Noticed this vapour trail from the Sydney to Perth flight overhead at 31000feet at about 1pm, still there after 20 minutes, a good sign of moisture aloft ...
- Vapour Trail 1.jpg (23.2 KiB) Viewed 9471 times
Then after 25 minutes it looked like this...
- Vapour Trail 2.jpg (17.42 KiB) Viewed 9471 times
Kelvin-Helmholtz waves, caused by instability in the upper levels.
So we've got good moisture and instability up high, and severe gales down to the surface with an active front rushing in from the west, somethings got to happen.