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Thread: Wave watch: Dec 19-21

  1. #1
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    Wave watch: Dec 19-21

    Late day Thu to mid-day Saturday, looks like a good north wind wave day (from this mornings GFS):
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    Thurs 4p Fri 4p Sat 4a

    Around Goat to Diablo during this time, the 850mb is 15-25 knots, and the 500mb peaks at 70 knots Thu afternoon, slowly dropping to 45 knots Saturday afternoon. Looks like Friday is the best, but first half of Saturday also looks good. This is 7 days out, so a bit speculative, hence the wave "watch", not "alert". However, I've watched this for several days and it hasn't changed much esp. considering there's a small cutoff low passing through Tuesday to mildly disturb things.
    Kemp
    ASH-25 (FNX)

  2. #2
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    Re: Wave watch: Dec 19-21

    Thanks to Kempton, we are presented with another good study in reading charts.
    As Kemp said two days ago, the cut-off low passing through on Tuesday will, and has already, mildly disturbed that longer range fcst, but the wave fcst still persists.

    We all recall the superb flying conditions that followed Kemp's alert for conditions in Late November -
    https://www.williamssoaring.com/news/...-%28Thu-Fri%29

    Compare those conditions to what we have this week...

    First look at the similarity of the two charts -
    The first one is from the post on Nov 18 for the Thursday Nov 21 sky at 300 mb
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    This next one is for the sky at 5 PM on this Thursday. 12-19
    Click image for larger version. 

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    Similar but different.

    The best way to observe the development of this soaring and study opportunity is to go to the unisys pages and display the 300 mb chart for 300 mb for 3.5 days from now - as I write this. By tomorrow (Tuesday AM) that will be 2.5 days from now, etc.
    http://weather.unisys.com/gfs/gfs.ph...region=us&t=3e

    This is different because (at the moment) the forecast does not indicate that this trof will develop into a full blown cut-off low while it is overhead our location and thus it will continue to be steered by the jet stream.

    Note the way the trof of low pressure moves rapidly with each 12 hour fcst period.
    Fri 00z - which is 5 PM Thursday the winds overhead at 30,000 are a solid 130 kts.

    Now jump down to the 500mb level ( keep remembering this is a three dimensional model) and see the winds drop off rapidly from Thursday through Friday as the apex of that trof moves rapidly southward (and becomes a short-lived cut-off low at this 500 mb level, just before it dissipates) and the High in the NW part of the Pacific shows that it is much stronger than what we had during our late November event.

    Stepping through the 700 mb level shows it is a cut-off low at that level but in a far different location than we had in November.
    .... strong winds from the north will prevail at 10,000 ft on Friday afternoon.

    All really interesting stuff.
    Last edited by Peter Kelly; 12-16-2013 at 11:06 AM.
    Peter Kelly

  3. #3
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    Re: Wave watch: Dec 19-21

    In a related story, not necessarily deserving its own thread, see this info on the shortest day of the year.

    http://earthsky.org/earth/everything...ember-solstice

    Doing a bit of editing to extracts from the above page, here is the bottom line...

    When is the solstice where I live? The solstice happens at the same instant for all of us, everywhere on Earth. In 2013, the December solstice comes on December 21 at 11:11 a.m. CST. Thatís December 21 at 17:11 UTC, and for Williams Soaring fans that is 11:11 AM, this coming Saturday. Itís when the sun on our skyís dome reaches its farthest southward point for the year. At this solstice, the Northern Hemisphere has its shortest day and longest night of the year. Happy solstice, everyone!

    No matter where you live on Earthís globe, itís your signal to celebrate. For us on the northern part of Earth, the shortest day is here! After the winter solstice, the days get longer, and the nights shorter. And, for us at WSC, soaring conditions get progressively get better!
    Peter Kelly

  4. #4
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    Re: Wave watch: Dec 19-21

    Forecast is holding, with Saturday looking better due to the lighter winds, but still a good profile up through 18,000 ft. Saturday looks best to do an early launch, then have all the day available. I'll not be flying, but have this task in mind:
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    The arrow are the winds at 5,000 ft on Saturday, the black bars are the expected location of the wave. A flight to the ocean is quite doable as this is a CROSS wind task, not downwind/upwind as the case was with my earlier flight. From 18K at Goat, you can easily go to the next black bar, and retreat back to the previous lift if it is not there. Rinse and repeat until you are over the beach.

    Who will give this a go?
    Kemp
    ASH-25 (FNX)

  5. #5
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    Re: Wave watch: Dec 19-21

    Quote Originally Posted by Kempton View Post
    Forecast is holding, with Saturday looking better due to the lighter winds, but still a good profile up through 18,000 ft. Saturday looks best to do an early launch, then have all the day available...
    .....
    Who will give this a go?
    I agree with Kempton, but it's hard to get too excited, since we are working on a fcst that is five and a half days away.

    I see a ridge (white lines, shaped like the top part of a circle) showing on the chart that is poking north, up the central valley - that may disrupt the wind fcst a bit.

    Chart- 5.5 Days, GFS, 850 mb, valid 00z SUN 22 DEC ( 5,000 ft at 5 PM on Saturday)

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    Peter Kelly

  6. #6
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    Re: Wave watch: Dec 19-21

    Well, my personal excitement" register is mid-range to increasing since the forecast has had little drift, and it's moved to the weekend. Further, I like as little wind as possible. For cross country wave, the least amount of wind that triggers the wave in a systemic, meaning everywhere, manner is best. I focus more on the 850mb for this to gauge the ridge line winds. It's also been my experience that there are often times when there is so little wind that I wouldn't expect wave, yet it is there…...
    Kemp
    ASH-25 (FNX)

  7. #7
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    Re: Wave watch: Dec 19-21

    Quote Originally Posted by Kempton View Post
    Forecast is holding, with Saturday looking better due to the lighter winds, but still a good profile up through 18,000 ft. .....
    you can easily go to the next black bar, and retreat back to the previous lift if it is not there.
    Rinse and repeat until you are over the beach.

    Who will give this a go?
    I'm not sure that I want to go "over the beach" - in an earlier time that had a different meaning than what I think Kempton is proposing. But, I like the idea of a crosswind xc wave task as opposed to a downwind rocket ride followed by a long slog home into the wind late in the day.

    Nice graphic Kemp. Simple and easy to read. Therefor, it must be true eh?


    I think I'll give it a go if the forecast holds.

    Maybe Friday, maybe Saturday.
    Jim D. - 1B

  8. #8
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    Re: Wave watch: Dec 19-21

    The objective of the plan is to do this in a safe, easy manner. The ability to retreat to a known lift spot, so long as they are not far apart, is the key. Other than the Goat and Snow waves, I have no proof that the marked waves exist. But if I were able to fly on Friday or Sat., I would execute this with high confidence that the waves are in the marked positions. And if I'm wrong, just retreat to the last wave and try again, slight different spot.

    *Added part of tactic. You must leave the lift above 15K, preferably 17.5K. for maximum safety. Lampson is the safety airport.

    The wave has existed before mankind was in California. It will be there after we are all gone. That's what's great about it, it is very repeatable, we just need the GPS markers to confirm where they are in a given wind & weather. My highest goal for WSC wave days is to map all of them within range, so when a given wind blows we can have high confidence of going out to the ocean as a "milk run". Now wouldn't that be the coolest thing on earth!

    So, Jim, and everyone else. WE can all map the sky. It's a long term project. But 2-3 years of mapping on wave days would see us have a very reliable map to go to the beach. We all would have "Magic on Demand". Who's with me? 8^)
    Last edited by Kempton; 12-17-2013 at 08:29 AM.
    Kemp
    ASH-25 (FNX)

  9. #9
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    Re: Wave watch: Dec 19-21

    I'm with you Kempton. Your approach is simple, safe and provides a discipline that appears fairly easy to follow. You can ignore the arcane and somewhat facetious reference to the phrase being "over the beach" as scary. Having always been fond of cartographic experience, a "reliable map to go the beach" is quite appealing to me. I'll do what I can to support it.
    Jim D. - 1B

  10. #10
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    Re: Wave watch: Dec 19-21

    I am currently planning to fly OJ on Friday (with Saturday as a backup day) if 1) the forecast holds, 2) the surface winds at Williams are not above my comfort level (>15 kts) and 3) there is at least 5 hours of O2 in OJ (still waiting to hear back from Rex and Noelle on this one). I have been reviewing Kempton and Ginny's flight on 12/9/12 (https://www.williamssoaring.com/news/...aturday-Sunday), my flight with Kenny on 1/22/11 (http://williamssoaring.blogspot.com/...1_archive.html), as well as Kempton and Matt's flights on the same day (http://mattsoaring.blogspot.com/2011...-wave-day.html). I will not be attempting to fly to the ocean. My initial plan is to tow to Goat, climb high enough to press to Snow, and if I can get high enough there I may press to Hull. But Kenny and I did not have much luck at Hull (In reviewing the flight on SeeYou, I think we may have stopped just a little too soon). We'll see how things go. If I don't go to Hull, I will consider either a downwind run to Konocti (as I did on 12/2/13) or Boggs (as Kempton and Ginny did on 12/9/12), or maybe an attempt to get over to the Sutter Buttes (as Matt did on his solo fight after flying with Kempton on 1/22/11).

    Pat

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