DrJack's way off?

[KirkLewis]

On Saturday it's been saying there is going to be really weak lift (like 200). But if you look at the soundings the lapse rate looks fine and it isn't suppose to be more than partly cloudy. I've been following drjacks this season and this isn't the first time I've seen it disagree with the ridgely soundings by a wide margin. I'm almost regretting even paying for it since it doesn't seem to be accurate at all. Am I missing something here?

[KirkLewis]

Oh I should mention I'm talking about ridgely lol.

[RedBaron]

wunderground.com to check wind speed, direction, temperature and cloud density

Done.

I average about 2 sled rides per year with this.

[hang_pilot]

I find that if you don't subtract the glider's sink rate, you get a good enough number.

~Daniel

[KirkLewis]

Ya I don't know. Now the two seem to be more in sync. Dr. Jack's has gotten more optimistic and the soundings have gotten less optimistic. It's just weird because I thought dr. jacks was suppose to use the soundings. I think I'm just going to make myself a website that says "CONDITIONS WILL BE AWESOME" and then I'll never be tempted not to go based on forecasts that are usually only accurate the day of if anything

[Dan T]

I have a hunch that if we followed Kirk's "it's gonna be awsome" model, we'd all fly more and soar more.

Dan T
in kuwait

[silverwings]

So is going to be good on Saturday at Ridgely or are you being optimistic/delusional?

[Matthew]

I've found Dr. Jack's to be right 50 percent of the time. So, flip a coin.

My rule of thumb is-- if there is sunshine, there will be thermals!!!

I may not be able to get up in them or find them-- but they will be there.

Matthew

[KirkLewis]

John you know all you need to know about my forecasting ability from my weather prediction before the last lesson I had with you lol.

But I'll be showing up at ridgely. It's suppose to be sunny, with more moderate winds than we've been having for most of the season and a pretty small possibility of thunderstorms latter, so I don't see how it can't be too bad. According to the soundings it looks like relatively low cloudbase (2500) though. Which is just as well because that way I can release off tow and claim I made it to cloudbase

[carweill]

For Saturday the weather seems to be all over.
Hard to tell how will it turn out.
I'll be checking.

Carlos

[John Simon]

Hi Kirk,
Yeah, like Daniel I never subtract the gliders sink rate and this has been consistent for me. I find Dr. Jack or XCSkies useful for a quick look at lift, winds across a large area, B/S ratio is nice too plus top of lift. It's not always on... because sometimes we just don't get the sunshine on the ground or the winds are stronger. If we get the sun Dr. Jack predicts it's usually pretty good but there lies the rub. Tomorrow may be a bit less sun than we would like.

You can use other sources to get a rough idea without Dr. Jack, but I still use it and like what they do. Soundings are very nice too, but an unstable sounding still generally requires some heating to get lift working. The last day of this years' ECC had a nice sounding but was totally overcast... There was still enough lift to stay basically at 2000' under overcast skies but that was it. If the sun ever came out it might have been pretty good.

See you there tomorrow.

John

[KirkLewis]

When I said saturday was going to be good I meant sunday...

Still had fun though =P

[Ashley Groves]

No one tool is going to be perfect all the time. Note the stated variability in the forecaset. When he predicts top of lift is 3500 ft, great! But when he predicts 3500 ft +/- 3000 ft, just know the model is unsure of itself

Dr. Jack's should be one of many tools used to forecast, and it helps to know weakbessess and strengths of a tool to help understand it. Dr. Jack uses an estimation of the energy of the sun strength on the ground. The model over predicts on days with high cirrus well or very wet ground. (The day John Simon was referring to was very wet on the ground from the rain. Dr. Jack had an opptomistic forecast, but the moistur produced cloud cover that was too thick to be any good.) Also it does not take into account effects such as marine air or benefits from convergence. The position of Ridgely makes sounding interpolation a little difficulty with it's position in the bay and the positions that take the soundings.

I think Dr. Jacks is a very powerful tool and I use it, but it certainly is not gospel at any site all the time.