Isaac Tests Levees, Dams and Social Media

UPDATE: The water level below the dam break at Osyka, Miss., is now forecast to be worse, not better, than original estimates and the river's height forecast has been raised from 17.5 to 21.5 feet, exceeding the record level by 2.3 feet! You can look at a loop of the three forecasts here.

It may be the third day of Isaac, but things are "getting real." (What they really mean by this, grammatically speaking, is that things are getting really realistic quickly.) The hurricane may not have breached or over-topped the new federal levee system in New Orleans, but it did over-top one to the south of the city Wednesday night. Early this morning, another levee was breached in Slidell, La. All of this is detailed on our Live Blog page, and terrifying photos of homes under water are shown on our photo page. When I came into work, I checked the MS DOT webcam in Pascagoula, after noting heavy storms training over them, and took this screenshot video:

No sooner had I finished a tweet about that than I saw this information pop up on the NWSChat:

I gave the information to our news crew, who tweeted it out, while I waited for the Flash Flood Warning to be issued. When it came out, it read: "AT 810 AM CDT...LOCAL EMERGENCY MANAGEMENT AND LAW ENFORCEMENT OFFICIALS REPORTED THE LAKE TANGIPAHOA DAM IS EXPECTED TO FAIL. SEVERE FLOODING IS EXPECTED DOWNSTREAM... WATER LEVEL RISES ARE EXPECTED TO BE NEAR 8 FEET BELOW THE DAM TO 6 FEET AT OSYKA..." I retweeted our @breakingweather account, noting the "DAM IS EXPECTED TO FAIL" language.

Next I sent out the Flash Flood Warning to our AccuWeather.com Facebook fans in Louisiana and Mississippi. Fortunately, when the river folks at NWS made the new river projection, it was not as high as they had initially expected and fell 1.2 feet short of the record stage at that location:

CNN now puts the number of customers without power near 1,000,000, but the legacy of Hurricane Isaac is definitely its longevity. Two days after the storm was making landfall, it's still in Louisiana! The meandering track is shown below courtesy our Google Hurricane Tracker:

Shell Beach, La., had to endure a two-day storm surge as high as 11 feet!

The rainfall has just been incredible; our live blog says "23.31 inches in Gretna, La" -- this morning the rain has been falling at rates of over 4 inches per hour:

And that was after the storm had already dropped over 17 inches of rain in the same general area by last night:

More stats for Hurricane Isaac are available in this news story.

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