Wave Bars at Keepit - by Dave Shorter

Briefing this morning (Monday) took place under a solid cover of cloud, with predictions for clearing and blue. Temperature markedly lower at 24 and winds from the west getting progressively stronger with height.

 “H’mmm” I said to my wife in a quiet voice, “could be wave about” and thought no more about it.

Everyone looking decidedly unenthusiastic, our NZ visitor organising a game of golf, I decided to accompany my wife shopping in Gunnedah. On the way out through the boom gate I noticed signs of wave clouds in the far East over Tamworth on the edge of the receding cloud bank. But too far off to be of interest, and all was turning blue overhead. Good decision to go to Gunnedah!

Then, driving back from Gunnedah we started noticing ahead bands of wave clouds receding away from us, arrayed every 5-10 km in each direction from NW to East. I’ve never seen anything like it – often lenticular wave clouds will show with secondary/tertiary bars of cloud downwind from the source, but this display seemed continuous, repeated wave bars going forever. And where was the source of the waves? It was obviously not the Kelvins.

Back at the club I dashed to the hangar and towed out to have a launch. Jay Anderson was just taking off and Bob Emery lined up in the LS7. No other gliders anywhere. The wave clouds were still there although rapidly diminishing – instead of long bars of cloud stretching off to the NE they were now each maybe a kilometre long, and nowhere near as thick. But still looked very promising. Jay took a long tow across towards the Manilla range and contacted lift at around 3500-4000ft. Bob and I followed suit.

By the time I arrived at that cloud it had stopped working and I flew on to the next cloud, found lift and started climbing. This was at a point just off the Manilla Range, somewhere over Gaineys. Bob joined me below and we worked that cloud, beating back and forth in front of the cloud until we were up at 8000ft and looking down at the most beautiful sight below. The top of the lenticulars was around 6000ft, and they appeared to be triggering off the Kaputar range, with regular wave bars coming all the way from Kaputar, and extending as far as the eye you tell in the opposite direction towards Tamworth. Lift in the smooth laminar flow air was up to 4knots.

After reaching what appeared to be the maximum we could achieve in front of that cloud, around 8200ft, we jumped forward to the next cloud and floated around in front of that one, while watching the system evaporate.

Pity we didn’t get up an hour earlier – it would have been superb then, although I would have to say it was just a magic experience as it was.

By now it was all reverting to blue, and I decided to push upwind to see what I could find. After a few Kms of horrendous sink I contacted another wave, now completely blue running across the range at the Bora hangies’ launch point. Beating back and forth there I regained another 1000ft in 3½ - 4 knts, using the “snail-trail” on  my LXNav display to find the strongest lift each beat. But that too eventually faded. But we’d had over an hour’s thrilling experience flying above the cotton wool.

PS The tell tale info at briefing was the wind forecast – 2000/20, 5000/25, 7000/30, 10000/35. A stable atmosphere (blue conditions to the west) with increasing wind are the pre-existing conditions required for wave.

Dave