Facebook

Login

Support Sailonline

If you haven't already - join the SAILONLINE YACHT CLUB!

Please also consider making a donation - all amounts are greatly appreciated!

Board » General Discussion » Weather - Brain Storm

Page: 1 2 3 Next

Posted by
bonknhoot


Users avatar

Posts
104
Registered at
2013-08-06 21:35:15
2020-09-02 08:59:38 - Weather - Brain Storm
Recent chat in the M2O 2020 about the weather that we import into SOL has prompted this new thread, hoping that concerns and ideas may gravitate towards some sort of consensus or conclusion. Whether anything can be done with such a conclusion is another matter.
Remember: SOL is a 'cooperative' and everything that happens is done by volunteers. Any change in the fetching of weather is likely to require changes to the software (the racing engine) that runs on the server. This is no sinecure, and the volunteer resources that we have that can attempt this are scarce.
I'll get the ball rolling with a separate post about the status quo.
Clipping along
Posted by
bonknhoot


Users avatar

Posts
104
Registered at
2013-08-06 21:35:15
2020-09-02 09:15:54 - Re: Weather - Brain Storm
Currently, we have the capability to fetch three sources for weather with the following 'tags' - global_gfs, nam_awip12 and wrfems, updating every six hours.
global_gfs is what we use most often and it is rough-and-ready. I'm not hugely familiar with meteorologist terminology but I think it is what is called 'synoptic', which I think means it is primarily based on surface pressure variation; in other words, there is no modelling of local coastal effects. The highest resolution we can fetch is 0.5 x 0.5 degrees, in other words the data - that is then interpolated by the server (or a router) - is given at nodes set 0.5 degrees of longitude and latitude apart.
0.25 degree resolution is in fact available, but we can't fetch it. With 0.25 resolution the amount of data describing the wind over space and time increases by a factor 4, and obviously routing or SOP-ing through this becomes commensurately trickier.
I'll write a second note later.
Clipping along
Posted by
Zorba777


Users avatar

Posts
67
Registered at
2020-06-06 08:22:54
2020-09-02 14:51:37 - Re: Weather - Brain Storm
Thanks for setting up this brainstorm, Jan. My concern is: what happens if GFS (or other WX sources we use) start updating every 3 or 4 hours? I have the impression that even with the every 6 hour updates it is already difficult for some people to combine SOL with their professional or family life (as well as sleep). So, maybe we can discuss that in one go.
But in keeping with my first question I want to submit this article which takes a good look at where weather forecasts could be going in the coming years. Some techniques seem to pave the way for accurate forecasts that are 8 times longer than we now have: https://metro.co.uk/2019/09/18/will-weather-forecast-ever-100-correct-10751641/
Posted by
bonknhoot


Users avatar

Posts
104
Registered at
2013-08-06 21:35:15
2020-09-03 09:10:25 - Re: Weather - Brain Storm
That is a very interesting article, Dan, but I suppose it all depends on what NOAA consider 'accurate' or 'correct', when it is quoted to state 'a seven-day forecast is accurate around 80% of the time' or 'a five-day forecast is correct approximately 90% of the time'. One can imagine that the assertion is correct about something like 'it will rain in The Peloponnese tomorrow', but, as we know from experience, it doesn't imply that the wind strength and direction forecast for 120 hours ahead at a specific lat/lon posn will be re-forecast as exactly the same 6 hours on, now 114 hours ahead.
I would like to think that that sort of accuracy will remain impossible for very many years yet. So, that aspect of our game - forecast volatility and second-guessing the met service - is not much at risk, IMO.
I do agree with you that once gribbed free-issue forecasts become available with a frequency of every 3 hours, it would reduce the attractiveness of our game if the game were to fetch these every 3 hours as well. I see little reason (though not none) for simply keeping our own fetch frequency at 6 hourly; especially if 'accuracy' has improved anyway.
Indeed, I would suggest it could mean an opportunity to reduce our fetch frequency to every 9 hours, which would give everyone around the world a midnight WX every couple of days.
Clipping along
Posted by
bonknhoot


Users avatar

Posts
104
Registered at
2013-08-06 21:35:15
2020-09-03 10:25:33 - Re: Weather - Brain Storm
My agenda is not so much a concern with ever more and better forecasts, but a concern with the rough-and-ready nature of global_gfs, our standard 'go to' weather. The question and the challenge I want to raise is 'Can we do better?'.
For the long distance ocean races, this question is not so important, as, out in the middle of the ocean, modulation for whatever should change little to a forecast, and because guessing what is the best thing to do given the uncertainty about what the wind will really be a week ahead will continue to be a challenge for SOLers.
It is the races of say 3 to 4 days maximum that I feel/find are or have become somewhat mathematically deterministic. You have to have the tools to do the math, but once you have such tools working for you, a race becomes primarily a "do" exercise.
Clipping along
Posted by
ij


Users avatar

Posts
33
Registered at
2018-06-09 20:33:19
2020-09-03 17:24:22 - Re: Weather - Brain Storm
I'm sorry to spoil the party but I'd prefer to always sail on WRF weather. Obviously that's not "feasible" in the most straightforward manner for races over large areas. However, if it would be possible to limit calculating the wrf forecast only to areas where there are boats, where the boats can reach, and only calculate very short-term wrf, like 12h-15h (mostly to cover across a single wx update failure), it could bring down the amount of processing power needed for the forecasting.

So we'd be having sort of composite wx with a base layer of 0.25x0.25 gfs to visualize longer term forecast and act as a backup wx. Which parts of the base layer would be selectively replaced by wrf would be dynamically determined as the race progresses.

Whether we have computation capability to do that (or would be able to get the necessary processing capacity) I have know idea but I certainly would want to know how big area would need to be calculated. Even in ocean races boats tend to keep in packs (although wrf itself might impact the dynamics that typically lead to it with gfs). The biggest problem in this approch IMHO is the long tail of boats because they'd require disproportionate amount of the all processing.

If that turns out still infeasible, some additional filter could be applied which allows using wrf only under conditions where wx seems unstable (based on the corner wind components it's possible to estimate this I think) or when there's landmass.

It's very complex to realize technically though, we cannot even run the 0.25x0.25 gfs part of that currently so it may remain wishful thinking.

--
i.
Posted by
ij


Users avatar

Posts
33
Registered at
2018-06-09 20:33:19
2020-09-03 18:11:38 - Re: Weather - Brain Storm
I agree with bonk that 80% reliability is really a joke. Even 90% is not really something I'd boast about. It's worth to remember the error starts to rapidly accumulate. It's unlikely to be dropping linearly but more like larger error also leads to much larger error accumulation (and thus uncertainty).

I've never seen the definitions of that kind of % metric anyway (so if somebody has pointers to some scientific papers evaluating forecast long-term accuracy, please, I might read myself). But I wouldn't be surprised if it turns out quite bogus or irrelevant to measure what kind of accuracy we're talking here.

--
i.
Posted by
ij


Users avatar

Posts
33
Registered at
2018-06-09 20:33:19
2020-09-07 22:16:10 - Re: Weather - Brain Storm
Comparing 0.25x0.25 wx grid with 1x1 (I forgot to make the arrow density the same so please disregard that difference):

https://postimg.cc/F19n3Yjp

--
i.

--- Last Edited by ij at 2020-09-07 22:18:39 ---
Posted by
ij


Users avatar

Posts
33
Registered at
2018-06-09 20:33:19
2020-09-09 21:00:45 - Re: Weather - Brain Storm
Just a minor note from some ECMWF validation report now that I came across one: in 10m wind at 5 days the frequency of large errors is around 4% (+/-1 due to year cycle) now so it's in ballpark with those 90/80% numbers. (And in temps slightly worse.)

GFS is likely somewhat worse than that given ECMWF is generally considered slightly better although both can be shown to be better in selected cases.

What is means to routing accuracy is hard to know without looking deeper into the report (if it's told at all). The distribution of the large errors over time matters too much. But if distribution would be uniform (it very likely isn't), one would very likely hit one large deviation in almost every 2 weeks long race. And how bad the large error % gets when consider beyond 5 days, no idea.

--
i.


--- Last Edited by ij at 2020-09-09 21:01:19 ---
Posted by
Zorba777


Users avatar

Posts
67
Registered at
2020-06-06 08:22:54
2020-09-10 08:30:59 - Re: Weather - Brain Storm
Hi Bonk and Ij,

I don't know how accurate the weather models will become. Even the experts don't agree on that question. We can probably just agree that they keep getting better and look at possible consequences for SOL simulations.

I agree with Jan on the possible problem that shorter races are moving closer to "fixed solution". If there is only 1 (or even no) WX change during a race we are on a fixed weather map where good math tools can figure the winning route and then it just becomes a question of who executes that route more optimally. But some SOLers like that kind of challenge, so I wouldn't take that away.

If long term weather forecasts get more accurate then even the medium term (3-4 day) races would become more like sprint races where execution of near optimal route is more important than anticipation of weather changes.

In the long ocean races it will not be anytime soon that weather models can give us a near optimal route for more than 2 or 3 days. But if WX updates become more frequent then we would have to think about SOLers' sleep.
We can decide to skip some updates and only update the maps that SOL uses every 6 or 8 hours. But even in that case some players would gain an advantage by looking at the GFS updates we skip, because they will already show in what direction the weather is changing. Perhaps it would be more useful to change to a more detailed, but less frequently changing, source of weather data as ij suggests...

--- Last Edited by Zorba777 at 2020-09-10 08:47:58 ---

Page: 1 2 3 Next

Please login to post a reply.

Races

Next Race: 00d 00h 00m

Current Races:

Valparaiso to San Francisco 2025

Get ready for an exhilarating new challenge as we set sail on the fourth leg of the 2025 Ocean Championship Series! Following in the 19th century footsteps of Isabel Allende's heroine, Eliza Sommers, 'Daughter of Fortune', this all-new route takes us across the vast eastern Pacific, from Valparaíso, Chile, to San Francisco, California - a 3500nm journey of endurance, strategy, and pure sailing adrenaline. This leg will be raced aboard the powerful Rapido 60, pushing sailors to their limits as they navigate the open ocean. Do you have what it takes to conquer the Pacific? Join us and put your skills to the ultimate test!
PRIZE: SMPF
Race #1900
INFO by brainaid.de
Rapido 60 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: OCQ2 - OCCH - SUPSOL - SYC
Race starts: Apr 07th 11:00 Registration will open soon
▶ Flash
GO TO RACE

Red Eye - Round White Island 2025

We remain in New Zealand for our second “Red Eye Special” and another IRL Kiwi classic - the Round White Island! IRL still “currently on hiatus” following the island’s eruption of 2019, this race was last raced on SOL in 2020. It’s about 300nm there - out the Hauraki Gulf and south down to the island in the Bay of Plenty - and back to Auckland. This year we’ll be racing in our ever-popular take on the TP-52. Hau tika!
Race #1844
INFOby brainaid.de
TP-52 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC - RED
Race starts: Apr 06th 12:00 Registration will open soon
▶ Flash
GO TO RACE

Moheli PYOC 2025


For our first sprint of Q2, we will re-visit the African archipelago nation, L’Union des Comoros, and its most southern island, Moheli, in the Mozambique Channel. Created by MustangMark in 2014 this is a “Pick Your Own Course” round the island, approximately 20nm in our First 27. Expect winds to be light and variable; we are in the Tropics.
Race 1907
INFO by brainaid.de
First 27 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
SPRQ2 - SPRCH - SUPSOL – SYC
Race starts: Apr 05th 09:00 Registration will open soon
▶ Flash
GO TO RACE

Africa by Sea - Tangier to Abidjan


Whatever about pharaoh Necho II’s Phoenician expedition of the 7th C BCE, the Carthaginian Hanno the Navigator with more certainty sailed south from Tangier to explore the West African coast two centuries later, but how far he got is a matter of more conjecture. However, if he did the 2300nm to today’s Ivory Coast he would have found little there other than good shelter in the vast lagoons behind the dunes, much the same as today, excepting the highly industrialized port of Abidjan. Not a great haven for a stop-over but let’s take the 90ft Monohull anyway.
Race #1855
INFOby brainaid.de
90ft Monohull PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC - ABC
Race starts: Mar 26th 17:00 Registration Closed
▶ Flash
GO TO RACE

Sea Lion TIMED Race 2025

Come on down South for long days of sunlight and strong bracing winds to race our Finngulf 43 as many times as you like - 117nm as the albatross flies - through some of the islands of the Falklands archipelago. This is a TIMED race, so you may RE-REGISTER HERE to try again, after finishing a run. You will have 13 days and 11 hours to test your skill and decision making after the race opens.
Race #1903
INFO by brainaid.de
Finngulf 43 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
TRQ1 - TRCH - SUPSOL - SYC
RACE CLOSE: Saturday,
05 April at 23:00 UTC
Race starts: Mar 23rd 12:00 Registration Open!
▶ Flash
GO TO RACE

Melbourne Osaka Cup Double-Handed Yacht Race 2025

Welcome once again to what these days is Sailonline’s almost annual virtual Melbourne to Osaka Yacht Race. In real life, this double-handed 5500 nm race between these two sister cities, one deep in the southern hemisphere, the other high in the northern hemisphere, is run every four to five years, and this year is such a year. So, this year’s online version is in sync with the Melbourne Osaka Cup 2025 organised by the Ocean Racing Club of Victoria (ORCV), and the Sandringham (SYC) and Osaka Hokko (OHYC) yacht clubs. We’ll be racing the well-known First 40, a popular size of boat which should be a good match for many of the boats entered in the real race. With the doldrums unavoidably lying across our course, you can expect to be at virtual sea for at least a month!
Race #1669
INFO by brainaid.de
First 40 Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC
Race starts: Mar 16th 06:00 Registration Closed

▶ Flash
GO TO RACE

Go to race archive

SYC Ranking

  1. Sailonline Yacht Club Member Patrick70119
  2. Sailonline Yacht Club Member WRmirekd
  3. Sailonline Yacht Club Member CriticalHippo
  4. Sailonline Yacht Club Member vida
  5. Sailonline Yacht Club Member KaSToR
  6. Sailonline Yacht Club Member rafa
  7. Sailonline Yacht Club Member FreyjaUSA
  8. Sailonline Yacht Club Member Kipper1258
  9. Sailonline Yacht Club Member bonknhoot
  10. Sailonline Yacht Club Member rumskib

View full list

Series

Mobile Client

SYC members have the benefit of access to our mobile/lightweight web client!

The mobile client