Missing Data for swell 1 on gfsWave

[b.rochut]

Hello,

We are experiencing some weird data with swell 1 values on gfsWave API.
We're getting higher swell 1 than the total wave height.
Ex :

• Timestamp : 1681257600 (04-12 00:00 UTC)
• Position : 29°N ; 89°30W
• Wave Height : 1.0397
• Wind Waves : 1.0397
• Swell 1 : 2.5998

We checked on windy and it seems there is missing data for swell 1 with gfs model (see picture)

Is there an explanation for that ? Why is the API giving some weird value instead of a NaN or something like that ?

Moreover, it seems that there is some difference between the API result and the windy picker for same timestamp and location.

Regards,
Basile

[idefix37]

@b-rochut
I can’t verify what you observe in the API.
In Windy these gray tiles show that the Swell is near 0ft (10cm if you set heights in metric). Same for Swell 2 and Swell 3 but on a larger area. I guess GFS don’t provide swell data in these gray areas where swell height is almost zero.
While Waves layer is locally showing 1ft and Windwaves 1ft too. It means that the total sea (Waves) is only produced by the local wind right now and according to GFS prediction.

[b.rochut]

Hi @idefix37 and thanks for your quick answer !

Yes that's what I was thinking for the website, missing values means 0 m.

My question is then why the API is giving a different value for the same location and same timestamp ?

Here is my API call code :

And here is the result (I reduced it to get the last timestamp on the one we want 1681257600 (04-12 00:00 UTC) :