Thursday, December 22, 2016

Getting Ready For New Zealand - Weather Software

Only a few days before we leave for New Zealand!  Today I updated my own custom software which downloads global GFS model weather forecast data, calculates parameters relevant to soaring, and displays them in easily viewable form on a map.  From past experience, I trust the GFS model more than any other data.  The popular RASP forecasts show more detail but are actually nothing more than GFS data filled in with more detail based on a finer model mesh and slightly more detailed topography model.  I find I can fill in these local details, more or less, in my head. Thus, this very same graphs is likely what I will be using during the X-Alps as well.

Below is the current forecast for the 28th of December, our first full day in the Wanaka area of the South Island of NZ.  In the background of the weather data is this map:

The map shows coastlines of the sea and major lakes, roads, flying sites (red X's) and some location names in abbreviated form (QNT=Queenstown, WNK=Wanaka, COK=Mt. Cook, etc.).

Here is the surface wind forecast on the 28th, at 1300 Local Time:

The Wanaka area has light south winds (about 2 m/s).  Though the takeoffs face north, probably, it will be possible to fly due to local effect of the thermal blows.  Or, one can fly from the south-facing takeoffs in Queenstown.

Here is the sunshine percentage graph.  It's still a bit under development, so actually the magenta color, though it says 75%, actually shows full sun.  We can see that although Wanaka has sun, unfortunately there is a solid bank of cloud to the north.

Here is the inversion level (Planetary Boundary Layer Top) altitude (in 10's of meters).  This is around 2000m in the Wanaka and Queenstown area, but much lower to the north, again due to the clouds blocking the sun.  It increasingly looks like an out and return Wanaka to Queenstown flight is maybe the best one can do in these conditions.

And finally, the expected thermal updraft velocity (m/s).  Again, the effect of the cloud cover to the north is obvious.

BTW, about 320 different data parameters can be graphed with this software, from winds, tempereatures, humidities at many different altitude layers, to completely irrelevant things such as the temperature and moisture of the soil 30 cm under the surface!  But it's because it includes such factors, the GFS model is, in my opinion, the most robust and accurate of all global weather models, and most local ones too!

Well, anyway, this is a 5-day forecast, so it's still a toss-up, what will happen on that day.  This was just a test run to make sure my software works for NZ.  Now, onto sorting out the next few things for the trip, such as electronic maps, gear, and clothes!

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