13:45 Hello everyone and welcome to AUTOSPORT Live for continuing coverage of round 16 of the 2009 FIA Formula 1 World Championship.

The most remarkable season in years is drawing to a close and this weekend could see Jenson Button - a driver almost out of work 10 months ago - claim his first world title at Interlagos.

Sebastian Vettel will be trying hard to stop him, as will the man who the patriotic Paulistas have come to cheer on this weekend, Rubens Barrichello.

Another highly-charged day of action is about to unfold at the Brazilian Grand Prix.

13:46 Late last night, the weather prospects changed once again with a trough line of heavy rain forming to the south-west of Sao Paulo.

So far this morning, the band of rain has developed into a severe weather feature and is currently tracking east and slightly north towards the city.

The big news is that the first of the heavy bursts of rain has arrived in the last 20 minutes. Torrential rain and flooding are now threatening the running of this final practice session.

Further thundery downpours are expected throughout the day.

13:47 Today, we will guide you through the final practice session with minute-by-minute commentary as the teams and drivers face an uphill struggle to prepare for qualifying.

Third practice will begin shortly, with commentary ending 15 minutes after the session has concluded.

Later, at 16:45 GMT, we will return for live coverage of the all-important qualifying session and the battle for pole position. AUTOSPORT Live will end the day with a detailed Sunday weather forecast, on the Brazilian Grand Prix weather page.

13:49 Light rain showers disrupted yesterday's two 90-minute sessions of practice, leaving something of an inconclusive feel to the final classification.

The threat of rain meant most drivers headed out early in the first session, despite a lack of rubber on the track surface. Mark Webber set the early pace for Red Bull before Rubens Barrichello snatched the top spot as showers threatened the circuit.

The action came to a halt while the circuit was briefly too slippery for slick tyres, but running soon resumed after the rain eased off. Conditions were still tricky, however, and Romain Grosjean demonstrated this perfectly by sliding wide at Juncao, demolishing a brake marker. The session had to be stopped to clear the scattered polystyrene debris.

Following another brief shower, a late string of improving times left Webber quickest from Barrichello, Vettel, Kovalainen and Hamilton.

Webber tops first practice at Interlagos

Rain clouds continued to hover near the circuit for second practice but mostly deposited their contents away from the track, leaving the teams busily comparing the two tyre compounds.

Graining was a common complaint, particularly with the harder tyre, which is designed to operate in much warmer conditions than experienced on a gray day at Interlagos.

The fringes of a passing shower forced the cars off the track for a while and Giancarlo Fisichella's stalled Ferrari caused a brief stoppage, setting up a final flurry of activity.

Sebastien Buemi set the pace for much of the afternoon in his Toro Rosso before Fernando Alonso grabbed the best time with a late effort on the super-soft tyres. Barrichello, Webber and Button completed the top five.

Alonso leads second Interlagos practice

13:51 AUTOSPORT forum members are invited to join the fun throughout the weekend, offering thoughts and opinions as the event unfolds.

• Will the ever-changing weather catch the teams out in their bid to get serious work done today?

• Who out of the three championship protagonists will emerge on top from today's action?

• McLaren and Ferrari have the benefit of the KERS power boost up that long hill towards start-finish. Can they move towards the front of the pack in practice and qualifying?

Tell everyone what you think.

Click the SHOW LIVE FORUM link in the red bar at the bottom of your browser window if you would like to join the debate.

13:53 With torrential rain falling in the lead up to the session, the teams face major disruption to their final preparations ahead of qualifying. We are set for at least a very slow start to the hour, if it even begins on time, as drivers wait in the hope of the track eventually draining enough to allow some running.

Asside from the risk of further heavy rain rain for qualifying, Sunday's forecast suggests that at least some of the grand prix will be dry, meaning the teams face a very difficult set-up choice before the cars enter parc ferme - particularly if they don't get much running in the next hour.

The teams dodged using wet rubber during Friday's light showers, meaning the allotted four sets of intermediate and three sets of full wet tyres per driver remain ready for action. The teams are now more likely to head out to test the grip levels, if the track ever becomes safe enough to run, particularly with the threat of rain hanging over the decisive qualifying hour.

13:55 Final practice is due to get underway at Interlagos in five minutes.

13:56 The start of practice has indeed been delayed due to the medical helicopter being grounded by the terrible conditions.

13:57 The medical car is now taking a lap around the Interlagos circuit to check out conditions, which are impossible for driving at the moment.

13:57 The track temperature is 16 Celsius with a 17 degree ambient.

13:59 The medical car crosses start-finish and pulls off the track into position at the top of the hill at the Senna S.

13:59 The rain has eased off in recent minutes, having been torrential in the lead up to the session.

14:01 The drivers are obviously in the team garages watching the weather situation closely.

14:02 Practice time is now being lost due to the medical helicopter but track conditions remain impossible for Formula 1 cars to navigate at speed.

14:02 Sebastian Vettel and Giancarlo Fisichella are in their cars at the moment, waiting for further advice from their race engineers.

14:04 Adrian Sutil is told on the team radio that the circuit can expect lighter rain for a time but the next deluge is just ten minutes away.

14:05 The rainfall has increased again as more showers approach the circuit.

14:06 Incase you have just joined us, the final practice has been delayed due to horrendous weather at Interlagos. The medical helicopter cannot fly due to the very low cloud base and poor visibility.

14:07 Rubens Barrichello gives the drenched fans in the grandstands a wave on the big screen as the rain hammers down.

14:10 There is lots of standing water on the circuit, meaning the cars wouldn't be able to run safely, even if the helicopter could fly.

14:12 The last time we experienced rain like this at Interlagos was on the Sunday morning of the 2003 event.

A similar deluge before the race flooded the circuit at the Curva do Sol and resulted in firetrucks pumping away water from the track surface.

14:13 Jenson Button has climbed aboard the cockpit of his Brawn Mercedes and is watching the monitor intently while the mechanics fettle his car.

14:14 A massive strike of lightning hits the circuit as another thrunderstorm drenches the track.

14:16 The fans in the spectator areas are loving the weather. They are of course well used to these intense storms.

14:17 Torrential rain is again adding to the flooding on the circuit.

14:18 Tonio Liuzzi is resting his crash helmet on top of his head as he watches the monitor for positive signs of some running, but none are coming.

14:18 The next deluge has hit the circuit with full force. Torrential rain with thunder and lightning once again and prospects of running in the next 30 minutes look grim.

14:21 Sebastien Buemi is entertaining himself by capturing the incredible scenes with a broadcaster's TV camera.

14:22 Adrian Sutil enquires on the team radio about the weather once this latest storm passes over. He is told that in five minutes the rain should ease off.

14:23 Sutil then asks about the forecast for qualifying, and is given the information that we have known for several hours - more storms on the way.

14:24 Lewis Hamilton is keeping himself busy by reading the news on a website - AUTOSPORT.com!

14:25 The rain is still hammering down and as yet there is no further update regarding conditions for the medical helicopter. The waiting continues.

14:27 In the distance we can see brighter skies approaching, but for the moment it is very wet indeed with a lot of standing water on the track surface.

14:29 At Force India the strategy game continues on how to best use any track time available to them.

14:30 Adrian Sutil is told that they may get around ten minutes of running. If this proves to be the case, they will go straight into fast laps with no installation routine.

14:32 A team of marshals are brushing away standing water from the helipad, but the chopper remains grounded due to the low cloudbase.

14:33 Lewis Hamilton has climbed aboard his McLaren Mercedes as the rain eases over the circuit.

14:36 It's back to the old days for the teams now. Nick Heidfeld is told on the team radio that the rainfall radar has stopped working, because it was struck by lightning.

14:37 The teams will therefore have no advanced information on any approaching showers. This will force them to think on their feet.

14:37 As Mark Webber proved last time in Japan, any serious crash in final practice can be very costly. If the chassis is damaged beyond repair, the driver is forced to start from the pitlane in a new car built around the spare tub, which can only be submitted for scrutineering on Sunday morning.

14:37 The session will start at 11:42 local time.

14:38 The 18 minute session will allow the teams a chance to sample the tricky conditions, which will be vital with more rain expected for qualifying.

14:39 Many teams are already working towards just one long run on wet tyres for this short session.

14:40 The rain has finally stopped all around the circuit and conditions are brightening up quickly.

14:41 With standing water on the circuit, the chances of a major accident are very high and the drivers will certainly have to be cautious.

0 min: The 18-minute session is underway.

0 min: The crowd roars as the first brave souls venture out onto the sodden circuit.

0 min: Fisichella and Kovalainen lead the cars out of the pits to test the severely wet circuit.

1 min: Fisichella has the full wet tyres on his Ferrari as he navigates through the standing water.

1 min: Nico Rosberg joins them, with Sebastian Vettel, Sebastien Buemi and Jarno Trulli also out there.

2 min: Fisichella pits, while Kovalainen splashes into a timed lap.

3 min: Rosberg is behind Kovalainen on the road and he too launches into a wet lap of Interlagos.

3 min: Vettel, Trulli, Buemi and Kobayashi have all come back into the pits.

4 min: Kovalainen completes a steady tour for the first time of this truncated session - 1m31.716s.

4 min: Many drivers are completing a single installation lap for now.

4 min: Rosberg flashes across the line and he is 1.233 seconds quicker than Kovalainen after that first timed lap.

4 min: Lewis Hamilton slots in second in the order with a 1m30.772s first effort.

5 min: Jenson Button and Kazuki Nakajima come out onto the circuit, as Rosberg lowers the target time to 1m26.712s.

6 min: The McLaren pair continue to lap with Hamilton currently a second off Rosberg's leading pace.

7 min: Kovalainen briefly takes the benchmark time.

7 min: Fernando Alonso is beginning a flying lap in his Renault.

7 min: Rosberg is consistently quicker than Kovalainen on each lap as they both improve their times. This is a great display of talent from the German.

8 min: Rosberg has the top time for the moment - 1m25.060s with Kovalainen six-tenths of a second behind.

9 min: Alonso clocks a 1m27.074s to slot in fourth.

9 min: The rain has returned to hamper any circuit drying process. Rosberg lowers the benchmark to 1m24.169s.

9 min: Romain Grosjean has spun at the first corner, but resumes after a trip backwards onto the grass.

10 min: Rosberg is flying. He is now a massive 2.2s quicker than Kovalainen. Nico's latest lap being a 1m23.396s.

10 min: Team-mate Alonso has improved to second quickest with a 1m24.125s effort.

10 min: Kazuki Nakajima goes second to his Williams team-mate with a time of 1m23.832s.

11 min: Fernando Alonso is also testing grip levels on the grass with a wild ride as he lost it on the standing water exiting turn five.

12 min: Jenson Button is up to third place in the Brawn with a lap of 1m24.122s.

12 min: With the majority of cars now on track, the spray is hanging in the air as the drivers continue to sample the tricky conditions.

12 min: Romain Grosjean has crashed his Renault.

12 min: Alonso is now fourth and Sutil is up to fifth in the Force India.

13 min: The session has been stopped.

13 min: Like team-mate Alonso, Grosjean lost the car on the standing water at Turn 5 and speared hard into the barriers.

14 min: Wow! Replays show that Grosjean lost control in heavy standing water exiting the Curva do Lago. He aquaplaned off the road and had a big accident.

14 min: With the clock still counting down, it is likely that the session will end without any more running.

15 min: The Renault took off briefly as it hit a raised part of the bumpy grass, landed luckily on its wheels and then crashed head-on into the low armco barrier.

16 min: The damage to Grosjean's car amazingly is quite light, but thankfully the Frenchman is fine and emerged unscathed.

17 min: One minute remains as red flag conditions continue.

18 min: The clock has run down and the session will not be restarted.

15:00 Grosjean had just leapt up the order to sixth position and was gaining confidence quickly in the conditions. Perhaps he was a little too quick, too soon.

15:01 Prior to the stoppage, Nico Rosberg managed to find even more time and posted 1m23.162s. He ends the shortened session fastest.

15:03 Kazuki Nakajima made it a Williams one-two with Jenson Button third, Fernando Alonso fourth, Sutil fifth and Grosjean in the wall, sixth.

15:04 Such a short session leaves all the teams with a major challenge to prepare for qualifying, which could have similar tricky conditions.

15:07 The round-up of a very short final practice is now available:

Rosberg tops shortened practice three

15:07 A chaotic morning ends with Williams topping the pile and Romain Grosjean giving the Renault boys some serious work to do to get his car ready for qualifying.

The three championship protagonists kept their powder dry, completing 14 laps between them and now they can look ahead to qualifying.

Torrential rain and thunderstorms have shaped the morning. Will this weather continue to disrupt the all-important qualifying session? Join us at 16:45 GMT for more from Interlagos.