Well, this is slightly alarming

[mmcirvin]

Something very strange is currently happening with NOAA's storm-surge model:

http://www.nhc.noaa.gov/refresh/graphics_at3+shtml/211847.shtml?gm_esurge#contents

it seems to be calculating a 10% chance of a storm surge of more than 30 feet in Massachusetts Bay and Cape Cod Bay. The surge is so big, in fact, that it exceeds the available display range, probably by a large amount, so for all I know it could be predicting a 50- or 100-foot wall of water crushing the South Shore. (Update: In fact, you can click in there to get individual values, and some of them seem to be as high as 92 feet.)

I can only guess what's going on here, but I assume this is some kind of freak scenario in which Hurricane Sandy moves back out to sea in a few days, strengthens and parks somewhere in the vicinity, shoveling vast amounts of water in around Cape Cod. It doesn't really make any sense, though, since that's something like four times as high as what you'd expect from a Category 4 hurricane.

I assume the credibility of these results is rather low. If you increase the threshold probability to 20%, it goes away. It's probably some kind of numerical hiccup, but I'm certainly going to be keeping an eye on it.

The next day: Yes, in fact, it went away as mysteriously as it appeared.

Comments

Hurricanes and storm surge

[infrogmation.livejournal.com]

I presume you're right about it being a glitch. However storm surge can depend on so many things in addition to wind speed, there has been talk of separating "Category" designations.

Hurricane Isaac flooded some areas that escaped flooding in Katrina, Camille, and Rita -- it was category 1 winds, but slow moving and at such an angle as to flood LaPlace, Louisiana, which only experienced something similar in the severe category 4 Great Hurricane of 1915.

Stay safe.

Re: Hurricanes and storm surge

[mmcirvin.livejournal.com]

Sandy is certainly causing far more flooding in Atlantic City and New York than one might naively expect from a Cat 1. The wind field isn't strong as hurricanes go, but it is gigantic in extent, so it's sweeping up a huge amount of water. Atlantic City is a mess, and it sounds like the city government really screwed up managing evacuation.

In reality, things haven't been that bad in northern Massachusetts: the storm surge on the Merrimack is too small to worry about, and the winds have barely gotten up to tropical-storm intensity. But some trees have come down and there are power outages about in some neighborhoods. As for mysterious super-surges in Massachusetts Bay, I'll believe something's in the offing when I hear someone who knows something talking about it...

[muffyjo]

I was surprised to see Powderhouse square under water on the map...I'm guessing it's a glitch.

[muffyjo]

Video of water surging over long wharf
http://northendwaterfront.com/2012/10/video-hurricane-sandy-churns-boston-harbor-on-waterfront/

Pretty cool!

[jwgh]

Looks like this is gone now -- I wish I'd thought to get some screen captures.

[mmcirvin.livejournal.com]

Yep, the phantom tsunami of Plymouth vanished as mysteriously as it appeared. It's like an episode of Space: 1999.

(There's a nuclear plant there that is of the same design as Fukushima Daiichi!)

[mmcirvin.livejournal.com]

Apparently a few of the most alarming news reports out of Manhattan were the work of a lying tweeter:

http://buzzfeedpolitics.tumblr.com/post/34623254677/how-one-well-connected-pseudonymous-twitter-spread

(Seen via Patrick Nielsen Hayden, who seems to have ridden it out OK.)

Not to say there wasn't plenty of alarming stuff going on anyway.