It should be doable, but it depends on what speed you lose weight at as everyone is different!?
But taking into consideration this will be your first week and people report bigger losses on their first week, technically if you lost 4lbs in your first week then 2lbs thereafter, it would be doable in 6 weeks.
Personally id start today or tomorrow if I were you, that way you have 7 weeks... meaning an average loss of 2lbs per week!!!
14lb in 6 weeks - more then doable if you want to achieve it. it's 2 and a third pound a week on average.
It's likely to take a lot of dedication toget there, especially with it being Xmas, but go for it. Christmas though is but once a year - if you don't quite make it ready for that, then at least you made a good stab at it, and should be happy with that too. (and then the new year comes along to help you complete your journey)