All of the testing that I've done for this first round so far has been in Free Practice -- mostly just to see what the weather does.
From what I seen, the weather moves very slowly. The race always starts with a dry track.
If there is rain along the moving edge of weather, it hits the track toward the end of the the 5th lap. If it is just the lightest blue rain on the radar, it is probably safe to go another lap, but anything darker, the moisture gauge will be well over the first tick before the 6th lap is out. Best to pit for rain tires at the end of the 5th if there is any moderate or dark blue on the track.
Even with the lightest blue rain, the water accumulates on the track. In the one 20-lap session I did, which was mostly light blue with some medium blue, it continued to accumulate until it was just over the second tick on the moisture gauge, showing just a sliver of blue. It took until lap 10 to reach this level, then stayed there until the band of weather cleared the track on lap 16. Once the rain stopped, the moisture gauge was very slow to drop. It did come down under the second tick, but stayed well over the halfway mark until I got to the end of lap 20.
It looks to me like we can get three basic patterns of weather:
- Completely dry - I still have to do some testing on this, but the obvious thing to do strategy-wise here is pit midway through, change tires, and take on whatever fuel is need to to get to the finish.
- Rain to the end - Rain comes on lap 5 and soaks the track to the end. It seems like the W tires are the best choice since the moisture gauge gets pinned to the second tick mark or slightly above for the rest of the race.
- Band of rain - This is a toss-up between W and IMs. The IMs will be faster while the water is accumulating and clearing, but Ws will be faster while everything is soaked. I suppose I'll just play it by ear if I find myself in this situation.
Since the weather is random, I fully expect that my races will be completely dry because that's what always happens. I hope I'm wrong. I like racing in the rain. It's one of the few things in this game that I feel I'm pretty good at.