A very high spring tide... you get springs twice a month - at new moon and full moon - every month, not just during the season of spring! However, spring tides get even more extreme in the season of spring and autumn around the vernal and autumnal equinoxes.
Knowing the relationship between our planet, the moon and the sun is vital for us inhabitants of a blue planet. Especially with global warming and rising sea levels... new and full moons and the spring tides they cause are times for London to watch out!
Visit http://www.alunatime.org/html/tides.htm for more info on the moon and tides.
