Tropical regions have high humidity and frequent storms due to .

B.  Crest and trough meet/combine to cancel each other out.

Explanation:

Listening to music from two out of phase speakers.  Depending where one is located the destructive waves will decrease the sound level, but in another location the sound waves can reinforce each other (constructive interference).  Which is why acoustical absorption material is used to absorb sound waves not reverberate/reflect them.

From formal description and image:

Interestingly, the meeting of two waves along a medium does not alter the individual waves or even deviate them from their path. This only becomes an astounding behavior when it is compared to what happens when two billiard balls meet or two football players meet. Billiard balls might crash and bounce off each other and football players might crash and come to a stop. Yet two waves will meet, produce a net resulting shape of the medium, and then continue on doing what they were doing before the interference.