Clouds as Signposts

     The most obvious signs in looking for thermals are cumulus.   However, don’t forget that clouds only tell us what is happening (or not happening) where they are.   The challenge for us is to interpret them in relation to the air where we are.   Moreover, since cumulus sometimes remain visible long after the lift that caused them is gone, any cloud chosen randomly and without regard to genuine signs of convective action may prove to have no tactical value.     View the world from aloft as divided into two arenas, sky and ground, distinct from each other yet highly interactive.   Before deciding to search beneath a particular cloud for thermal lift, estimate the height of cloud base above ground and divide by two.   Below that median altitude, dismiss the clouds (except as producers of shade and indicators of wind aloft) and look to features on the ground for ideas.   Above the halfway height, consider clouds as primary indicators and terrain as secondary.     What does the ‘best’ cloud look like?   Most of us easily recognize a classic ‘popcorn’ cumulus when we see one, but skies displaying none of these may be booming nonetheless.   Useful markers range from hazy patches in a cloudless sky to darker areas in an overcast.   In their minimal form, cumuli may look more like wadded tissue than popcorn, and ragged scraps no larger than your aircraft may provide essential information.   When those few small wisps are the only clouds, they almost certainly mark lift.   If you also find thermals where there are no clouds, then even such small cumuli probably mark the best lift available.Always look for patterns of cloud development, whether indistinct lines or recurrent clusters.   Two clouds imply a possible line of lift, and three or more may confirm it.   Such patterns can even be periodic…