Sandy Is 'An Extraordinarily Unusual Confluence Of Events'

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Brendan Loy over at Weather Nerd is just transfixed by the data coming out about Hurricane Sandy and so am I -- in the way that someone standing on railroad tracks is transfixed by an oncoming train. Sigh...

It isn’t just the barometric pressure that has folks alarmed, of course. So many of the potential tracks would bring devastating coastal flooding. The official NHC track could be calamitous for Delaware Bay. The latest GFS model could bring devastating flooding to the shores of Long Island Sound. And of course there is theNew York Harbor nightmare. Or, Washington, D.C., the Delmarva and Chesapeake Bay could be crushed. Or the New Jersey shore could. It’s important to emphasize that we don’t know exactly where Sandy will go, and won’t for a while yet. But at this point, it’s hard to find a reasonably likely track that wouldn’t be a serious disaster for someone, in a region that’s so heavily populated.

Moreover, because Sandy is so huge, its impact will be widespread and long-lasting. North and east of the landfall point, its relentless onshore winds will pile up a storm surge over a wide area through multiple tide cycles — making each successive high tide higher than the previous one. With astronomical high tide on Monday, this is a particularly big problem. AccuWeather meteorologist Mike Smith (an AGW skeptic and non-alarmist) writes on his blog: “Based on some media coverage I’m seeing, the threat of flooding in coastal areas is being underplayed. Especially, if you live ten feet or lower above sea level, you need to be prepared to evacuate should the order be given.” I completely agree with that statement.

While we’re on the topic of ocean flooding, models suggest Sandy will stir up the ocean to an almost unbelievable extent, with offshore waves that are, well, just huge:

I’m picking up some skepticism of all this “hype” from commenters and on Twitter, by folks who say this is “just” a Category 1 hurricane or “just” a big Nor’easter, and the media is jumping the gun again, like they did with Irene and various other storms. (Actually, Irene arguably lived up to much of the hype, but I’ll leave that argument for another day.) This sort of critique, which is often more rote media criticism than actual storm-specific analysis, routinely fails to recognize that weather forecasting is an inherently uncertain probabilistic enterprise — meaning most worst-case scenarios, warned of days in advance, don’t happen; if we wait to discuss them until they’re likely or certain to happen, it’s too late to prepare — so you have to judge the validity of “hype” contemporaneously, not with the benefit of hindsight. And, given that fact, the “overhype” critique is particularly misguided and wrong-headed in the present situation. The currently available data suggests, almost unanimously, that the universe of realistic scenarios for Sandy ranges from “bad” to “very, very bad.” The moment that data shifts, and starts suggesting a lower probability of disaster, I’ll let you know, just as I did with Irene and Isaac when the data shifted toward more favorable outcomes in those cases. But right now, that’s just not what the data says.

Some folks — local TV news departments probably being among the worst offenders — will always hype every semi-serious storm, and even more folks (including national cable news writ large) routinely fail to walk back previously-justified hype when the data changes, or events on the ground prove the data wrong. But those of us who take our roles seriously only hype those storms that deserve it, and tamp down the hype when conditions change such that the storm no longer deserves it. Right now, this storm deserves it.

It’s also critically important to remember yesterday’s quote from meteorologist Brad Panovich: “Don’t let the Category of the storm or whether it’s ‘just’ a Nor’easter dictate your response. Your personal memories of previous storms are no use in this unique situation.

Why, you may ask, is it so unique? Why is all of this happening? Why is a Category 1 hurricane so potentially devastating? The Capital Weather Gang gives the most succinct answer I’ve seen:

[T]he clash of the cold blast from the continental U.S. and the massive surge of warm, moist air from Hurricane Sandy will cause the storm to explode and the pressure to crash.

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