Cloud tops on Foreflight

[arb65912]

Gentlemen, where do I find clouds tops on ForeFlight? Thank you. Cheers, AJ

[Anthony Santanastaso]

Hi AJ,

I consider myself a regular user of ForeFlight, and after carefully looking through the application, I did not find a direct way of determining cloud tops. My assumption is that you would want to cross reference the observed weather reports with the available PIREPs that can be obtained through the Imagery tab. Once you have analyzed the trend information with the reported conditions, I would think that you can surmise a logical guess as to the cloud tops.

In a quick Google search, I found three websites in which you might be interested.

ADDS Experimental Flight Path Tool
http://weather.aero/tools/desktopapps/flightpathtool

e-WALL Observed Weather Conditions
http://www.meteo.psu.edu/~fxg1/ewall.html

Meteorologist and Pilot Chris Dunn's take on how to use the above links:
http://www.theflyingweatherman.com/Weat ... _tops.html

I hope that this helps!

Anthony

[arb65912]

Hi Anthony, thank you very much for the response and links. I will definitely take a look at them. More things to study. Cheers, AJ

[Anthony Santanastaso]

AJ,

I thought of something else that might help you in determining cloud tops. It only requires some simple calculation.

First, understand that the standard atmospheric lapse rate is 2 degress Celsius per 1,000 feet. I will revisit this a bit later.

Second, take a look at an observed weather report (METAR). Let's look at the METAR for KSTL.

KSTL 221751Z 25011KT 10SM OVC019 01/M03 A2997

Notice the temperature which is 1 degree Celsius.

Next, go to the NWS Aviation Weather website and take a look at a colorized Infrared display of the Satellite image.

http://aviationweather.gov/adds/satelli ... e&itype=ir

This will give you the temperature as reported at the top of the cloud layer. If you use the guide at the top, you can see that the temperature of the clouds nearest KSTL is approximately -8 degrees Celsius.

Find the difference between the METAR temperature and the satellite image: 1 - (-8) = 9.

Back to the lapse rate from before. Considering the standard rate of 2 degrees Celsius per 1,000 feet, let's divide the difference by 2 (9/2 = 4.5). This concludes that the top of the clouds is approximately 4,500 feet above the surface.

Remember the METAR? It told us that the base of the cloud layer was 1,900. Subtract the top (4,500) from the bottom (1,900) and that will give you an idea for the height of the cloud, which would be 2,600 feet.

In other words, once you enter the overcast layer at 1,900, you will have to fly another 2,600 feet until you reach the top of the cloud layer.

Assuming my math and understanding of the matter is not incorrect, this should help you determine the tops of clouds based upon observed information.

[Keith Smith]

The Skew T Log P chart is not taught in any FAA material, which is a tragedy. I learned about it just a few years ago, shortly after getting my instrument rating. It is an incredible tool.



This chart shows an expectation of there being solid cloud cover from around 8k up to FL200 (where the thick temperature (red) and dew point (blue) lines come together).

I use the Skew T Log P for detailed flight planning, but it's not easily accessible during flight or from ForeFlight.

Cloud tops are not part of the standard weather reporting tools (METAR/TAF), so it's not as easy to get hold of this information through those standard sources.

You can access this tool at http://rucsoundings.noaa.gov. For IFR pilots, it's a must have, IMHO, along with sufficient training on how to use it. Scott Dennstaedt has a site called AvWxWorkshops (http://avwxworkshops.com) which has excellent training on this tool, and many other topics. I purchased one of his courses on this topic and found it to be tremendously helpful. For VFR, you can get by without it, I suppose, but on the other hand, it's never too early to start using the tool and building an understanding of how the atmosphere works.

[Anthony Santanastaso]

Cloud tops are not part of the standard weather reporting tools (METAR/TAF), so it's not as easy to get hold of this information through those standard sources.

Keith, can't you (as a simple and quick calcuation) calculate it through the use of a METAR and Satelitte Image like my post above yours which takes into account the standard atmospheric lapse rate? In that sense, you can use a more conventional means in order to calculate a rough idea of the vertical structure of the cloud layers.

[Keith Smith]

Indeed you can, however the two problems the arise are:
1) as can be seen from this chart, the 'standard lapse rate' is frequently disregarded by the atmosphere. Just today, in fact, I took off with surface temps of -1, while it was +6C up at 4000ft.

2) the RUC Soundings site gives has forecasting abilities whereas satellite imagery is past and present data only afaik.

Lastly, looking up ruc soundings for multiple points along a proposed flight track for multiple periods of time is quick and easy with the RUC tool. I'd argue that this is simpler and quicker than the satellite imagery technique. As complex as the Skew T Log P appears at first glance, obtaining the bases and tops is very simple. You can also determine if there are going to be multiple layers, and what each thickness is going to be.

[Anthony Santanastaso]

Ah, that's right Keith. I forgot to take into account atmospheric stability. I suppose to use that method you would have to first evaluate the stability of the atmosphere (actual lapse rate).

I'm not familiar with the resources you presented. I look forward to checking them out!

[arb65912]

Gentlemen, thank you for a great replies.
As per last Keith's response it seems that RUC Soundings is the way to go.
As a total newbie at this subject, I would like to ask a question.
Would it be just as easy as plotting few Soundings along the route and " see" the clouds tops along the route where red line gets close to the blue one which is where the solid clouds are?
Cheers, AJ

[Keith Smith]

Where the three red and blue lines come together (starting from the bottom), that's going to be the bases. Where the line separate, that will be the top for that layer.