Bad and Even Worse

By: Bryan Norcross , 3:20 AM GMT on August 30, 2012

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I was looking over last night's blog and realize now all of the hazards I didn't list. I was concentrating on the effects in southeast Louisiana, which all came to pass except that Grand Isle seems to have lucked out... or we haven't heard yet.

My rainfall estimates look low... I said up to 20 inches and that much fell just today at Audubon Park in New Orleans. It looks like some areas will get 30 inches of rain or more!

And then there's the unrelenting severe weather in Mississippi and some in Alabama as well. I expected heavy rain and wind there, but a band set up near Gulfport and Biloxi and arced up to then north all day. Communities in that channel of storms got pounded. To a somewhat lesser degree the same thing happened near Mobile.

Major storm surge flooding hit the western Mississippi coast and the area east of New Orleans outside the levee. And... another thing I didn't mention, it looks like there will be significant flooding around Lake Ponchartrain as well.

A couple of days ago, I talked about the nightmare scenario of people not evacuating or taking protective measures because Isaac was a disorganized tropical storm. To make it worse, it was a no-show in Key West. Indeed, that happened in Plaquemines Parish. It's incredibly lucky that nobody died when the levee there was topped and the water went up to people's roofs.

No doubt untold tens or hundreds of thousands of people are going to wish they had more batteries and food and other storm supplies since they'll be trapped at home with no power and trees down all around them. Travel isn't going to be possible in many areas for at least a few days due to downed trees and flooding.

Isaac is a monstrous vortex with a tremendous amount of momentum (think a huge, heavy spinning top). Even with the friction of the ground, it's going to take a long time to spin down. Making it even worse, in the Gulf of Mexico the storm had more rain on its back side than its front due to the dry air it was encountering. That is still the case. Hopefully some of that will weaken as the storm moves north, but there is a LOT of the tropical circulation still to come ashore.

The last 20% of a storm like this is always the worst. Trees, bridges, sea walls, levees, and anything else subject to the pounding wind and/or rising water is more likely to fail or be topped at the end of the storm. I'm expecting more and more evacuations and reports of neighborhoods isolated because of the wind, rain, and surge effects of the storm.

I'm hoping for the best... but fearing the worst.

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10. bigeasystormcaster
12:36 AM GMT on September 04, 2012
I am from here in the area and no one got 30 inches of rain. the biggest water issue was storm surge and river flooding. The President is here now. Don't know how much assistance that will provide to the people. My be just a photo-op but we will see.
Member Since: July 30, 2011 Posts: 0 Comments: 109
9. leftlink
2:07 PM GMT on September 01, 2012
Quoting bnorcross:

I talked about the nightmare scenario of people not evacuating or taking protective measures because Isaac was a disorganized tropical storm.


Bryan - thanks for your work and your thoughts here. Fortunately it looks like enough people got out of the way of Isaac to avoid a major loss of life in the US. But the scenario you are talking about could easily happen again the next time there is a "monstrous vortex" that has never reached cat 2 status but has developed the storm surge characteristics of a much stronger storm.

Who knows, it could even happen in the next week if the storm currently in the atlantic travels west towards atlantic city and then rides up the NJ coast just as high tide approaches.

Is there any discussion ongoing about changing the TS/Hurricane warning system to allow the really dangerous large-vortex storms to be reported at higher intensity levels than the wind readings currently allow?
Member Since: December 28, 2010 Posts: 0 Comments: 134
8. StormDrain
2:23 AM GMT on August 31, 2012
Thanks, shoreacres.
It is good. People could barely text in 2005. Now we got tweet and retweet.

From the page at your link, an interesting tweet by NWS New Orleans August 29...
We have gotten a report relayed to us via HAM Radio that the Belle Chasse Ferry Landing had a wind gust of 113 mph at around 1:40AM CDT.

Belle Chasse is across the River from Braithwaite. Some pretty strong wind pushing the surge.
Member Since: October 9, 2005 Posts: 13 Comments: 495
7. shoreacres
11:25 PM GMT on August 30, 2012
Quoting StormDrain:
Read that Joplin report last Spring. Plenty statements from Braithwaite residents that sounded similar. Human nature is what I attribute this to.

Since December and the big pow-wow about Weather Ready Nation, NWS had made a big effort to include media as partners and I could see that concept at work during Isaac. Maybe baby steps - but the word was getting out, loud and clear. I don't think the media or the NWS failed to put the word out. It's that human nature thing. "It won't happen to me." Don't want to leave my home. Previous experiences, with other storms or with with being overwarned. Will be a while, or maybe never, before the public listens.


One of the differences I noted during Isaac was the NWS presence on Twitter. Each office was doing its own thing, but they often were re-tweeting one another's postings. They were succinct and understandable - not always possible in 140 characters. You can see examples here on the NWSNewOrleans page.

The best part is that those NWS tweets were being re-tweeted by "just folks". If Isaac's any indication, they've started something good.
Member Since: October 4, 2004 Posts: 205 Comments: 15288
6. StormDrain
10:47 PM GMT on August 30, 2012
Thanks for your blog, bnorcross!

Been puzzling over Braithwaite since Wednesday morning. Been looking at maps of the new ACE walls and of the River delta to try and understand. Isaac's angle of approach probably contributed but exactly how did it happen? (rhetorical ?)

The Plaquemines flooding, and the flooding on north shore of L. Pontchartrain. Residents of both areas were quoted over and over saying nothing like this happened with K storm or Gustav. The two police officers who went out to check Plaquemines east bank levee early Wednesday morning and had to be rescued when the flood advanced so quick they could not get out and had to be rescued - maybe they can shed some light on it. And I hope this is looked at in the post-season analysis when NHC has time to take a closer look.


Mississippi River in SE Louisiana
image credit: NASA


image credit: NOLA Army Corps of Engineers

Lower right: See Braithwaite. Dark green line along River is new wall on west bank. Gray line the east levee.
Member Since: October 9, 2005 Posts: 13 Comments: 495
5. StormDrain
10:30 PM GMT on August 30, 2012
@FunhouseFX, comment 2:
Read that Joplin report last Spring. Plenty statements from Braithwaite residents sounded similar. Human nature is what I attribute this to.

Since December and the big pow-wow about Weather Ready Nation, NWS has made a big effort to include media as partners and I could see that concept at work during Isaac. Maybe baby steps - but the word was getting out, loud and clear. I don't think the media or the NWS failed to put the word out. It's that human nature thing. "It won't happen to me." Don't want to leave my home. Previous experiences, with other storms or with being overwarned. Will be a while, or maybe never, before the public listens.
Member Since: October 9, 2005 Posts: 13 Comments: 495
4. weatherappeal
2:10 PM GMT on August 30, 2012
Love the blog, Mr. Norcross! It's nice to hear a little from the heart. New to this blogging stuff but not new to weather. Good luck to the southern US. Praying and hoping Isaac will speed up and break apart. Was in Gilbert in Cancun in 88, Loma-Prieta in 89. I'd take Loma-Prieta any day and I was 2 miles from the epicenter. House didn't come apart but there was damage. Gilbert was something I needed to forget. It was like being in a bad Wizard of Oz movie.
Maybe someone can figure out how to move all that water to Iowa, Nebraska and Kansas??
Member Since: August 30, 2012 Posts: 0 Comments: 0
3. TexNowNM
6:20 AM GMT on August 30, 2012
Thank you for this blog. I had not thought about about the last 20% of a storm as the worst but it makes sense. I look forward to future blogs.
Member Since: October 14, 2008 Posts: 0 Comments: 179
2. FunhouseFX
5:40 AM GMT on August 30, 2012
Excellent blog, thank you for posting it. You wrote:

"A couple of days ago, I talked about the nightmare scenario of people not evacuating or taking protective measures because Isaac was a disorganized tropical storm. To make it worse, it was a no-show in Key West..."

This is all true, but in my opinion it misses another important factor: public perception of forecast accuracy. I am referring specifically what might as well be called "danger burnout" from sensationalized reporting. I understand that reporting the weather is not simply a science, but also entertainment, and scary sells, but the downside of this is a public trained to largely dismiss the dire warnings they seemingly hear every time a storm is on the horizon.

I am embarrassed to say that I fell victim to this myself with Isaac. It was disorganized, struggling to even remain a tropical storm, no winds, sucking in dry air, yet it had a news media screaming the obviously false headlines that it was just like Katrina. As a result i dismissed the entire storm and the potential danger as just more media hype. I was wrong. It wasn't just like Katrina, but it wasn't the marshmellow I predicted.

My concern is obvious.

One of the lessons of the Joplin tornado was that the people there ignored the sirens and they ignored the warnings leading up to the storm. They waited for their friends to call and warn them instead. Many waited and died. And this is a direct result, in my opinion, of a reporting system that failed to differentiate absolute danger from potential danger.

I would be interested in seeing something like this applied to tropical storms as well. Nor do i believe it is important to get the entire scientific or meteorological community on-board. A "Threat Level" warning, combining all the factors and information available, is something the weather channel and wunderground can implement themselves, and immediately. Where a simple category designation gets ignored, this might not.

Anyway, great write up. I will be reading you in the future.
Member Since: April 11, 2009 Posts: 0 Comments: 18
1. KEEPEROFTHEGATE (Mod)
4:35 AM GMT on August 30, 2012
there is alot
shaken their heads
going this was a cat 1
Member Since: July 15, 2006 Posts: 165 Comments: 52383

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This is the official blog for Bryan Norcross, Hurricane Specialist at The Weather Channel.

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