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August 28, 2011

NWS: Storm surge no longer a worry

Now that Irene has gone by us, and winds have swung around to the west northwest, the danger of damaging storm surge from Hurricane Irene - to the extent it ever was a real worry - is past, according to the National Weather Service. 

"I would venture to say, yeah, for Baltimore Harbor and the Western Shore ... [storm surge] will not be too much of an issue now," said meteorologist Kevin Witt, at the weather service's regional forecast office in Sterling, Va.

Tides at AnnapolisAlthough city officials and many regular folks worried that Hurricane Irene might deliver the kind of destructive, 8 or 9-foot storm in the Upper Chesapeake we all remember from Tropical Storm Isabel in 2003, a big surge was never in the forecasts for this region. Unless your property is vulnerable to flooding caused by rain, most of the sandbags deployed Saturday probably were wasted.

That's because Irene tracked well east of the bay. That meant the wind out of the south, on the cyclone's east side, was blowing over the ocean, not up the bay. Isabel, by contrast, passed to the west of the bay, putting the south winds directly onto the Chesapeake, driving water north and into the bay's creeks and rivers.

Witt said there does remain some risk of high water today on the Eastern Shore of the bay, as the west or northwest winds at 30 to 35 mph slosh water toward the east.

So rather than a storm tide, Witt said, "we're looking at more of a blowout tide," where west northwest winds blow water out of the bay, producing stunted high tides and unusually low low tides. You can see the wind effects on the tide chart, above, for Annapolis. The Saturday morning high tide was more than a foot below predictions. 

The prospect is much the same for the ocean beaches, where west northwest winds will begin to calm the waters. "Later this afternoon, east coast tides and waves will be coming down," Witt said.

Posted by Frank Roylance at 9:58 AM | | Comments (4)
Categories: Hurricanes


Serious storm surge may not have been in the actual forecast, but....form late Wednesday until early Saturday, several of the more reliable models showed a track WEST of the Bay. Had that occurred, the storm surge probably would have matched or exceeded Isabel. Sand bags wasted? I don't think so. Given the cone of uncertainty while people were preparing, all of the precautions were smart. Suggesting that these were wasted efforts is only likely to discourage some people from making the right moves the next time a serious storm threatens.

I guess those models aren't that reliable afterall, huh? The efforts weren't wasted, but most models concurred on a more NNE track along the coast. A quick observation of the predicted wind directions (from NE and then NW) would easily tell anyone that surge would not be an issue.

FR REPLIES: Forecast models vary in their reliability, depending on conditions. The one that works great today, may be off the beam tomorrow. That's why forecasters look for consensus among the majority of models, disregard the outlyers, and add their own knowledge and experience. I thought the predictions for Irene turned out to be quite good, start to finish.


The ONLY times I saw the projected storm path going West of the Bay was when Irene was still well off Puerto Rico, before she turned away from due West. After the turn, only a couple of storm prediction softwares took the storm even close to the Bay, let alone West of the Bay.

(And off-topic, but funny - my two word 'verifier' starts with 'disasters'!)
You might be correct about predicted paths from a week ago, but not after Irene turned away from due West.

Boat US sends out four plus updates a day on approaching hurricanes, drawing primarily onNOAA data. One product shows about 10 models, and as late as Thursday night/Friday morning, several of their tracks were directly over or west of the Bay. The consensus was a track east of the coast, and this turned out to be right. But when multiple models show a western track and the forecast cone includes the
western shore during the time that you need to be pulling boats or otherwise
preparing, it makes sense to be cautious.
Frank's assessment of the process is right
on, and that's why the forecast - despite
some individual models - said " east." But when your boat or your business is vulnerable, you count the outliers too.

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About Frank Roylance
This site is the Maryland Weather archive. The current Maryland Weather blog can be found here.
Frank Roylance is a reporter for The Baltimore Sun. He came to Baltimore from New Bedford, Mass. in 1980 to join the old Evening Sun. He moved to the morning Sun when the papers merged in 1992, and has spent most of his time since covering science, including astronomy and the weather. One of The Baltimore Sun's first online Web logs, the Weather Blog debuted in October 2004. In June 2006 Frank also began writing comments on local weather and stargazing for The Baltimore Sun's print Weather Page. Frank also answers readers’ weather queries for the newspaper and the blog. Frank Roylance retired in October 2011. Maryland Weather is now being updated by members of The Baltimore Sun staff

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