Zezo forum: Windshadow

Windshadow

Post by Flying Dutchman | 2018-02-16 | 18:34:20

@ Cvetan
Does zezo router take into account windshadow of the islands?

13 Comments

Post by Flying Dutchman | 2018-02-16 | 18:39:59

The route brings me close to the Solomon islands Auki and Kirakira with highest speeds but wonder if this taking into account the windshadows

In VR.... Does VR take into accoount windshadow?
Remember that on leg 2 some boats including MOM passed just sound of one of the Cape Verdi islands and did not seem to suffer at all....where I thought that I needed to avoid the windshadow.

Anyone any knowlegde of the real world wind shadows compared to the VR game and zezo router?

Post by karriv | 2018-02-16 | 18:44:21

The router uses the same wind model as the game. The router takes any wind shadow into account exactly to the extent the game does.

Post by Flying Dutchman | 2018-02-16 | 18:55:38

Thanks Karriv for your quick reply... but that brings me to my second part of the question. Does VR and zezo really take it into account?

Post by zezo | 2018-02-16 | 20:19:19

It's not about the router, it's about the weather model used.

GFS does not have enough spatial resolution to care about islands. That's why it's not really useful for coastal navigation, but pretty good for ocean passages.

Post by zezo | 2018-02-16 | 20:25:43

Open https://www.windy.com/?gfs,-5.723,156.050,8

Switch from GFS to ECMWF to see the difference. And this is the best possible 1/4 degree GFS output. The game uses 1-degree resolution data.

Post by Flying Dutchman | 2018-02-16 | 21:25:05

Thanks Cvetan, I use Windy too. Great charts. I think I understand your explanation about the resolution.

Maybe I have to ask a different question.....
Does the game and the router take the windshadows into account as in the real world or can they not? (A little the same as the game has a 4 kt minimum where the real boat experience 0 kt).

I seem to have noticed in leg 2 that some boats passed really close under the Cape Verdi islands in windshadow areas seemingly without having any less wind.

Post by zezo | 2018-02-17 | 08:48:26

1 degree resolution translates to 100 km linear size near the Equator, so objects smaller than about 50 km just don't exist in the game wind field. And GFS is not very good with topography to begin with - see this paper https://soaringmeteo.org/GFSw/helpGFS.pdf about flying in the Alps. Pretty much the same idea as sailing around islands.

Post by Flying Dutchman | 2018-02-17 | 10:23:58

thanks Cvetan....learning each leg:)

Post by zezo | 2018-02-17 | 10:46:16

There is some difference even with GFS and it's not bad to keep an eye on it - see the current weather around the Solomon islands. Just not like in real world where you would see 20 knots on the windward side and 2 knots on the leeward.

Post by Flying Dutchman | 2018-02-17 | 11:45:34

Yes it shows that GFS (and so the virtual race) does take an avarage and there is certainly not as much windshadow as in the real local situation.
Shows again we are sailing a totally different race which needs a total different strategy than the real boats.

The current forecast around the Salomon Islands and after seems very unstable at the moment. big decisions to be made soon......some already made it:)

Post by WretchedExess | 2018-02-17 | 14:48:23

Speaking of WINDY, is there a way to format the position field in DASHBOARD so that it can be cut and pasted into WINDY? The way it is now, it puts me somewhere in Africa. I have been highlighting position, right clicking, selecting "search Google" and then cutting and pasting the decimal coordinates. This at least puts me in the right location.