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These two variables represent maximum values in the past 6 hours derived from hourly model output. For example an 18UTC value will be the maximum of the values at 13, 14, 15, 16, 17, 18 UTC (computational constraints prevent use of every model time step).These two variables represent maximum values in the past 6 hours derived from a combination of (A) standard hourly model output, that has been delivered separately to users for some time, and (B) values of CAPE and CAPE-shear computed every time step (450 s for HRES and 720 s for ENS) at gridpoints where the convection scheme is active. Please note that the way in which CAPE is computed in output (B) differs physically from the way it is computed in (A). These new parameters may help users to better assess the potential for convection than using instantaneous values. 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.
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