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Written by Wally Anderson
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Thursday, 23 March 2006 |
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I would like to talk about a condition that happens at Ed Levin in the wintertime. When high pressure sets in the winds tend to blow off-shore (NE). The velocity & direction depend on the position & strength of the high pressure system. This creates wind over the back at the top of Ed Levin. Often the lower hills are still flyable in this condition & this happens so often that folks, especially new pilots don’t pay attention to the wind at the top. What is happening is that the warm inverted lower level air mass is diverting the upper level wind over the top of the LZ and out towards San Jose. This is all fine & good, but at some point the cold NE valley wind will overcome the inverted air mass and suddenly avalanche down the hill. This happens suddenly & with little or no warning. In my experience it can occur with as little as 15 mph velocity & is very likely when the wind aloft gets in the 20’s or above. This event is extremely dangerous & can literally slam a glider back down to the ground.
I was down at Ed teaching earlier last month. Early in the day the wind talker was indicating 10-15mph but was increasing throughout the day & eventually peaked at an average of 27mph with gusts to 37mph. a mixture of hg’s & pg’s were flying from the 300’ hill. I launched a couple of my critters but stopped when I saw the 600’ wind sock switch down. We waited a while & had a sudden 15mph gust come through, roll up the laid out pg’s from the back & tumble a couple of parked hg’s. While we were waiting I explained the condition to my students with hg pilots listening in. What scared me about this incident was even though my group bundled up & rode down the hill. The hg crowd did not. Upon reaching the LZ I was amazed to see hang gliders launching off the 300’ hill! I don’t know what they were thinking as the wind sock on the 600’ hill was pointing towards the lake & standing out stiff. Fortunately they got away with it, got away with it being the operative words here. I was relieved when the last pilot made it safely down, but that wasn’t all. I noticed a pilot walking back up the hill. At this point I conferred w/a WOR senior pilot suggesting that we should close the launch & he agreed. As quick as I could I drove up the hill to talk to this person. The only reason the pilot hadn’t launched was that the glider had sustained a broken batten when it had previously rolled over. The pilot was apparently thinking of fixing the batten & flying. While I was explaining that the site was closed & why a sudden strong dust devil ripped through the set-up area & as it left the wind switched down at 15 or so, this all happened in less than 3 seconds.
Ed Levin and Slide Mountain are the only two sites in our area that I can think of where we launch on the lee side of the mountain. It is extremely important that you are aware of the conditions above you. Also realize they can change so your last observation may be outdated. I have seen a couple of incredibly scary flights off of slide when the pilots launched too late in the summer time & got rotored all the way into no-mans-land at the base of the mountain.
Be sure to be aware of the big picture not jus the wind sock in front of you. It’s wise to check the winds aloft forecast, the position & strength of the highs & lows, the closeness of the isobars & of course the wind talkers before deciding when & where to go flying. In winter it’s common for us to be starved for airtime & willing to accept less than ideal conditions & accept more than normal risk to get a flight, any flight.
May your spirits soar (even if your bodies sometimes can’t)!
Wally |
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Last Updated ( Sunday, 02 April 2006 )
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