Why 2011 is set for a sensational final grand prix

We are set for a sensational sign-off to the season on Sunday.

That's the message coming through loud and clear looking at the data from Friday practice for and combining it with the latest Brazilian Grand Prix raceday weather forecast of changeable conditions interspersed by thunder storms. If accurate, that's in stark contrast to the beautiful conditions of the first practice day, during which Lewis Hamilton's McLaren was fastest in terms of headline lap times from the Red Bulls of Sebastian Vettel and Mark Webber.

Hamilton topped P2, but on long runs was 0.9s off Webber © sutton-images.com

But it is the context behind those hard numbers that reveals the full story.

If we assume, as always, that Red Bull was running the low-fuel part of second practice with around 10kg more than McLaren, that would account for around 0.3s. Vettel trailed Hamilton by 0.167s, suggesting therefore that Red Bull is favourite to take its 18th pole from the 19-race season.

As usual the lap times of the two cars are delivered in very different ways, the Red Bull much the fastest through the tight twists of the middle sector, the McLaren faster down the straights of sectors one and three.

Interlagos is the least sensitive circuit on the calendar to wing settings - you can do very similar lap times with high or low wing levels, and although the Red Bull trails the McLaren's speed by the time they are at the end of the straights, it will be entering them faster and Red Bull will be looking to have pitched its wing levels and gearing to keep as much of its infield performance as possible whilst not leaving its drivers as sitting ducks on the straights.

The end-of-straight speeds therefore don't tell the full story and you need to visualise where each car would be relative to the other with one entering the straight faster, the other going faster at the end. The crucial thing is when - or even if - on the straight the McLaren catches the Red Bull. Obviously for both teams there's an element of assumption about what the other is doing when they make these choices.

Webber's long-run pace shows Red Bull holds all the cards © sutton-images.com

But that weather forecast may very well play a major part in their respective choices. If it is to be believed that it will be wet on Sunday, teams will want as much downforce on their cars as possible.

How much Red Bull and McLaren respectively commit to that forecast - and how the conditions actually turn out - could have a big bearing on the pattern of the race. It may even be possible that one or both teams split their strategies on wing choices to 'broaden their bandwidth'. Jenson Button does appear to be doing something different to Hamilton, though there is no difference apparent between the Red Bulls.

In terms of race pace, the last 25 minutes of Friday afternoon practice was devoted to race simulation and - in contrast to the low-fuel part of the session - Red Bull tends to run lighter than McLaren. During these laps Webber's Red Bull was fastest on peak times, slightly ahead of Vettel but a full 0.946s faster than Hamilton's best. But apply the usual pattern of first stint loads (McLaren) with second stint loads (Red Bull), assuming a three-stop race, and the picture appears incredibly close.

A first stint fuel load would be in the order of 140kg, a second stint load around 105kg. The mean of the fuel weight penalty quoted by engineers up and down the pitlane over the years for Interlagos is 0.27s for every 10kg.

The educated guesswork difference of 35kg between Red Bull and McLaren therefore equates to 0.945s - almost identical to the gap between Webber and Hamilton!

Ferrari appears, as usual, to have better race pace than over one lap © sutton-images.com

And where is Ferrari in all this? Flattered by the fuel weights, as usual. Fernando Alonso was within the same tenth as the Red Bulls in qualifying simulations, but reckon on that difference stretching by between 0.3-0.4s.

But on peak race pace, it looks quite competitive, as usual appearing to retain its tyre performance for longer.

Alonso was struggling with an oversteer balance and actually interrupted his race stint run to reduce his front wing angle, but Felipe Massa's best of 1m17.959s was only 0.15s slower than Hamilton - and by the end of the stint he was lapping faster than Hamilton.

The Red Bulls appeared to be hanging onto their performance remarkably well, but they did have a few blisters on the rear tyres by the end, suggesting they may indeed be running more of a wet weather wing setting, in the knowledge that the McLaren can usually generate tyre temperature more quickly than them in damp or cool conditions.

Bet on a Red Bull pole but an incredibly closely-contested race in variable conditions - and plenty of incident.

Ferrari (well, Alonso anyway) is by no means out of the Sunday equation, but the McLaren's ability to generate tyre temperature in the damp may be the most valuable trait of all. All it needs then is two truly great wet weather drivers - which actually it just happens to have.