Longtime DCist readers know we love a good documentary. We’re particularly interested in a triple header WETA has lined up for tomorrow examining Hurricane Katrina and what lessons it left behind. The evening starts at 8 p.m. with the premiere of a NOVA on Hurricane Katrina titled “The Storm that Drowned a City”, examining the science behind the hurricane and how it caused so much destruction in New Orleans. Then at 9 p.m. is the…