Testing at Jerez in November is always a little bit of a gamble, but not a shot in the dark. The weather is usually good, but not reliably so. It can be cold in the mornings and evenings, but the sun will warm the asphalt up enough to make testing worthwhile. The real enemy is the wind, which tends to be rather blustery at this time of the year.
The weather gods are looking relatively kindly on the MotoGP test this Thursday and Friday. It was warm and sunny on Thursday, with much the same expected for Friday. Cooler morning and evening temperatures meant nobody went out until well after 11am, and there wasn't much going on after 5pm, except for the practice starts at the end of the day.
A full analysis of the test will have to wait until it is over, and all the data is in. But there was plenty to see and hear on the first day of the test.
It being the first full test ahead of the winter break, there were a lot of new parts, but they were not evenly distributed. Riders across all factories were sharing parts to test, one getting parts on Thursday while another will get the same parts on Friday. After all, there is no point making enough new parts for all of the riders, if those parts are going to be discarded if they are found wanting.