The way 'king tides' flood coastal streets during a full moon

The ocean doesn't always wait for a storm to gatecrash the party. Sometimes, on a perfectly clear day, the big blue just decides to take a stroll right down Main Street.

This isn't some freak swell; it’s the moon pulling a power move. When that silvery orb goes full and tucks in close to Earth, its gravity gets a serious grip on the tide, dragging the water way past the dunes and up through the city storm drains.

It’s nature’s way of reminding us who really runs the show, turning your local car park into a saltwater lagoon without a single cloud in sight.

Wait, so the moon’s orbit isn't just a perfect circle then?

Spot on, mate. The moon doesn't just sit in a perfect ring around us like a halo. It’s more of an egg-shaped track, what the science blokes call an elliptical orbit.

Think of it like a surfer carving a big, loopy turn. Sometimes she’s way out the back, and other times she’s right in the pocket, hugging the shore.

When that 'perigee' hits—that’s the moon’s closest point—the gravity isn't just a nudge; it’s a full-on yank. That extra proximity is what turns a regular high tide into a proper king.

Hold on, if it gets that close every month, shouldn't we be underwater constantly?

Good eye! The moon hits that close point every month, but for a monster king tide, you need the whole crew. It’s all about the lineup.

The sun is also out there pulling its weight. Usually, the sun and moon tug from different angles, which mellows the vibe. But a few times a year, they align perfectly.

When the sun’s gravity stacks with that perigee moon, it’s like two big blokes paddling for one wave. That combined muscle is what finally pushes the water over the seawall.

Does that alignment only work if they're both pulling from the same side?

Nah, they don't have to be shoulder-to-shoulder to cause a stir. It works whether they’re teaming up on one side or playing a high-stakes game of tug-of-war from opposite ends.

Imagine stretching a balloon. If you pull from both ends at once, the middle gets thin and the ends bulge out. That’s exactly what happens to the ocean when the sun and moon line up on opposite sides of our planet.

Whether it’s a New Moon or a Full Moon, as long as they’re all sitting in a straight line, the gravity stacks up and the tide starts charging toward the dunes.

But doesn't that perfect line-up happen every time there's a full moon?

Not quite, mate. It’s usually a near-miss. Imagine three surfers trying to line up for a photo; most of the time, someone is sitting a bit too high or low to be perfectly centered.

The moon’s path is actually tilted, like a wobbly frisbee. Because of that slant, the moon usually passes slightly above or below the direct line between the Earth and the sun.

Only a few times a year do the orbits cross perfectly. When that 'bullseye' alignment hits, the gravity stacks up and sends the ocean charging into the streets.