Determining Cloud Tops

AggieMike88

AggieMike88

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The original "I don't know it all" of aviation.
Today's weather (rain, 600-1000 ft ceilings, light to moderate wind) got me wishing I was training for my IFR since it would have been a good day for it.

It also got me wondering how how you figure out where the top of the clouds would be. I'm thinking the Skew-T applies here, correct? If so, what am I looking for in the temp and dewpoint lines to answer this?
 
When I took ground school I asked this question after we talked about how to calculate the altitude of the observed cloud base. The answer I got was that there wasn't a similar calculation for cloud tops.

A google search led me here, though: http://weather.aero/tools/desktopapps/flightpathtool

The Flight Path Tool can overlay multiple fields of interest: icing (probability, severity, and super-cooled large drops), turbulence potential, convective diagnosis and forecast, ceiling, visibility, flight category, winds, relative humidity, temperature, radar (base and composite reflectivity), satellite observations (visible, infra-red, and water vapor wavelengths), AIRMETs and SIGMETs, METARs, TAFs, and PIREPs.


All 3D data can be sliced horizontally at selected flight levels or vertically along a flight path. All data can be animated in time.


The tool lets you zoom in to any location on the globe. It automatically switches to the most appropriate projection for the viewed area. High-resolution basemaps show selectively more detail as you zoom in.


In addition to the vertical cross sections along your flight route, the Flight Path Tool allows you to generate meteorograms of observed and forecasted conditions for any METAR or TAF surface station.


Preferred views can be saved for quick recall later.
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edit: the tool linked at that site doesn't work for me. Not sure if it's the extremely slow speed of my internet or not, but your mileage may vary. :redface:
 
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You can also check the "FA" (Area Forecast) on the NOAA website for your region.
 
This has always puzzled me. I have yet to find a good source for info on tops. XM weather has an overlay, but it is wildly inaccurate. Ask me how I know. :rolleyes:
 
AggieMike88 said:
Today's weather (rain, 600-1000 ft ceilings, light to moderate wind) got me wishing I was training for my IFR since it would have been a good day for it.

It also got me wondering how how you figure out where the top of the clouds would be. I'm thinking the Skew-T applies here, correct? If so, what am I looking for in the temp and dewpoint lines to answer this?
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If you look at the skewT, I believe you're looking for where the temp dew point lines diverge by more than a few degrees. That suggests that the dew point is decreasing more rapidly than temps and condensation will no longer occur.

Admittedly I'm pretty new to reading these things in any detail so your mileage may vary.

Here is a good link - http://www.ssa.org/myhome.asp?id=141&mbr=3981940746&show=blog

It's soaring focused but has a ton of great info.
 
scottd said:
There are several formulas to calculate the cloud base
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The easy formula for cloud base is (temp - dewpoint)/4.4 x 1000

You're right its not always accurate but will at least get you in the ballpark.
 
I suggest using Skew-T diagrams from the RUC/RapidRefresh site. It is important to remember that these are the uninterpreted output of forecast models so treat them appropriately. Look for the points where the temperate and dewpoint lines diverge.

PIREPs are your best source of information about current conditions (and this is also a good reason to take the time and give a PIREP, something I always wish I was better about myself).
 
scottd said:
That describes only how to determine tops for warm stratus. Doesn't work for cumuliform or cold stratus clouds.
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Thanks Scott. How would you evaluate tops for the latter? Cumulus would be capped by inversion or otherwise could go way up? No idea about cold stratus.

Any additional insight would be welcomed!
 
Scott; When we get to that point in your seminar, you might remember my question here and use as an example.

The thought be hind asking was for filing an IFR flight plan if I was to launch during this precipitation and cloud event. If I could determine where the top of the cloud deck is, I could possibly plan on filing a cruise altitude that put me VFR on top.
 
1. Climb into cloud
2. Note altitude when exiting cloud top.
 
Like was said, PIREP is probably the most reliable provided it was recent. Tower may be able to provide that for you real time, but obviously for flight planning purposes you would need to get it from another source.

Another one I use frequently with fairly accurate results (at least +/- a few thousand feet accuracy) is the IR sat imagery on the ADDS site. You see where the highest tops are in your area, denoted by color, and then determine how high that is by using standard temp lapse rate given your local surface ambient temp. Not an exact science by any means, but it will give you a ballpark estimate. Probably a little more useful in the FL's than down low just due to less standard vertical temp spread below those altitudes, but it is a decent tool IMHO.
 
There are so many variables that exist. I've had PIREPs that have been very wrong because of a cloud top that is varying tremendously as I keep flying. I ended up at 15,000 ft once from that when tops were reported at 11,000.

I'll normally look at skew-Ts and area forecasts. That will give me a rough idea, and then ask for local PIREPs while I'm flying.

Normally I only care about tops if there is a potential for icing. Otherwise, more actual is more better. :)
 
Geico266 said:
That was his overhead break & zooom! One post and we never see him again! :rofl:
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This forum moves to fast :).... thanks for the welcome, I should probably change my screen name to RV 10 I recently sold the 8a and am flying a 10...or better yet purchase a 8... I miss that plane.
I know Mike, I'm sure he wont mind the thread drift. :)
 
tecprotb said:
This forum moves to fast :).... thanks for the welcome, I should probably change my screen name to RV 10 I recently sold the 8a and am flying a 10...or better yet purchase a 8... I miss that plane.
I know Mike, I'm sure he wont mind the thread drift. :)
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Don't mind the drift one bit.

Just give me a ride in the -10 and we'll call it even!!!
 
Scott, I see you have a couple of workshops coming up, unfortunately those dates aren't going to work for me. You wouldn't have anything scheduled in the Denver area this winter by chance? If not, I'll make sure I make the one in Minneapolis on May 31st.
 
scottd said:
Yes, the program in Houston on the Skew-T is just about the same as the one in KC. So, hopefully it'll be a good review for you.
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I'm also thinking about doing the premium workshop you have available in preparation for the class. In KC, I got the basics easy enough, but when you started in on the deeper parts of what was shown and how to apply it, I wasn't grokking and subsequently don't recall much of what you shared then.

The premium workshop plus the Houston program should do the trick.
 
scottd said:
What about non-precipitating cumuliform clouds (towering Cu)?
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Well, I also have a stormscope to detect any lightning when relevant. As far as general bumps, good pilots should be comfortable with turbulence and practice dealing with it.

Since you're trying to nitpick my simple point that most pilots don't get enough actual IMC and should seek it out rather than avoid it (I'm looking at the sky today and thinking I should leave work to go fly), I'll note that obviously I pay more attention to the weather and have an idea of what's going on and what to expect as far as various hazardous conditions.

My general point for Mike is to answer his question, but also give him the note that, especially as an IFR student, he should know how to find tops and also seek out actual IMC.
 
Ted DuPuis said:
My general point for Mike is to answer his question, but also give him the note that, especially as an IFR student, he should know how to find tops and also seek out actual IMC.
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I agree I'll get that how-to information once I start digging into the knowledge and practical. Today it is more of a "curious pilot looking out the window" request for the answer.
 
I'm a happy user of Scott's training material. His workshop on SkewT charts is worth its weight in gold.
 
Here's an example:

The Moline Illinois airport is overcast with stratus clouds today:
[FONT=Monospace,Courier]KMLI 162052Z 27007KT 10SM BKN024 OVC031 11/06 A2994 [/FONT]

There is a PIREP: base 2700 MSL, top 5000 MSL
UIN UA /OV UIN/TM 1949/FL050/TP FA20/SK BASES 032 TOPS 050/RM ZKC FD

Below is a Skew-T. Look to see the altitudes where the red curve (temperature) and broken curve (dew point) kiss -- you expect a cloud layer there. The altitude for the top, however, is not exactly the top of the kissing zone, though -- it's a little higher, where the temp and dew point have diverged by about 3 degrees -- in this Skew-T that happens at about 2448 m MSL, which is about 7900' MSL.

So in this example, the Skew-T predicts a top at 7900 MSL, pirep was 5000 MSL.




131016213051.gif


There is more than one model for forecasts. Choose another model and you predict a top that's at 1933 m, which is about 6200' MSL.

131016214700.gif
 
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scottd said:
Dan,

Right now I don't have any plans to do one in Denver this year or next. Am looking at a location in Oklahoma for the spring. I'll have one in Charlotte and will likely do one in SoCal and the Northeast. So Minneapolis or Oklahoma might be your best option - but Minny is set at this point (I've ten local pilots that are already coming as a group which means that I will probably fill that one to capacity by early spring).
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What would it take to get those plans to change? Anything? Would absolutely attend if it was in Denver, otherwise I guess I'll keep an eye open for OK in the spring.

Steve
 
...and the top of the deck was at about 5,100 today :)

Pireps are great, if you have 'em. But you need to know your stuff esp. if they don't exist.
 
I would be interested in working with any of Scott's graduates around DFW to test the accuracy of the skills they learned in the class. The idea would be to pick a complex IFR day, using just the weather data Scott uses and nothing else to build a weather profile. I will use my eyes, radar, pireps, satellite, metars, knowledge of local weather patterns, and all of the basic pilot type weather tools. Then we'll go fly it and see how accurate either of us are.

I have no doubt that Scott with his skills and education can do a great job, I'm just wondering if it is possible to translate that to a student in such a short period of time.

It might be fun and that is the spirit of it.
 
Alexb2000 said:
I would be interested in working with any of Scott's graduates around DFW to test the accuracy of the skills they learned in the class. The idea would be to pick a complex IFR day, using just the weather data Scott uses and nothing else to build a weather profile. I will use my eyes, radar, pireps, satellite, metars, knowledge of local weather patterns, and all of the basic pilot type weather tools. Then we'll go fly it and see how accurate either of us are.

I have no doubt that Scott with his skills and education can do a great job, I'm just wondering if it is possible to translate that to a student in such a short period of time.

It might be fun and that is the spirit of it.
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I'd be interested in participating once next week's event is done. The email on my profile is functional if you wish to contact me.

This would be good practice of Scott's information and good exposure of how another IFR pilot preps and executes.
 
AggieMike88 said:
I'd be interested in participating once next week's event is done. The email on my profile is functional if you wish to contact me.

This would be good practice of Scott's information and good exposure of how another IFR pilot preps and executes.
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Sounds good.
 
Good point, Scott... I likely will take advantage of that. I remember how useful the one-on-one was during the spring. Doing it again will definitely be of value.
 
That's a great offer, Alex. I hope someone takes you up on it and you report the results.
 
scottd said:
Probably not stratus clouds given the variable base layers. Instead this is a stratocumulus deck
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I was there, and they looked like stratus clouds to me.

Anyway, one could get the impression that you use these forums as an advertising medium, and as a marketing ploy make the basic knowledge look overly complicated so that readers think they have no hope of doing anything useful without spending money on instruction. The spirit of this forum is offering a simple free explanation that's good enough to get the job done, and that's what I'm doing. Hopefully some reader found it useful.
 
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NoHeat said:
Anyway, one could get the impression that you use these forums as an advertising medium, and as a marketing ploy make the basic knowledge look overly complicated so that readers think they have no hope of doing anything useful without spending money on instruction. The spirit of this forum is offering a simple free explanation that's good enough to get the job done, and that's what I'm doing. Hopefully some reader found it useful.
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I've typically gotten that impression. Not that I think the training isn't valuable, but there's a reason he's been in my city twice and I have chosen not to go. It's not because I know everything. But I haven't been surprised by weather often, and I have even flown through small towering cumulus clouds. Oh the huge manatee.
 
Ted DuPuis said:
I've typically gotten that impression. Not that I think the training isn't valuable, but there's a reason he's been in my city twice and I have chosen not to go. It's not because I know everything. But I haven't been surprised by weather often, and I have even flown through small towering cumulus clouds. Oh the huge manatee.
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I haven't been surprised -- REALLY surprised -- by weather very often either. The main reason is that the last time I put enough stock in a forecast to be REALLY surprised was in 2005, not because I know everything or even have particularly good weather sense, outside of local patterns. If you always have plan B and plan C in mind and practice conservative ADM, you can go a long way with basic knowledge. More in-depth knowledge is still better. I've learned a fair amount from Scott's online workshops and I hope to learn more. Scott's services are extremely valuable as far as I'm concerned and I wish I could have attended his recent training in Cinci. If he schedules one in my city I will do anything within reason to make it.

It might be that the reason Scott makes weather seem difficult is that it is -- it's a lot more complex than most applications of physics, including I dare say the internal combustion engine. Despite that he's given a lot of folks on this board free advice many times. I don't get the impression he's holding out here any more than I do from Bruce. His products and services aren't free, but nothing of value is.

That reminds me, my membership on his site runs out this month and I've got to renew...
 
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