Inflight replanning is only applicable if you replan in such a way that you change your original plan with a new destination or new alternate. You therefore have to perform a new dispatch calculation if performing a replanning.
There is no requirement for doing a REPLAN in air if the weather conditions change after takeoff. Only operational calculations apply. No factors, unless your company require you to do so. Regulations doesn't.
Dry regulatory requirements are factored 1.67
Wet regulatory requirements are factored either 1.92 of dry data or 1.15 of wet data whichever is higher.
Contaminated regulatory requirements are either 1.92 of dry data or 1.15 of contaminated data whichever is higher.
With regard to winds you must also perform another calculation based on the most favorable runway in no wind conditions. Should you require a specific wind component to land on the runway most likely to be designated you may dispatch using two alternates satisfying the above criteria.
I could go on and write a lot more, but these are the basics. Need to go now..
Later!