Old age or weather conditions

Originally posted by boatshed

   Agreed Clive.  The models/thinking tend to assume this generally horizontal, or at least consistently off horizontal flow where the reality on a cold, especially gusty day, and especially somewhere like BCYC with a steep sided dam and surrounding hills, then the breeze is moving in chunks (in MAtt's Vocab of Wind (no link I'm not a published author,'it's blowing chunks' - the allusion is deliberate).  Those chunks have much more vertical movement than normal breeze.
I like to classify gusts as rollers, movers, lines and splats.  A variety on splat is the bouncer which doesn't do a conventional splat fan and spread, but stops and starts on it's progress down the lake (you need a long lake and a good vantage point to see this effect).