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Profile for ij



Name ij
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Posts21
  • Re: Weather - Brain Storm
    Board » General Discussion
    Of the available forecasts, these regional ones certainly seem interesting for higher than GFS precision:
    - ICON-EU
    - AROME
    - NAM conus & maybe caribbean nests

    For global models, I don't think there are freely available alternatives with enough incentives to make it worth replacing GFS, and many have clear disincentives such as non-even forecast lengths for different times.

    Without at least seriously trying out with GFS 0.25 x 0.25 first, I wouldn't spend too much effort on the other global models that are freely available. (ECMWF is not freely available, if it would be, it would certainly seem attractive enough).

    In practice, the blocker for any high-res wx is the lack of tiled wx support which requires too large modifications before some other blockers are removed first so it's not going happen over a weekend (I've definitely made some progress towards that direction but it's a big task with rather limited help so far). Even the WRF weathers which we've not been able to use for some time were somewhat big data sizewise for anything else than those small sprints (but certainly made the races much more interesting, IMHO).

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    i.
  • Re: Weather - Brain Storm
    Board » General Discussion
    Many numbers you see on those lists are not correct. ECMWF updates 4 times per day but only to +90h on every second run (Similar to some other forecast runs with other models).

    Also, they explicitly mention not-for-profits in their license selection guidance so you're just dreaming and there's little point in trying to ask anything from them.

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    i.
  • Re: Weather - Brain Storm
    Board » General Discussion
    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 ---
  • Re: Weather - Brain Storm
    Board » General Discussion
    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 ---
  • Re: Weather - Brain Storm
    Board » General Discussion
    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.

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    i.
  • Re: Weather - Brain Storm
    Board » General Discussion
    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.
  • Re: Public testing new HTML5 client
    Board » General Discussion
    Stable version of the client was updated yesterday (2020-06-29). Long list of changes (new lines added here and there to make it easier to read):

    - Day/Night mode, see Settings if you don't like the defaults.
    - Automatic contrast correction for fleet boat colors.

    - Complete overhaul on network logic to allow client side retries. While the default timeouts are quite lax, please let the us know if you encounter challenges in starting up the client.
    - Clock offset correction at the start of the client. Stable offset should no longer cause problems to the client. If clock is changed (jumped a lot) by something after the start of the client, client reload may still be necessary to recalculate the correction.

    - Predictor takes the current performance into account. Other improvements to predictor accuracy with more accurate starting point.
    - Improvements to predictor and DC dot consistency during the towback period.
    If you depended on predictor during towback, the time markers are now different from the previous to match the DC delays that must be used.

    - Land polygons participate in the zoom in/out effects.
    - Boat type related layouting improvements.
    - Boat type based boat lists have been added (only available in multiclass events).
    - Setting for default weather step added.

    - Support for polar curves >30kn if different from the others.
    - Polar curve drawing order derived from the difference to the current TWS.
    - Polar curve modes added (low TWS, <=30kn, default).

    - New chat messages alert triangle added.
    - Boat keys can be added to map (with the same max limit as in legend bottom left corner). These are known to suffer from small visual glitches that are hard to fix.

    - VPP polar link added.
    - Quick help added.
    - VMC added to steer tool info box (when VMC instrument is enabled).

    - WX slider tics added (black = absolute hours, red = WX updates, wide green band = race start time).
    - Improvements to the initial zoom in, zooms to the "remaining" race course.
    - Allow disabling initial zoom (to workaround missing marks issue with Chrome).
    - Clicking a boat name on chat or on boat legend highlights the boat.

    - Ability to degrade into chatless contingency mode if chat messages cause problems to the core functionality of the client. Once the problem is resolved, the client automatically leaves the chatless mode.
    - Automatic reauthentication support added (needed when the IP network changes).

    Please let me know if encounter some problems with it. If the updated versions fails to work for you, the old version is accessable by appending ?version=old to the URL and reloading the client.

    --
    i.

    --- Last Edited by ij at 2020-06-30 08:36:00 ---

    --- Last Edited by ij at 2020-06-30 08:36:50 ---
  • Re: Public testing new HTML5 client
    Board » General Discussion
    It would be tricky to realize 1) because the WX has not yet been loaded when the initial zooming takes place so no idea how far the predictor will go. I guess it could be possible to find out polar max speed and use that as a rough guide. However, there's small improvement to this in the dev version as it zoom to the remaining course rather than entire race but of course it won't help when still near the start in a long race.

    Can't you zoom using other means than with + button which is kind of slow?

    2) I can consider adding it but I need to find some place for that show/hide thing (the most obvious place is taken in the dev version for selecting the polar curve mode). ...And the next thing people will tell is that they want to see the both polar and DCs at the same time :-). It would make the steering tab quite crowded.

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    i.
  • Re: "newby" doing Newport Bermuda Race - Expedition & Wx advice
    Board » Technical Support
    Minor correction to what Dingo said. Current GFS grid can go down to 0.5x0.5, not below that despite NOAA providing also 0.25 GFS. This may change in the future though. In some races, the weather data size is reduced by using larger wx grid cells such as 1x1 or even beyond that in some long ocean races.

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    i.
  • Re: Weather Gribs
    Board » General Discussion
    Please check this site:

    https://www.nco.ncep.noaa.gov/pmb/nwprod/prodstat_new/

    Status at 07:05 UTC tells that GFS 06 UTC is only in "SCHEDULED" state.

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    i.

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San Francisco Bay 2020
Many a Sailonline race has started or finished at San Francisco's Golden Gate, but never have we raced inside The Bridge on The Bay. This 27nm sprint corrects that oversight with a fine sight-seeing tour past Alcatraz, Yerba Buena, Brooks and East Marin Island. Our rarely raced Fox 9.50 is your boat of choice. She's a nippy little thing. Enjoy!
Race #1369
INFO by brainaid.de
Fox 9.50 Particulars
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0245 / 0845 / 1445 / 2045
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In 2012 Sailonline lost one of its more remarkable racers, Aaron Gage, the creator of the Flash client and all-round awesome human being. In his memory, Tyger created a superb series of races around the island of Australia - the A3 (Agage's Around Australia) Series. This race is Leg 8 of the series - a race of 1860nm in Orange 125ft Catamarans from the laid back north to the booming mining capital and yachting centre of Perth in the south of the state of Western Australia.
Race #1386
INFO from brainaid.de
Orange 125ft Catamaran Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: A3 - SYC
ALT CLIENT:Classic
Race starts: Sep 22nd 21:00 Registration Open!
HTML5 Client (beta) GO TO RACE

Foveaux Strait TIMED Race 2020
Welcome to southern New Zealand, and welcome to this TIMED race through the South Island’s Foveaux Strait. According to a Maori legend, the strait was created by Kewa the obedient whale when traditional Maori ancestor Kiwa summoned the whale to create a waterway. It is a rough and often treacherous stretch of water. Our 98nm quadrangular course goes around some small islands in the strait. To zoom around these islands in style, we will pull our Seacart 30s out of the shed and let them fly. Enjoy!
RE-REGISTER HERE to race again after finishing a run.
Race #1375
INFO by brainaid.de
Seacart30 Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
RANKING:
TRCH-SUPSOL-TRQ3-SYC
ALT. CLIENT: Classic
RACE CLOSE: Monday,
27 September at 2300utc
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Welcome to the Caribbean and Sailonline's 2020 Pirate Name PRIZE race, running with Bart's Bash and ahead of International Talk Like a Pirate Day on 19 September. This is a 1759nm slalom through the rum islands of the Caribbean, for the first time in a Clipper, collecting barrels from the region's distilleries and carrying them to the rum-parched beaches of Cancun, Mexico. If ye scurvy swabs are up ter it, then ye be invited to attire yerselves in a piratical disguise by becoming an SYC Member and requesting to change your boat name for this race only!
Race #1384
INFO from brainaid.de
Clipper 240 Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC
ALT. CLIENT:Classic
Race starts: Sep 10th 17:00 Registration Closed
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Welcome to Melbourne for Sailonline's Melbourne to Osaka 2020 Double Handed Yacht Race - a 5000 nautical mile 2-handed yacht race and the only one running from the southern hemisphere to the northern hemisphere. This year we're racing the Riptide 50. It could be a long race!
PRIZE: SMPF
Race #1372
INFO by brainaid.de
Riptide 50 Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: OCCH - OCQ3 - SUPSOL - SYC
ALT. CLIENT:Classic
Race starts: Sep 01st 19:00 Registration Closed
HTML5 Client (beta) GO TO RACE

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SYC Ranking

  1. Sailonline Yacht Club Member Kipper1258
  2. Sailonline Yacht Club Member bonknhoot
  3. Sailonline Yacht Club Member knockando60
  4. Sailonline Yacht Club Member rafa
  5. Sailonline Yacht Club Member nacrr
  6. Sailonline Yacht Club Member calmxy
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  8. Sailonline Yacht Club Member SimeMali
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  10. Sailonline Yacht Club Member Dingo

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