Jorge Lorenzo, winner from pole at both his previous Estoril MotoGP appearances, made the best of 'terrible weather' at the start of the 2010 Portuguese Grand Prix weekend.
After joining the majority of his rivals in sitting out the storm battered morning session, new world champion Lorenzo steered his Fiat Yamaha to better - but still fully wet - conditions in the afternoon.
With the track getting dryer by the minute, eleven of the 17 riders set their best time on their last lap of the day, including Lorenzo, who finished 0.135secs ahead of Ducati's Nicky Hayden.
Lorenzo's 2008 Estoril win was his first ever victory in the MotoGP class.
"I love this track, I have won here both times in MotoGP so I am very happy to be here," said Lorenzo, riding on European asphalt for the first time since clinching the MotoGP title at Sepang in Malaysia.
"Unfortunately the weather was terrible this morning and there was no point in riding, then this afternoon it was still very difficult, with a lot of water on the track and you had to be very careful.
"I felt good despite the conditions and step-by-step we improved so that at the end, when it was slightly drier, I was able to set a good time and we are on top."
Saturday's two track sessions, final practice and qualifying, have both been extended to one hour in order to make up for some of the time lost to the rain today.
"Tomorrow we will have two longer sessions so we will be able to recover some of the lost time, let's hope for no more rain!"
Lorenzo has won seven races this season, but has been off the top step of the podium for the past six races. Team manager Wilco Zeelenberg is working on finding more rear grip for his rider.
"The track was starting to dry towards the end of the session and we were able to make some small improvements to the settings," he said. "We have to concentrate on entry and exit grip on the rear on the corners so if it's wet again tomorrow we'll focus on that. P1 is always good but the times are very close so we'll see tomorrow."
Lorenzo's team-mate Valentino Rossi was third fastest, 0.361sec behind the Spaniard.