Silver Star Thursday September 9 aerology/flight report
mcoppock
There were two key questions re flight longevity for Thursday launch window of 2:30-3:30 on SS:
1.Would the departing high pressure ridge allow more lift than forecast by Meteoblue (MB) or RASP?
2.Would predicted high cloud shade out lift and cause premature landing?
From 11 am to 1pm strong thermals were kicking off over a wide area, and spreading out under low inversion at launch height. As noted on Telegram pics and post, the greatest number of birds in the air I have seen on SS formed wheeling gaggles that appeared to break through the inversion and reach ~5500’: eagles, red tails, falcons, crows. Groups of swifts were spinning through and up in the thermals on the hike up.
From 1 pm to 3 pm, only light thermal activity was felt along ridge and at N launch and the house thermal. No further bird activity occurred the rest of the day.
Winds were predicted West at 10 kts…once again, there was no meteo wind on launch from 2:30-3:00 pm , just intermittent thermic activity.
Smoke was predicted by HRRR to remain south, and Hood was swaddled in gauzy brown haze. N, Helens, Rainier were clear, except for cloud at 8k. Adams was clear. Bands of high cirrus, and stratocirrus moved across the area as the afternoon progressed.
Launched at 3pm in to light cycles. Ayvri file interesting in that it shows lift to about 4200’ along ridge, in tight thermals. SW toward Sturgeon rock, lift petered out.
Wanting to establish on Tarbell trail ridge, I pushed west in to 15-20 km/hr west flow, as predicted. Once again, meteo winds appeared once I was clear of the immediate ridge area…a consistent finding as discussed previously.
The Ayvri file shows a very obvious truncation of lift in my flight pattern at about 3500’ near Kloochman butte, which was predicted by RASP and SkySight.
Halfway through flight, I was shaded out by thick cirrus and stratocirrus, and moved to survival mode in zeros, and in amorphous lift just west of upper parking, at low AGL. Then about 10 minutes after high cloud diminished and there was increased solar heating, thermals became more coherent, and slightly stronger, and I was able to ride one up to over 5k, through the inversion. Impressive inversion turbulence was felt at 3500-3800’, closely predicted by models. Above that smooth, 0.9 m/s lift took me to a second inversion height, marked by Cloudbase at 5,000’ MSL.
Then pushing NW again led to the ever present marked sink that exists just east of the main N/S Tarbell ridge…is this down wash from thermal activity from sunlit west aspect of ridge? I have yet to figure this out. Unable to stairstep back up the west SS ridge, I took what lift I could find around quarry, and landed in relatively strong thermal activity in the 1900’ LZ.
Max up 2.6 m/s, down 3.4 m/s .
https://ayvri.com/scene/gdkzp9gl5z/cktdsieo900013a6fv8h265qh
Lessons learned:
1.Meteo winds appear to not affect 4100’ launch in typical high pressure, low inversion NW or W flow.
2.There is consistent, and strong sink N and W of Kloochman Butte for unclear reasons.
3.It may have been possible to fly from 11 am to 1 pm during the early generous and widespread thermal release, but it was not predicted by MB, RASP, SkySight, MM5.
4.SkySight, RASP and MB all predicted rapidly diminishing lift after 4:30 pm, and that is what happened. By the time I biked back up, it was dead calm around 5:30 pm.
5.If a thermal takes you through the inversion, you may find smooth lift above.
6.There were multiple levels of wispy thermal tendrils at multiple altitudes, suggesting larger thermals were able to breach the lower inversion. A second inversion at 10,000’ on Skew T clearly had multiple thermals reaching it in late afternoon..
7.West flow makes reaching Sturgeon rock more difficult, than with NW flow conditions.
8.SkySight has some interesting graphics, and needs more exploration to assess its utility.
9.As expected on weak days, the most consistent lift is usually around the house thermal near N launch.
Cheers,
M
Michael Coppock
Michael Coppock
Luke
Great flight and fun to watch on Ayvri. Thanks for teaching us so much about the site. For others following we are hoping to fly there tomorrow as well. It would be a great learning opportunity for many of us on what could be considered our local “wild” site!
Luke Danielson
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Michael Cook
Luke
I am going to Silver Star today (carpooling with David Le). I would like to be at the first LZ at 1pm (a good LZ intro is important). Give me a call (503) 757-5622) or respond here or telegram if you are interested in joining. I can't promise epic conditions but I can promise a nice hike, fresh mountain air and a good learning experience. It sounds like the best launch window is between 3pm and 4pm. It also wouldn't surprise me if we get glassy conditions at the end of the day. Mr. Coppock can also shuttle to the trailhead from 1900 LZ. I am looking forward to picking his brain about weather & Silver Star dynamics. Lets make it a party! My usual disclaimer is that we should hike up with the notion that you may hike back down.
Luke Danielson