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midtskogen
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05 Jan 2017 00:45

So did I, in particular the naive vs managed fund analogy. :)
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Watsisname
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06 Jan 2017 17:27

 
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09 Jan 2017 22:52

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10 Jan 2017 03:09

Both groups seem to have an appropriate reaction.  They may be games but anyone who has played Orbiter or KSP knows just how tricky such things can be.
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midtskogen
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10 Jan 2017 04:34

I think the video was intended to be funny more than to be accurate. :)

I was invited to follow the Philae landing from the office of the Norwegian Space Centre and took an early day off for this event.  The "touchdown" moment was a bit unclear.  As I recall it, there was a confirmation that the anchoring harpoons had fired, but it wasn't clear whether they had attached (and they did indeed fail, and, as we know, the lander bounced and settled in a pit, more or less).
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midtskogen
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11 Jan 2017 13:16

I'm getting more and more impressed with the short term forecasts by the Norwegian met office considering Norway's difficult terrain.  The forecasts have improved significantly over the past few years.  I occasionally check the quality for my location.  The grid size for short term forecasts have become very small, so the terrain gets modelled pretty well, and my exact location within that grid gets further adjusted elevation.  Below is a comparison of the forecasts 12 and 24 hours ahead with what was actually observed.  It's fascinating to see how they match, mostly within a few tenths of a degree C and also the timing of temperature changes (likely caused by changes in wind direction).  Accuracy is particularly important when the temperature is around freezing, so the forecast was very precise about when snow would fall and when rain would fall (or pre-shovelled snow as we call rain in Norway in the winter).  Forecasts are available at yr.no which has would-wide forecasts (but best accuracy for Norway)


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Watsisname
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11 Jan 2017 15:09

Remember way back when I said that forecast skill will improve not so much by improving our knowledge of the physics but by raising the computer power and grid resolution?  There ya go. :)

Now if only here in the US we could follow suit.  GFS is lagging behind the rest of the world's weather prediction capability.
 
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midtskogen
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12 Jan 2017 00:12

Watsisname wrote:
Remember way back when I said that forecast skill will improve not so much by improving our knowledge of the physics but by raising the computer power and grid resolution?

Yes, but just throwing more computer power at the problem will never take you as far as you can go.  You also need to be clever to find practical, perhaps less physical, ways to make the models.  And you need good measurements, both in terms of quality and quantity.
The recent improvements in the short term forecasts haven't only come from a smaller grid size.  The brute force-like grid forecast is the starting point for a number of ad hoc adjustments.  (The grid size is also adaptive, so the grids are smaller where it's likely to make a difference)  For instance, measurements from nearby weather stations are fed back along with the initial prediction using a Kalmar filter to make adjustments.  I.e. when the prediction of the original model doesn't quite seem to match actual measurements, the final forecast gets adjusted accordingly.  Adjustments are also made for elevation differences within a grid.  And for very short term forecasts, up to 90 minutes ahead, radar data is used.  A forecast for the next day can be 100% accurate in that there will be afternoon showers over an area, but it can not realistically predict where those showers will be.  Once the showers have formed, instead of rerunning the models with impractically small grid sizes, the movement of the showers can be tracked and predicted by simple algorithms.  Much like you would do manually if you sit at work and look at the weather radar trying to find the best time slot for riding your bike home.  Finally, it's always a good idea to read the text forecast written by a meteorologist experienced in interpreting the model output, who knows the limitations and local factors.
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12 Jan 2017 02:35

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