The moon rotates around the earth in an elipse every 29½ days.
The earth also rotates around the sun in an elipse, completing a full rotation once a year.
The earth is closest to the sun around January 2. Whenever the moon is closest to the earth during this period the gravitation forces are the greatest generating King tides.
Perihelion = a planet's closest distance to the sun
Perigee = another planet's closest distance to the earth
King tide erosion on the Gold Coast|
© CSIRO, Auatralia