Selecting the Parcel button launches a popup GUI to select the parcel lifting method for the Skew-T. The values are calculated as follows:
Current Surface - uses surface station pressure, temperature, and mixing ratio.
Forecast Surface - uses an estimate of the afternoon maximum temperature combined with the mean mixing ratio in the lowest 100mb of the sounding. The afternoon temperature is derived from taking the parcel at 850mb dry adiabatically to the ground, and then adding a 2 C superadiabatic "contact" layer.
Mean Mixing Layer - uses surface station pressure and the average temperature and mixing ratio in the lowest 100mb of the sounding.
Most Unstable Parcel - uses the largest equivalent potential temperature in the lowest 300mb of the sounding. Note that the theta-E versus height display illustrates the vertical theta-E profile.
Mean Effective Layer - uses the layer with parcels having CAPE > 100 J/kg and CIN > -250 J/kg.
User Defined Level - uses the parcel at the pressure level specified (in mb).