Thursday, November 7, 2019

Tuesday, September 10, 2019

Shear Wave


6,600' over Post Mills on Sunday
Sunday mark the beginning of wave season in New England.  It was kind of windy, thermals were generally weak, cloud base was low and the clouds sort formed streets (perpendicular to the wind).  The first 2 hours of my flight I tried to thermal to cloud base and then look for wave.  Most of the time was spent trying to get to cloud base in the weak thermals and avoiding the strong areas of sink.  Since the wind was out of the northwest, when I got to cloud base I would try to move toward the northeast (mistake) and generally found sink.

I found a strong thermal over Rich Starr's house (I guess there's a lot of hot air around there) that took me to cloudbase over the east ridge and from there I was able to transition to wave at about 5,000'.  When I looked around I noticed I was on the southwest side of the cloud street and the glide computer said the wind was 280 degrees at 20 kts.  Below 5,000' the wind was 320 degrees at 10 kts.

I think what was happening was there was cloud street that runs perpendicular to the wind (320 to 140 degrees).  The thermals push up into the inversion at 5,000' and forms a "ridge".  The inversion layer is moving at 20 kts from 280 degrees and hits the "ridge" at a 40 degree angle and has to go up and over the "ridge" forming the shear wave (see cloud street wave).

While the OLC points and the maximum altitude were unremarkable, it was a really fun flight.






Tuesday, June 25, 2019

SkySight Wave Forecast...Round 2

Sunday offered another chance to fly wave.  Strong NW wind in Summer is not normally considered prime wave weather but SkySight was showing areas of more than 7 kts and going to altitudes over 32,000'.

My flight started off with a tow to the northwest in a cloudless sky (at least in our area).  The tow was in sink from the time we past West Fairlee.  I held on to the tow until we got to 5,200' hoping that we would find some good air but we never did.  I continued in sink for a few more miles to the northwest.  Finally, I made a big left turn to the northeast.  It wasn't until I got over Middlebrook 4-5 miles north of the airport that I finally found my first traces of lift and slowly worked into wave and up to 12,000'.  SkySight had predicted the bad tow and the sink during the first part of the flight (the box showing -0.8 kts shows where I turned around and headed northeast).  SkySight also showed wave right where I found it (the blue dot), over Middlebrook and Lake Fairlee.


Thinking I would head to Mt. Washington I headed towards Franconia trying to use ragged clouds as wave markers.  Once I passed Dean Memorial I fell out of the wave and was never able to find it again.  I spent the rest of the flight in turbulent, broken, rotory, frustrating lift.  I made it as far as the Mount Washington Hotel but at 6,000' I again chickened out (see last posting) and did not make the transition to Mt. Washington.
 

For this flight SkySight got everything right.  I got sink off of tow where SkySight expected sink.  I found weak wave near PM right where SkySight said it would be.  And I spent the rest of the day in a futile effort to find wave where SkySight said there won't be any.

I had looked at the SkySight forecast the night before the flight and I saw the strong wave prediction but I really didn't pay attention to the exact location they were predicting wave.  The strong wave was predicted to be in the Pemigewasset wilderness to Jackson NH.   From the area from Franconia to Mt. Washington it would have been very difficult to safely access the wave through the sink (especially with only 6,000').  This picture shows the forecast wave cross section for a line drawn from the MW Hotel to Jackson, NH.  It shows - 5 kts where we normally expect wave and +7 kts over Jackson, much further downwind than normal.  I guess we'll never know if this forecast is correct.


If I had paid more attention to the forecast maybe I would have tried to pick up wave behind Smarts Mountain, using Plymouth and Wentworth as safety airports.  I can get SkySight downloaded to my Oudie but I have to signup for SeeYou Cloud $59/yr.  Maybe I shouldn't be so cheap.

I also looked at a flight by Nelson Howe from GBSC.  He did a nice job of following the wave upstream for 4 wave cycles.  In this case SkySight seems to have predicted the wavelength to be twice as long he found:

Thursday, June 20, 2019

SkySight Wave Forecast....Not!

I was able to contact wave during last Monday's flight.  After the flight I went back to see what SkySight had forecast for the day.

The thermal forecast was pretty accurate:


When I got to Twin Mountain (the mountain not the airport), it was completely blue to the North and East.   I was below 5,000' and the lift was broken up.   I figured if Mt. Washington wasn't working and there was sink between Twin Mountain and the Presidentials that I would end up scratching at 1000' over Twin Mountain airport (been-there-and-done-that-before) and I wasn't in the mood.  So I chickened out and instead of heading towards Mt. Washington I turned around. 

When I got back to Franconia I was able to find weak wave and work it up to about 8,000' where SkySight predicted no wave lift:

 

Once I was in wave I could maintain 7,500-8,000' as I drift back towards Twin Mountain (In an area SkySight predicted no wave lift).  At 7,500' over Twin Mountain I felt I could make a run at Mt. Washington and if it didn't work, return to Twin Mountain without too much stress.  As it turned out I flew over the summit with 1000' to spare and contacted weak wave right over the horn.  At times the lift averaged over 3 kts and I topped out at 13,500'.  SkySight was predicting 0.4 kts of lift:


 Recently Matthew Scutter wrote in RAS:
I'm biased because I wrote it, but;
For wave flying, the wave forecasts are so useful you'll wonder how you did it without it. Don't believe me - ask Dennis Tito or Morgan Sandercock, an OLC comment from on one of their 2000km flights, using SkySight in the cockpit:
“The SkySight forecast is so precise that we did not need to look at clouds to find lift. When the clouds went one way and SkySight went another way we found it was better to follow the SkySight prediction. We literally do not need to look out the window to find lift.
I have flown blue wave personally multiple times with SkySight and it really opened possibilities that were not there before. Predicting wave is quite easy because mountains don't move very fast and mid-to-upper level winds change slowly. The same applies to orographic convergences (i.e. wind splitting and joining behind an obstacle) or along the edge of plateaus/ridges. Overlay some wave flights on the forecast with the IGC Upload to see for yourself.
In highly dynamic or unstable wave conditions (fronts passing through etc) though your mileage may vary as to the placement of the wave hour by hour.
While SkySight might be good at predicting wave with big mountains in places like the Owens Valley, Patagonia, the Pyrenees, etc.  I think it still pays for us in New England to look out the window.

One thing that SkySight might have gotten right is the convergence forecast.  Often the transition from Twin Mountain to Mt. Washington is stressful because you are flying downwind, into rising terrain and there is often sink, and if things don't work out, you have to turn around and go upwind through the same sink to make it to the safety of Twin Mountain Airport.  On Monday the transition was easy, there was lift in this area (or zero sink) and little altitude was lost during the transition.  SkySight had predicted 0.4 kts of convergence lift:



P.S. - Thanks for the tow Andy!

Monday, June 10, 2019

Does SkySight Work?


SkySight is a soaring forecast website that claims high resolution (both spatially and temporally) and accuracy forecast.  It is available for an annual subscription of $80.  Because it makes predictions for specific locations on an hourly bases it is possible to check the validity of its model.

Last Friday (6/7/19) was the best soaring day this spring.  I took Moshe's OLC trace and compared it to the SkySights prediction of thermal height.

Here is what I found:

Here is his trace superimposed on the SkySight (SS) prediction for how far an 18 meter could fly that day.  It is a daily prediction and does not change as you scroll the time bar at the top (ignore the hour).  SS rightly predicted it was going to be a good day.  Moshe in his 13.5M glider scored 494 OLC points (322 actual km flown).


At 12:55 he thermaled up to 6,660'.  SS predicted the top of climb (toc) to be 7,444'.


 At 13:12 he thermaled up to 6,861'.  SS predicted the top of climb (toc) to be 7,251'.

At 13:45 he thermaled up to 8,102'.  SS predicted the top of climb (toc) to be 6,923'.
 
At 14:33 he thermaled up to 9,042'.  SS predicted the top of climb (toc) to be 7,677'.

 At 15:17 he thermaled up to 6,700'.  SS predicted the top of climb (toc) to be 7,710'.  When you right click on SS it gives you the prediction for that spot.  In this case it was 7710' but the color would indicate that the toc should be 8-9,000'.  

At 16:05 he thermaled up to 9,811'.  The high point of his flight.  SS predicted the top of climb (toc) to be 1,345' and the color would indicate a predicted toc between 5-6,000'.  Again, the predicted value was different if you right clicked vs. looking at the colors.  By 4 pm, SS was predicting the lift to be spottier which seems correct but it did not accurately predict which spots were best.

He then flew to Twin Mountain Airport with out finding much lift.  He struggled there until he finally work back up to 6,672'.  SS predicted poor lift along his route and that the toc would only be 3,379'.  SS predicted that if he had flown over Mt. Washington and Twin Mountains (the Mountain not the Airport) he would have done much better.  I think he avoided the high country because it showed signs of over development.  Was there better lift in the mountains?  We will have to look at JD's and DW's traces who were there at the same time (or BU, NT, and EA who came thru a little later).


His final climb was at Moosilauke at 17:45 where he got to 8,682'. SS predicted 6,594'.


In conclusion, I have not made an conclusions about the usefulness of SS to me.  When its booming everywhere I think making accurate predictions is easy.  SS makes prediction about how the lift is going to die at the end of the day.  If it can predict where the lift will be at 18:30, that would be truly useful.

Saturday, June 8, 2019

Central Maine

Here's a picture of Moosehead Lake, which is about 180 miles from here.


Dan took the photo yesterday, and then flew home.

Monday, June 3, 2019

Weekend report June 1 - 2

May is normally the peak month of the soaring season.

A sign of how disappointing May has been this year is this quote from Tim:  "We used to complain about our bad luck on weekends.  This year we lost the whole month."

The Slackers were so desperate that they went with a mediocre forecast and showed up on the last day of the month, just in case a day could be squeezed out.  It couldn't.

So far, June hasn't been much better.  Saturday was grey all day, a perfect day for flight test prep.  Evan and Peter took advantage of that opportunity with a solid day of ground and flight instruction.


David, both Andys, Skip and Rick sat around most of the day, and ALaw took a short flight in the 1-26.

By far the highlight of the day was the cookout at the end.  This time our heroine, Laurie, provided... well... everything.  It was a great party.

Sunday was a drizzly dud.

Tuesday, May 28, 2019

Weekend report May 25 - 27

After a disappointing three weekends, the month of May finally produced some decent weather for the Memorial Day long weekend.

In a reversal of what normally happens around here, the weather was much better than forecast.  Unfortunately, the pessimists who believed the forecasts missed out on Sunday, the best flying day of the year so far.

Saturday was a training day, mostly.  Henry and Michael each had two flights, and we met Rick Walters, who has joined the club, and who will be bringing his ASW-24 to the field soon.  Skip did his field check and did a nice job with a non-standard landing pattern.  Kari (2C) practiced some more.  Tim towed all day, and we were able to put everything away before the rain showers started around dinnertime.

There was no instructor scheduled for Sunday, and there were only four flights!  Pete (3BA) flew all over the place and came home after a little more than 3 hours.


Both Don (JM) and Skip (JS) had good flights, but they both had flight recorder failures, so we won't be able to see their flight logs.  At the end of the day, Moshe (RU) showed up and was able to get 1.5 hours in the Russia.

Finally, on Monday, we had a normal turnout.  Moshe flew in the 2-33 with two students - Fred and Henry - and everyone else flew solo.  There were good climbs to 7000 feet once the day got going, and Paul (S1), Greg (JD), Tim (BU), and Evan (T8) all managed to stay in the air most of the day.  It took Dennis (DC) and Karl (HK) two tries, but they managed good flights as well.  Karl claims he got to 9300 feet in wave, but he doesn't have a flight recorder, so we don't know whether to believe him.  Pete (3BA) had another long flight in the Blanik, and just as the overcast moved in at the end of the day, Peter showed up and flew 505, just to prove that the lift had died.

Dan (EA) had an opportunity to land out at his home field, but he managed to get back to Sterling.

Outside of flying, we had a terrific weekend of volunteerism.  Thanks a million to Fred, Henry, Don, Pete, and new member Sam Strohl, who manned the golf carts, ran ropes, moved a trampoline, mowed grass, and pumped gas.  Pete, who had to go back home today, de-greased the towplane, washed, waxed and repaired the 304 trailer - and organized the clubhouse, which included putting up some nice pictures.

Saturday, May 25, 2019

PMSC at the races

They've been running the ridges at the Region 2 contest in central Pennsylvania.

Our guys (Dan and Evan) are having a great time and are doing well, for a couple of ASW-20 drivers.  They are competing in the combined Standard/15m class, so their high wingloading, combined with their handicap keeps them competitive.

On Wednesday, Evan won the day, flying 212 miles at 83 mph.  Dan flew a bit too fast and fell off the ridge, going from 100 mph to a landing in just 4 minutes.

Yesterday, they assigned a "Long MAT," which is intended to be too long to complete.  You're supposed to collect as many turnpoints as possible in (at least) 4 hours before dashing for the finish line.  It also requires you to program about a dozen points into your glide computer before takeoff.


Dan must have programmed it right, because the preliminary results show that he won the day!  He averaged 90 mph over 5 hours.

Evan decided to maximize his distance, rather than his speed, and was actually able to claim all the turnpoints before coming home 15 minutes before sunset.  His total was 622 miles (1001 km), having spent about 8 hours in the air, and he got OLC credit for 856 km - the 4th best flight in the world that day.

Today is the last day of the contest.  The final results will be published here.

Thursday, May 23, 2019

Slacker day

After the crummy weekend, everybody was looking for a good day to go flying.  Wednesday was nominated, and when the day came, the usual suspects bolted from their day jobs.  One of them didn't even bother to change into his flying clothes as he went out the door.


In all, 8 pilots made 10 flights.  The weather wasn't quite as good as we wanted.

Don wrote:
The day started out breezy and improved as the afternoon progressed. Thermals were around but all chopped to pieces by the wind. During my brief flight, indications were northerly in the 20s-30. At 3000-5000’. 
Flights that started later in the day tended to stay up. Tim (BU) and Moshe (RU) made two flights, so had twice the fun. I had to leave before Tim/Dennis/Moshe returned so don’t know their stories. Eric (NT) started early and made it to Mt Washington and back. Kari (2C) made an hour plus flight in his Jantar.

Don took this picture of Moshe on his first flight.  Note the scummy sky and lack of cumulus.


Peter and Dennis (DC) made long local flights later in the day, both over 2.5 hours.