Less than three weeks after Superstorm Sandy came ashore on the East Coast, three television networks will offer the chance to relive the experience on the same night. PBS’ “Nova” series will air a one-hour special on Sandy on Sunday evening, the same night that History is scheduled to run “Superstorm 2012: Hell and High Water.” The National Geographic network first airs its Sandy special on Thursday but is rerunning it on Sunday night. Two of the specials, on PBS and National Geographic, will directly compete with each other Sunday at 7 p.m. Eastern time. Still, many of the people affected by the storm will be unlikely to see the TV specials. Thousands of homes remained without power Thursday.