Chinook - Still Hitting Back 3 (Merged)

[walter kennedy]

I took this shot from the north of the Mull when a gentle, steady wind was blowing – not enough for the “ground-hugging” mist to form.
This is classic orographic cloud and is quite common if you look for it.
The Mull slopes are ideal for its formation by virtue of their profile and their sticking into the sea with a prevailing wind onto them.
After an average summer's day, when the air cools towards evening and the prevailing wind is blowing, this type of oro cloud is just about guaranteed here and certainly could be relied upon days ahead with a favourable weather forecast.
It hides higher topographic features hindering orientation and casts a shadow on the slopes that hinders judgement of distance.
On the fateful day, the strong wind was causing a phenomenon termed “speed-up” whereby the lower layer of air is compressed, thereby speeding up and dropping in temperature, reaching its dew point in advance of the bulk of the airmass, and giving rise to a layer of mist that follows the slopes until it merges with the oro cloud higher up.
A person who was posted to guard the site was said to have commented that he was at the lower end of the site and his legs were in mist but he was in bright sunshine and was said to have said that he was surprised that he had not been called as a witness – pity he could not be persuaded to speak publicly.
The procurator fiscal (who called the FAI) himself who is a local and was at the crash site that evening described to me how the mist was layered like a cake with bright sunshine breaking through intermittently.
I have posted (years ago) a link to a video that shows its formation on the Mull – here it is again.
MullMistVideo video by grauniad - Photobucket
I took this video at the crash site but at a different time of year in conditions less benign to the formation of such mist such that it is seen forming higher up the slopes and very intermittently - however, demonstrates rather well, I think, how the appearance of the slopes is affected by such mist.
On the day, by all accounts, this up-slope mist started at the level of the light house and merged with the oro cloud at 800-900 ft – as the yachtsman (Mr Holbrook) described, some colour of the ground/lighthouse could be seen through the mist from where he was – but anyone used to coastal navigation in those conditions can tell you that, while you could be well aware of the presence of the landmass from even a great distance, the problem is that details on the surface are blurred/obscured such that judgement of distance off is very difficult whatever speed you are approaching it.
These conditions would be so typical in a summer late afternoon/evening that anyone interested in this crash could have gone up for a weekend (with the prevailing south westerly forecast) and seen it for themselves – why, after so many years, there is so much uninformed waffle is disappointing.