Ahead of today's practice session the air temperature is 23 degrees C, while the track temperature is 35 degrees C. It is overcast and muggy.

That said, the talk this morning isn't about the weather, or even the impending Typhoon Phanfone but the news that Sebastian Vettel is leaving Red Bull at season's end. According to a clearly emotional Christian Horner the team only learned of his decision last night.

As we await news of where he is heading - Ferrari, McLaren or maybe even Mercedes - the confirmation that Daniil Kvyat is to partner Daniel Ricciardo ends talk of the Spaniard 'swapping' seats with the German. Interesting times.

Back to the present and while Nico Rosberg was quickest yesterday morning, teammate Lewis Hamilton topped the sheets in the afternoon. The biggest surprise - or maybe not - was the dominance of the Silver Arrows with over a second over their rivals, bar Fernando Alonso.

Grip, or lack of it was a major issue, with drivers running wide everywhere and a couple, including Ricciardo, ending up in the barriers.

Tyre choices are hard and medium with most of the opinion that maybe medium and soft might have been a better option... no pun intended.

Nonetheless, all that pales into insignificance compared to the news from Red Bull and the impending game of musical chairs.

The lights go green and Bottas leads the way, followed by Grosjean, Chilton, Kvyat, Bianchi and Massa.

As more and more drivers take to the track for the obligatory installation lap it's worth noting that the latest update on Typhoon Phanfone suggests that it will arrive after tomorrow's race and that while the event will be held in wet and difficult conditions it is the packing up process for Sochi which is under threat.

Maldonado reports a brake issue, the Lotus driver already facing a ten-place grid penalty under the new power unit component rules.

Vergne, who had a torrid time yesterday, gets things underway with a 1:36.886, as Gutierrez has a very big and scary moment at 130R. The Mexican does well to keep the Sauber out of the barriers.

No sooner has one Sauber had a moment than the other goes straight on at the chicane, the C33 clearly suffering balance issues.

As Ericsson spins at the chicane, Vettel heads down the pitlane. It is surprising that he isn't pursued by a gaggle of journos... or whatever the collective noun is.

Button posts 36.299 to go quickest, ahead of Ricciardo, Magnussen, Vergne and Hulkenberg.

As Button locks-up at the chicane, Ricciardo posts 35.885 to go quickest. Elsewhere, another off-track moment for Gutierrez, this time at Spoon.

Just 16 minutes into the session, Vergne makes the switch to the option rubber, the Frenchman having had little running with it (or any rubber) yesterday. He immediately goes quickest, crossing the line at 35.494.

Offs for Grosjean and Perez, the Mexican going wide at 130R and appearing to incur a little damage in the process.

Back on track following his brake issue, Maldonado locks-up at the chicane and cuts the corner.

With 37:00 remaining, only 15 drivers have posted times, Chilton, the Ferrari, Williams and Mercedes duos yet to get their names on the doors. That said, all but Chilton and Hamilton are currently on track.

Raikkonen immediately goes third, stopping the clock at 35.995. Moments later, Bottas posts 35.380 to take the top spot, only to be leapfrogged by Williams teammate Massa (35.165).

As Rosberg goes top (34.516), Raikkonen reports that he has no power. Hamilton posts 34.210 to go quickest.

At half-time, it's: Hamilton, Rosberg, Alonso, Massa, Bottas, Vergne, Ricciardo, Button, Raikkonen and Magnussen. Vergne is still the only driver to have tried the softer rubber, while the Mercedes duo remain 0.3s quicker than their nearest opposition (Alonso again).

In the Ferrari garage Raikkonen is out of his car and has walked off.

Button reports that his rears are continually locking as he enters the hairpin.