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Due to computational constraints these These two variables represent maximum values in the past 6 hours derived from hourly model output (not at each . For example an 18UTC value will be the maximum of the values at 13,14,15,16,17,18UTC (computational constraints prevent use of every model time step). These new parameters should help users to better assess the potential for convection than their instantaneous counterparts. As the plots below illustrate, the new fields tend to be smoother and more continuous. This is because model CAPE at a given location on a given day can increase and decrease quite sharply, over timescales much less than 6 hours.
Maximum CAPE versus instantaneous CAPE (left) and Maximum CAPE-shear versus instantaneous CAPE-shear (right).