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Spotting Thermals

In article <CB6wyp.CK8@tug.com> andrew@tug.com (Andrew Beattie) writes:
>
>We are discussing the problem that I had of flying a 15 square meter light
>weight kite at an altitude of 300' (with CAA clearance).  I hit a thermal
> [...]
>I'd like to know how to spot a thermal, just by observation.
>
You're probably out of luck...
If the conditions were 'calm' you could spot a thermal by the breeze it
creates as it drifts by.  We often watch several windsocks on the airfield
all point at a thermal, etc...
You are flying the kite in a breeze, so I doubt this would work.
Some suggestions:
- Do your experiments in the morning or late evening, thermal activity is
  minimal at these times.  But - mid morning is when small, low thermals
  are best for radio-controlled soaring, these are probably not strong
  enough to be a factor.
- Thermals are generated by unstable airmasses, so avoid post-frontal days
  ...of course, that's when the wind blows :-(
- If the wind is very steady with no gusts, there are possibly no thermals,
  but you never know what's happening a couple hunderd feet up.
- Cumulus clouds indicate thermals.  Stratus generally means stable air.
- If its raining (drizzle) there are probably no thermals, but you'll
  get wet!
- None of the above.  I have experienced thermals at the strangest times
  and places.
- Avoid being downwind of ridges that generate lenticular clouds.  This
  indicates wave/rotor - this is not a thermal, but the list is even more
  powerful.

I hope these help you enjoy our wonderful unpredictable atmosphere.

Tom
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