I just was looking at these again....check out the "Good La Nina" Decembers.....a lot of them had crappy totals through 12/10 and then all hell broke loose later in the month:
1970, 1975, 2000 (not on there but was paltry through 12/10), 2007, 2008, 2010....and both 2005 and 2017 had big events on 12/9 with not much before that....which may still happen this year.