The Tides, They Are a-Changin’

10 years ago

Well since we played around with a musical theme in the title, let’s continue with “Sittin’ on the Dock of the Bay”. The thing is, if you *were* sitting on a dock in Eastport, assuming it was an old-fashioned wooden one on pilings, you’d see a 19-foot variation between high and low tide. But that’s nothing compared to the Bay of Fundy, where certain areas see a 50-foot (that’s five stories folks!) difference between high and low tide!

So, we know that we have tides, and most folks know that the tides are due to the gravitation “pull” of the moon.
But, what happens if a storm comes along, and you happen to have vacation plans at the shore and you hear that tides are forecast to be 10 feet above normal? What exactly does that 10 feet refer to? Does it mean that the high tide line will simply be 10 feet farther up the beach, or does it mean something else entirely? Answer: it means something else entirely!
For when you hear that tides are going to be above normal, that is referring to a *vertical* rise in the ocean, not a horizontal movement! So, using 10 feet again, next time you are down at the coast, picture the entire surface of the sea going up a basketball hoop in height! That would be a tide 10 feet above normal.
Hurricane Katrina, in 2005, generated an astounding tide of 28 feet above normal in Gulfport, Mississippi. Imagine that! A vertical rise of 28 feet, with waves on top of that. And the water is moving. And the water has all kinds of debris in it. And it weighs about 9 pounds per gallon. It is truly just like a wrecking ball for coastal structures.
So, if you are ever vacationing in a place where there is an approaching hurricane, or even a Nor’Easter (the Blizzard of ‘78 inflicted tremendous ocean-related damage in coastal Massachusetts), and if you hear tides will be well above normal, take heed of the advice of local authorities. Because while you may think you are a safe distance from the ocean, when the ocean goes vertical, it can move inland a truly stunning distance!
Ted Shapiro holds the Broadcast Seal of Approval from both the American Meteorological Society and the National Weather Association. An Alexandria, Va. native, he has been Chief Meteorologist at WAGM-TV since 2006. Email him at