Weird wind direction by HRDPS model

idefix37

You seem to be absolutely right. In your example on the sea, the wind angle predicted by HRDPS relative to the isobars is really not plausible and too important. Moreover, this direction is not consistent when compared to other models and to the forecasts you have shown.
The developers should seriously take a look at this issue.

Edit: On the west coast, the HRDPS forecast wind direction seems more consistent when compared to those from ECMWF, GFS and HRRR Alaska. This is strange.

tawmdotcom

@idefix37 Yes indeed, that is strange.. I chose a point 55°N 135°W and the extreme cross-isobaric flow noted on the HRDPS depictions for Atlantic Canada are not apparent. Also, the wind direction arrows in the time-series depict a southeast flow as expected. So it would seem there's something odd going on with the HRDPS wind directions in the Atlantic Canada domain, cheers..TDC.

Windy HRDPS time-series 55N135W 10-12-2024.jpg

idefix37

@Wheats
Any thoughts about this weird problem with HRDPS wind direction forecast ?

Filip_K

Hi @tawmdotcom and @idefix37,
I agree that the wind direction suspicions, so I've checked the data. I checked point N49.196, W60.029, for 2024-12-12 21.00, run time 2024-12-12 06.00 where HDRPS predicts surface (10m AGL) wind straight from 180˚ (so basically only v-component)

while ECMWF predicts same wind from 220˚ (40˚ difference!)

When I load gribs for this forecast step (u-component available here and v-component here) in QGIS, for example, I get same result (+15m/s in v-component and almost zero in u-component):

So I believe we (as windy) are displaying the data correctly. Unless u/v-components are not east/north components, but rotated (since HRDPS is using rotated latlon projection, as stated in the docs). But that would mean that all wind directions are displayed wrong, which doesn't match Your observations.

Wheats

@idefix37
Definitely something fishy going on...
Windy

MSC AniMet

https://eccc-msc.github.io/msc-animet/?layers=HRDPS.CONTINENTAL_PN%3B0.75%3B0%3B1%3B0%3B1,HRDPS.CONTINENTAL_UU%3B0.75%3B0%3B1%3B0%3B1&extent=-10919169,3542499,-3460008,7081715

I don't know if there is a difference between the HRDPS I see right from MSC and the HRDPS Windy gets but the direction is definitely off, even isobars are much more smoothed out on Windy.

Wheats

@Filip_K
I don't know if this is helpful but info on the site I referenced is here.
It's all on github as far as I can tell
https://eccc-msc.github.io/open-data/msc-animet/readme_en/

Filip_K

Hi @Wheats, thanks for AniMet, good idea. For the same spot, I get different values for u/v-components:

I'll try contacting MSC and reference this thread as it contains all info needed for debugging the issue (at least I believe so).

Caefix

👀

Filip_K

The fix has been deployed, wind direction from reference time 2024-12-17T12:00Z on should be correct.

idefix37

@Filip_K
Thank you it seems correct now

06Z before fixing

12Z after fixing

The wind direction is now consistent.

Thanks to @tawmdotcom and @Wheats

tawmdotcom

The HRDPS cross-isobaric flow looks OK now, many thanks for looking into this and implementing a fix, cheers.. TDC.