2 RASP

This is a continuation the post to Williams Today – https://www.williamssoaring.com/news/showthread.php/1243-Flying-Saturday-10-20

We are evaluating soaring conditions for this Saturday – in real time. The preceding web page was the first post to this thread, this is the second post to that same thread.


Thursday 11 AM, Launch minus two (2) (days, that is)

No need to go to UNISYS charts any more. Andy has the RASP model looking forward on a “three day forecast.” and it was first run late last night.   We now have today’s RASP run (that was run this morning) thus it is a two day forecast for Saturday.  When it is re-run tonight and again tomorrow (Friday) morning, it will be even more accurate.  The closer we get, the more accurate the forecast becomes.

Here is how I go through the RASP products to see if it will be good soaring this coming Saturday. I’ll keep all charts at 1400 hours, since that is time that the max temp will be reached. That will be the best part of the day.

1. First I look at Hcrit.   1400 hours – the heat of the day.
I see very little lift, marginal height at Goat, with a touch at height at Yolla Peak (maybe 9,000 ft.)

[Note: the images shown below were not on the posting].

 

 2. B/L Top 

The top of the convection level – no mixing above this height.
maybe 4,000 at 3 sisters.
maybe 6,000 at Goat.
touch of  8,000 on the west side of Snow
11,000 is at Yolla, but not likely to get there.

 3. thermal strength (thermal updraft velocity)


less than 400 fpm – that is weak!
Why so weak? Is the BS ratio low?

 4. BS Ratio


mostly less than 4 and 5 – that’s too low.
do we have a surface wind?

5. Surface wind
less than 8 kts.
check the winds at 5,000 and 10,000 ft

 6. V V at 850  7. and V V at 700 

guess the problem is either clouds or stable air.
Look at the soundings.

 8a. Black Butte
No cirrus – blue line well to the left (thus no clouds)
Verify if you doubt it – see cu cloud base – (8a1) and percent of cloud (8a2).
Wind is laminar all the way up to 10,000 and from the east.
yup, that’ the problem off shore breeze.
The air has been heated by the land mass
Air is too stable.
Mixing (convection) will be minimal
surface wind (near 10 kts) is too high for the weak thermals, even though the warm air is being forced up the east facing canyons.

cu cloud base  percent of cloud 

  8b. Goat sounding – worse

 8c. Three Sisters TP
Bad!.
But, at least a bit of an inversion, with thermals to 2,000 ft, so that means we might be able to tow to cooks and work our way to the gun club before we enter the pattern , but let’s see wsc.

 8d. WSC sounding

inversion over WSC is even lower than 3 sisters – about 1,000 ft, and a north wind to boot! no thermals today. By 3 or 4 pm we can easily land to the south and there is about zero convection indicated.

Looks like a no-brainer to me! For sure, I’m certainly not going to fly x-c on this next Saturday.  It’s still a good day to fly, for training and/or landing practice, but I’m current on my training and I  don’t care for sled rides.

Now, if I was really desperate to get in some cross-country flying time, and if I was really current on digging out of low situations and working my way back up the hill, and if I would be willing to accept that I could probably log three hours of sweaty flying time, and probably not get past Black Butte and never get above 9,000 ft …. then maybe  I would study this again tomorrow and also again on Saturday morning and try to convince myself  that I could somehow pull this off safely and/or I had made an error in my predictions.  But, I’m not interested in following up. Maybe we’ll see more info on the Forum on this thread.

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