How to read the chart
The Skew-T Log-P plots the vertical structure of the atmosphere. Pressure decreases logarithmically going up, and isotherms are tilted 45° to the right so that real soundings are easier to compare visually. The two heavy lines are the actual model forecast at the selected hour:
Quick reading: if the temperature profile slopes steeper to the left than the dry adiabats — the layer is unstable (warm air below cool air aloft, thermals will rise). Where T and Td meet — clouds form. The freezing level is where T = 0 °C. CAPE is the area between a lifted parcel path and the environment temperature; positive CAPE means storms are possible.
Caveat: Open-Meteo pressure-level data is interpolated to standard pressure surfaces (1000, 925, 850, 700, 500, 400, 300, 250, 200, 150, 100 hPa). It is smoother than a real radiosonde sounding, especially across inversions. Compare with the Tallinn-Harku 00 Z sounding on the briefing page for ground truth.