A question about small vortex forms over the sea

[Marko Korosec]

Hi all,

I was chasing extreme wind event at the coasts of Adriatic sea, gusts were exceding 150km/h. During the event I've noticed numerous of small vortexes around the gulf and also over the open sea. Here are some pics that you can imagine what I mean:

(notice two vortexes on the right side)
http://www.weather-photos.net/gallery/albums/userpics/10001/13_03_2006mk2.jpg

(a wide vortex)
http://www.weather-photos.net/gallery/albums/userpics/10001/13_03_2006mk7.jpg

(this is how it looks when wind smashes into the sea)
http://www.weather-photos.net/gallery/albums/userpics/10001/13_03_2006mk14.jpg

(another pretty obvious vortex)
http://img126.imageshack.us/img126/3397/img52467pq.jpg

I've also noticed these vortex forms in my last chase few weeks ago. There were no cumulus or any other convective clouds, just the usual Ac/As clouds.

What do you think could cause these small vortex to form?

Here are all pics from this event:
http://www.weather-photos.net/gallery/thum...ls.php?album=84 (http://www.weather-photos.net/gallery/thumbnails.php?album=84)

Thanks,

[Andrew Khan]

I'll take a quick guess at this....I think it could have to do with two small conflicting wind directions, hitting against each other. Like those little eddies, you perhaps have seen in your lifetime, of twigs, or leaves rotation around, this might be the same thing? A very strong directionaly wind, collides with a smaller set of wind, not as well defined, and makes a rotation vortex?

[David Wolfson]

I might be wrong but I'd think these are the result of the localized vertical stretching of the foehn rotors as the flow descends and "smashes" into the ocean. This could be caused by the disruption of the laminar flow due to irregular coastal topography.

[Andrew Khan]

Are you implying that the irregularity of the coastal topography is rendered by the force of the winds, temporarily, or a more permanent irregularity specific to this body of water?

[David Wolfson]

What I mean to say is that a foehn rotor is normally a horizontal vortex (roll cloud) where the ends connected to the ground ("Doswell's Law") are diffused. I would imagine that the effect of a valley opening to the coast would tend to "pull" the horizontal roll downward and concentrate the terminal vorticies.