RBR has found something, for sure... The car looks to be a lot better than the rest handling wheelspin, as evidenced by Vettel onboards, where he goes very early on throttle even in the damp conditions. New enginemap?
But the real star is Alonso. Semi broken car (front wheel alignments probably not exact after repairs) that is also a bit behind technically but still managing a really good top time in heavy rain.
I think that if the rain persists at this rate, experience will be deciding factor in the race. My bet is now Hamilton wins ahead of Alonso, with Vettel third... Then maybe Rosberg. Biggest climber will be Button.