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We plot the Secular Light Curves (SLCs) of comets C/2011 L4 Panstarrs andC/2012 S1 ISON. The brightness of C/2011 L4 Panstarrs and C/2012 S1 ISONincrease steeply after discovery but both decrease in slope sharply at ~4-5 AU,a characteristic of Oort Cloud cometary light curves that we refer to as aSlope Discontinuity Event (SDE). After the SDE, the SLC of C/2011 L4 continuesto increase and has a surge near perihelion. The SLC of comet C/2012 S1 ISON onthe other hand, is very odd and exhibits a SDE plus a near-standstill after theevent. We found five comets with similar behavior: C/1996 Q1 Tabur, C/1999 S4LINEAR, C/2002 O4 H\"onig, C/2010 X1 Elenin and C/2012 T5 Bressi, all of whichdisintegrated. Thus we predict that comet ISON will disintegrate too. Wecompiled published production rates of water, dust and CO and used them tocalculate the Mass Loss Budget. We use this information for ISON to calculatethe diameter and to plot 29 comets in an Evolutionary Diagram that separatescomets by class. We find a diameter D = 1030+-70 m in excellent agreement withthe upper limit found by Delamere et al. (2013), D(mean) < 1126 m. It isevident that the Secular Light Curves, exhibit complexity beyond currentscientific understanding. Note: The comet disintegrated as predicted (CBET3731), while this paper was being refereed.

The Location of Oort Cloud Comets C/2011 L4 Panstarrs and C/2012 S1 ISON, on a Comets' Evolutionary Diagram