Gfs upgrade v16.3
Good evening everyone
It is known that there is a gfs update with v16.3 with an accuracy of 0.25 and a horizontal accuracy of 13 km on 29/11/2022. Is there an update on the gfs maps in windy as it is now with an accuracy of 22 km as the site mentions?
Hi, afaik GFS v16 is computed at a 13km resolution but displayed for each with 23km resolution. You say 0.25°, a quarter of 1° which is 111km. It is therefore not less than 23km. Nothing is changed for horizontal resolution and GFS was always been computed at 13km but displayed at 23km.
What has been improved is the vertical resolution.
O.25° = 0.25x60nm = 15 nm =27.8 km
Yes Mate, you are right or in another way
1° = 111.1km
0.25° = 1°/4 = 111.1 / 4 = 27.8km
which is not 13km as said above.
Then, the question is why does Windy say the GFS resolution is 22km, not 27km?
The NOAA gives the resolution as measured on the parallel of Washington (39°N) which is about the parallel in the middle of USA. But parallels are not great circles.
0.25° measured on this parallel is not 27km, it is 22km as shown by this sketch.
This way of specifying the resolution of a global model seems to be a sort of standard now. The ECMWF center says that its model (IFS) has a resolution of 0.1° or 9km. It is obviously measured also on 39° parallel (which is not however in the middle of Europe).
Hope my sketches are clear.