Various Sounding Diagnostic Parameters


Precipitable Water (PW)
The total amount of (condensed) water available within the lowest 400 mb of the sounding.

K-Index (K)
((850 mb Temp - 500 mb Temp) + 850 mb Dewpoint - (700 mb Temp - 700 mb Dewpoint)).
This index attempts to identify steep mid level lapse rates (850-700 mb temperature differences) in the presence of substantial moisture in the low-mid levels (850mb dewpoint minus the 700 mb dewpoint depression). Values greater than 30-40 tend to be associated with deep convection, while thunderstorms are much less common with lesser values.

Mid-Level Relative Humidity (MidRH)
The average of relative humidity values at 150 mb and 350 mb "above" the surface pressure (roughly 850-650 mb at sea level).

Low-Level Relative Humidity (LowRH)
The average of relative humidity values at surface and 150 mb "above" the surface pressure (roughly surface-850 mb at sea level).

Significant Severe Parameter (SigSevere)
(MLCAPE * 0-6 km bulk shear), with units of m3 s-3. Please refer to Craven and Brooks, 2004 for more information.