Hurricane Sandy: Storm surge and high tides worsened by full moon.

Why Tides Will Remain High Even as Sandy Moves On

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Oct. 30 2012 9:02 AM

Tides Will Remain High Even as Sandy Moves On

As Hurricane Sandy batters the Eastern seaboard, drenched reporters up and down the coast are trying to explain what makes this storm so fearsome. Of particular concern: storm surges compounded by rising tides, which are being amplified by the full moon.

It's a bit of grade-school science you might have forgotten: With a full moon, the Earth, sun, and moon are in a line, and the moon and sun reinforce each other's gravitational pull. This sends tides up about 20 percent higher than normal, even in calm weather.

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And a "gravitational lag" means that the sharpest effects of the full moon will come Tuesday or Wednesday, possibly worsening flooding, long after the storm's main rains and winds have died down in coastal areas.

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