Buoyancy/Shear Ratio

[Soartech]

What do you think about the BLIPMAP Buoyancy/Shear Ratio parameter?
Is it accurate that less than 7 makes the day difficult to work?
I have found lately that this seems to be true but my sample size
is small. I am in the northeast US. Location is probably a factor.

[Steve Leonard[_2_]]

I had heard 5 was where it started to get tough. I have gone cross country on days with the forecast of 2. Not easy, but if cross country was easy, any monkey could do it! I would not pass on a day just because the forecast B/S ratio is low. I have had fairly smooth thermal climbs with winds of 35 to 40 MPH here in the midwest. I have also had very rough and broken climbs with winds less than 10 MPH.

Steve Leonard
Wichita, KS

[Tony[_5_]]

Usually accurate but like Steve I've had good thermals on days with very low B/S, like when I flew 525 miles in a 30-40mph tailwind

[Tango Eight]

On Saturday, August 1, 2015 at 10:55:32 AM UTC-4, Soartech wrote:
> What do you think about the BLIPMAP Buoyancy/Shear Ratio parameter?
> Is it accurate that less than 7 makes the day difficult to work?
> I have found lately that this seems to be true but my sample size
> is small. I am in the northeast US. Location is probably a factor.

The best thermals on any given day have better buoyancy, so better B/S ratio.

Days with a lot of shear put an absolute premium on thermal selection. I'd put the number where things start getting choppy at around 5.

-Evan Ludeman / T8

[Papa3[_2_]]

Agree with Evan and Steve above. A lot depends on your course selection as well. Crosswind legs on low B/S ratio day can be brutal. Upwind/downwind usually better. Also depends a lot on pilot thermaling ability. Low B/S days typically require "dynamic" thermalling (push/pull/stomp - whatever it takes to go up).

P3

On Saturday, August 1, 2015 at 11:50:46 AM UTC-4, Tango Eight wrote:
> On Saturday, August 1, 2015 at 10:55:32 AM UTC-4, Soartech wrote:
> > What do you think about the BLIPMAP Buoyancy/Shear Ratio parameter?
> > Is it accurate that less than 7 makes the day difficult to work?
> > I have found lately that this seems to be true but my sample size
> > is small. I am in the northeast US. Location is probably a factor.
>
> The best thermals on any given day have better buoyancy, so better B/S ratio.
>
> Days with a lot of shear put an absolute premium on thermal selection. I'd put the number where things start getting choppy at around 5.
>
> -Evan Ludeman / T8

[Ramy[_2_]]

Agree with all the comments above. In general windy blue days are more difficult. I normally don't check the B/S ratio as the BLtop, wind, cu potential and cu base (as well as convergence and total cloud cover) provide sufficient information.

Ramy