Following Sunday's season-ending Valencia Grand Prix, a two-day post season MotoGP test began at the circuit on Tuesday.
However rain began falling shortly after the track opened and the circuit has remained wet ever since. The fastest lap times were set on slicks just before the rain.
The test marks Valentino Rossi's first Yamaha laps since 2010, while Rossi's Ducati replacement Andrea Dovizioso is making his Desmosedici debut.
Despite the conditions, Rossi (pictured) - who did not complete a flying dry lap - has put in lengthy wet weather runs and has now completed more laps than any other rider.
By contrast, Moto2 stars Marc Marquez (Honda), Andrea Iannone (Ducati) and Bradley Smith (Tech 3 Yamaha) are yet to make their first official MotoGP appearances - Iannone has previously tested for Ducati.
Former MotoGP racer Loris Capirossi rode Smith's bike this morning, posting a lap of 1m 35.954s, which has since been dropped from the timesheets.
Ben Spies, moving from Yamaha to Ducati for 2013, is not present due to recent surgery. His place is being taken by new Ducati test rider Michele Pirro.
Testing concludes at 5pm local time and is due to continue on Wednesday, although Yamaha may switch to Aragon for day two.CLICK HERE
for extensive picture coverage from the Valencia MotoGP test...
1. Alvaro Bautista
ESP Honda Gresini (RC213V) 1m 35.936s
2. Stefan Bradl
GER LCR Honda MotoGP (RC213V) 1m 36.198s
3. Andrea Dovizioso
ITA Ducati Team (GP12) 1m 39.868s
4. Hiroshi Aoyama
JPN Avintia (FTR-Kawasaki CRT) 1m 42.239s
5. Valentino Rossi
ITA Yamaha Factory (YZR-M1) 1m 43.736s
6. Aleix Espargaro
ESP Aspar (ART CRT) 1m 46.060s
7. Michele Pirro
ITA Pramac Racing (GP12) 1m 46.829s
8. Karel Abraham
CZE Cardion AB Motoracing (ART CRT) 1m 47.129s
9. Claudio Corti
ITA Forward Racing (FTR-Kawasaki CRT) 1m 48.020s
10. Randy De Puniet
FRA Aspar (ART CRT) 1m 48.351s
11. Colin Edwards
USA Forward Racing (FTR-Kawasaki CRT) 1m 50.853s
12. Hector Barbera
ESP Avintia (FTR-Kawasaki CRT) 1m 56.992s
(9/12) Danilo Petrucci
ITA Came IodaRacing (Suter-BMW CRT) No Time Dani Pedrosa
ESP Repsol Honda (RC213V) No Time Andrea Iannone
ITA Pramac Racing (GP12) No Time Cal Crutchlow
GBR Yamaha Tech 3 (YZR-M1) No Time Shane Byrne
GBR Paul Bird Motorsport (ART CRT) No Time Nicky Hayden
USA Ducati Team (GP12) No Time Marc Marquez
ESP Repsol Honda (RC213V) No Time Jorge Lorenzo
ESP Yamaha Factory (YZR-M1) No Time Bradley Smith
GBR Yamaha Tech 3 (YZR-M1) No Time Official Valencia MotoGP records:Best lap: Dani Pedrosa
ESP Honda 1m 30.844s
(2012)Fastest race lap:Casey Stoner
AUS Ducati 1m 32.582s