July 29, 2018 didn’t look like the typical epic soaring day. Only a handful of pilots headed out to the airport for what appeared to be a typical stable smoke-filled midsummer day in the Cascades. Following Ron and Henry’s great flights six days prior, most of the energy was sucked out of the west-side foothills and replaced by smooth sled riding conditions. While on the surface, things didn’t look great, a look at Skysight gave a sliver of hope – a small window of opportunity that I did not ignore.
As is the case every year around summertime in the Pacific North West, stable marine air works its way from the coastline to the foothills. To get any chance of connecting with pockets of unstable air persisting over the higher mountain tops, ambitious glider pilots tow further away from Arlington – often a pricey bet. The chances of success were further complicated by forest fires that enshrouded the surrounding area in smoke. Not knowing what lay behind this veil of fog, I only had the day’s forecast to go by. Energized by Ron and Henry’s success – and slightly frustrated with the disappointing season so far – I decided to put all my chips on the table and go for a long tow into the hazy sky.
Skysight that morning correctly forecasted flat conditions in the foothills with thermal heights barely reaching Three Fingers’ peak at 8,000 ft. The first lift over 10,000 ft appeared behind Mt Pugh, 15 miles further east. With some hope of staying airborne on Three Fingers’ south-facing ridges, I set out on a tow towards Mt Ditney. Releasing at 6,800 ft., I glided east towards Goat Flats, slowly losing altitude in the inanimate air between my glider and the ridges beyond Goat Flats. I finally felt the first bumps of air pushing up against the rocks protecting the Quest-Alb glacier from the midday sun. Barely strong enough to keep me above 5,500 ft, I held on to the smallest whiffs of air until – half an hour later – a weak thermal broke loose and lifted me over Three Fingers’ fire lookout.
Admittedly surprised, my mindset quickly changed from flying back to Arlington to checking the view of Darrington airport – barely visible through the smoke. At 8,500 ft, I was still far removed from Skysight’s promising forecast area. At this point I could have taking a few shots of the beautiful glaciers and call it a day or push further east – knowing that weak lift would result in an all but certain night at a fine Darrington establishment. The siren call of cumulus cloud sticking its head above the smoke in the distance convinced me to carry on. I left my comfortable position above Three Fingers and glided at best L/D in the general direction of Mt Pugh, a mountain I had come to love as a reliable thermal generator.
My newly acquired confidence in the day’s conditions quickly eroded as I was unable to find any meaningful lift above 8,000 ft. By closely following the terrain lines below while assessing wind flow and sunshine, I managed to continue the 15 mile journey between 8,000 and 7,400 ft. With its peak at 7,200 ft, this was barely enough altitude to cross the Sauk river valley. Luckily Mount Forgotten produced just enough energy to throw me across the river and line up my Discus over Mt Pugh’s ridge line. To keep things exciting, a first circle around the pointy peak was a dud. The depressing low tone coming out of my vario started to pitch higher as I headed further south and finally hit the jackpot with a boomer that propelled me to 12,000 ft.
Having reached Skysight’s promised land, the joys were plentiful. Despite poor visibility the central mountains produced strong 10 kt thermals with cloud bases up to 14,000 ft. The contrast was surreal – leaving an hour long 20 mile journey over desolate land behind me. I lined up under a cloud street facing north-east and simply kept pushing the stick to cross Lake Chelan just 30 minutes later. Turning around at Oval peak, near Twisp’s Methow valley, I headed south towards Mt Rainier. Within the hour I left the Alpine Lakes Wilderness behind me and headed towards Mt Stuart to then follow a convergence line over the Snoqualmie ski area. I finally turned around at Stampede Pass, 20 miles shy of Mt Rainier, and set my final waypoint to Arlington airport.
It’s fall time here in the Pacific North West. The main soaring season is behind us. Most of us have put their glider away for the winter while a few of us keep an eye out for those rare days when the wind hits Mt Pilchuck the right way to allow ridge soaring or even wave flying. Windy.com provides a nice interface to check for favorable conditions. In this post I show you how to quickly asses favorable conditions.
Remember: For Mt Pilchuck to work, we like to get at least 10 to 15 kts of wind at a SW to SE direction with no clouds below 6,000 ft.
Go to windy.com and type “Mt Pilchuck” in the search bar. Windy will zoom in on the mountain and open a weather forecast overview. Click the “Airgram” at the bottom of the page. The lower window now shows a 5-day forecast. The lower half indicates clouds at altitude along with colored bars to indicate precipitation. The upper half shows wind speed and direction at altitude. You want to looks for days with no clouds below 800 hPA (~6,000ft) and >10 kts wind coming from the south. You can further adjust the wind presented on the main map by moving the slider on the right from “surface” to 850 hPA.
Following my article on Riding a Lucky Wave, I’ll go into a bit more detail on how you can create your own Wave analysis in a few simple steps. You’ll need two pieces of software: BUFKIT, available for free here, and Excel. If you don’t already own Excel you can download a free alternative here.
After installing BUFKIT, you need to tell it which weather models to download. You can do this by clicking “Get Data” in the top-right corner. This will bring up a window with a couple of sample download links in the top section of the window. You’ll want to replace these with the files for your station of interest. For Arlington, you’ll want to download the models for KPAE. You can copy and paste the links below in the top part of the window and remove what’s listed there by default. Those who are reading this from a different neck of the woods, can head to The Bufkit Warehouse to find a location close to their favorite soaring site.
You can save this list for future use by click the red “A” button under “Save Profile List.”
Note that 5 different weather models will be downloaded. They are roughly ranked from lowest resolution to highest resolution. Models with a lower resolution will extend further in time but contain less information. For example, the GFS provides a 180 hour view into the future at a 28 km resolution, whereas the HRRR provides an 18 hour window at a much higher 3 km resolution. As you get closer to the day of interest, you’ll want to compare models, and give more weight to those with the higher resolution.
With the list of models added, you can go ahead and download the data by clicking the “Get Profiles” button. If everything goes well, you’ll see the following output:
Close the window with the “Exit” button. Now on to reviewing the data you just downloaded…
First, you need to select the model and location of interest from the top-left options. Click “GFS3”, then “KPAE.” The sounding will load in the main window. On the left side, under “Overlays”, you want to check the “Clouds” checkbox. Depending on current conditions, you may notice light gray to white horizontal lines across the sounding to indicate areas of cloud. Check the screenshot below to check your setup against mine.
The sounding window is interesting, but to get a quick overview of things to come, I prefer switching to BUFKIT’s meteogram view. Go ahead, and click the big “Overview” button in the top-right corner. Before diving into the details of the overview window, I want you to synchronize your settings with what I have. Check the screenshots below to set the settings useful for soaring flight.
Relative Humidity: make sure this checkbox is checked. It will help you identify layers of cloud. The legend below the checkbox tells you what level of humidity to expect based on the different colors. Anything green will indicate a cloud layer. Purple often coincides with rain or other unsoarable conditions.
Next, move on to “Precip” and make sure the “Precipitation” and “Snow” boxes are checked. Your meteogram will now get enhanced with impressive green, gray, and blue bars to indicate times when it’s inappropriate to fly.
Now, let’s move on to my favorite tab: “Wind.” Here you want to check “VWP”, “Color”, press the button to the left until you get to “A2” and click the “5” radio button. This will change the wind barb color by 5 kts increments.
Click the “Fire Wx” tab to check the “Mixing Layer Height” checkbox. This last one is not relevant to wave forecasting but will help determine the top of lift on thermalling days.
Finally, click on the “Controls” button and make sure the “Cursor” box is checked.
Everything said and done, your meteogram should look similar to something like this:
On first sight, this looks like a messy bunch. There is however a ton of information packed into this screen. You can expect rain on the day this model was loaded, while the rest of the week (Monday through Friday morning), the area is covered with low clouds. On Friday, the sky opens up while winds increase to ~12 knots. The next day, conditions get interesting as wind speeds to 16 knots at 5,000 ft AGL (BUFKIT heights are AGL); there is no wind shear above mountain height; plenty of headroom left between the rocks and the clouds, and; the wind is perpendicular with the mountain ridge. The illustration below highlights the key elements you’ll want to review.
(A) Vertical wind profile: The wind looks good as it’s strong enough, coming from the right angle, with no sudden changes in direction or reduced speed at altitude. (You can also notice some humidity around 15,000 ft. Expect lenticular clouds or light overcast under these conditions.)
(B) Humidity: On Tuesday through Thursday there is high humidity throughout the lower layers, which means cloudy days. (Times are shown on the bottom brown bar.)
(C) Precipitation: Light rain is expected on Wednesday (green bars) and possibly a little bit of snow on Wednesday morning (blue bars).
(D) Altitude: The altitude is shown in feet above the ground. Match this to your wave trigger’s altitude AGL.
You get the point, BUFKIT’s meteogram is a great tool to get a quick idea of things to come.
Once you’ve identified a time that looks interesting, you can click the meteogram to move the cursor (a vertical white line) to the point of interest. When you close the window, you get back to the sounding view with the selected time loaded. If needed, you can further adjust the time with the scrollbar at the top. With the right time selected, you are ready to move on to the next step: calculating the Scorer Parameter.
The Scorer Parameter
The Scorer Parameter provides a mathematical evaluation of the wind profile and air mass’ stability. Mountain waves tend to occur when the value of the parameter reduces with altitude (trapped wave) or when it remains constant with altitude (vertically propagating wave). I’ve created a spreadsheet which takes away the complexity of running the following formula:
In the next part of this tutorial, I am going to show you how to import data from BUFKIT to Excel to calculate the Scorer parameter. First, you need to verify your BUFKIT settings and set the location for data exports from BUFKIT. Click the “Set Up” button in the top-right corner and set the “Directory to save exported profiles.” In the screenshot below I am exporting profiles to my Windows desktop. Click “Save” and restart BUFKIT for this change to take effect.
Next, navigate back to the sounding of interest and click the “Controls” button on the left. Then click “Export” to write the sounding profile to the location you previously defined in the set up window. This action will produces two files; one ending with a “bsp”extension, the other with “nsp” (e.g. HRRR_kpae_170128_11z_F07.bsp and HRRR_kpae_170128_11z_F07.nsp). Next, you’ll import the “bsp” file in Excel.
Download the Wave Forecast spreadsheet and navigate to the “Import” sheet in Excel. Complete the following steps to load and review the data.
With the “Import” tab highlighted and the first cell (A:1) highlighted, click the “From Text” button under the “Data” menu.
Select the “BSP File” from the folder where you’ve exported the BUFKIT profile. Note that you may have to select “All Files (*.*)” from the drop down to list the BSP file. Click “Import”
The “Text Import Wizard” will now guide you through the import steps. In the first step, you need to select the “Delimited” radio button and change the “Start import at row” value from “1” to “7.” Click “Next”
In step 2 you need to check the “Comma” checkbox. You can close the wizard by pressing “Finish.” (There’s nothing to do in Step 3).
The following dialog pops up. You can leave everything as is and press “OK”.
You will now copy the data from the “Import” sheet to the “Data” sheet. Copy the data from A:1 through F:50. Note that you’re excluding the “%END%” line at the bottom.
Select the first cell (A:1) of the Data sheet and paste the data. This will update the data used to calculate the Scorer parameter.
Finally you may need to adjust the data range for the chart shown on the “Wave Forecast” sheet to reflect the altitude of interest. You can do this by clicking on the chart line and adjusting the range of the data.
That’s it! You now have a view of the Scorer parameter. Happy hunting and safe flying 😉
Have feedback or ideas for improvement? Please use the comments section below to share your thoughts. Thanks!
On Saturday January 28th 2017, I was fortunate to enjoy almost 6 hours of soaring at a maximum altitude of 13,600 ft. I started the day with low expectations as the conditions were not in line with what we’d typically expect from a Pilchuck ridge soaring day. The wind was coming from the west, which – as I already learned from previous experiments – does not align well with Pilchuck’s south-facing ridge line. While ridge soaring was unlikely to work, I was encouraged by the favorable wave conditions so I bet $100 on another science experiment. The bet paid off!
About a week prior to my lucky day, I noticed a strong jet stream at 300 hPa moving towards our area. The jetstream shown on windytv.com was shaped like a horseshoe – a shape favorable for wave formation in our area as it provides strong airflow along the south/north axis. This jetstream is caused by the polar vortex, an area of low pressure around the North Pole, and rotates around the pole, passing through our region every once in awhile to produce good wave soaring conditions – assuming the timing is right (daylight hours, clear sky, etc).
Over the next couple of days, conditions remained consistent across model runs. Every morning I’d open up BUFKIT to download the latest GFS forecast for Everett and check the key conditions for a wave day: 1) wind coming from the south; 2) at least 15 knots at 5,000 ft; 3) wind increasing with altitude; 4) no wind shear, and; 5) no clouds within the first few thousand feet above Pilchuck. When I get closer to the day of interest, I run a script I wrote to assess the day’s vertical profile against the HRRR weather model, a high resolution weather model, and check the sixth ingredient required for wave formation: the vertical temperature profile.
The Scorer Parameter is used to predict the formation of gravity waves and takes into account the vertical profile of the horizontal wind AND the stability of the air. Trapped mountain waves typically occur when the value decreases with altitude. [There are other nuances like wave length, which I am ignoring for now.] The horizontal blue line in the chart below shows the maximum altitude reached (13,600 ft). The curving blue line shows the Scorer Parameter (Y2) with altitude. Almost exactly at my achieved maximum altitude, the value of Y2 curves to the right.
While, in theory, everything looked great; there was one spoiler in the mix. The wind forecast was more westerly than what we’d typically expect to support ridge soaring on Mt Pilchuck. On past expeditions, I was unable to sustain flight against Pilchuck’s ridge without the wind blowing from the south. Textbooks will tell you that the wind needs to hit the ridge within a +/- 15° angle perpendicular to the ridge line. Saturday’s forecast predicted a wind direction between 220 and 240, far outside the usual range. To my surprise, this did not turn out to be an issue for catching wave straight off tow.
The figure below shows the areas of rising air as measured by my logger and the areas where the wind is expected to hit the mountain at its highest velocity. The wind vectors draw below are created with Windninja, free software produced by the USDA. I’ve plotted Saturday’s flight in orange and added two other wave flights in blue to provide an idea of the wave’s location with a south wind. All of the data below was stitched together with QGIS, another free piece of software used to create maps. Reviewing the diagram, it appears that a north-facing crest may have triggered the wave.
It was fairly tricky to stay in the wave as the area of lift was small and the wind at altitude strong (up to ~40 knots). XCSoar proved to be of great help in identifying the area of best lift and positioning my glider in the wave’s core. The screenshot below shows how how my glider’s trail is colored green in rising air, with varying thickness based on lift strength. After locating the best part of the lift, I flew back and forth, always turning into the wind to avoid getting blown out of the wave. XCSoar will detect the straight line of rising air and automatically draws a thick blue line to indicate the path to follow. Additionally, with a strong cross-wind, XCSoar will draw a thin gray line to indicate my actual course. The wind direction and strength is shown as a dark gray arrow. Getting an initial wind reading is important as it helps position the wind relative to the terrain below. Getting off tow, I’d make three circles to get an initial reading. As you can see below, I had to crab into the wind to stay within the wave. You may also note that my flight path is not exactly perpendicular to the wind. This is because I am maximizing a limited area of lift triggered by a small mountain section below. If the wind was perpendicular to a longer straight ridge line, then the wave’s core should be expected parallel to the ridge line.
With a good grasp on the wave’s location and an initial climb to 13,600 ft, I was ready to have some fun and explore the area. I first headed towards Big Four mountain, located downwind to the east. I got to the eastern edge of my detour in 10 minutes, losing 1,100 ft of altitude. I found a small area of weak zero-lift wave behind Big Four, but it wasn’t strong enough to comfortably hang out with a strong headwind waiting for me on my way back west.
Getting back to the wave took 23 minutes, and cost 4,300 ft of altitude. All of a sudden my glider’s 1:70 L/D, heading east, turned into a mere 1:20 L/D (!), heading back west. One moment you feel king of the world, 10 minutes later you’re sweating to make it back home! [XCSoar did a good job setting expectations, telling me that Green valley remained in glide range despite a strong headwind. Also, wind speed drops with altitude so my performance would have improved as I got lower.]
Back at Pilchuck, I worked my way back up to 13,000 ft and headed out south, crossing Spada Lake. From there I flew back to my elevator in the sky and took another ride up to then head out north towards Three Fingers. Coming back to Pilchuck, I noticed a thin layer of condensation was getting thicker. Until then I was comfortably warm even at high altitude. With the sky closing in above me and the sun setting on the horizon, the greenhouse effect of my canopy stopped producing heat and I quickly turned cold. I took one last long glide towards Port Susan and touched down at Arlington 15 minutes before sunset.
Here’s a recap of a 1/7/2017 entry into newly discovery “Goat Wave”: Leaving Pilchuck wave at 7,700 ft, I reached Goat Flats at 6,100 ft (1). After half an hour of ridge soaring along the southern face of Three Fingers (2), I transitioned above ridge height by flying figure-8’s in the eastern bowl of the mountain (3). Reaching 6,700 ft, I had enough altitude to explore the air behind Goat Flats and make it back to the ridge in case nothing interesting was found (4). Mt Bullon (located 2 miles north) didn’t produce any usable lift. (It did however, give me a good beating in turbulent air.) Making my way back to Goat Flats, I ran into a smooth and strong wave system. I flew the wave for about 10 minutes to gain 2,000 ft (5). At 8,000 ft (1,500 ft over Three Fingers’ peak), I now had enough altitude to make it to White Horse mountain, where the ridge worked very well, boosting me up over its peak (7). A quick exploration over the town of Darrington didn’t result in the discovery of wave that might have been triggered by White Horse, so I turned back to Pilchuck to close out my flight and wrap up the day with a beer at Skookum Brewery.
Pre-flight preparation: I put my flight documents in a water-tight zipper bag. I add a sealed bag with a change of clothes and add a 30ft rope.
After a long straight flight over inhospitable terrain without landable fields, I see the forest and several lakes. I see no fields nearby. I am still looking for a thermal, but if I find no lift, I decide to land safely in a lake nearby. I find myself at 900ft altitude. During a briefing I have learned that my glider can float for about 25m and thus I should have sufficient time to pull my glider out of the water.
I relax and focus. I am giving my exact position to my flying buddy. With a quick look at the flight computer, I determine the wind direction and speed. I will land into the wind. Very carefully I look for big boulders and other obstacles hidden under the water surface. To land, I approach the side of the lake near a road or town (not the side where there’s only forest).
I intend to land parallel to the shoreline or slightly converging (never facing the shoreline directly). The distance to the shoreline is about 60 to 90 ft. I avoid landing in the grass close to the water to avoid potentially hidden rocks.
I prepare for landing like usual.
I am on downwind and run through my checklist:
I tighten my seat belts
I lower the landing gear
I close the ballast
I close the ventilation
I shut off the electricity
I inhale deeply and continue downwind.
I mentally imagine my final approach, parallel to the shoreline. I check my altitude. I am approaching the water surface. My air speed is the one I am supposed to have, as low as possible (just above the yellow triangle).
I feel the wheel touching the water surface. I gently pull the stick back, at the same time, I slowly retract the air brakes. The glider brakes hard and water splashes over my canopy. Even though the cockpit has immersed in the water for a moment, I know it’ll come back up soon as it floats well. Water can get into the cockpit but it stops at wing level. All is quiet now, and everything went as expected. My glider is floating quietly on the water. I have 25 min. before me. I breathe slowly and deeply.
I check my exit:
I detach my seatbelt
I detach my parachute straps
I open the canopy
I take my documents, if I can do so now, as well as my dry clothes and 30ft rope.
I can sit on the back of the fuselage and prepare the rope to be attached to the winglets
If I can I take my clothes and document to the shore, if not I attach the rope to the winglets and pull the glider to the edge of the lake.