Small Smoker ???

I use the WSM and I haven't found the ambient temp to affect the smoker temp all that much. Summer or winter I've found wind is more of a concern. As for gravity air flow I think convection air flow from the bottom up through the top is a more accurate description of how a verticle smoker works. Another thing I've found that make a world of difference as to the quality the final product is a clean burning fire with proper ventilation. This requires air flow. With the 22" weber I can load the ring and using the minion method get 10-13 hour of cook time by leaving the top vents wide open and just adjusting the bottom vents for what ever temp I want. Butts at 275 and ribs at 230.