using available weather data to determine "VFR on top" possibilities

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Brad W

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I feel like I should know how to find this out, but I've gotta admit my skills and memory are rusty. So let's say the weather is some multi layered scattered/broken situation. You look up and see clouds at a few different levels...and even see some blue.

Observation data will tell you something like say for example few at 1,000, scattered 2,500, broken 7,000
...whatever it is....
How can a pilot determine if there's likely to be a wide enough layer up there to make a reasonable VFR flight?...
don't want to fly below 1,000 ft to stay below everything.... instead need to basically determine the tops of the 2,500 scattered layer for example

Are pireps the only answer? based on my experience it's unlikely to have enough pireps to be useful for this purpose.
 
aviationweather / gfa / products / clouds. It's a crappy interface since their latest refresh, and it's a coarse look, but it'll get you a good idea what kind of tops you could expect.

Better than parsing through skew-T potato.
 
Skew-t. Rucsoundings.noaa.gov is the best source I've been able to find. They're complex, but it's pretty easy to determine cloud layers.

Awc's cloud product is good, but it shows the highest and lowest level. Often there's a high status layer shown as tops.
 
Jim K said:
Skew-t. Rucsoundings.noaa.gov is the best source I've been able to find. They're complex, but it's pretty easy to determine cloud layers.

Awc's cloud product is good, but it shows the highest and lowest level. Often there's a high status layer shown as tops.
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The GFA product prioritizes the lower tops, so it's usable. See example of lower tops with cirrus above it:
1705194617446.png
 
hindsight2020 said:
The GFA product prioritizes the lower tops, so it's usable. See example of lower tops with cirrus above it:
View attachment 124342
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Fair. I maintain it often gives a false picture. For example, today at home it showed bases at 1500 and tops at fl220 at home, but based on pireps and skew-t, it was clear between about 3500 and 10k.
 
PaulS said:
You can’t know reliably. This is a classic situation where an instrument rating makes not knowing not a problem.
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Well, he's talking about VFR on top, so presumably he is already rated and on an IFR plan.
 
GeorgeC said:
Well, he's talking about VFR on top, so presumably he is already rated and on an IFR plan.
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PaulS said:
Doesn’t feel like that to me, maybe he’ll clarify.
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both are correct. I'm a very rusty instrument rated PPL
but the spirit of the question was meant to be VFR only flight
and when I made the post I was struggling to come up with wording for the title. I know it's not technically VFR on top. I was looking for short wording to define flying VFR over a cloud layer

What is this GFA product that hindsight2020 posted?

I guess I should learn about these Skew-T diagrams. I sure don't remember them being a "thing" back in the days I was active.
 
Brad W said:
but the spirit of the question was meant to be VFR only flight
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Things are are theoretically a little easier now with ADS-B in that you can see sky coverage, but even that may be stale and/or inaccurate, so I wouldn't bet on it. I'm instrument rated but my plane is not equipped, so, with few exceptions, I choose not to fly over bkn/ovc.

Even scattered fair weather cu can be sucker bait. I flew over a layer last summer, no big deal... then went to do the same after lunch and very nearly went VFR into IMC trying to get on top. It was later in the day=warmer temps=higher tops=less climb performance trying to get over the higher tops... duh. Ended up getting on top and then descending through the next hole since I'd had enough excitement.
 
PaulS said:
@scottd has written a book on using Skew T and is teaching an online class also. The book is awesome, I have not done the class yet, but it's on my list of things to do.

Here is a link to the class: https://www.avwxtraining.com/service-page/mastering-the-skew-t-diagram-1

His weather tools are awesome too. ezwxbrief.com
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Thanks for the plug Paul. Like the Weather Essentials for Pilots class that's currently underway, I expect this one will reach capacity before it starts in April.
 
PaulS said:
You can’t know reliably. This is a classic situation where an instrument rating makes not knowing not a problem.
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This needs an asterisk: * Icing can be a problem.
 
Pugs said:
Yep. They can provide a tremendous amount of information but it can be confusing but watch a couple Youtube videos and it becomes really easy to determine layers.
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FYI you can also view forecast soundings in Windy.
 
Aviationweather.gov is showing a solid ceiling of 1000 all day yet it is completely clear skies. What gives?
 
Chrisgoesflying said:
He does say "VFR on Top" which would indicate he's instrument rated. Maybe he meant to say "VFR over the Top" which is a purely VFR operation.
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I’ll bite! What’s the difference? (Beyond semantics)
 
Iflydogs said:
I’ll bite! What’s the difference? (Beyond semantics)
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VFR over the top is a VFR flight where you climb over a cloud layer maintaining VFR at all times. Of course you must have a hole to descend VFR to your destination. VFR on top, as mentioned, is a specific clearance on a IFR plan.

NOTE-

  1. When an aircraft has been cleared to maintain “VFR‐on‐top,” the pilot is responsible to fly at an appropriate VFR altitude, comply with VFR visibility and distance from cloud criteria, and to be vigilant so as to see and avoid other aircraft. The pilot is also responsible to comply with instrument flight rules applicable to the flight (e.g., adherence to ATC clearances).
  2. Although IFR separation is not applied, controllers must continue to provide traffic advisories and safety alerts, and apply merging target procedures to aircraft operating VFR‐on‐top.
 
Iflydogs said:
I’ll bite! What’s the difference? (Beyond semantics)
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Not much to add but since you quoted my specific post, I thought I'd answer as well. In a nutshell, one may take you through clouds, while the other explicitly prohibits you from ever entering clouds during the flight.
 
Thanks I think I get it. If I understand it correctly, if you can get down without going through clouds you are vfr? That is pretty much the rule I always follow, the distinction without a difference threw me.
 
Iflydogs said:
Thanks I think I get it. If I understand it correctly, if you can get down without going through clouds you are vfr? That is pretty much the rule I always follow, the distinction without a difference threw me.
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For what it's worth, in Canada you actually need a separate rating on your PPL for VFR over the Top. In the U.S. it's included with your standard PPL, just like night flight - separate rating in Canada but included in your PPL in the U.S.
 
Iflydogs said:
Thanks I think I get it. If I understand it correctly, if you can get down without going through clouds you are vfr? That is pretty much the rule I always follow, the distinction without a difference threw me
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You are not VFR because the weather is clear. You are VFR because you are not on an IFR clearance. But I guess if you feel being on an IFR flight plan and clearance is meaningless, I guess it’s a distinction without a difference.
 
I am just confused by the terms “VFR on the top” and “VFR over the top”. They sound identical. If I understand the conversation correctly, one is VFR and one is IFR, yeah? Here is an idea: call the VFR one “VFR on/over the top” and the IFR one “IFR on/over the top”. Much less confusing.
 
Iflydogs said:
I am just confused by the terms “VFR on the top” and “VFR over the top”. They sound identical. If I understand the conversation correctly, one is VFR and one is IFR, yeah? Here is an idea: call the VFR one “VFR on/over the top” and the IFR one “IFR on/over the top”. Much less confusing.
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1706659827775.png​

  • VFR over-the-top (OTT) refers to flying over top of clouds in visual flight, rather than with reference to instruments. This is usually done for brief amount of time to avoid weather or turbulence. The plane does not have to be under ATC control.
  • When an aircraft has been cleared to maintain “VFR‐on‐top,” the pilot is responsible to fly at an appropriate VFR altitude, comply with VFR visibility and distance from cloud criteria, and to be vigilant so as to see and avoid other aircraft. The plane is under ATC control and the pilot is also responsible to comply with instrument flight rules applicable to the flight (e.g., adherence to ATC clearances).
  • Although IFR separation is not applied during VFR on-top, controllers must continue to provide traffic advisories and safety alerts, and apply merging target procedures to aircraft operating VFR‐on‐top.
With VFR on top, the plane remains on an IFR flight plan and must remain in contact with ATC and comply with ATC clearances and instructions. With VFR over the top, the plane does not have to be on any flight plan at all and is not required to be in communication with ATC.

Does that help?
 
I would rather renew and update my IR chops than learn arcana like Skew-T, and I think it would be a better use of your time OP. Flirting with clouds is fun until it isn't. I'd rather have some recency of IR skills somewhere in my toolbox, even if not a full IPC signoff.

I use pireps more and more when I'm trying to suss tops out. The aviationweather product hindsight posted is pretty nifty too, but I don't entirely trust it yet. :)
 
Half Fast said:

  • VFR over-the-top (OTT) refers to flying over top of clouds in visual flight, rather than with reference to instruments. This is usually done for brief amount of time to avoid weather or turbulence. The plane does not have to be under ATC control.
  • When an aircraft has been cleared to maintain “VFR‐on‐top,” the pilot is responsible to fly at an appropriate VFR altitude, comply with VFR visibility and distance from cloud criteria, and to be vigilant so as to see and avoid other aircraft. The plane is under ATC control and the pilot is also responsible to comply with instrument flight rules applicable to the flight (e.g., adherence to ATC clearances).
  • Although IFR separation is not applied during VFR on-top, controllers must continue to provide traffic advisories and safety alerts, and apply merging target procedures to aircraft operating VFR‐on‐top.
With VFR on top, the plane remains on an IFR flight plan and must remain in contact with ATC and comply with ATC clearances and instructions. With VFR over the top, the plane does not have to be on any flight plan at all and is not required to be in communication with ATC.

Does that help?
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Thanks, honestly the terms sound the same but I understand the difference as explained, well done!
 
Iflydogs said:
I am just confused by the terms “VFR on the top” and “VFR over the top”. They sound identical. If I understand the conversation correctly, one is VFR and one is IFR, yeah? Here is an idea: call the VFR one “VFR on/over the top” and the IFR one “IFR on/over the top”. Much less confusing.
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You must have a lot of difficulty with aviation terms if you find this one is confusing. Thats too bad. There’s a lot of jargon in this world. What stage are you in with your training?
 
midlifeflyer said:
You must have a lot of difficulty with aviation terms if you find this one is confusing. Thats too bad. There’s a lot of jargon in this world. What stage are you in with your training?
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I generally agree with you on most things, but I have to call this one out. These are very confusing terms and unless you use them all the time, darn hard to remember. Similar to Movement vs Non-movement areas at an airport. You have an advantage as an instructor referring to them frequently. That helps with memorization. In 5 years since my PP I have had no need to refer to the movement area terminology. I know from the markings when I need permission to taxi vs not, but don't ask me which is which. The "on top" vs "over the top" is pretty much the same. Unless you have a need to use it frequently, there's not a lot in the terminology that is self explanatory.
 
Hang 4 said:
I generally agree with you on most things, but I have to call this one out. These are very confusing terms and unless you use them all the time, darn hard to remember. Similar to Movement vs Non-movement areas at an airport. You have an advantage as an instructor referring to them frequently. That helps with memorization. In 5 years since my PP I have had no need to refer to the movement area terminology. I know from the markings when I need permission to taxi vs not, but don't ask me which is which. The "on top" vs "over the top" is pretty much the same. Unless you have a need to use it frequently, there's not a lot in the terminology that is self explanatory.
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One is an IFR clearance that VFR pilots cannot experience and even seasoned IFR pilots may rarely actually say or hear. The other is something that VFR pilots can do every day of their lives without actually saying or hearing. It is easy to understand pilots (especially those without instrument ratings) getting lost in the jargon here.
 
Hang 4 said:
In 5 years since my PP I have had no need to refer to the movement area terminology.
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I don't think it's about being a CFI at all. Where we disagree is not the potential for confusion when you don't know, but the reality of widespread use of aviation-specific jargon. If we can't learn to understand and accept it, it's going to be a long term problem for us, especially when dealing with ATC (maybe fear of ATC is nothing more than an outgrowth of low language aptitude). Or, at least, one ends up joining the whiners whenever jargon gets changed. I still remember the hue and cry when "taxi into position and hold" morphed into the horribly confusing "line up and wait," (let alone when TCAs and ARSAs became Class Bs and Cs o_O o_O ).

On movement vs non-movement? In over 30 years of flying and 20 years based at a busy Class D, I don't think I have ever heard the phrase said over the radio. But I sure know the difference and I hope any pilot who heads into a towered airport knows it too.
 
midlifeflyer said:
On movement vs non-movement? In over 30 years of flying and 20 years based at a busy Class D, I don't think I have ever heard the phrase said over the radio. But I sure know the difference and I hope any pilot who heads into a towered airport knows it too.
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Right.

Movement areas are those where you need to have permission to move, and non-movement areas are those where you're free to move about as you like. Makes perfect sense, like clicking "Start" to shut down a PC.
 
Mxfarm said:
if your VFR on top, can you use VFR only, such as GPS for navigation?
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As I understand it, you're still on an IFR flight plan and have to abide by ATC vectoring, but you revert to VFR rules for altitudes and cloud separation and you're responsible to watch for traffic.

VFR over the top is just plain old VFR, except you can't see the ground. No ATC interaction required.
 
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