So, I emailed meteorologists Michael Kelting from KRON4 News and Bill Martin from KTVU Channel 2 News...
It was fun to get a professionals analysis / insight on the shears we fly...
Here was my question:
I am a hang-glider pilot who flies Fort Funston on a regular basis. We often time enjoy flying in what we call "shear". I've flown in many shears and would like to gain insight you may have on the scientific elements of this weather condition. I am aware of horizontal and vertical shears. We fly in what I assume is a horizontal shear at Funston, and can often time see them rolling in with a distinct line of white caps along the ocean. The flying often time is spectacular in shear conditions! Each shear seem have its own texture and make-up, so no two shears are alike by what I've experienced. Could you please share any insight you may have on this weather condition?
Thank you,
Christopher Valley
Vice President
Fellow Feather of Fort Funston Hang Gliding Club
Michael Kelting's Response:
Good question Christopher, I never get good science questions.
It sounds like you know about as much as I do about shear. It’s any change in wind direction or speed with distance. So shear is everywhere. Vertical wind shear changes with altitude and is influenced by surface friction and instibility. Shear creates vorticies which I’m sure you ride on all the time. More instability in the atmosphere and you can have more vertically stretched vorticies. In fact, I think what you’re describing as “rolling in with the white caps” are vorticies. They are just spinning areas of air. I can’t give you too much more. I’ve been out of school for 15 years now. I hope this helps a little. You’re pics didn’t send so I couldn’t see those.
Michael Kelting
KRON Weather
Bill Martin's Response:
Hi Christopher,
First let me say I love watching you guys fly. I have been surfing OB for well over 30 years and remember when they first started flying that area. I also build and fly RC Gliders and have a huge fascination with the elements of lift. Especially along a coastal headland.
In Meteorology we usually think of shear in the Meso Scale or that of a large Cumulus Cell. Tornadoes and severe weather are almost always a product of strong Vertical and Horizontal shear. My basic understanding of shear is that it is the boundary between two oppositely moving air parcels. With that in mind I can only imagine all the possible variations that you might experience along Fort Funston. What I have found is that in the slope lift environment the best way to get a handle on the lift is to fly the sh.t out of it in every possible condition. I am also sure that there is a large sea-surface temperature and texture component playing into the equation as well.
I wish I could add some great insight here but I fear my knowledge is limited. When I try to visualize it in my mind’s eye I see a river with many rocks creating many eddies and currents that feed into each other.
We used to surf near point conception at a place called the Ranch. In the afternoon we would light a fire under the bluffs near Government point to stay warm. It was fascinating to watch the smoke plume mimic the air turbulence along the bluff.
It would be a fascinating Masters or PHD project.
Bill
***********************************************************
Fly safe Brothers and Sisters!
Chris
