weather products and presentations have made that obsolete. No, I'm not saying Skew-T is obsolete, I'm just saying it's not a primary (or even secondary) tool that most professional pilots regularly use.

Look, I know I'm not going to out-meteorology you, your signature says you're a meteorologist! I just know that, of all the training departments at the multiple major airlines, cargo airlines, corporate aviation departments I've flown for or flight schools I taught at, none of them emphasized Skew-T. None of the chief flight instructors, chief pilots, line-check airmen, APD's, etc. at any of those operations. I guess they're all just a bunch of dummies? My airline has its own meteorology department with its own meteorologists. I can access their webpage which links to all of the wx products that they use. No Skew-T. Why? I get it, you're smarter than all of them, too.

By all means, sell your products & services. Just don't oversell it.

 

[flyingcheesehead]

Look, I know I'm not going to out-meteorology you, your signature says you're a meteorologist! I just know that, of all the training departments at the multiple major airlines, cargo airlines, corporate aviation departments I've flown for or flight schools I taught at, none of them emphasized Skew-T. None of the chief flight instructors, chief pilots, line-check airmen, APD's, etc. at any of those operations. I guess they're all just a bunch of dummies? My airline has its own meteorology department with its own meteorologists. I can access their webpage which links to all of the wx products that they use. No Skew-T. Why? I get it, you're smarter than all of them, too.

And I wouldn't be surprised if those meteorology departments are using Skew-Ts. But if you have a department, your pilots don't need to know it. They can just say "Hey, can I go?" And frankly, there's not much that keeps the big iron from moving. IMO, the Skew-T is much more useful for us flivvers that don't have our own meteorology departments and have to make our own decisions...

 

[bbchien]

Amen to the preceding. What most are upset about is that there is a investment you have to make. Pilots don’t like to spend time nor money on education...apilotb sez as much. Way back when Scott was on CD format I bought all 3 for ~297 iirc.

I couldn’t see being a CFII without teaching knowledge of this tool. And it makes the weather brief very, very quick. AggieMike’s post yesterday about 3pm- that’s a very saturated cold layer with very clear tops. That layer is full of ice (slope is to the right) Not a 767 problem, but it is for most cirri....

About eight years ago some philistine on the red board chastised me for not teaching them for free on the board. But to “get” parcel theory you need good graphics. All of my IR Stu’s “get it”, they don’t get signed in off without it. Otherwise they will join the ranks who can’t stand FSS’ droning about VFR not advised and airmen zulu for icing...and then fly into significant ice...

But if there is going to be a “warm nose” out there, i’ll be in it, even with FIKI. Heck, it’s only a Seneca....no bleed air.....

Don’t leave home without ‘em....

 

[Skepilot]

And I wouldn't be surprised if those meteorology departments are using Skew-Ts. But if you have a department, your pilots don't need to know it. They can just say "Hey, can I go?" And frankly, there's not much that keeps the big iron from moving. IMO, the Skew-T is much more useful for us flivvers that don't have our own meteorology departments and have to make our own decisions...

I only mentioned the met department of my current airline because of the conspicuous absence of Skew-T log P charts on their list of met products. Believe me, the vast majority of my career I didn't have one. I started in GA and continue to fly GA today. "Big iron" is only the latest chapter in my 30+ year flying career.

What I tire of is the "I know something you don't know" type posts I often see in GA forums. The snarky post I quoted seems to have been subsequently deleted, but that didn't stop the same poster from ad hominems against those who simply offered different ways to get much of the same wx information by calling them haters and ignorant. Certainly doesn't make me want to buy anything from you.

I'm sure that one can mine some gems of meteorological knowledge from the Skew-T log P that you can't get from other sources, but pilots can also be perfectly safe using a variety of other met products. That's all.

 

[apilotb]

Amen to the preceding. What most are upset about is that there is a investment you have to make. Pilots don’t like to spend time nor money on education...apilotb sez as much. Way back when Scott was on CD format I bought all 3 for ~297 iirc.

Actually, pilots spend a great deal of time and money on training, ratings and recurrency, so the above statement is not a fair statement. But training and information are two different things. Information in today's 'information age' is generally low-cost or free. Look at all the FAA handbooks. They are superior to many commercial manuals, but don't cost you a single dime. People buy Sporty's or King's training software only because they are produced in a more appealing format easier to digest, not because they contain new information not found elsewhere. I have a PhD in physics, and although I'm not a meteorologist, I have spent a good deal of time to learn sounding charts. They are precise, quantitative, have a lot of computed parameters, very useful for forecasters, etc.. etc.. I get all that. I know and understand thermodynamics, vapor pressures, equivalent temperatures, virtual temperatures, wet bulb temperatures, convective temperatures, LCL, CCL, CAPE, CIN, LI, WBZ, LFC, EL etc.. etc... It is intellectually gratifying to know how all these fit together. But I have not seen concrete examples where they provided useful information for ADM not contained in other standard aviation products. Every time I see something that looks interesting on a sounding, I have not failed to see that same information in an airmet, sigmet or prog chart, with the only exception of tops. An unstable saturated layer with a stable cap on the skewT does not just get an airmet zulu, it also gets an SLD threat warning in the briefing. Pilots need information to make aeronautical decisions. The theory behind that information is for intellectual curiosity. Perhaps this is why the FAA does not produce skew T for pilots. My feeling is pilots who learn to use sounding charts feel empowered by knowing the underlying physics of weather, hence they imagine it to be more useful than it really is. In that sense, this is a bit of an emperor's new clothes syndrome. I am by no means an expert on this, but if I am going to spend a few hundred bucks, I need to know that I am going to learn something that I don't already know, and that it is going to be useful for ADM. Based on all of the books, videos and seminars I have seen on this topic, I remain unconvinced, and it seems the FAA agrees with me.

 

[MooneyDriver78]

The FAA still puts out weather information in teletype format, so I would not use them as a standard.
Skew Ts are great, but ...
1. They are still a forecast which means they may be wrong.
2. They are very localized, for flight planning I need the whole picture, the aerovie/gramet format is nice, aviation weather government website is good to.


Tom

 

[dtuuri]

I know lots of retired professional pilots and I doubt any of them ever heard of a Skew T. My opinion on flying knowledge is, "The more you know, the more you have to worry about," which isn't a bad thing, btw. For flights in well equipped aircraft flown by experienced pilots and also novices in marginally equipped ones I think a standard briefing with off-the-shelf weather products suffices. After all, the briefer gives us forecasts based on Skew Ts as well as a professional opinion based on far more weather analyses than any pilot has ever done for themselves. Both groups make go/nogo decisions on worst case scenarios. Where Skew T information shines, imo, is when marginally equipped aircraft are pressed to fly trips in conditions near their operational limits. Undertaking such flights safely requires better than usual tools and the knowledge to use them.

 

[apilotb]

Where Skew T information shines, imo, is when marginally equipped aircraft are pressed to fly trips in conditions near their operational limits. Undertaking such flights safely requires better than usual tools and the knowledge to use them.

Can you give a specific example of a flight in a marginally equipped airplane benefiting from skew T information?

 

[dtuuri]

Can you give a specific example of a flight in a marginally equipped airplane benefiting from skew T information?

No, because I am not able to read Skew Ts. If I were to try fly non-deiced or minimally deiced airplanes during the northern winter months, on a demanding schedule, though, I'd learn about them and use them in the expectation of increasing my dispatch rate.

 

[flyingcheesehead]

The FAA still puts out weather information in teletype format, so I would not use them as a standard.

Fair point... And to some extent, the Skew-T is a bit overly weather-geeky, so the FAA may never adopt it. That doesn't mean it's not a useful tool for pilots.

I know lots of retired professional pilots and I doubt any of them ever heard of a Skew T.

So what? That proves absolutely nothing in terms of usefulness. Again, they have meteorology departments that probably ARE using Skew-Ts. I don't have a meteorology department, so I look at them myself. They also are equipped to deal with nearly anything when it comes to icing, so it's going to be largely irrelevant to them.

My opinion on flying knowledge is, "The more you know, the more you have to worry about," which isn't a bad thing, btw.

My opinion is that the art of being a pilot is largely the art of making good decisions. The better the information you have to go into making those decisions, the better decisions you will be able to make.

 

[dtuuri]

So what? That proves absolutely nothing in terms of usefulness.

It proves they weren't needed... because:

They also are equipped to deal with nearly anything when it comes to icing, so it's going to be largely irrelevant to them.

My opinion is that the art of being a pilot is largely the art of making good decisions. The better the information you have to go into making those decisions, the better decisions you will be able to make.

Skew Ts seem to enable a pilot to cut closer to the bone. Without their more detailed resolution more trips would cancel because of less certainty, no? That's my impression from reading the accolades posted here and elsewhere. If they enable you to get more from your airplane without sacrificing safety, they're a winner. But if they entice you to take more risks, they aren't. So, you're still back to "the art of making good decisions." (IMO, from the outside looking in.)

 

[sarangan]

Amen to the preceding. What most are upset about is that there is a investment you have to make. Pilots don’t like to spend time nor money on education...apilotb sez as much. Way back when Scott was on CD format I bought all 3 for ~297 iirc.

I couldn’t see being a CFII without teaching knowledge of this tool. And it makes the weather brief very, very quick. AggieMike’s post yesterday about 3pm- that’s a very saturated cold layer with very clear tops. That layer is full of ice (slope is to the right) Not a 767 problem, but it is for most cirri....

About eight years ago some philistine on the red board chastised me for not teaching them for free on the board. But to “get” parcel theory you need good graphics. All of my IR Stu’s “get it”, they don’t get signed in off without it. Otherwise they will join the ranks who can’t stand FSS’ droning about VFR not advised and airmen zulu for icing...and then fly into significant ice...

But if there is going to be a “warm nose” out there, i’ll be in it, even with FIKI. Heck, it’s only a Seneca....no bleed air.....

Don’t leave home without ‘em....

The national weather service uses some of the most heavy lifting supercomputers in the world. AWS has icing forecasts including intensity levels. I would not try to outguess their forecasts using a Skew T and improvised techniques. That would be a liability issue for me as a CFII.

I use a Skew-T for estimating smooth ride altitudes and for cloud thickness. Not much else. I do not make a go/no-go decision based on it.

Parcel theory is not a "theory". It is just an ascent of an air mass. I don't see what there is to "get" about it. If you know how a hot air balloon flies, you know parcel theory. Calculated parcel values have a lot of assumptions and built-in approximations. Dry adiabatic rate is not really dry because no air is truly dry. That is why we have virtual temperatures. Supersaturation is not captured by any parameter, which is critical for icing. There are many subtle details. It is intended for atmospheric science. If someone wants to tinker with skewt that's fine and great, but I would not recommend any of my students to make a flight decision based on it.

We lose pilots every year because they ignored the official advisories and flew into adverse conditions. No one died because they failed to consult a skew T.