Quote:
Originally Posted by philiphart
Glad we've got you convinced Marcus 
I haven't imaged at long focal lengths so seeing has rarely bothered me and consequently I'm no expert on the topic. Do you notice a good correlation between seeing and other forecast parameters? It's easy to create a seeing index based on high altitude wind speeds but only worth doing if it yields meaningful results. What we don't want to do is create a black box formula which spits out impressive numbers without a good basis.
What else do you look at apart from 300hPa wind? Does good seeing correlate better with light winds, no wind or strong wind at ground level? This last point can probably vary a lot between sites.
Phil |
Hi Phil,
I confess I'm no expert on these matters either! I don't really know what parameters contribute to seeing conditions but just recently, as suggested above, I overlaid surface winds with jet-stream maps and that seemed OK. That is, low surface winds plus low jet-stream winds = good seeing (on two nights). I haven't tried this often enough to be sure it's a reasonable measure though but so far so good. I imagine it's not that simple though. EG: I'd guess perhaps convection from warm surface temperatures into a cold sky will throw a spanner in the works even when there is no wind (??). Also, even small amounts of intermittent high level cloud seem to mess up seeing - esp at a FL of 3.1m.
The great news is that so far CFN has produced
very reliable short term cloud forecasts. Longer term maps aren't bad but I generally only look at the short term maps anyway so I know whether to bother going out.