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Why Nemo Didn’t Flood the Sound

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Vol. II, No. 84

Winter Storm Nemo

The recent nor’easter/blizzard, Nemo, was supposed to produce a 100-year flood (3-5 ft. surge) on top of depositing a prodigious amount of snow. At least that was the warning of the National Weather Service starting two days prior to, and right up to, the blizzard itself. We, here on western Long Island Sound, got the snow but, once again, not the flood.

The heavy coastal beating took place on the Cape and the communities surrounding Massachusetts Bay.  Here, in Fairfield County, there was no meaningful coastal flooding to speak of.  Why? The forecasters got the timing a little off. The blizzard was actually 2 storms which joined forces off the coast. Neither storm was all that impressive, but the combo certainly was. The intensification when the two systems merged didn’t occur as far south of us as originally expected.  Had it done so, there almost certainly would have been a flood in the western Sound due to strong easterly wind driving in a rising high tide.

It is the combined effect of a high tide plus easterly wind which creates coastal flooding. But when the tide started to come in (which takes over 6 hours) the center of circulation had just started to move northeast of us, causing the wind to shift farther north. Without the more easterly component the storm surge risk fades quickly for us.

Nevertheless, the National Weather Service never called off the local warnings until after high tide. They get partial credit for reducing their surge predictions from 3-5 ft. to 3-4 ft. in the last few hours before high tide; but they never called off the local warnings altogether until high tide had passed.  Why?

I am starting to lose track of just how many predicted storm surges were supposed to create 100-year floods just in the last few months.  Hurricane Sandy, in late October, certainly was among them. But all the others were complete duds, no-shows.  Regular readers of this blog perhaps recall the No-Show Nor’easter which followed closely on the heels of Sandy:

(http://blog.ctnews.com/kantor/2012/11/09/the-%e2%80%9cno-show%e2%80%9d-nor%e2%80%99easter-flood/

Then too, dire predictions of 100-year storm coastal flooding proved to be incorrect.  A pattern is emerging. It is a pattern of coastal flood warnings followed by no flooding at all. The danger is that someday when there really is a flood on the way, coast dwellers will simply ignore the warnings – assuming that the forecasters are just butt-covering again, and there really is nothing to worry about.

My gripe has never been about getting it wrong, though there is room for improvement. Coastal flood warnings, even when occasionally incorrect, are much appreciated by everyone who lives or works on the water. My beef is in failing to call off the warnings after it has become clear that the danger has passed. Beach dwellers, who stand vigilant in their waders through the night, really appreciate knowing when it is okay to go to bed.

In a sidebar to all this, the on-air Weather Channel “Storm Surge Specialist” the night of the blizzard claimed that the new- moon-generated “highest tide of the month” would coincide with the storm’s peak and make the flooding worse. Well, not exactly.  First, the new moon occurred the day following the storm. Second, the above average tides associated with both new and full moons actually occur in the few days immediately following, not exactly on the date of, full and new moons. Any tide table could have shown him that.

-JK

Categories: WaterViews

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