Pirelli has decided that today will be the mandatory day of wet running for all the F1 teams.
The 2014 rules call for one of the pre-season test days to be given over to wet tyres.
Pirelli has originally planned to use Friday, but with rain due today anyway the company has decided to make the switch, and a tanker is wetting the track before the session starts in order to give nature a helping hand.
Meanwhile the McLaren MP4-29 is due to run its first laps this morning.
Adam Cooper F1 
Will they learn anything? Doubt there will be many laps run at maximum pace, and how effective will wetting the track with the tanker we’ve seen be at producing a surface requiring full wets?
Wet test idea has merit, timing and execution are woeful.