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Posted by Ray
on 5/9/2008, 8:45 pm
66.67.227.195
Sorry that I forgot to post this earlier, but....last Sunday at Dansville some interesting things were going on in the atmosphere. After a late start usable convection got going, albeit with a low (maybe 3800 MSL) cloud base. I noticed that there was a fairly small but distinct and persistent blue hole over the valley....which means there MUST be a wave, although not necessarily a soarable one. This one was...I was able to get the Grob into it and work my way up the sides of the clouds in the sunshine to about 5,000 MSL. I saw the Pagasus at cloud base on the west side of the valley and tried to talk Riz and anyone else into it, but unfortunately I remained alone. After less than an hour the hole filled in, "something" changed, and everyone abruptly fell down (me too). Then, a couple of hours later, Jari got up to something like 6,000 MSL in thermals which went up to the "new" cloud base. What happened?
The following analysis is (informed) speculation. Waves like to form when a hydrostatically stable layer is sandwiched between two unstable layers. There was probably initially a low (~4,000 MSL) inversion, likely blown off the relatively cold Lake Erie. This provided the stable layer for the wave (note that the air above cloud base when I had the wave was perfectly smooth). Then the wind shifted so that Dansville was no longer downstream from the lake, i.e. the stable layer was wiped out. After a couple of hours, the new air mass ripened and allowed convection to go up to the new level which Jari later reached. Very interesting.
So, for my first flight of the year apart from the spring check ride, not bad.
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