XCSkies and Skysight

On Saturday, 13 June 2020 20:54:15 UTC+2, Bret Hess wrote:
It seems that NAM forecasts (12 km and 3 km) on XCSkies are very helpful for soaring in Utah. I haven't seen a benefit of HRRR over NAM. I'd be interested in hearing from other pilots who fly in the mountains comparing NAM with HRRR or Skysight for thermal predictions.

I'd also like to hear a discussion of why a 3 km resolution model is a great improvement for soaring over a 12 km model, for example. Higher resolution models generate more detailed forecasts, and maybe they show better what kind of variation you might see, but the variations at this scale don't seem pinned to the earth at an accuracy of 3 km.

You'll see detailed explanations in my talk above about resolution (https://www.youtube.com/watch?v=Ez9Xjo4llT8) including real world examples of the impact of resolution in the mountains. Over hilly or mountainous terrain the improvement from higher resolution can be significant. On flat terrain the influence is less, although if there's convergences or storms it may still be important.

Unless you're 4km or so you won't meaningfully resolve wave, convergences, or
convection. Instead you need to parameterize [ https://en.wikipedia.org/wiki/Parame...heric_modeling) ] the cumulus and convection, which has drawbacks.

I can't offer a comparison to NAM 3km or 12km, but I can show you the predicted tracks versus the route taken by Jim last week with their record flight (https://www.facebook.com/SkySight.io...type=3&theater)

The model that is working best this season in the Northeastern USA is GFS. Winds, top of lift, cu predictions all right on the mark. Skysight not horrible or anything, just not as good as GFS. Dr Jack NAM totally broken: dew points much too high, surface forecast highs much too low. Sun on the ground, boundary layer top, winds work.

HRRR has never been useful for soaring here.

T8

On Saturday, June 13, 2020 at 3:22:25 PM UTC-4, wrote:
On Saturday, 13 June 2020 20:54:15 UTC+2, Bret Hess wrote:
It seems that NAM forecasts (12 km and 3 km) on XCSkies are very helpful for soaring in Utah. I haven't seen a benefit of HRRR over NAM. I'd be interested in hearing from other pilots who fly in the mountains comparing NAM with HRRR or Skysight for thermal predictions.

I'd also like to hear a discussion of why a 3 km resolution model is a great improvement for soaring over a 12 km model, for example. Higher resolution models generate more detailed forecasts, and maybe they show better what kind of variation you might see, but the variations at this scale don't seem pinned to the earth at an accuracy of 3 km.

You'll see detailed explanations in my talk above about resolution (https://www.youtube.com/watch?v=Ez9Xjo4llT8) including real world examples of the impact of resolution in the mountains. Over hilly or mountainous terrain the improvement from higher resolution can be significant. On flat terrain the influence is less, although if there's convergences or storms it may still be important.

Unless you're 4km or so you won't meaningfully resolve wave, convergences, or
convection. Instead you need to parameterize [ https://en.wikipedia.org/wiki/Parame...heric_modeling) ] the cumulus and convection, which has drawbacks.

I can't offer a comparison to NAM 3km or 12km, but I can show you the predicted tracks versus the route taken by Jim last week with their record flight (https://www.facebook.com/SkySight.io...type=3&theater)

Interesting T8, I have found the opposite to be true out west. HRRR, and Nam 12, see to be most accurate on the day of and 1 day before, GFS totally useless if not only for long term 3-4 days generalities.

CH ASW27

On Sunday, June 14, 2020 at 1:30:47 PM UTC-4, wrote:
Interesting T8, I have found the opposite to be true out west. HRRR, and Nam 12, see to be most accurate on the day of and 1 day before, GFS totally useless if not only for long term 3-4 days generalities.

CH ASW27

Yesterday GFS and SkySight made similar predictions, GFS more optimistic. The win for the day goes to SkySight, especially for forecasting things winding down at 5pm, right on the money (GFS predicted 6pm). Blue day, sky revealed nothing except a significant inversion when you could get high enough to see it.

T8

On Wednesday, June 17, 2020 at 10:44:53 AM UTC-6, Tango Eight wrote:

GFS more optimistic.

Using XCSkies I also find a similar relation between GFS vs NAM: GFS is always too optimistic for thermals, and NAM is better.

It seems to me that GFS on xc skies always is high on its prediction of surface and altitude winds by about 5 to 10 mph high out west. Dont fly much back east and last year at Perry and Bermuda high I think I only looked at the Nam and Hrrr.

CH