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Weather (cloud top estimation)

bnicolette

By bnicolette
in Miscellaneous Aviation Talk

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bnicolette Veteran

bnicolette

Posted
Posted

Thought I would start a new thread for this one.


Winter and cold clouds are fast approaching us here near Pittsburgh and I don't have TKS.  Obviously, we have great ways to determine cloud bases.  Does anybody have a good source for approximating cloud tops?  Other than a UA?


I have played around with the ADDS flight path tool and they try to estimate them via humidity and the couple times that I actually paid attention to it this summer, it worked out pretty fairly over my commute to Wilmington, DE. (185nm trip)  Just wondering if anybody has found another method for determining this?

Seth Grand Master

Seth

Posted
Posted

PIREPs 


And remember, the top of the cloud is where the most moisture is lurking.  If you look down on a cloud from above and a rainbow like circle is eminating from the cloud there is a LOT of moisutre in that upper layer.


-Seth

bnicolette Veteran

bnicolette

Posted
  • Author
Posted

Yes, PIREPS (UA), but has anybody come across the ADDS flight path tool and used it with any amount of success or any other tool?


For instance right now it is forecasting via relative humidity that the tops would be around 10K and there was a UA (PIREP) over PIT for tops at 8000'.  And over DCA ADDS is showing tops at 6000' and the PIREP says 6300'. So it is pretty close today.


PIT (PITTSBURGH, PA) UA /OV PIT180010 /TM 1620 /FL080 /TP B712 /SK BKN-TOP080


DCA (WASHINGTON DC, VA) UA /OV DCA300007 /TM 1726 /FL063 /TP E170 /SK BKN054-TOP063
        /RM DURC

bnicolette Veteran

bnicolette

Posted
  • Author
Posted

Quote: N4352H

I know they're a pain in the butt to read, but I was into it for a while...Skew-T. It's a great approximation tool usually confirmed by other info. Kind of like learning Latin.

Cruiser Grand Master

Cruiser

Posted
Posted

Skew-T were developed and are used by weather forecasters. There is a TON of info in those charts. Several places offer training on their interpretations. Google skew t


For clouds you can roughly estimate where the two sounding lines touch there are clouds.

MARZ Mentor

MARZ

Posted
Posted

Quote: Cruiser

Skew-T were developed and are used by weather forecasters. There is a TON of info in those charts. Several places offer training on their interpretations. Google skew t

For clouds you can roughly estimate where the two sounding lines touch there are clouds.

John Pleisse Grand Master

John Pleisse

Posted
Posted

Quote: Bnicolette

John, I almost dropped into the 3rd dimension when I looked at that graph!  LOL  Very interesting though.  I have never heard of that one before.  When we sometime get together, we're going to sit down and you're going to explain how to read that graph!!  It could be great to go along with the other info.....UA/ADDS/etc.

Shadrach Grand Master

Shadrach

Posted
Posted

Quote: Bnicolette

John, I almost dropped into the 3rd dimension when I looked at that graph!  LOL  Very interesting though.  I have never heard of that one before.  When we sometime get together, we're going to sit down and you're going to explain how to read that graph!!  It could be great to go along with the other info.....UA/ADDS/etc.

N513ZM Collaborator

N513ZM

Posted
Posted

in many hundreds of IFR flights from OH to CT (crossing PA just north or south of PIT) I have not found any accurate method other than PIREPS for determining cloud tops. I tried skew-t for a while and the ADDS planner but these have worked out to be rough estimates at best and wildly off at worst.


let me know if you find something reliable


Mike


 


 

jlunseth Grand Master

jlunseth

Posted
Posted

Go into www.aviationweather.gov .  Click on Satellite.  Click on Iinfrared.  Note the color of an area you are interested in and read the temp. of that area in degrees C off the legend.  Subtract the ground temp. in degrees C, divide by 2 (standard lapse rate in degrees C) and and you will know within a reasonable range what the actual cloud tops are in that area.  Not a forecast but a current reading.  Works pretty good.  It is necessary to understand that inversions or nonstandard lapse rates can affect this.  My admittedly limited experience is that inversions rarely have an affect on this method, because the satellite is measuring the temp of the first "object," i.e. cloud top, and the inversion is typically above that and typically clear (nothing for the sat. to read).  So, for example, a couple of months ago I flew out of KSUX and there was an inversion.  The cloud tops were just a little warmer than 0 C, but the air immediately above was clear and about 9 C.  The satellite would be reading the cloud tops, and the temp. from the ground to the tops was approximately the standard lapse rate.  I have not yet run into a situation where the air above an inversion layer was also cloudy, that would definitely affect this method.


Scott Dennestaedt (AvWxWorks) does not like the standard lapse rate and thinks it is inaccurate.  This may be true for reading the height of the bases, but seems to work pretty good for getting the tops.


I look at quite a few other things to confirm.  Radar (for precip), METARs and TAFs, Area Forecast, and Visible Sat. picture.  I do not understand the SkewT LogP yet, but am trying to find one of Scott's live workshops so I can learn it. 


The satellite infrared has the advantage of giving you a picture of the location of the highest tops.  The "satellite visible" just tells you there are clouds there, but not how high.   On the "infrared" view, the darker red colors this time of year are generally going to be ground temps, meaning there is no appreciable cloud cover for the satellite to "see," the yellows, blues, etc. are going to be clouds at various altitudes.

bnicolette Veteran

bnicolette

Posted
  • Author
Posted

Quote: borealone

Canadian GFA charts (see http://www.flightplanning.navcanada.ca/Latest/gfa/anglais/Latest-gfacn33_cldwx_000-e.html?Produit=GFA&Region=33&Langue=anglais&NoSession=NS_Inconnu&Mode=graph) might be semi-useful for those of you closer to the border. My experience is that they are usually pretty accurate, both for cloud bases/tops and ice forecasts. 

kortopates Grand Master

kortopates

Posted
Posted

The best/most useful site I am aware of and easy to interpret cloud height forecast is a NCAR site at http://weather.rap.ucar.edu/model/


You'll see cloud heights forcasted at 6K increments - not the desired resolution we'd like, but it gives me a quick idea of ability to top the clouds. It'll tell you if cloud tops go above 6K, 12K and 18K and will also tell you if they go below 6K and they also give you information about being above or below freezing. From that web page you can also click on the "upper air" tab and quickly access the skew-T for all the main sites here in North America. NCAR is a very good site.

carusoam Grand Master

carusoam

Posted
Posted

Duats also has cloud heights.  They are always taller than I usually jump.


Look for radar, winter weather and cloud heights.  They are different ways of looking at the same important data.


Nothing beats a pirep.


Best regards,


-a-

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