I will be backpacking for 12 days in Barcelona and Granada this December. Any tips about their weather and how to pack as light as possible!!! I knew that i will pack 5 tops ,2 pants, 1 coat and one walking shoes. That's how light i want it to be.
Plenty of weather is possible at that time of year. I've been in Granada in December and had thunderstorms but then t-shirt weather later the same day.
5 tops seems a lot if you're trying to go ultralight. Bet you could survive with 3. ;-)
My only tips for making it lighter are to reduce the toiletries bag brutally (taking 100ml of the essentials and not bothering with expendables like face creams and conditioners), and keeping the electricals to a minimum - which for me is a smartphone, usb charger and earphones. For blokes i recommend trying shave oil - 5ml lasts me weeks.
Andyf is right, you can never know with weather in December, so make that coat light, but warm!
Here's a web app that gives you the est. average temperatures (http://bit.ly/1GKl5k0), but make sure you check again before leaving and adjust accordingly.
The rest sounds good to me - I'd definitely bring a towel though (-1 top, +1towel?)
The most important thing is to layer your clothing.
Three shirts is fine. A light-or medium-weight fleece jacket, plus a waterproof shell (rain coat) will help keep you warm and protect against the wind. Bring a hat, too.
You'll definitely need to keep warm if you're going into the mountains near Barcelona, such as the Pyrenees in Andorra.
Your packing list is OK to go. Happy trails!