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Wind Forecast - Is it accurate?

Discussion in 'Alpine & Southern' started by IZN, Aug 1, 2007.

  1. IZN

    IZN Hard Yards

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    Hi,

    After two years of voyeurism I decided to post for the first time…anyway back to the topic…

    I have two questions about the Wind Forecast:

    How accurate is the wind forecast in comparison to, let’s say, the precipitation or temperature forecast?

    Would “moderate to strong winds†be enough to put the lifts on wind hold?

    As an example, bellow is Frog’s forecast for Saturday:

    Sat 4 moderate to strong SW-WSW winds, cloudy at times with the chance of light scattered snowshowers to around 1200m (1-4cm)

    If I go to Perisher this Saturday I will let you know my observations…


    Cheers
     
  2. Yardsale

    Yardsale Part of the Furniture Moderator

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    Normally lifts will run until the wind hits gale force. I can't speak for Perisher, but what lifts close will depend on their exposure to the prevailing wind.

    You can expect strong winds to close some lifts, you can expect gale force winds to close quite a few lifts.
     
  3. IZN

    IZN Hard Yards

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    Tks for your reply Yardsale. I kind of have the same feeling for the NSW resorts, but my question to the weather gurus still remains
    How accurate can the wind predictions be if compared to precipitation and temperature?
     
  4. ocker

    ocker Hard Yards

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    I have been watching four forecasts for wind and they have all been different
    Frog, Ski.com.au, BOM and Weather.com I am just going to go up and chance it.
     
  5. ortz18

    ortz18 First Runs

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    In regards to frogs forecast of gale force winds about the peaks on sunday, would this be likely to close lifts?

    If it was at the peaks I would assume maybe only the basin T bars would be closed?
     
  6. tomtankman

    tomtankman Addicted

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    Wind forecasts are generally more accurate than rain forecasts because rain can sometimes be a bit hit and miss. Particularly rain that comes from convection. As for Sunday the strongest winds will be in the early morning so by 10am winds will be below gale force.
     
  7. The Frog

    The Frog Old n' Crusty

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    Sundays winds at Perisher were moderate and then quite strong at the top from about lunchtime.
     
  8. IZN

    IZN Hard Yards

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    Forecast for Saturday (BOM) was that the wind speed would increase towards the end of the day.
    Find bellow my observations:

    I went for a "day trip" from Sydney to Perisher on Saturday, arrived at 07:30AM with blue skies and zero wind, 5cm o freshies to be enjoyed.
    Started at Smiggins and made my way to Guthega stopping at Blue Cow Terminal for a coffee.
    By the time I got to Guthega the visibility was poor improving at times. Came back from Guthega around 12:30PM visibility was very poor and winds were picking up.
    At 2PM temperature dropped dramatically and winds were strong, visibility was still very bad. We decided to give up and go back to Sydney.

    Conclusion: Wind forecast was reasonably accurate but the major factor affecting the ski conditions was visibility.

    Question: Is it possible to forecast "visibility"? I had a couple of days this season were visibility stopped me from boarding, not blizzards/winds…
     
  9. Podlet

    Podlet Part of the Furniture

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    It's not jsut the wind speed that will close lifts, it's actually more determined by the direction.

    Wind running up a lift line isn't so much of a problem and lifts will be able to stay open in stronger winds (without extra strong gusts) up to higher wind speeds than if it were running across the lift which swings chairs and t bars side to side. This brings about the added dangers of damaged chairs, lift towers, people and the biggy of derailment or in the case of a detachable possibly slippage on the line, although that is extremely rare.

    A detachable chair will close with much lower wind speeds around, regardless of direction as it can play havoc when the chair detaches from the cable and runs around the bullwheel area on the track causing incomplete re attachment etc.
     
  10. Conservative forecaster

    Conservative forecaster First Runs

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    I cannot stress the importance of observations enough in the opportunity of improving the forecasts. Clearly one only has to look at the observations, either at the Bureau's site or even those at the Perisher Blue page that some of you may have seen. The variability in location and over time is impossible to be adequately reflected in a few words.

    Outside of a couple of visibility observations each day there are no routine visibility observations that can be stored for any possible development of any worthwhile forecasts. I'm sorry, you can rant and rave about the poor quality of the forecasts, but without any routinely available and reliable observations, how can you possibly do any worthwhile forecasts?

    Visibility in the ski fields would be a function of the wind, the temperature/humidity and the snow circumstances. I remember looking at some Canadian observations [METARS = avaiation observations] and in the snow prone regions they use to report the snow state once each day, eg. hard, loose etc. Obviously this was done to allow the forecasters to be aware of how the snow pack was in relation to the potential for blowing snow. Presumably they then have a data set that would allow them to connect the wind, temperature/humidity and snow state to determine the chances of blowing snow and hence poor visibility at that location. Without this information the ability of good, reliable forecasts is reduced.

    Some of you might be aware of a site on the Internet that deals with re-analysis of past weather. I am most surprised that I don't see any references to it when I occasionally browse through this forum. There is an enormous resource for some worthwhile study of past snow events. I have looked at it a bit and done some work but there are only 24 hours in 1 day and an infinite number of research opportunities within the weather field, that goes way beyond focusing on snow.

    The site, at: http://www.cdc.noaa.gov/Composites/Hour/ allows you to plot a chart of various weather variables at 6 hourly intervals. I have, for example, generated snow %'s based on some of this data. The charts aren't perfect, but they represent a better reflection of the weather than would have been available back at the time. Now think about it..... Such a reanalysis will be done again in the future, lets say in 2015. With greater knowledge in satellite interpretation than is presently available and better modelling capabilities etc, it is painfully obvious that they will analyse the current weather in a better manner than is available today. But such advances would not be fully exploited if there are no observations to connect with these analyses.

    Just imagine if some intelligent, thoughtful and well meaning group of people got together and, in the spirit of the like minded people who have made such data routinely available for free, took regular observations of visibility, snow conditions etc and archived them. Along comes 2015 and the new re-analysis, and the opportunity arises to compare them with the output from such data. Suddenly the prospect exists to find patterns between the analysis fields and the reduction in visibility. Armed with this information, the profession could then filter such a relationship through the forecast guidance of the day and arrive at better forecasts as a result.

    What could be better? Rather than bemoaning the quality of the forecasts, a rewarding opportnity exists to help in the improvement of future forecasts by simply systematically taking observations of the kind that many of you are clearly interested in knowing about and regularly observe. There are a lot of win-win opportunities but modern day society just doesn't know how to operate in this manner.

    I repeat an earlier rant about this very issue, it is, in my view, such an obvious and intelligent use of a forum such as this. Any of you who pursue the above link will see that these charts are generated 4 times daily at 00Z, 06Z, 12Z and 18Z [10AM, 4PM, 10PM and 4AM local during the season], so to fully exploit this particular data set you'd require a systematic obtaining of observations at the same location close to any of these times.

    I would applaud any efforts by those involved in this forum to plan and initiate such observations in the future. It can only help.


    Dave.
     
    #10 Conservative forecaster, Aug 7, 2007
    Last edited by a moderator: Nov 14, 2013
  11. IZN

    IZN Hard Yards

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    Hi Dave,

    Now, that was a long reply [​IMG]

    I think it is time for this thread to R.I.P., but your idea makes a lot of sense and I believe it deserves its own thread.

    If there was a structured way we can contribute to refine the forecast providing our observations I think a lot of us would be willing to help.

    The challenges are also huge because observations for the same event might vary from individual to individual as they are based on their own perception. We could smooth this out by having a large number of people providing info at the same time...I guess...

    Honestly at this stage it sounds like utopia, but hey ... I promise if you create the thread you will have at least one reply [​IMG]

    Cheers
     
    #11 IZN, Aug 8, 2007
    Last edited by a moderator: Nov 11, 2013