Why was there a hurricane that formed from a tropical storm 2 days before the 9/11 terror attack, and headed straight towards the city, turning away on the morning of 9/11? Was this showing off by the extraterrestrials, or perhaps a backup plan to complete the destruction or cover up evidence that proved to be unneeded?

This, as you saw it intuitively, was Extraterrestrial Alliance mischief. They were indeed planning a one-two punch initially, and this is the reason the storm was set in motion, and then just shortly before the date of the attack the storm system increased to hurricane strength and was making a straight-line approach to New York City. It was on the morning of 9/11 that the hurricane stopped and made an almost right-angle turn and began to meander Northeast in the following days, so the confluence of events was averted at the last moment. The reason for this was that they wished to have the tower destruction fully on display for all to see and not have it potentially overshadowed by a massive storm coming through that would serve to disperse the debris, and would begin to blur things in the minds of the witnesses as to the proximal reason for the destruction and corresponding distress of those who both experienced and also witnessed the event, even remotely, via television, all were traumatized because of its horrific nature. In the immediate aftermath of the attack it was seen to be overkill that could, in fact, detract in some ways, so the storm was redirected elsewhere as it was no longer needed.