Two Leeside Flights

On Wed. Nov. 2 (yellow) and Fri. 4 (red), there were decent if tricky leeside conditions at Kuratake, although the forecasts did not indicate it.  Wednesday was forecasted not to be flyable due too much leeside wind (blowing from the NE, or right side of this image), whereas Friday was supposed to be virtually windless and easy flying.  In fact, both days were very nearly identical, with marginal soaring, short takeoff windows, and great opportunities to practice flying in tricky leeside conditions.

Seizing a takeoff opportunity during an upslope blow.

Wind report from the excellent FreeFlightWX live access weather station we have installed at the Kuratake Launch.  Green zones correcpond to flyable conditions at the SSE-facing site.  During the fall/winter/spring season, the prevailing wind is generally northerly but flyable leeside conditions often happen when it's sunny and the north wind is not too stong, as you can clearly see on the graph.

As you can see on the wind graph, the morning started with rather gusty easterly wind which I know is just the NE wind wrapping corkscrew-like around the mountain.  Not the greatest for flying.  However, things proceeded to calm somewhat, although the wind directions became much more unstable, alternating between catabatic and thermal.  I took off at 1348, pretty much expecting a bumpy sleddy to the bottom.

However, a decent wall of leeside thermals did build up just in the offing of the launch and I was able to top out (the summit of Kuratake is about 230m above the launch, which is actually what makes leeside flying possible here and makes Kuratake a year-round site).  But I soon lost the thermal (where did it go?), and upon trying to repeat the strategy I was not so lucky and soon ended up below the launch.  No choice but to drift on the wind to the west, where the Yahazudake ridge sometimes offers a last-chance thermal.  This ridge looks really good but frequently only splits the wind like a ship's prow, so getting up there, if possible at all, is never too easy.  This time, with some delicate moves, it eventually worked and soon I was topped-out again.  By now I was running out of time (I work in the afternoons), so it was time to head west.  The wind was blowing around the massif creating a turbulent venturi I had to go against; a 50% deflation at full bar came but on a Delta 2 presented no problem; I shook it with the bar still half-way in.

This image is looking SE at the next phase of the flight.

Getting onto the windward side of the mountain, conditions became much more pleasant.  Heading for the Sumoto LZ (lower right of the image), I was not too surprised to pick up a nice thermal above the sunlit valley.  I decided I had enough altitude to cross the next set of hills.  It was on the way to work anyway!

The Sumoto valley, looking upwind, after topping out in the thermal.

LZ in Shimoura on first flight.

Now truly out of time, I had to land but there were ground thermals everywhere.  Some spiraling and awkward turning eventually did the trick (note the high-tension powerline).

On the 4th, now with full knowledge of being an X-Alps athlete, it was time to huff up the hill with the pack on!

The forecast was a total wash.  It was much windier than 2 days ago.  Maybe the massive inversion above was causing it.  We lay around on the lawn waiting....actually it was quite nice and luxurious in the autumn sun.

To make it in time for work, I absolutely had to begin running down the mountain at 1350.  The catabatic wind continued until a brief calm spell.  Although I was not set up for front takeoff, I hauled the glider running backwards, and... it worked!  Within seconds afterwards, the katabatic wind resumed.

This time (red trace) the wall of leeside thermals was a little better developed, and now there was much less wind and no turbulence.  Moving as fast as I could, I topped out in the Yahazu thermal and turning west, floored the bar...

Today the wind was more northerly and there was no lift over the valley, which is actually the more typical situation. It was necessary to seek the elusive Domeizan thermal on the north side. The Domeizan mountain is somewhat isolated and not steep so it does not block the wind well, with the result that the leeside thermal, if there, pops up at unpredicatable locations somewhere over the south slopes on the mountain. After some searching I found it and so was able to continue more or less along Wednesday's path, albeit slightly lower...

View of Shimoura village on final approach Friday.

Although I could not make it quite as far as Wednesday, I landed nearby, with Leanne on my heels. No time to even fold the glider, off to work...

XC Stats: Wednesday: 10.0km  Friday: 9.4km

Can you see why Kuratake, although only 682m high, is still a great place to train for the X-Alps?