Flying into the white stuff – at 39,000ft?!

[LenM]

Not wanting to hijack a similar thread on the forum (viewtopic.php?f=16&t=14939), please find attached some images of ‘the white stuff’ at 39,000ft.
This was taken on Friday, 4 February 2011 on SA346 between JHB and CTN approximately 25 minutes before FACT. I was marvelling at the cloud pillars being pushed in the air, when we approached a very fine ‘misty’ cloud ABOVE our altitude?! The pilot executed a number of steep turns to manoeuvre in between the cloud, but at times I had trouble seeing the wingtip - albeit without any turbulence whatsoever...
I ‘fly’ this route on a weekly basis and have had far harrowing experiences, I just found it amazing that even at THIS altitude, you find the white stuff!
Although not to clear on photo 6 and 7 there was a particular cloud column that pushed far higher than our Flight Level!

My question, to the more experienced on the forum, is simply: What cloud type was the misty bank on top of the CB’s?

[FO Gyro]

Hi Len,

Thanks for the great photo's. The type of cloud that you would have been flying in was Cirrus type cloud. This mostly consists of ice crystals. Normally when we fly in cloud, when the temperature is below 10 degrees C, we have to select the engine anti-icing on, which heats up the leading edges on the engine cowls. If the temperature gets colder than -40 degrees C, which is roughly around 33 000ft and above, Boeing says one can switch off the anti-icing. This is because the water molecules are so cold, they are no longer in liquid form, to form ice, but are in a solid form, ie. ice crystals, so that can't "stick" to the leading edges.

Cirrus cloud is that whispy cloud you see from the ground. Sometimes it's smooth to fly through, and other times it can be slightly turbulent. I can get very rough however, when you fly just in the tops of it, that's where the turbulence is worst. One must either be in the middle of that cloud layer, or above it. Unfotunately, the weight of the a/c determines how high we can go. Len, on the Boeing 737-800 (the a/c you flew in), with a passenger load of around 100 out of 157, we can go to 39 000 ft. When there are maybe less than 70 passengers, we can go to 41 000 ft. This definitely doesn't mean we always get over it. Sometimes Cirrus cloud is above 45 000ft!

When a fully developed thunderstrom (Cumulo Nimbus) starts to dissipate, the upper air westerly winds create a long anvil shape cloud, that is mostly cirrus type cloud. This can be turbulent to fly through, and normally we try and fly upwind of the thunderstorm to stay away from the anvil.

In the attached photo of our on board weather radar, the red radar returns are the most intensive parts of the thundestorm that are completely to be avoided, the yellow is medium intensity precipitation, and green is low. We fly through the green bits, but it's normally slightly turbulence there. The green bits are the anvils coming from the Cumulo Nimbus.

[LenM]

FO Gyro

Thanks for the inputs! Much appreciated!!
I assume it's not worthwhile mounting a weather radar in my little Challenger II?!