——————— THIS IS A DRAFT AND “IN PROGRESS” ——————–
Published in preparation for Seminar #2 of the VSA Winter Seminars, to be held on Jan 12, 2019 at WSC. The purpose of the seminar is to share practical information between pilots on how select the “right day” to go flying. The info is intentionally structured to be non-technical, and as practical as possible, using tools/ charts available to all pilots. How do other pilots go about selecting the right day to go flying?
Structure and Content
Seminar will be held at WSC in the “club house” where we have tables and chairs, and use of the projector.
The recognized standards for such meeting :
- No more than 50 minutes without a break
- No more than three hours for the entire program
- Controlled environment (heat, light, noise, etc)
- Controlled noise – since the room is naturally a noisy place
- Tables and chairs arranged to accommodate the presentation and the vis aids
- narrow aisle between projector and screen, one table next to projector, 3 or 4 tables on each side of the projection aisle with three or so chairs behind each table, thus room for 24 pilots to sit facing each other. if more people show up , then go two rows deep on the chairs.
- Moderated with only one speaker at a time, each speaking in place from their seat.
- Panel members sitting among the pilots, behind the tables with everyone else
- Possible beverage and snack being available – or people to bring their own
- Probably an afternoon program, about 3 hours long, Start at 1 PM, end at 4 pm.
- Overview of the program for the day, including all needed intros
- A lead off with a “topical review” of this page
- Review which charts to review and when to review them
- Step through a series of example charts, illustrating what to look for on each chart
- Provide examples of forecasts for a specific day and the actual experiences of the pilots who flew that day
Forecasting the Soaring Weather
By Peter Kelly
By definition, a glider is always in a descent. The air air you are traveling through may be going up at the same rate that your glider is going down, thus you maintain your altitude, but if the air is not going up fast enough, then you will soon land. You need “up” air – we need “lift” to stay airborne.
We all agree the air is always in motion – due to heat on the ground or due to sunlight, which causes convection – warm air to rise, which causes changes in atmospheric pressure and that causes winds, etc.
Even on a cloudy overcast day, if you see some shapes to the clouds, other than 0n a low flat bottomed cloud deck, then there is convection happening. Just depends on how much lift your particular glider needs to stay in the air, and how far apart the columns of rising air are situated.
It takes a certain expertise to be able to keep your glider in the “up air” as opposed to just passing through the ups and downs of the mixing atmosphere. If you were smart enough, and fortunate enough to be able to attend the earlier seminar in this series, presented by Peter Deane, you are have reviewed and are more aware of what to do and how to do it, in order to travel cross-country. Later in this series, Kempton Izuno will address how you should plan your cross country flight, how to optimize it and how to get back on track if you get stuck somewhere along the way. In this seminar, we are reviewing techniques that will enable you to pick the right days to fly based on the weather, and to NOT miss the good ones. There are three levels of what soaring pilots will often call a good day to fly.
Three levels of good soaring conditions
Good day for pilots with limited cross-country (x-c) experience. The weather forecast indicates you may release from tow and probably remain within glide distance of the gliderport, but some x-c expertise may be required if you travel too far from your release point.
Another good day to fly at WSC – for qualified cross-country pilots, . Most pilots will launch, knowing that they will be able to log several hours, but they may not travel very far, for concern of landing out.
The potential exists for a great day to fly, but many will not travel very far due to conditions. If it is a Racing Day, most all contestants pilots will be able to start the race, but not all will be able to return to the gliderport if they don’t exercise techniques of advanced expertise. Some may complete more than 300 kilometers and fly for over three hours, while others may get into trouble and experience a land-out (landing somewhere other than back home again).
Selecting the right day to fly, based on the weather forecast.
This is a panel discussion, led by Peter Kelly.
Additional panel members are Ben, Ed, Pete-98, and nearly everyone in the room.
This is a group participation seminar. If you have thoughts to share, plan ahead, prepare a few notes, and make you questions and comments clear and concise. If you want to ask a specific question about a specific chart or make a point, then bring visual aids. JPG on a USB stick will work, (but have the image in a top level folder by itself – so it can be easily accessed and displayed within seconds.)
Prep material ?
I’ve been wrestling with this for a day or so. This is more difficult than I had imagined. Too wide of a variance in the experience levels of the audience to make a single presentation of how to read weather.
need to come up with the objectives.
Probably need to divide the material into
1. Qualified to fly solo, but no license yet.
2. Licensed pilot, but not cleared cross country north of snow or south of walker.( is this a realistic category?) Do we have that level?
3. New cross country pilots that haven’t done their first 300 k
4. Experienced x-c pilots looking for the 500 k days.
Forecast can/ should always be done the night before the flight. do we all agree on that?
What things to check the night before? Well – it depends on your experience level and what you hope to accomplish on your flight.
– Can we always tell if we will be able to stay aloft for more than a straight glide home? I say yes we can. and here is why…
Basic parameters for staying up more than 30 minutes.
Maybe let’s state what conditions guarantee you won’t stay up?
No convection –
– Stable air mass
– No surface heating
– adverse conditions – too windy- raining, etc.
As I read this in the light of day, and being almost 24 hours removed from the high I was on from that great flight yesterday to Round Valley, I see much of the above is a bit “over the top”. Guess you’ll have to bear with me as my enthusiasm ebbs and flows. Peter.
I plan to place all of the following on a separate web page!!!
I will expect that every person who is present at the seminar will have read and practiced every line of this page – BEFORE SHOWING UP AT THE SEMINAR AND ASKING STUPID QUESTIONS! This is a “must read” prerequisite for anyone who is going to participate in the seminar. No, you don’t need to salute when I walk in, or call the room to attention, but you better damn well prepare, if you want to get anything out of the seminar.
We need to state, up front, that this is NOT about how to find thermals or lift.
This IS about:
- what charts to look for and how to read those charts.
- what to watch and study several days in advance.
- what charts to change to as you get closer to that GOOD day and
- which products are “must read” the morning you plan to take a tow.
There is a time line to deal with in deciding when to go soaring. Aside from selecting a day the gliderport is open, and then scheduling a rental ship, a pilot could often select which day to go flying two days in advance and would be correct 85 to 90 percent of the time, if he followed the advice on this page. Further, I suggest that if the RASP for the selected day is evaluated at 8 AM on the scheduled day, a Pilot would be able to reliably plan the duration of the flight as well as the planned route of the proposed flight – all by reading the RASP charts/ products! There is no excuse for not knowing what you will find and where you will find it. Kind of a stern statement, but I can assure you it is true. I don’t fly as often as I used to. Now a days,it is very expensive to rent a ship and to take a tow. I limit my flights to days when I am confident that I will have a good soaring day! (unless of course,I haven’t flown for over 30 days, in which case I’ll take any day that is flyable, and convenient for my personal schedule).
Where do you start?
Let’s look at the next week. We could examine charts up to 16 days in advance, but the further out you try to forecast, the more of a guessing game you are playing. We don’t need to be guessing, so let’s narrow our search for a good day to five days from now. Then revise our estimate four days out, then three and then two days.
As an FYI, you may use the 2018 Weather page on the VSA web site to select each of the products we are discussing, including the long range 16 day forecast, which we are dismissing for the purpose of this discussion. I will simply tell you which pages I select and what I am looking for on each page. I’ll identify the items that will encourage me to do further study, or will tell me to to simply come back another day.
The Five Day forecast. Select UNISYS charts on the wx page. The see “Filter Options”. Select the following:
- SOURCE = GFS
- CHANNEL = 300 mb
- REGION = US CONUS
- VIEW = ANIMATED
Push the filter menu into the left margin, scroll down so you can see the time line dots on the bottom line and adjust your screen so you can see the entire chart, including the top margin of the chart – in this case “300mb Wspd/Hght/Wind GFS analysis for 12z xx OCT 18″
Go to the bottom of the screen and select the second dot (from the left) on the time line. you will see this is the GFS 12 hour fcst.
You have arrived. You are looking at a horizontal slice of the atmosphere at the 30,000 ft level. The pressure patterns, with the highs and lows identified, the wind arrows, the wind speeds. So what’s it good for? Know this – the lower pressure patterns at the lower levels are normally controlled by the upper level air. This level steers (or at least has major influence on) the lower level. You need to know the dynamics that are going on over the next four days (Launch minus 5 days, -4 days, – 3 days and launch minus 2 days). so you will be coming back to this page every day for the next four days as you look ahead for that good soaring day that is coming up.
Now select one dot at a time, watching the shift occur, until you come to the middle dot – the 5 day fcst. Study it! Where is the jet stream” is there a jet stream at all? Is our flying area under the influence of a high dominating the area or are there low pressures coming in?
Go back to the filters (make it reappear on the left side), select 500 mb CHANNEL, hide the filters again, now what do you see?
You are looking at a horizontal slice of the atmosphere at the 18,000 ft level. So what! Most all weather happens below 30,000 ft and most of that is at 18,000ft and below. If there is a low at this level it will be sucking the air up from the 10,000 ft level and, it will be steering which way the lower pressure patterns are going to slide. Know what is happening above you.
At the 300 mb level, there is only 30 percent of the atmosphere remaining above, that is there is 70 % less atmosphere here than at sea level. At the 500 mb level we are 50 /50 half the atmosphere is above this level and half is below. You need to be aware of pressure patterns above our area because it will most certainly drive the motion of the lower patterns Upper air drives both the vertical!! and the horizontal action – think three dimensional. Wind is not simply a horizontal construct. At least not for our purposes.
What do we see on this 500 mb chart?
Legend says it displays: “AVort/ Hght/Wind”. See the pressure patterns with the high and lows identified, see the wind arrows, see the Avort… More pink, going to red the air is going down – that’s probably under a strong high pressure with a stable air mass below. More light blue is good, the air is going up, but going to green and then yellow, the air is going up too fast for us, because condensation will occur, and yellow often means precip, with a capital P.
Back to the filter. Select 700 mb. we have only 30 % of the atmosphere above us. 70 % is below us. This is where it’s happening.
See: “VVel/ Hght / Wind”
See the pressure patterns with the high and lows identified, see the wind arrows, see the VVel. Now the wind arrows are more meaningful. The closer the Isobar lines are together, the stronger the wind, the bigger the arrow. If you are looking for wind direction, note that the arrows always favor pointing into the low and away from the high. The color scale and the numbers on that scale? I only look for one thing – the colors over my flying area. Dark blue the air is going down (not a good thing), light blue is more neutral, green is going up and yellow going to red is really going up (more precip with a capital P).
Back to the filter. Go to the 850 mb (= 5,000 ft level). This chart is guess work on a major scale more than a couple of days before launch. I hardly look it, but it does show guesses on wind and temps at 5,000 ft.
Next, filter over to my favorite chart, the “Rel.Humidity/Showalter Index”See MnRH/Show” Too pink going towards red means too dry – no cu and poor adiabatic lapse rates in dry air. Too blue going to light blue and the air is too wet – probably precip, or at least heavy clouds. I look for the 40 to 70 % Relative Humidity. Watch for the hash marked area of very unstable air. Heavy white lines appear every 10 units of change. Showalter Index (SW) of 10 and above indicates relatively stable air – I wouldn’t expect too much convection in that area. SW of 7 or less, I get excited. SW of 4 down to 0 with a dark blue background – we’re going flying!
Note there are lots of explanations on the bottom of every page mentioned above. Study those notes as needed, to comprehend it all.
OK. you have been looking at the charts every night for weeks, and now the day is approaching that you think the UNISYS charts said there would be lift. It’s now time to switch to a more accurate and comprehensive forecasting tool… the RASP.
Like the fighter pilots used to say (probably still do) during air to air combat…. “we’re too close for rockets, time to switch to guns”
The RASP is what soaring pilots of yesteryear used to dream about. Thanks to Dr Jack, you have been blessed. I can’t say enough good about the man. The RASP simply takes most of the guess work out of the soaring flying forecast. If I talk to a pilot on a fly day, and he hasn’t studied the RASP for the day, I pretty much consider him a non-pilot. He is simply someone who just doesn’t care to do a proper pre-flight.
On the VSA Weather page select RASP – the next three days.
If you have been preparing for this flight for the past few days, you know the location and intensity of the pressure patterns that are influencing our day. What you don’t yet know is how the local geography will influence the convection and the winds (both vertical and horizontal! winds).
First up – Height of BL Top (about 36 hours from now) – I am assuming I am launch day minus one in his practice scenario.