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As it happened: Brazilian Grand Prix Weather
By Emlyn Hughes
The live commentary has ended. No further updates will be posted.
Mon 15:00 The Autodromo Jose Carlos Pace at Interlagos has played host to the last four title deciders and Jenson Button will be hoping that it becomes five this weekend as the teams prepare for a potentially decisive round 16 of the 2009 FIA Formula 1 World Championship - the Brazilian Grand Prix in Sao Paulo.

Preparations for the event have intensified over the weekend, with the packing crates unloaded in the pitlane, daily road sweeping taking place on the track surface and other essential tasks such as kerb-painting and taking care of the run-off areas.

Not to be outdone, the weather wants to play a part in deciding the championship again, just like it did last year.

Major South American sporting events have already been influenced by heavy rains in the last few days - as anyone who saw the recent world cup soccer qualifier between Argentina and Peru can relate to, when a major storm exploded over Buenos Aires on Saturday.

That area of wet weather is making a move north, affecting parts of Brazil today, with more showery outbreaks likely towards the weekend.

Early forecast

The current forecast for the grand prix points to showers and longer spells of rain on Friday and Saturday. Precise timing is almost impossible to predict at this stage, but it is reasonable to expect showers on the first two days of track action.

Saturday currently has the worst forecast of the three days, with heavy showers expected, before the rain reduces to a slight risk of light showers for the track action on Sunday.

Temperatures in Sao Paulo have been unseasonal lately and this is set to continue into the weekend, as air temps struggle to make it over the 20 degree mark on all three days.

The forecast today merely offers a pointer for the Brazilian Grand Prix weekend. Given the unsettled conditions, we will take another detailed look at the prospects on Wednesday when further calculation of the forecast models may offer a more certain picture, closer to the event.

Brazil 2008Wed 13:00 Forecasts of washout conditions will send many Formula 1 fans into overdrive, as the build-up continues to the 2009 Brazilian Grand Prix at Interlagos, scene of last year's thrilling, rain affected title decider.

Wildly changing projections of rainfall totals and - critically - timing of the showers are likely to turn round 16 of the FIA Formula 1 world championship into an adventure, and will keep the teams very much on their toes as they plan strategies and programmes of work for the various sessions.

There has been a distinct shift 'forwards' since our original forecast on Monday, with possible showers on Friday and Saturday but heavy rain now moving into the prospects for Sunday.

It should be noted that there is still considerable movement within the weather models and their rainfall projection charts, so further changes to the following forecast for the weekend are likely ...

Interlagos Forecast

Today will easily be the best of the lead-up days to the grand prix, with some good clear spells - particularly this afternoon and evening before another frontal system moves in from the south.

Thursday will be mainly overcast with just an occasional glimpse of the sun early in the morning before the clouds roll in, with the potential for a storm by mid-afternoon.

Friday will continue the mainly cloudy and overcast theme. Some light rain and drizzle is possible, but the threat of showers has reduced since our Monday forecast. Temperatures will reach just 19 degrees Celsius for the afternoon practice session.

On Saturday, the dull and damp conditions should continue with some drizzle at times and the chance of some heavier rain later in the day as atmospheric conditions begin to change.

The potential weather story for the weekend is now a dramatic breakdown for Sunday, with much lower pressure moving over Sao Paulo, combined with a rise in convective energy, giving a high risk of heavy showers and thunderstorms. Temperatures will climb throughout the event from that lowly 19 mark on the first day, reaching 20 Celsius on Saturday and up to 23 Celsius on Sunday.

The forecasts are clearly moving around at a rapid pace, so AUTOSPORT Live will continue to monitor all the data and we will publish our latest evaluation of the weekend weather on Thursday evening.

InterlagosThu 19:11 A brief but intense thunderstorm this morning, and a soaked Interlagos circuit, gave the Formula 1 family a portent of what might be in store for round 16 of the 2009 season, as the teams finalised their preparations for the Brazilian Grand Prix.

The storm had blown through by lunch time and overhead the skies have remained heavily overcast ever since. The weather is certainly going to be a talking point as we move into this critical race meeting.

Weekend Forecast

On Friday, a weak cold front is set to move north, over and through the Sao Paulo region. Rainfall totals won't be particularly high, but we could see light rain at times in the morning with more general light rain during the afternoon. This is likely to be enough rain to cause the teams a headache as they try to get through their important practice programmes. Overcast conditions are expected for the day and a maximum temperature will only just make it to 20 degrees.

The situation will change for Saturday as slightly higher pressure sits over the south-east corner of Brazil, allied to the clearing of the cold front. The morning will start with heavy cloud cover and possibly a damp track, but towards midday we could see a glimpse of the sun (the big yellow thing, remember that?).

Qualifying is very much a 50/50 split at the moment. It is likely to remain dry and mostly cloudy, but a slight rise in convective energy could set off a stray shower in the afternoon - most probably after the grid has been decided. The temperature will be up a click from Friday's mark at 21 Celsius.

Sunday is still the big one in terms of weather, and the latest computer weather models released this evening are maintaining the wet theme.

Race day will start dry but mainly cloudy with just an odd sunny spell here and there. Towards the afternoon, conditions are set to change and there is the potential for convective showers to bubble up and fall over the circuit during the event.

It is a situation that needs watching closely for Sunday, but the forecast for the first two days of the event looks well set now. A damp Friday, drier Saturday and a wet Sunday afternoon are your bullet-points weather-wise for the Brazilian Grand Prix.

Tomorrow the talking stops and the action begins. Can Jenson Button, Rubens Barrichello or Sebastian Vettel steal a march on the competition during the opening day of practice? Join us from 12:45 GMT on Friday for the battle of Brazil.

Rubens BarrichelloFri 20:03 Showers to the west, south and east dodged and weaved their way mostly around Interlagos all day as the drivers took to the circuit for three hours of Friday practice.

The weather remained decidedly 'iffy' throughout the afternoon, and the prospects for Saturday are similar to today, with light showers possible, but on the flip side Sunday could turn out to be a much better day than originally thought, albeit with a hurdle to get through in the morning first.

Weekend Forecast

The movement of a weak cold front expected today over Sao Paulo has slowed somewhat over the last 24 hours. The initial showery pattern showed up during the Friday sessions, with more prolonged light rain expected through this evening and overnight.

Saturday morning should dawn with most of the prolonged rain having cleared the region, but overcast conditions and light showers from time to time are possible.

Once again these showers will be hit and miss, but with only 60 minutes available in the morning leading into a very important qualifying session, any rain could really upset the form book and, consequently, the grid for Sunday's race. The air temperature will rise up to 22 degrees Celsius.

Sunday is very much split into two parts. Heavy rain is expected just as dawn breaks and the circuit is set for a thorough soaking. However, the rain is predicted to end a few hours prior to the start of the race, leaving us with a mainly dry event and just an outside chance of some light moisture from time to time. Conditions will remain mostly overcast with just an odd brief sunny spell and a maximum again reaching 22 Celsius.

The timing of any rain on Sunday is of course key to the outcome of the weekend and AUTOSPORT Live will continue to monitor the latest forecasts. But, before then, we have final practice and qualifying to deal with.

Can Jenson Button find the all-important balance to take forward into the qualifying session? Join us from 13:45 GMT on Saturday to find out.

Sat 05:19 Saturday weather update - Heavy rain expected

The rapid development of a tropical weather system in the last 12 hours is set to have a major bearing on Saturday action at the Interlagos circuit.

Late on Friday evening, model data suggested that there could be much more rain in the Sao Paulo region than anticipated earlier. Overnight, further model runs have maintained that theme, resulting in a much changed forecast for final practice and qualifying.

In just a few hours, Saturday will dawn overcast but largely dry. However, throughout the morning heavy rain is expected to sweep across the city from the south-west - possibly in time for the final practice session.

Conditions are expected to remain wet for qualifying with thundery downpours possible.

Join us at 13:45 GMT for the second day of action from Interlagos as the teams battle to cope with the changeable conditions.

RainSat 22:00 Thunder and lightning, fried radars, flooding on the circuit, countless medical car inspection laps, delayed starts, red flags, spins, crashes and a pole position for Rubens Barrichello in front of his adoring public ... it has been quite a day at Interlagos!

As predicted, the weather played havoc with the two sessions today, culminating in Barrichello's sensational pole position lap taking place two hours and 41 minutes after the scheduled start of qualifying.

The question, as the dust settles on today's action, is whether the rain clearing at the end of qualifying is the end of the story now, or whether we can expect more chaos tomorrow ...

Sunday Forecast

The trough line that developed quickly and brought us today's chaos is finally clearing the Sao Paulo region. A shower or two is still possible early this evening, but things should quieten down considerably overnight, leaving the circuit to finally dry out before dawn.

Tomorrow morning should be dry, but still with a thick layer of cloud. Gradually the odd break will appear, allowing the sun to poke through from time to time, but as it does so the temperature will rise and so will the energy in the atmosphere.

Convective potential will increase as the sun appears. A shower or two is possible throughout the afternoon, but precise timing is of course difficult to determine until we see exactly what conditions are like tomorrow.

Any showers in the afternoon will be less severe than we saw throughout today. We could be looking at a repeat of Friday with light, drizzly showers from time to time - just enough to make for an exciting race. A repeat of last year's conditions during the grand prix is not beyond the realms of possibility.

The temperature will rise a little to 23 degrees Celsius and it will feel quite pleasant during those short sunny spells.

Can Rubens Barrichello finally achieve his dream and win at home to take the title battle down to the final race in Abu Dhabi? Join us here on AUTOSPORT Live tomorrow from 14:30 GMT to find out.

Rain at InterlagosSun 11:03 Good morning race fans!

Overnight, some minor changes have been computed by the forecast models and these are likely to have a bearing on the race. Firstly, the convective energy level is up slightly on the values forecast on Saturday evening. As a direct result of this, the potential rainfall amounts during the afternoon are also up very slightly.

It's a beautiful morning around Sao Paulo, but as we said yesterday, the sunshine will bring up the temperature quickly to its maximum value, meaning more energy in the atmosphere and a higher chance of the clouds bubbling up later.

Throughout the morning and into the early afternoon, more and more cloud will build. Radars are now of little help to us in these convective situations - at least until any rapidly-developing showers are picked up by the Meteo France system at the circuit.

It will come down to how quickly the clouds build through the critical late morning to early afternoon period, but showers during the race are more likely than they were 12 hours ago.

Join us from 14:30 GMT for all the build-up to the Brazilian Grand Prix.

Monday 12 Oct Start GMT
 Brazilian Grand Prix Weather 15:00
Friday 16 Oct
 Friday Morning Practice 12:45
 Friday Afternoon Practice 16:45
Saturday 17 Oct
 Saturday Morning Practice 13:45
 Qualifying 16:45
Sunday 18 Oct
 Race day at Interlagos 14:30
Emlyn Hughes and Geoff Creighton are's live commentary team. The dynamic duo have developed an inimitable style and a reputation for fast, accurate and insightful commentary. With unrivaled access to events unfolding at the circuit, they bring you the very latest, as it happens.

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