Wind: 5-10 kts out of the SE early in the day, then 15 kts., gusting to 20 kts. plus, out of the West and SW later in the afternoon.
Altitudes: 9000 ft. MSL by Mario Pauda in the 1-26 from a 2000ft tow.
Time Aloft: 3.0 hrs by Mario Pauda in the 1-26
Temperature: 91deg. F. at about 3:30 PDT
Comment: The RASP was spot on in predicting a good convergence in the later afternoon right over Avenal.
Tow pilot: Jim Rickey
Mark Neal and Alex at about 7500 MSL over the Kettleman Hills.
We had a very good day of flying at Avenal today. A strong convergence, predicted very accurately the night before by the RASP, developed early over the Diablos. In the later afternoon, it moved right over the airport and then over the Kettleman Hills just to the East of the airport. The altitudes obtained, winds, clouds, along with the timing of the events, were all predicted by the RASP with uncanny accuracy today.
Glider pilots showing up were Sergio Grejada, Mark Neal, Alex Caldwell, Mike Paoli, Joe Anastasio, and Richard Walker as well as Jim Rickey who performed as our tow pilot. I believe I also saw Ed Mandibles, although I didn't see his cool Mooney Mite anywhere, so he must have driven out. I think Ed may have been working on the 2-33.
Early in the day, the wind was out of the SE, but very light, and we made a couple of tows downwind off runway 31. But a little later in the morning, the wind increased to about 5-10 kts from the SE, so we moved operations to runway 13. Late in the day, around 3:30 or so, when the convergence arrived over the airport, and as it moved further east over the Kettleman Hills, the wind filled in strongly behind the convergence and shifted fairly abruptly to the West and SW and came up to a steady 17mph with gusts over 20mph. We started getting some blowing dust in localized areas in the valley, along with some very large dust devils along the convergence line. We also saw a few very whispy, transitory cumulus clouds along the convergence line parelleling the Kettleman Hills and extending up towards the San Benitos north of Coalinga. See pictures below.
Sergio and Alex flew one flight in the early morning. Sergio is doing the take-offs and tows by himself and boxed the wake on his own today. He found it much easier to practice this in the smoother morning air. He's got his student license now, and is studying for the pre-solo written test. Next, he'll be continuing to sharpen up his pattern and landing judgement, and starting practice for various emergency procedures.
Mark Neal and Alex had a great flight in the Orange Crush for 1.5 hrs plus. We got to 7600 MSL in the convergence over the Kettleman Hills. We then descended to about 2000 MSL, over the airport after unsuccessfully trying for a big dust devil over the power lines. Just as we were starting our landing checklist, we encountered lift that allowed us to get back in the convergence and we climbed again to the same altitude, with lift at times steady at 8 kts, and briefly even seeing 9 kts on the vario.
One of the large dust devils forming along the convergence line.
Mario Pauda in the 1-26, working the convergence over the Kettleman Hills. He eventually climbed to 9000 ft. MSL!
Mario Pauda in the 1-26, working the convergence over the Kettleman Hills. He eventually climbed to 9000 ft. MSL!
Flying with the Birds
(Alex asked those of us who flew on Saturday Oct 3 to write a short summary of the afternoon flights, with attention to how we found the forecasted convergence, how we are doing on our training. So here it is, hoping some of us newer glider pilots may benefit from it.)
I was in the 1-26 in a 50 degree right-hand turn, climbing with the vertical velocity indicator (VVI) pegged on the positive side, sharing the thermal with three black birds (most likely common vultures, but as close as I was to them, they looked as big as condors to me). I was over the Kettleman Hills, just south of Avenal, where the RASP predicted the convergence would be around 2 PM. The forecast was for the convergence to move further east in the afternoon, as the winds out of the west became stronger.
As for staying in the convergence band, I used the “drunk flying” technique that our own Morgan describes in his presentation, Convergence Flying in Central California: fly in the general direction you expect the convergence to extend, then, when you hit the wall of sinking air at the edge of the convergence zone, make a slight course correction to stay within the band of lift, just like a drunk B-52 pilot trying to stay on his feet. There were no clouds to mark the general lay of the convergence, although I did follow the three black birds as they played in the lift, porpoising as I went from thermal to thermal (a first for me).
And what beautiful thermals they were. The 1-26 is so light, and flies so slowly, that cranking it around at 50 degrees of bank in the core of the thermal was a blast (note to Harold, my instructor: my turns to the right were coordinated!). I saw Alex and Mark thermalling in the 2-33 just a little north of my position, still over the Kettleman Hills. I went to join them. They were above me, circling in nice lazy circles. We had a gaggle of five: two gliders and the three black birds. I reached 9,000 feet MSL in this thermal. From this lofty height, I could see the intersection of roads 41 and 46 south-southwest of Avenal. I headed in that direction, flying out of the Kettlemans and out of the convergence…and into the sink. The sink was too much for the 1-26 (not to mention for the pilot of the 1-26). I abandoned that goal, and instead, went to look for thermals in the foothills east of Black Mountain (I was nowhere near Black Mountain itself). No luck. So I turned back to the field, now flying with the wind.
I was nearing three hours of flying time. I was thinking it would be nice to log three hours. So I kept going past the field into the Kettlemans, pushed by the westerly wind, hoping the convergence was still there. It was, but it, too, had been pushed by the wind, and now it was closer to the east edge of the hills (and further away from the field). I was down to 4,000 feet; I found a weak thermal. With each turn, I climbed just a few feet, but got pushed east one hell-of-a-lot. Time to go home. With the nose down, flying at 65 to 70 mph with caution and avoiding sudden control inputs, I flew directly to the field, reaching it at about 1200 AGL. I flew a tight pattern because Alex and Mark arrived in the 2-33 at an extended downwind just as I crossed the field. Once again, they were above me. The wind sock was “stuck out” horizontally, at almost 90 degrees to the runway. I practiced my crosswind landings, did not ground loop the glider. After climbing out of the glider, I had the opportunity to watch Alex land the 2-33 in the crosswind—very nice, Alex.
It’s good to be back!
Thanks to everyone who helped me put the glider away. And thanks to Jim for towing me to lift!
Total flight time: 3 hours
Max altitude: 9000 ft MSL
Release altitude: 2000 ft AGL
PS don’t forget to wish Sergio Grejada a happy 21st birthday (Oct 8)
Editor's Note: I think the birds were Ravens. We also saw them doing rolls and split S's as they flew with us.
Mario filling out log book after a good flight!
Mike Paoli's report:
Saturday, I made my third flight in the Libelle. Jim Rickey gave me a great tow to near the crop circle, where I climbed to 6,000 ft. Over the next hour, I was maintained from 3,500 to 5,000 ft. along the base of the Temblors, near the power lines; along the west side of the Kettlemen Hills, near Avenal; and in the area from the gliderport to the prison. I could have stayed up longer but I was becoming increasingly concerned about the surface winds.
The wind at noon was from the SE at 2 mph, gusting to 9 mph. By 5:00 PM, it was from the SSW at 15 mph gusting to 27 mph. At times, the windsock would blow in one direction while at the same time dust near red barn was blowing in another.
The wind blew directly across the runway and into our trailers while we disassembled our gliders. Thanks to great teamwork, we completed the process without mishap. I will bring a shovel next week to clean out my trailer and cockpit.
Thanks to all for the assembly and disassembly help and the encouragement throughout the day.
Joe Anastasio's Flight:
The RASP promised a strong convergence, passing over the field at about 1600. I launched at 1500 and found good lift to 4000' west of the airfield. Heading for the hills I found sink, some zero sink, but the lift was to the east. The convergence moved through as scheduled, but I fell out of it as it swept over the Kettleman hills, and did not have the altitude and stones to push to the east, especially as a strong wind started blowing in from the west.
I got to practice a crosswind landing, By 1630 the winds were gusting from the west, raising a lot of dust.
We all had to pitch in to get the gliders put away, as we had quite a dust storm to end the day.
A couple of videos by Mark Neal from the Orange Crush while flying with Mario in the 1-26:
Amateur analysis of weather predictions for the day.
One thing to remember is, while the RASP and some other self briefing tools are very helpful to us soaring pilots, they do not by themselves constitute an FAA recognized preflight briefing. They do not include things like NOTAMS, TFRS, SIGMETS, AIRMETS, METARS, Terminal forecasts, Area Forecasts, Winds Aloft forecasts and other important things you get with an FAA recognized briefing.
The synoptic situation i.e. the "big picture" was interesting, with a closed low digging down into California from the Pacific NW. as shown by this NOAA GFS (Global Forecasting System) computer model forecast from Friday evening showing the 500mb "Heights" and "Vorticity". 500mb is a pressure level corresponding to about 18,000ft. and generally gives you the "steering winds" which parallel the lines of equal "heights", or pressures, and give you a good idea of the large scale motions and pressure patterns in the atmosphere. This forecast was generated Friday at 5:00p.m. PDT for Sun 10/4 at 0000Z which actually 5:00pm PDT Saturday, about when we were getting the best lift of the day. This time of year we can get some good soaring days as we start to get winter weather patterns, with low pressure systems moving in periodically. The days are still long enough to allow heating of the still dry ground. This tends to generate good thermals when combined with these low pressure systems bringing in cooler air aloft from the north. Often the low pressure systems do not have enough moisture and the atmosphere is still warm enough to keep the relative humidity low. Extensive cloud cover and precipitation often does not develop until later in the season, leading to good local soaring conditions for a number of weeks longer. This time of year, you need to pay closer attention to the bigger synoptic scale picture and be more selective in choosing the best days to fly, if you want to get in the best soaring.
This is a "Water Vapor" animation from the compostite GOES West and East satellites shows what actually happened from about 7:00a.m. to 4:30p.m. PDT on Saturday. You can see the same general pressure patterns, with the closed low digging down into Northern California. The Water Vapor Satellite imagery shows pretty much what the GFS computer model was predicting the evening before, perhaps the closed low is very slightly further to the East than the GFS predicted. Of course this Water Vapor animation was only available AFTER the events actually took place, whereas the GFS forecast was from the day before. Sometimes you can look at the Water Vapor or other Satellite animations up to the current time, and sort of "project" them forward a certain number of hours in your mind. This actually often works fairly well in predicting arrival of fronts or that maybe things will be rather stationary for a while, as long as it's just a few hours ahead that you're trying to predict.
Here is what the RASP model was saying by late Friday Evening. The next 3 images are for the "BL max Up/Down" or "Convergence" from 1300, 1500 and 1700 PDT. The convergence was over the Diablos at 1300 PDT, but the RASP was predicting that it would move to the East and be over the Kettleman Hills by 1700 PDT
The predicted "BL top" from the next 3 RASP blipmaps was about 9000 MSL at 1700 PDT just over the Kettleman Hills. The BL top is the highest thermals should go. Often you can't quite get that high, especially in a low performance glider, but Mario Pauda climbed to 9000 MSL in the predicted location of the convergence and best BL Top RASP forecast at that time.
The surface winds changed dramatically as the convergence arrived and moved over the airport to the East. This was predicted quite well by the RASP as well. You can see the very light winds still at 1300 PDT, shifting by 1700 PDT to the West and SW and increasing in strength on the next 3 blipmaps. You can also see that the winds on the East side of the convergence are still out of the SE and fairly light. Also note the very sharp change in wind direction and strength along the convergence line just to the East of Avenal roughly paralleling the Kettelman Hills and I-5.
The RASP also predicts cumulus clouds. It predicted there would be very few or no cumulus most of the day, even though the convergence lift was still forecast to be quite good along the Diablos early in the day to the West, and later in the day as the convergence moved East, over the Kettleman Hills. It showed on the 1700 PDT "Cu cloudbase where Cu Potential > 0" forecast that there would be a few cumulus with bases at 8500 MSL over the Kettleman Hills in a line towards Coalinga and the San Benito Mts. North of there. We did see some individual persistent cumulus clouds over the San Benitos with nice flat bottoms. We saw some transient more whispy ones along the predicted convergence line over the Kettleman Hills. The cloud bases were estimated to be pretty close to what the RASP predicted.
One of the whispy cu's the RASP predicted on the convergence line.