The Grey's Anatomy hospital Grey Sloan will be hit by a crippling natural disaster in the season nine finale, according to sources close to the ABC medical drama. After several cryptic tweets from showrunner Shonda Rhimes, insiders tell the Hollywood Reporter that a 'superstorm' will rip through the institution on May 16, 2013.

The natural disaster will actually begin in the penultimate episode of the season - titled 'Readiness Is All' set for May 9 - though will hit full force on the May 16 episode, titled 'Perfect Storm.' The storm will affect the recently renamed hospital and causes the entire staff to go into crisis mode in an episode being described as "very intense" with lots of "major thing changing for the characters in the final two episodes."

Rhimes has previously said the Grey's writing staff made some "very bold [and] shocking decisions" with the final, following "very intense discussions." It had led many fans of the show to suggest some characters could be killed off, though Rhimes only offered, "I warned you about the GA finale so you could brace yourself.Hug a friend."

Grey's Anatomy has a history of big season finales, with Derek's (Patrick Dempsey) estranged wife Addison (Kate Walsh) being introduced, Denny's death, George's bus crash and the heart-stopping hospital shooter. Will the season nine finale live up to expectations? The show returns on Thursday at 9pm for the first of its final four episodes of the season.

Shona RhimesShonda Rhimes Has Promised Big Things For The Grey's Anatomy Season Nine Finale