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The “No-Show” Nor’easter Flood

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Vol. II, No. 73

A tide table shows expected tide height each day based on the lunar cycle, but weather systems can either increase or decrease the height of the water that we actually experience.

It seems we have a 100-year flood several times a year these days – two just in the last 10 days. At least that is what you might think if you trust the forecasters’ prognostications without looking out the window and seeing for yourself.

The recent nor’easter, a week after Hurricane Sandy, was supposed to bring a 4 to 5-foot storm surge. A 5-foot surge over and above the regular 7-foot astronomical neap tide would make it a 12-footer. That is a 100-year flood around here according to FEMA and local zoning regulations. By day’s end there was no perceptible surge at all, just a normal, regularly-scheduled, high tide.

I don’t bash forecasters unless they deserve it. Forecasting is often not easy. There are all manner of micro-climates where land and sea meet. Their interaction is dynamic, complicated and difficult to predict accurately with precision. Even high-powered computers struggle with it, as one learned WaterViews reader (who does such computer modeling) recently pointed out to us. My beef in this case is the slowness of the forecasters in not standing down sooner when it became apparent that flooding was not going to happen.  The forecasters, including the National Weather Service, on whom many in the retail weather predicting business rely, could have saved many skittish beach-dwellers a lot of hassle and anxiety.

If you live and work on the Sound as I do, you woke up Wednesday, heard the coastal flood warnings, and said “uh-oh, here we go again”. It looked like a bad one. Any time there is a chance the water will reach 12’, you pack the kids off to aunt Gertie’s, move the furniture to the second floor, and put on your high-water boots. Hurricane Sandy, just 9 days earlier, reminded us of what a 12 – 13-foot flood can do. With foul-weather gear at the ready and tie-down rope in hand, I paused to look out the window before starting my now familiar 100-year flood prep routine. I did a double-take. Whoo-hoo! The nor’easter had suddenly become a “norther” – meaning the wind had shifted left 45 degrees. Game over! It meant there would be no 100-year flood, maybe no flooding at all. And, it turned out, there wasn’t.

Okay, here’s my beef. If I, a meager sailing instructor, could predict that there would be no flood, hours before high tide, why couldn’t the National Weather Service? Even the local forecasters missed the obvious. None called off the flood warnings. They could have spared many nervous beach property owners a ton of anxiety.

I watched, out of curiosity, to see when the forecasts would catch up. Surely these guys could detect a persistent wind shift. It signaled that the storm had moved north faster than expected. The snowfall (huge flakes I might add) was further evidence that we were now on the backside of the center of circulation. The danger of storm surge, associated with northeast winds on the Sound, was over. There would be no flood.  Yet, even at the time of high tide, many forecasters were diligently parroting the National Weather Service in warning (not a watch, but a warning, mind you) of “moderate flooding”.  Huh? It was tantamount to saying a team will win a game after they had just lost.

The instant communication afforded by the internet makes it possible to spread the word about virtually anything virtually instantly. Why didn’t it happen? Someone, evidently, was sleeping at the switch on this one.

The episode has made me more skeptical of forecasters. You have to pick carefully among them to find those you trust. The point was further driven home to me again last night. In all the post mortem regarding Hurricane Sandy, one network weatherman spoke of the 14-foot surge it brought to New Jersey. WTF? I ranted about such poor choices of words in a recent WaterViews post, Why Sandy Wasn’t Worse. There is tide (an astronomical event), and there is storm surge (a meteorological phenomenon). To determine the height of coastal floodwater one adds the two together. The weatherman meant, I presume, that Sandy’s flood waters (tide plus surge) reached 14 feet, total, in some areas of New Jersey, not that there had been surge alone of 14 feet.

Had there actually been a 14-foot surge in addition to the astronomical high tide during Sandy, there almost certainly would be no one left alive on the New Jersey shore today. Moreover, keep in mind that waves ride on top of the surge. Ocean waves in a storm like that are easily 30 feet high or more. Imagine a combined total of 50 feet of water washing over Atlantic City. That is the kind of dramatic overstatement which occurs when forecasters don’t get their own terminology straight. Had it actually occurred, there would be slot machines washed up on the Princeton campus. Okay, that is a bit overstated as well. But you get my point.

-JK

Categories: WaterViews

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