How to Catch a Wave: From BUFKIT to Scorer

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.

ftp://ftp.meteo.psu.edu/pub/bufkit/GFS/gfs3_kpae.buf
ftp://ftp.meteo.psu.edu/pub/bufkit/nam_kpae.buf
ftp://ftp.meteo.psu.edu/pub/bufkit/NAM4KM/nam4km_kpae.buf
ftp://ftp.meteo.psu.edu/pub/bufkit/RAP/rap_kpae.buf
ftp://ftp.meteo.psu.edu/pub/bufkit/HRRR/hrrr_kpae.buf

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.

overview-humidity — Check “Relative Humidity”

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.

meteogram-overview-1 — BUFKIT Meteogram Overview

(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.