Pseudo-Adiabatic charts and skew-t/log-p charts


Gang Member
Trying to figure out how to read these. I know that is shows plots of measured temperatures aloft. Fig 6. in the FAA commercial written supplement has an example.
The FAA Glider Flying Handbook has write-up beginning on Page 9-8.

I have that book - seems to make sense to me, until I actually try to compute the TI at a given altitude. For example:

[FONT=Times New Roman, serif]174. PLT062 COM[/FONT]​
[FONT=Times New Roman, serif](Refer to figure 6.) With regard to the soundings taken at 1400 hours, from 2,500 feet to 15,000 feet, as shown on the Adiabatic Chart, what minimum surface temperature is required for instability to occur and for good thermals to develop from the surface to 15,000 feet MSL?[/FONT]​
[FONT=Times New Roman, serif]A) 58 °F.[/FONT]​
[FONT=Times New Roman, serif]B) 68 °F.[/FONT]​
[FONT=Times New Roman, serif]C) 80 °F.[/FONT]
Well, to see what the parcel temperature is you would move up the a dry adiabat from the surface and then read the temperature. The environmental temperature would be reading the temperature from the given height. I might be missing how the TI value is calculated, but it looks like none of the answer would provide the 'right' TI value.

Does the book not tell you what the correct answer is?