# Thermal likelihood formula

Background: I use the X-Plane flightsimulator for flying and gliding. In the program we have real weather (clouds, winds, etc...) but thermals are not well implemented, they don't have any connection with clouds or weather, they are just blue thermals. We can control its altitude, climb rate and coverage (percentage). I am thinking about writing a small plugin to control these preferences based on the real weather.

Can you give a simple formula to roughly calculate thermal parameters based on data in METARs (temperature, drew point, cloud coverage/type, wind). Thanks!

• I would just calculate the vertical velocity using the vertical momentum equation and examine it's value. Negative values represent lift and positive subsidence. – gansub Jun 4 '19 at 8:56
• Boundary Layer Method by Roland Stull check that book out – gansub Jun 4 '19 at 9:07
• Thanks for the tips. I'll check the book out, but since I'm not if physics, it's possible that I'll not understand a word!:) I found this: meteoblue.com/hu/id%C5%91j%C3%A1r%C3%A1s/el%C5%91rejelz%C3%A9s/… that had indexes and so in it. I don't need anything complicated and precise just some heuristic to determine the thermal coverage percentage and so. – Stone Jun 4 '19 at 14:45
• the meteoblue link you provided does talk about vertical velocity. The formula for soaring index is here - ssa.org/files/member/Methodology.pdf – gansub Jun 4 '19 at 15:35
• Thanks for the link. It seems that this hole is deeper than I thought... – Stone Jun 5 '19 at 10:18