Weird wind direction by HRDPS model

[idefix37]

@tawmdotcom

Personally, I don’t see any problem with the wind angle relative to the isobars when using the HRDPS model.
Over the sea, we can generally observe that the wind forms an angle of 15°/20°. Here, over Hudson Bay, the angle is a little larger.
Over land, it is generally 30°/40°, but it increases if the terrain is more rugged.
In the mountains, especially in the high mountains, this angle can reach 90°, as you can verify with other models over the Rockies. This is what we observe in British Columbia.
These changes in angle relative to the isobars are due to increased friction on the earth's surface.

[tawmdotcom]

@idefix37 Hello, I have to respectfully disagree. If you examine the attached images of the spot location 54°N 055°W off the south Labrador coast for the Tuesday Dec 10 evening period, both the ECMWF and GFS are consistent with the pressure pattern by rightly depicting northwesterlies with a cross-isobaric flow of about 25° more or less. Meanwhile, the HRDP is depicting a west-southwesterly flow, nearly at right angles to the isobars. The situation becomes even more suspect upon examining the HRDPS output using the Spotwx app for same location and time-period. Both the time-series and tabular forecast data are correctly depicting a northwest flow. Furthermore, the official marine forecast for the South Labrador Coast is predicting northwesterlies for the period in question, consistent with the ECMWF, GFS, and Spotwx. On a related note, I'm a marine meteorologist with close to 3 decades in the biz, so based on my experience I strongly suspect there's something amiss with the HRDPS wind direction as depicted on Windy. Cheers.. TDC.

[idefix37]

@tawmdotcom

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.

[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.