Ahead of today's opening session the air temperature is 26 degrees C, while the track temperature is 45 degrees. It is bright, sunny and very windy.
As ever, the teams are obliged to reveal their updates for the weekend, and they are as follows:
Mercedes: front wing flaps, mirrors and rear wing flap
Red Bull: front brake cooling, floor stay and floor edge
Ferrari: rear wing and mirrors
McLaren: rear wing, bodywork (cooling) and front wing flaps
Alpine: sidepod inlets, rear wing flap, beam wing and front wing flap
Alpha Tauri: front wing flaps and beam wing
Alfa Romeo: front wing flaps and rear wing
Most teams have trimmed their front and rear wings, while Red Bull has added an external wire to support the floor plus modifications to the floor for more downforce. Ferrari has its Miami rear wing, which they did not actually use there.
The lights go green and Bottas leads the way, followed by Gasly, Sainz, Zhou and Ocon.
As more drivers emerge, most are on mediums, though the Ferraris are on hards and the Aston Martins on softs.
Soon all 20 drivers are on track.
Vettel reports that his car is "wandering on the straights", which, while he thinks is steering related, could actually be the wind.
On-board footage reveals that Hamilton's Mercedes is bouncing. Similarly, Sainz is enjoying a very rough ride. "The bouncing doesn't feel nice," admits the Spaniard.
Of the first wave, Verstappen goes quickest (48.574), ahead of Perez, Leclerc, Bottas, Norris and Hamilton.
"I have no power," reports Schumacher after heading into the escape road at Turn 12. "We have to stop the car," he is warned as a replay shows water pouring from the Haas.
The VSC is deployed.
Gasly goes third, ahead of Ricciardo, Leclerc and Sainz.
Vettel lists a whole number of corners where he's struggling with his car's steering. Nonetheless, he improves to fourth with a 50.002.
No sooner has Alonso gone quickest (48.390), than Verstappen posts a 46.932 and Perez a 47.705.
"Had a little touch," admits Stroll as replay shows him brushing the barriers at Turn 15.
"Wind is pretty insane," reports Verstappen.
"The car just died," reports Latifi as the VSC is deployed for the second time when he parks up at Turn 1.
Leclerc splits the Bulls with a 46.999.
After several minutes the VSC is withdrawn and the session resumes.
The Red Bulls are both bouncing, but nothing like that being experienced by the Mercedes and Ferrari.
Perez retakes second with a 46.545, as Tsunoda goes fifth (47.908), slotting in behind his Alpha teammate.
Ocon goes eighth (48.616), ahead of Hamilton, Magnussen and Ricciardo.
At half-time, Magnussen switches to softs, as do Ricciardo, Bottas and Albon.
Verstappen follows suit.
Gasly is another driver taking a pounding, as Mercedes has both of its car in the garage as it seeks a solution.
Stroll goes off at Turn 4, momentarily bringing out the yellows.
Albon goes ninth (48.419) on his softs, while Bottas goes 11th (48.622).
On the red-banded rubber, Verstappen posts purples in the first two sectors, finally crossing the line at 45.810.
On board reveals the RB18 to be bouncing heavily, while the DRS flap is waving about wildly.
Sainz improves to third with a 46.012, ahead of Leclerc, Alonso, Tsunoda, Norris and Russell.
A 46.966 sees Hamilton go fifth, as Zhou improves to 13th (48.222).
With 15 minutes remaining, the Alpines have yet to try the softs.
As Perez goes top with a 45.476, Leclerc splits the Bulls with a 45.603.
"Be careful not to go four wheels over the pit entry line," Hamilton is told. "It was so bumpy I couldn't see the line," he replies.
You need to remove this beeping in Strat 1, man," urges Hamilton, "it's crazy."
Gasly goes off at Turn 15 following a big lock-up but is able to continue.
Gasly has completed the most laps (23), ahead of Verstappen, Tsunoda, Stroll and Zhou (22), and Russell and Magnussen (21).
The session ends... but there's still time for Verstappen to complete a 180 degree spin at Turn 15. "I don't know what's going on," he admits, "all the time I'm off-throttle the car still pushes."
Perez is quickest, ahead of Leclerc, Verstappen, Sainz, Alonso, Hamilton, Tsunoda, Russell, Gasly and Ocon.
Norris is eleventh, ahead of Stroll, Magnussen, Vettel, Bottas, Zhou, Albon, Ricciardo, Latifi and Schumacher.
Check out our Friday gallery from Baku, here.
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