Aston Martin did not think there would be enough rain to warrant switching to Intermediate tyres when they called in Fernando Alonso for a potentially race-deciding pit stop.
The Spaniard was already running longer in the first stint due to starting on the Hard tyre, but the threat of rain added another element to their strategy as they tried to manage the gap to Max Verstappen.
When it started to hit the track on Lap 52 it only hit the middle sector, which became slippery while the rest of the track was dry. Alonso was asked by the team over the radio if it was worth a switch to Intermediates, but the Spaniard could not give a definitive answer due to the dry parts on the track.
Aston Martin elected to pit him for a set of Mediums, with him coming in a lap prior to Verstappen who stayed out as the rain started to intensify.
"When it started raining into turns five, six, and seven, I was with Hard tyres and they were quite old with 50 laps, and it was difficult to put temperature on them in that part of the circuit," said Alonso to media, including RacingNews365.com.
"So we thought about stopping and the decision was to stop for the Mediums or the Inters. I asked about the forecast, they said there's going to be a short shower, but it should not be too heavy.
"I said we go for the drys because [between] turns five, six, and seven there was a few drops of rain and everywhere else was dry."
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Krack: Intermediate gamble would not have made a difference
By this stage the rain had spread across the track and forcing drivers to switch to the Intermediate tyre. The extra lap out on his warn-out Medium's enabled Verstappen to retain his lead, as Alonso had to pit again for a set of Intermediates.
Aston Martin Team Principal, Mike Krack, said the team only anticipated a short shower that would dry quickly due to the high track temperature.
"We did not anticipate so much rain, to be honest. So we thought that it would just be a short shower and dry quickly because the track was very hot," he explained.
"Normally, you would say 'Okay, we stay out one more, two or three more laps' but the tyres were worn quite a lot, and we saw the temperatures going down, so that was a bit of a risk.
"When the car came in then, with this information we said 'Okay lets fit the Mediums', but when the car left [the pit lane] shortly after we saw that it was really a lot of rain and we had to come back."
Alonso first pitted when he was 13 seconds behind Verstappen, but lost his advantage when he had to pit again for a set of Intermediates. When asked if he thought it was a lost opportunity, Krack believes that Verstappen had enough of a margin to pit and maintain the lead.
He added: "I don't think it was a lost opportunity because if we had fitted Intermediates Max would have fitted Intermediates as well, and he also had the gap. So I don't think it would have changed much."