In my experience lift in cloud is stronger only if the cloud has a lot
of vertical development – say several thousand feet, which of course
developing CBs do have, and provided you can stay centred in the lift,
which as Jim points out is harder if you can’t see the real horizon. I
have found that expanding the GPS scale helps a lot in keeping in good
lift, in VMC or in IMC. (I still do not advocate people teaching
themselves to do the latter these days – if it goes wrong in a
slippery glider, it can do so very quickly and very badly.)

In the more usual “good” conditions in the UK when we get them, an
inversion stops vertical cu development and they are often only a few
hundred or 1-2000 feet deep. Then, as Jim says, it is usually faster
to keep in the energy where you can see it, in VMC. With very shallow
clouds, it is not even worth going up to cloud base – the lift weakens
before getting there. Even if it does strengthen briefly at and into
cloud, I usually lose more in the fumble of coming out on the wrong
heading, or on the right one but into another cloud and in its sink,
than staying below, if achieved speed is what you are after.


Chris N