Question

Sounding plotted on skew-T diagram

This sounding was taken at North Platte, Nebraska, at 1200 UTC 24 July 2000. It was associated with a severe supercell thunderstorm.

What is the wet-bulb potential temperature (theta-w) for the temperature and dewpoint at 850 hPa shown in this sounding? Enter your answer in the text box below, then click Done.

Theta-w (850 hPa) = °C

Answer: Theta-w = about 22°C.
From the 850 hPa dewpoint (Td = 8°C), proceed up the saturation mixing ratio line. Simultaneously, from the 850 hPa temperature (T = 26°C), proceed up a dry adiabat. From the intersection of the 2 lines, proceed down along a saturation adiabat to the 850 hPa isobar. The temperature at this point equals the wet-bulb temperature (Tw). Continue down the saturation adiabat to the 1000 hPa isobar. The temperature where the saturation adiabat crosses the 1000 hPa isobar is the wet-bulb potential temperature (theta-w).
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