Zezo wind update 1 hr after red line passes?
Post by iconPost by MidnightFoiler | 2020-06-29 | 05:10:59

Hi Cvetan can you explain why I saw this difference in zezo predicted wind - 1st was at 04:20 UTC, 2nd at 04:50 UTC ...



commenticon 20 Comments
Post by iconPost by MidnightFoiler | 2020-06-29 | 05:12:09



Post by iconPost by MidnightFoiler | 2020-06-29 | 05:15:17
I give up embedding ... I guess google drive does not give a raw image link.

https://drive.google.com/file/d/15fEuSD9cRFPzl9bmCUskWPZCpDTnqEfP/view


Post by iconPost by MidnightFoiler | 2020-06-29 | 05:15:50
It was Atlantic run
Post by iconPost by BooBill | 2020-06-29 | 09:55:07
Hey Midnight, I tried to look at that link, but it's restricted access. Or maybe you only wanted Cvetan to see that. Might explain why it won't work as embedded image.
Post by iconPost by MidnightFoiler | 2020-06-29 | 10:12:13
Thanks @BooBill. Fixed that and google'ed how to get a direct link ...
For anyone else .. https://www.mail-signatures.com/articles/direct-link-to-hosted-image/
Post by iconPost by BooBill | 2020-06-29 | 13:49:20
BTW, I experienced two instances during the Solo Maitre CoQ where something very similar happened. One was right at the start. The wind in the router and the game were dramatically at odds prestart. Running the router again 10 minutes into the race and the router had abruptly aligned with the game. If you look at that thread there is a discussion of it there.

The other was during the reach north after the first rounding of Ile de Re. Early GRIB updates as the fleet cleared the island indicated 60TWA. I ran it again an hour later and it had abruptly shifted, indicating 75TWA. Just about the entire fleet continued on at the tighter winds angle and a couple of notables even grounded on I'le de Yeu as a result.
Post by iconPost by MidnightFoiler | 2020-06-30 | 09:55:41
Yes, I have noticed this kind of thing before including those during SMC but never had such a clear example captured to ask Cvetan about.

I know Cvetan has said Zezo uses the old model for the first hour after the update and then the new model after that. I assumed that meant the calculations just after the update use the old model for first hour into the future and then new model later than that and that would mean there is no change 1 hour later but there seems to be a change 1 hour later as if something like the first 6 hours is updated after an hour?

As for the game I believe the forecast in the game updates as each time period becomes available and also does not change once applied - of course the server has whatever it has at the present time but does not really have a future/forecast.

Occasionally I have thought that I have seen a change in the game a bit later but it could well have been the UI not updating with the new forecast - it does seem to help to reload the browser to get it to update. Or it could have been some delay in the forecast becoming available at NOAA or VR. Occasionally zezo has similar issues and gets stuck on the old model. We sailed for a day or so with the same model in the last Dubai to Muscat (I think) because NOAA changed things and VR was not ready for it - Cvetan was faster of course :-)
Post by iconPost by Fouras_17 | 2020-06-30 | 10:29:59
Hello

For me on Record, big problem of mismatch on zezo between CAP and TWA

Translate google.
Pour moi sur Record, grand problème de decallage sur zezo entre CAP et TWA
Post by iconPost by SlyStarLeRetour | 2020-06-30 | 22:18:56
What do you mean by CAP (= heading HDG ?)
i can understand TWA :)
Si c'est plus facile en Français contacte moi sur mp
Bon vent

Post by iconPost by zezo | 2020-07-02 | 12:45:00
What I do is:

Use the old forecast (gfs18z+12) for 6:00 UTC
at 4:30 switch to gfs0z+6

That's why you saw abrupt change.

The game interpolates between the two, weighted by the current time

You rarely notice it in offshore conditions where you are seeking the most stable weather (unless crossing the doldrums), but in coastal/constrained/unstable condition it can be pretty bad.

It won't be too hard to get closer to the game, but I've been quite busy lately and can't find the day or so to implement it.
Post by iconPost by zezo | 2020-07-02 | 12:46:41
To put it another way, the first (currently in use) grib actually stays behind the red line and catches up at 4:30.


And yes, the game client and server seem to use different algorithm for the weighting of the two files which leads to internal discrepancies.
Post by iconPost by BooBill | 2020-07-02 | 14:48:32
So, just to be clear, when is it safe to go to bed? When is the grib in use by the router the one that will stick for 6 hours?

The 0600Z update starts coming down at 2337 my time. If I'm only concerned about transitioning through the next 6 hours, I've usually run a route at 2340est, which should give me the next 24 hours. After that, I set my course and go to bed. What you've said above should make that safe, but we've clearly seen cases recently where dramatic changes happened after that.

I guess if we don't know the exact times the game implements the updates, then the answer is staying up till the time stamp (0100EST Uggggg).
Post by iconPost by zezo | 2020-07-02 | 15:18:52
Everything gets perfectly in sync by 6:00 UTC and you have to wait for it in tricky conditions.

Most of the time you can go to bed when the red line passes your desired destination, if there is less than a degree or two and .1 -.2 knots difference, and even safer after 4:30 etc. half-way updates if the conditions match.
Post by iconPost by YourMomSA | 2020-07-02 | 18:37:34
It's never safe to sleep. Especially if I'm behind you. :-P
Post by iconPost by UUnet | 2020-07-02 | 21:10:44
lol :-) same to me when I try to catch you Your Mom ;)
Post by iconPost by BooBill | 2020-07-02 | 23:14:34
That's where I look to see you @YouMomSA. Behind me.
Post by iconPost by MidnightFoiler | 2020-07-03 | 03:18:58
Great thanks. Not particularly a problem and again adds another element of skill that it is not perfect. Would be nice to be able to go to bed earlier when things are tricky though ;-)

We all know you like to sleep through YM ...
Post by iconPost by MidnightFoiler | 2020-07-03 | 03:28:30
Before the switch at 04:30 how far out are you using the 18z model? Just to 18z+12 or out to say 18z+15?
Post by iconPost by zezo | 2020-07-03 | 09:08:49
Just the first one, old+12 (new+6). Past that point the game also uses the +6/+9
Post by iconPost by KelpiedSinglePlayer | 2020-07-07 | 20:55:53


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