Swell period values in the Eastern Mediterranean Dec 06 2017

[amielh]

Dear Sirs,
The swell period predictions for tomorrow Dec 6 2017, given by the ECMWF model after midday look very large and no other forecast gets to even a half of the values. I have never seen in this area swell periods of 25 sec.
Could you please check if this would need t be a misunderstanding?
Thank you,
Amiel

[TZ]

@amielh Hi, maybe you are right. If it is possible for you, please let us know, what the real value was.
It seems that we should add some other wave model for mediterranean.

[Gkikas LGPZ]

@amielh
Please send us a screenshot.
As I can see, for Dec 6 (after midday) the swell period in East Med. is forecasted 10 sec max.

[Gkikas LGPZ]

@amielh
Hmm, you are right.
Now I realized the problem ...
The ECMWF's prediction (10 sec) seems to be OK.
The Windy's visualization seems problematic.

[Gkikas LGPZ]

@TZ
I think at "wavegram",
in the section "swell period"
you visualize "swell3" instead of "swell"

[Gkikas LGPZ]

@amielh
This article may help.
https://community.windy.com/topic/3603/different-definitions-for-the-wave-periods-are-shown

P.S. Jean-Raymond Bidlot is a top wave modeller at ECMWF

[TZ]

@meteo-gr Your left screenshot probably shows period of total waves, not swell. When you switch overlay to swell, you will also see values bigger than 20 s.

[TZ]

@amielh, @meteo-GR
I was investigating whether there is some bug in our processing or not. In the black/white screenshot below you can see visualization of ECMWF WAM "raw data" in QGis software. Sampled value in eastern mediterranean is 27 s. So our processing and visualization seems to be correct.
Comment on topic of Jean-Raymond Bidlot, which meteo GR cited: We changed displayed parameter of ECMWF in last waves update, so now it should be comparable with Wavewatch. For both models we now display 1st swell partion as "Swell". Maybe definition of 1st swell in Wavewatch is different from 1st swell in ECMWF? @jrbidlot

[Gkikas LGPZ]

@tz

[Gkikas LGPZ]

@TZ

[TZ]

@meteo-gr The discrepancy between screenshots comes from different timelines in detailed view and mapview. In detail view there is local time of the picked place, but the map view timeline contains timezone defined in your computer. Try to move 3h back in mapview timeline (with closed detail) and you should see also value bigger than 20 s.

[TZ]

@meteo-gr Your last picture shows "Mean period of total swell", but as I said, we now display "Mean wave period of first swell partition" in order to display comparable values to Wavewatch.