spring ties
when the sun moon and earth all line up at new or full moon (as in the picture) then we get the highest (and indeed lowest) tides which are called spring tides (nothing to do withthe time of yea).
in fact it takes a bit of time for the enormous mass of water to move so the spring tide will actually occur a couple of days after the new moon.
because of the tilt of the earth on its axis at the equinox the sun appears to be over the equator and if there is a new or full moon at about the same time then all the forces contrive to create the highest of high tides and if the moon is also at perigee (closest to the earth in its orbit) then that will produce the biggest tides of all.