The King Tide is Back


You may not know this but today's high tide on Long Island Sound is the highest high tide of the entire year! The moon is new (sun-earth-moon all in line) and the moon's orbit is at perigee (closest pass of the moon to earth) which makes the gravitational pull of the sun and moon on earth the strongest. The stronger that pull the higher the tides.

When the moon is at first quarter or third quarter the sun and moon are at 90 degrees. This results in lower high tides and higher low tides as the gravitational pull of the sun and earth are not working in tandem -  we call this a neap tide.

Data from NOAA

This is a graph of the high tides in New Haven from January 1 to December 31, 2017. You can see a few of them spike up - corresponding to new and full moons every month. The biggest spike is tonight at 11:45 p.m. when the astronomical tide will be 7.97 feet MLLW. Most tides are closer to 6.5 feet MLLW. 

These tide predictions are assuming there's no contribution from anything meteorological. No heavy rain flowing into rivers and streams and emptying into the Sound and no strong wind piling water into Long Island Sound. Of course there's always some impact on tides from the weather. During Hurricane Sandy Long Island Sound was nearly 10 feet above astronomical tide level due to the wind. We call that storm surge.

Thankfully the storm we're dealing with today isn't much of a storm. Winds will diminish by high tide tonight and water levels will only flood the the typically vulnerable low-lying spots right along the Sound.

Flooding from King Tides is becoming more and more common these days thanks the sea level rise. What is known as "sunny day" flooding has increased substantially over the last 10 years as ocean levels climb due to melting ice and warmer oceans. The latest research indicates more than 50% of nuisance flood days can be attributed to human caused sea level rise in New London. When these king tides occur during a storm serious coastal flooding can be the result - and with rising ocean levels more serious coastal flooding is something we will have to learn to live with.

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