Distance Between Thermals

I have no idea why, but it’s often spoken about that the distance between the good thermals seemingly appears to be related to the depth of convection.  I say that again, the depth of convection.  This is from the ground level to the top of the cloud base, not the commonly perceived, base of the clouds which is the condensation level.  Typically, if we work on an approximation of 2.5 times the depth of convection, we can’t go too far wrong.

Lifespan of Cumulus

So as an example, if cloud base is 7000’ with the tops at 8500’ (2600m),  we can expect to find thermals typically, 6500m or 6.5km apart. How long does the life of a cumulus last?  Depends of course, but typically around 15-20mins.  Why is this question relevant?  Because it allows us to plan ahead, whether we need to get high soon, how many opportunities do we have left to climb before we start getting too low?  The advantage of this life span of 15-20mins, is that we can build a mental picture easily, has it just kicked off & is now building, or is it now at its peak or dying off?  We know how high we are at any given point in time, we know the typical spacing of the thermals for the day, and we know our own risk profiles regarding abilities, terrain, or competitive risk too. With this knowledge, we can now determine how quickly we need to find a thermal if it’s going to be possible to find one at all!  

Visual Cues of Lift

When looking for a thermal under cumulous conditions, we want to be looking at all available indications, namely movement, in the way of whisps, curl over, or the edges of the clouds with a seemingly rotating edge.  We are looking at the flat black base or the lighter dome within the cloud pushing up into it.  All these things build up the mental picture required, to build up your ‘best guess' as to where we’ll find the thermal, naturally then, put your glider there and turn to stay in it!

Banner photo by John Absolon, 'Got that shot' Images

 Adam Woolley was born into the gliding world, being the 3rd generation in his family. Going solo at 15, his thirst for efficiency in soaring flight & quest for a world championship title to his name has never wavered. One big passion is sharing his experiences & joy with other glider pilots all around the world. Adam is an airline pilot in Japan on the B767 & spends his off time chasing summer around the globe. He has now won 7 national Championships & represented Australia at 5 WGC's & 1 EGC.