Today's Brazilian Grand Prix, pretty much like yesterday's qualifying session, is all about one thing, the weather.

We saw yesterday that a number of drivers found their qualifying efforts compromised after they opted for a dry set-up in the hope that today's race would take place in altogether different conditions to those witnessed for much of Saturday. Other drivers pressed ahead, confident that conditions would remain the same.

After a marathon qualifying session lasting almost three hours we were left with a scintillating final few minutes in which local hero, and championship contender, Rubens Barrichello took pole, while his main rivals start from fourteenth and fifteenth.

To add to the drama, Mark Webber starts from second position this afternoon, ahead of Force India's Adrian Sutil, Jarno Trulli, Kimi Raikkonen and Sebastien Buemi. With the two Williams drivers, both of whom have looked good all weekend, particularly in the wet, both making it into the Top Ten.

This afternoon however, the weathermen appear to have got it wrong, for the dark overcast skies of Friday and Saturday are replaced with blue skies and sunshine. For many, strategy has gone out of the window.

Unsurprisingly, Barrichello was running on fumes in qualifying, and along with Heidfeld and Raikkonen will be among the very first to stop. Indeed, fuel load wise, Trulli is the best placed of those at the front of the grid, along with Buemi, Sutil and Rosberg.

While Barrichello is very light, Vettel is the second heaviest and Button fifth. However, it should be noted, particularly on the first lap as the field heads through the notorious Senna S, that just ahead of these two are three (relative) rookies, Kobayashi, Alguersuari and Grosjean, each of whom has 'history'.

However, bearing in mind what happened yesterday, and the uncertainty of the weather, today's race is almost impossible to call, for not only will the drivers have opted for all manner of set-ups, there has been minimal running on the option (super-soft) tyre this weekend, indeed, as the sun shines down on Interlagos, most of the running yesterday was on full wets and intermediates.

Therefore we have a unique race ahead of us, and let's not forget we have a World Championship title at stake - assuming that Brawn GP already has the Constructors' Championship in the bag.

Out front Barrichello must do all he can to convert his pole position into a win while teammate Button needs to finish in the first three if he is to avoid the title fight going on to Abu Dhabi. As for Vettel, his already thin hopes appeared to finally disappear yesterday afternoon.

Both McLaren drivers are starting from the back of the grid, however, like the Ferraris, it will be interesting to see how much they make of their KERS here, where the controversial device should come into its own on certain sections of the track.

The mixed up grid, the experimentation in terms of set-up and, of course, the uncertainty in terms of the Sao Paulo weather, means we could be in for a cracker of a race this afternoon. Last year we witnessed the drama of Hamilton winning the title in the last corner of the last lap while yesterday, despite the delays, we were served up one of the most thrilling qualifying sessions for years.

Tyre options for today are medium (prime) and option (supersoft).