Based on a recent experience I’d like to learn more from the experiences made by others.
Last Thursday around 1630Z I was climbing towards FL200 inbound OLBEN after departing Stuttgart EDDS. I don’t remember the altitude but only the temperature when I entered a cumulus type cloud. The temperature was around 0C and as I climbed I got some rain that changed to soft hail (Graupel) when the temperature decreased further. Soon it was -10C and that stopped. I was also out-climbing the cloud and entered VMC. My wings got covered a little bit with the small pellets. I had a good climb rate of 600-700 fpm at cruise climb speed of 130 kt. There was no turbulence just the sound of the rain and later the pellets hitting the windscreen and hull.
On the ADL sat WX image I believe I was passing through a green area but I might have been in a yellow area as there were a few here and there. Given the wind speed and lack of the image processing and transmission I can’t be sure.
Before I entered the cloud I looked around to have an idea for an escape route as I’m quite a bit suspicious of those cumulus clouds. I would have turned on the TKS at full rate and descended in that direction to leave the area.
Now I’m writing to learn more what to expect. I believe there might be signs that tell you when it’s enough and time to leave.
The radar images you get via ADL120, in my experience, cannot distinguish between rain and “Graupel”, light hail. My strategy is to avoid all the yellow stuff … and that’s about as much as I can say. I guess those were more of the “towering cumulus” kind, right? I avoid all of those. My experience after about 25 IFR flights with the ADL receiver: The rain is much more intense in the yellow areas.
I was passing through a green area but I might have been in a yellow area
I can’t see how these colours can be objectively quantised.
A typical European wx radar image (this is ex meteox.com) has a number of shades of grey (or blue, or whatever)
The colour table for the above image (with the land removed, just taking the radar data) is this
and if you ignore the blacks you see there is quite a range of shades there.
But sometimes one can see red in there. Took me a while to find an example, going back through the archive
which yields this colour map
On that one (a different source, not layered) I could not get rid of the land (green etc) but you can see the couple of reds at the bottom.
So using just a few colours is not going to be more than a very rough guide…
Peter, airborne weather radar is calibrated to make the colours predictable. Obviously if you only use a few colours they do lose information but it is meant to be simple.
Yes; that is what I am getting at.
Peter wrote:
I can’t see how these colours can be objectively quantised.
Most providers use a color scale that indicates precipitation rate. For example (I think this is the scale that the ADL uses, too): DWD precipitation radar (in German, sorry, but the relevant table is on p. 6)
There are many caveats, e.g.:
@Stephan_Schwab : for any raining cumulus cloud, I would expect to find solid precipitation somewhere in the cloud, and I would expect the size to scale pretty tightly with the rain rate at cloud base. I would also expect supercooled liquid cloud droplets (not a problem for a FIKI plane). The probability of finding supercooled precipitation droplets (a problem for any plane) increases with updraft strength.
Note that that’s what I would expect based on cloud physics, not based on what I’ve seen with my own eyes; my plane doesn’t “do” this kind of clouds.
What I’m looking for is something like “if you see X, get out while you can” or “if you see X and you are climbing fast enough, you can continue but expect Y for the next minute or two”
I understand that it is a complex matter, but in complexity there are patterns and I would like to learn about some of those observed patterns. I don’t expect a straight X follows Y answer.
That’s the answer most of us are looking for, I guess … I think your question comes down to “how high are the tops”?
I’ve tried a couple of things on my last IFR flights, especially I always had a look at “tops” via Telegram. But that was pretty disappointing: For my last flight to the Netherlands “tops” reported low cloud tops of maximum 6000 feet for the whole route – and in reality I flew i FL120, never more than 1000 feet above the solid cloud deck, so the tops were FL110 all the way to the North Sea.
Of course that was no problem, I climbed through that overvast in two minutes, and I realize that it’s a different thing to be in the clouds at FL200, trying to outclimb them … but that’s stuff I don’t do, probably because I don’t HAVE to fly anywhere, unlike you …
Flyer59 wrote:
I think your question comes down to “how high are the tops”?
No. I don’t care about that data point.
I care about what to expect and when to bail out. I have no general problem with flying in IMC for hours as long as my plane keeps flying.
I understand that ice will destroy lift at a certain point. I have a counter measure to get out of that condition either my going up to find very cold air or down to warmer air. I understand that other things (fuel) may also be affected by the cold. But the loss of lift is a more likely and direct adverse effect.
Flyer59 wrote:
I don’t HAVE to fly anywhere, unlike you …
The good thing is that I don’t HAVE to be somewhere at a certain point. It’s more a “want to” than a “have to”. I fly myself to be on my own schedule. I don’t fly to a meeting where I suffer a significant loss when I don’t show up.
