Ahead of today's second session, the air temperature is 25 degrees C, while the track temperature is 44 degrees. It remains bright and sunny but somewhat windy.
As a reminder, in terms of upgrades, Red Bull has a new Sidepod Inlet, Coke/Engine Cover, Floor Body, Beam Wing and Rear Wing, while Ferrari has a new Rear Wing, Coke/Engine Cover, Floor Fences, Floor Body, Floor Edge, Diffuser and Halo.
Aston Martin has a new Front Suspension, Front Corner and Rear Corner, while RB has a whole raft of upgrades including a new Front Corner, Coke/Engine Cover, Sidepod Inlet, Floor Body, Rear Wing and Beam Wing.
Stake has a new Rear Wing and Front Corner, while Haas has a new Rear Impact Structure. Mercedes, McLaren, Alpine and Williams don't have any upgrades.
Norris was quickest this morning, edging out Verstappen by 0.024s in a session which suggests that we could have a real fight on our hands this weekend, what with Sainz, Perez, Piastri and Hamilton in the mix.
Interestingly, the McLarens ruled S1, which is Verstappen's weakest sector, and though the Briton and Dutchman set the pace, just behind Sainz and Russell never used the red-banded rubber.
On the long main straight, the McLarens and Ferraris are understood to be around 4km/h quicker than the Red Bull, and 6-7 km/h quicker than the Mercedes and Aston Martin.
With the testing of the upgrades mostly undertaken earlier, we should now see the teams get down to the serious business of preparing for qualifying and the race.
Interestingly, just ten races into the season, Verstappen and Gasly have taken on their fourth internal combustion engines of the season, the legal limit before penalties are applied. Leclerc has taken on his fourth MGU-H, as have Verstappen and Gasly, with the Dutchman and Frenchman also on their last legal MGU-K.
The pitlane opens and Gasly leads the way, followed by Hamilton, Stroll, Bottas and Albon. Soon there are 18 drivers on track, Verstappen and Sainz still in their garages.
Bottas posts a 15.231, but this is soon beaten by Hamilton (15.057) and then Norris (14.197).
As Russell posts a 14.280,medium runners fill the first 13 positions, Piastri the quickest of the hard runners.
Verstappen goes third with a 14.447, ahead of Sainz, Leclerc, Hamilton, Bottas and Gasly.
A nasty wobble for Sargeant in the final corner.
Hamilton goes quickest in S1, as Bottas goes eighth overall. The Briton subsequently crosses the line at 14.294 to go third after making a mistake in Turn 10.
"The car is loose in the exits in general," reports Verstappen, "still weird understeer mid-corner. This car doesn't bite!"
Russell stops the clock at 14.089 as Ocon goes seventh and Magnussen eleventh.
"The car's still loose, I'm going to need that other wing," says Verstappen.
Some of the medium runners are finding more pace on their second and even third flying laps.
Just under twenty minutes in and Russell has the track to himself, until he too opts to pit.
After a brief lull, the Williams pair head out followed by Piastri. While the Grove duo are on softs, the McLaren driver is on hards.
"We've got a data issue, box this lap," Piastri is told as Sainz heads down the pitlane on softs, followed by his Ferrari teammate.
Albon improves to 14.807 and Sargeant 15.70, while Sainz posts three purples to stop the clock at 13.286.
"Massive, massive understeer," reports Albon. "It's at low speed, not high speed" he adds.
Hulkenberg, who handed his car over to Oliver Bearman this morning, goes fifth with a 14.053, before being demoted by Bottas' 13.924.
Stroll posts a 14.402 to go eleventh, as Tsunoda crosses the line at 14.211 to go eighth.
Quickest in the opening and final sectors, Verstappen can only manage third (13.504).
"He fully blocked me man, ****, can you tell me who was the driver, Racing Bulls," moans Zhou. Told that it was Tsunoda, he responds: "No surprise."
Ocon goes sixth with 13.766 as a 13.264 sees Hamilton go top.
Alonso goes eleventh with a 14.091.
Russell improves to sixth (13.722) but is demoted when Piastri responds with a 13.622.
Quickest in the final sector, Gasly goes fourth overall with a 13.443.
"I lost a lot of time with the traffic," explains Russell.
On his second flyer Hamilton posts a PB in the first sector, before losing pace in S2 and S3.
Perez is currently in his garage, the only driver yet to post a time on the softs.
With just over twenty minutes remaining, as Perez finally heads out on softs, Verstappen switches to mediums, as does Ricciardo, while Albon reverts to hards.
Perez goes thirteenth with a 14.081, 0.817s off Hamilton's pace, and around 0.5s off his teammate.
"All clear in front... drink system test, drink system test," Sainz is instructed as the long runs get underway in earnest.
With 15 minutes remaining, all bar Gasly, Leclerc and Perez are on track, the Mexican having only completed 11 laps thus far.
Norris lapping at 20.1, Verstappen at 20.2, Hamilton at 20.5, Piastri at 20.3 and Russell 19.9.
Verstappen posts a 19.1 and Leclerc a 19.9.
Alonso is warned to stay of the exit kerb at Turn 12.
Hamilton is on softs, as are Verstappen and Leclerc, while Sainz, Norris and Gasly are on mediums and Piastri on hards.
As the clock ticks down all bar Alonso and Zhou are on track.
The session ends. The session ends, Hamilton is quickest, ahead of Sainz, Norris, Gasly, Verstappen, Leclerc, Piastri, Russell, Ocon and Bottas.
Magnussen is eleventh, ahead of Hulkenberg, Perez, Alonso, Tsunoda, Ricciardo, Zhou, Stroll, Albon and Sargeant.
As was the case earlier, it's tight, with Hamilton, Sainz and Norris covered by just 0.055, and the top eight covered by less than 0.5s. Indeed, even Ricciardo, in sixteenth, is less than a second off the pace.
The good news for us, is that Red Bull remains under pressure and just from McLaren and Ferrari, but clearly from Mercedes also.
Indeed, Verstappen finished the day fifth quickest, behind Gasly as Alpine threatens to pull off a shock.
On the other hand a disappointing day for Aston Martin while that raft of upgrades doesn't appear to have done RB much good as yet.
Check out our Friday gallery from Barcelona here.
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