The weather was much better on Sunday, and Tim may have found some wave lift in the Champ. Andy towed Bill and Skip to investigate, and they met with limited success.
Wave season has arrived. We have been invited to fly at Sugarbush in September, and we are trying to get a measure of interest in going there. Also, we are looking for volunteers to work on the gliders and trailers this week. The oxygen systems need to be installed, and the trailer lights need some work.
It would be nice to get all these chores accomplished before it gets cold. Only 38 days left before Gorham.
4 comments:
Yesterday on the drive home from work around 5 there were wave clouds all over. They weren't lenticulars but looked more like hotdogs (sort of a cross between lenticular and cummulus clouds). Hard to tell how high they were but I would guess 5-6K. Looking at Blipspot from then it looks like the wind steadily increased to 20 kts at 10K. Direction was west-northwest with no big changes. Was this usable lift? On a day like this with weak/moderate thermals and weak wave is it easier to make the transition from thermal to wave? How can we forecast little waves over PM 12 to 24 hours ahead of time? While it was probably not a great xc day and achievable heights were probably limited it looked like a very interesting (or is it frustrating) day to fly.
Tim
Tim: Sounds like rotor cu.
The interaction between thermal convection and wave is (almost) always problematic because convection strong enough to climb in is (usually) disruptive to wave and frequently kills the wave altogether. Often there's this magic little window in time where the two coexist well enough that transitions are straightforward, but it rarely lasts for very long. We saw a classic example at Franconia this year.
The exception doesn't occur much around here... if you get strong convection with cloud streets topped by strong shear with direction change and stable air you can get strong wave above strong convection that is the sort of thing you'll tell stories about for decades. I've heard those stories, but don't have any of my own to tell.
-Evan
Adding to Evan's comments, the best way to find wave in the Upper Valley this time of year is taking a tow directly into the lift. Sounds good but when to roll the dice on a $50 tug follow becomes the crux move.
Just like trying to beat the casinos in Vegas you must try to stack the odds in your favor. For the true secrets of Post Mills wave Send your $39.95 to....
There re several websites which will help. Blip-somerthing maps have little value with wave prediction so the intrepid wave prospector must use the old method of lift prediction; the sounding. Just like 78 RPM records and 8 track tape, most of you have heard of these and a few might even have used them. The sounding isn't difficult to figure out and when you've mastered it will have the ability to outdo even the ubiquitous Blip-something websites. (Editor's note: Recall the fantastic day back in May? The sounding was what helped some of us make the call.) Enough blip-bashing. The sounding to use is here: http://www-frd.fsl.noaa.gov/mab/soundings/reply-skewt.cgi?data_source=Bak40&year=09&month_name=Sep&mday=2&hour=9&lon=-104.67&lat=39.87&airport=2b9 . Choose the bac40 data set and 2b9 as the location. Not all airports are in the database and 2b9 was added by request from an overzealous local wave pilot. Change the time to when you want to fly and the date up to 48 hours out.
For now, ignore the blue dewpoint line. What you are looking for is the red line to resemble some sort of stylized "Z". Recall the iconic 70's glam metal band KISS and the lightening bolt "s" if you still crave the musical references used above. Yes (another fantastic band), the Z and S are the mirror image of each other but you get the idea. The first change in direction or break in the line should happen near the 5,000' elevation. As long as the line above the break is vertical or leaning to the right the air is stable. The line below 5k should lean left indicating unstable air. Somewhere at the top of the red line it should also break and lean back to the left. This Z form indicates the stable air sandwich required for wave to set up. The thicker the stable air, the more wind needed to displace it and in general a more appearant break in the direction. The 5k break is the top of the generating feature over by Sugarbush which is the western spine of the Green Mountains.
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The wind speed and direction at the 5k mark should be in the mid 20s with a westward component. The speed should steadily increase with no sudden change in direction. If you see this there is a good chance of wave.
Next, check the Mount Washington home page: http://www.mountwashington.org/ . If you see a westward 50 mph matching the sounding then things look pretty good. Remember, the sounding gives wind speed in free air and the mountains compress and speed up the air so 25mph on the sounding will give 40-50 mph on top of Mount Washington. The sounding is also useful when going for a hike and choosing what to bring for wind gear. Also on the Mount Washington site are webcams. Sometimes you can see the clouds.
Mount Washington is important since wave is generated over there by almost any wind and if there is not favorable conditions there, I'll let you take the first wave tow and report back to the ground.
The next check is the satellite photo. If you see the cloud bands there is some sort of wave action. Is it usable for soaring? Might be but at least we know its working.
Lastly, call Sugarbush and ask if they have any reports of wave. The wave we fly at Post Mills is generated over by Sugarbush and they are always eager to sell a high tow and ill fill you in.
When you're convinced it's a good bet and make the decision to put the glider on the rope now what?
Take a highish tow. As wave propogates the bottom goes up and the top moves down as the wave flattens out. We're 50 k from the generator and the wave at Post Mills is the 8th or 9th wavelength. I've grabbed wave at 4k but 5 t 6 is a better bet. If your putting this much cash on the line stack the odds and spend another $12-15 and give yourself time to search and more vertical to hit the target.
The wave area over Post Mills runs from the west side of Lake Morey to the Straffod Copper mine. Somewhere along this line give the best odds for connection. When you find it don't expect Mount Washington primary rates of climb. Many times it starts as 1 kt or zero sink (What PMSC member made the phrase "Zero 'ain't nothing" a PMA catchphrase?) so take it and don't be impatient. The biggest wave killer is the pilot being too anxious about only finding .5 kts. and burning off altitude looking for the ripper lift. Most often 3 is the best you'll get at first. Climb and star mapping the wave by moving slowly and finding the sweet spot. Also, find some horizon marker directly upwind and search perpendicular to that heading.
The wavelength tends to be 3-4 statute miles. When you're high enough find the weakest lift and head directly upwind and keepo going through the sink and back into the lift which should be stronger. Start searching again and climbing. Repeat until in the Sugarbush primary.
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