Guy Elden Jr. wrote:

Second, the airspace around CDW, when 4/22 is open (right now it's closed
for repaving), is typically configured so that planes can only depart and
arrive on runways 22 and 27. They never, ever use runway 9 unless the wind
is blowing a good gale force straight down runway 9... The reason is because
if they did, planes would be streaming in directly in the path of MMU's
approach for runway 23. Runway 4 does get used, but only if the winds
absolutely require it.

Runway 9 is also rarely used because the wind rarely blows from the east
or southeast. I flew out of MMU for a few years and can't recall ever
using then-runway 12. Ever. Winter winds are mostly northwest and
summer winds (cue Sinatra, as long as we're talking about North Jersey)
are mostly southwest. The following poster is right, though, if the
wind is strong enough for CDW to be using 9, MMU is probably landing on 5.