Fwd: Silver Star Tuesday cold front aerology
Michael Coppock
Begin forwarded message:
From: Michael Coppock <copp...@live.com>
Date: September 15, 2021 at 7:58:25 AM PDT
To: Michael Coppock <mcopp...@gmail.com>
Subject: FW: Silver Star Tuesday cold front aerology
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From: Michael Coppock
Sent: Wednesday, September 15, 2021 7:55 AM
To: Cascade Paragliding Club
Subject: Silver Star Tuesday cold front aerology
Each flyable day at SS seems to bring a different palate of weather options.
Tuesday saw Kevin, Rika, Jim, Michael and Michael at elevations up to ~6000’ well east of the N/S Silver Star divide, and to beyond Tarbell Junction (M Cook). Kevin’s first visit to SS produced 7 m/s up in aerial “dusty” equivalents. Three of us enjoyed span management challenges. Rika soared high in clear air, the panorama of volcanoes turning endlessly around her.
Weather models were predicting the cold front to arrive around 5:30-6pm, which is exactly what transpired. Lenticulars at 10k were forming rapidly over, and downwind of Helens as we hiked up. Rainier had high wind cloud to near Paradise level. Adams grew down-wind lennies Initial approaching frontal cloud was visible over coast from start of hike, and by launch time, moisture was condensing out of the humid air tongue pushing ahead of the front near Longview. Lennies multiplied over and in the lee of Adams.
Light to Moderate thermals came directly up 4100’ launch, as we launched around 3:30. Lift was good over the ridge house thermal, and very strong at times to NW. Thermals drifted east in the 12 kt west flow, and there was a turbulent layer at 5k, which pilots climbed through as they drifted east toward McKenzie ridge, and east of Main SS summit. Tarbell S area had good lift.
The strongest thermals, many of them the most violent, that I have experienced on SS kept the focus on span management, and was were a fun challenge.
The Quarry and clear cuts N of it had interesting lift which Kevin exploited for quite a while. Michael Cook was able to push through the normal sinky Kloochman Butte area to fly N of Tarbell trail head, in an impressive demonstration of resolve. A sudden west wind shift, dramatic onset of lenticular appearing cloud at his altitude, increasing turbulence, and wind increase of 10kts from base heralded frontal push in to Silver Star /Tarbell ridge. He wisely ran east and south.
A number of pilots found impressive topographic constricted increased wind velocity that parked them east of saddle N of Squaw Butte (problematic if the downwash often experienced there kicks in.)
Jim soared up serenely over all, and was inspiring to watch in his mastery of the unfolding frontal approach, wind lines, and turbulence.
The LZ had light thermal activity on landing.
We enjoyed refreshments kindly supplied by Rika, and reveled in all that the “collective brain” described by Kevin prior to launch had experienced and learned.
The cold front’s humid nose condensed in dramatic spirals, ring vortex shapes, and tilted cloud tops around 5 pm. We were all happy to be on the ground, and not in the air!
Thanks to all for an absolutely fun and educational flight and post flight debrief!
Lessons learned:
- Model predictions by MB and SkySight were remarkably accurate for humidity, wind shear, frontal onset, temperatures, wind velocity and direction (excluding launch).
- SkySight has very interesting graphics for useable thermal height, Ridge Lift, convergence, lapse rate change, etc. that can be viewed in static, or loop formats that give a remarkable overview of the likely progression of the day.
- The usual sink at Kloochman Butte and on Tarbell ridge makes me wonder whether it represents wave downwash from the Bells Mountain ridge to the west, as it is often worse with west flow (which was the case yesterday.)
- It is possible to launch SS even with St. Helens, Rainier, Adams draped in lenticulars, but if Hood is forming lenticulars in a west or NW approaching cold front, I would be very cautious about staying in the air given risk of high winds mixing down from higher altitudes…not good to be in the air then.
- If a pilot makes the decision to launch in to an oncoming N cold front, it is critical to keep an eye on the speed of approach of the system, and remain NW of launch, and at an altitude that will allow safe descent as humidity, wind, and turbulence increase.
- SS can produce very strong thermals, even aerial “dusties” that can make span management very challenging…in both spring and fall, when the hours of daytime heating conspire with rising or disappearance of capping inversion…buyer beware!
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Cheers,
Michael
