Top entrances should help get rid of the water vapor during a honey
flow.
 
Water vapor is lighter than air-this is a bit counter-intuitive since
water is such heavy stuff,but it be so.It therefore always wants to rise
of its own accord.
 
Opening up an area further up the hive should therefore be easier for
the bees than having to waft the vapor down (against its natural flow)
and out through the lower entrance.
 
It's also why top ventilation holes in the cover board and roof are so
important for proper winter ventilation when there is no bee fanning to
keep the vapor moving.
 
Here in Scotland-not famed for dry winters- I've seen many of the old
beekeepers place part of a matchstick under each of the four corners of
the cover board to aid winter ventilation.
 
Happy honey hunting,
 
Alan Riach,
West Lothian,Scotland