Hurricane Isaac hits Louisiana, driving dangerous storm surges
Hurricane Isaac is ashore over Southeast Louisiana, having officially crossed the coast on the Mississippi Delta 90 miles southeast of New Orleans at 7:45 am EDT on August 28. Isaac intensified right up until landfall, striking with 80 mph winds and a central pressure of 970 mb. The storm's large size and large 50 - 60 mile diameter eye kept the intensification rate slow today, but it came quite close to becoming a significantly more dangerous storm. That's because at landfall, Isaac was in the midst of establishing a small inner eyewall within its large 50-mile diameter eye, a very rare feat I've never seen before. Usually, when an eye first forms, it gradually contracts, eventually becoming so small that it becomes unstable. An outer concentric eyewall then forms around the small inner eyewall, eventually becoming the only eyewall when the inner eyewall collapses. But Isaac is a very unusual storm that has continually surprised us, and this inside-out concentric eyewall formation fits the storm's unusual character. The storm isn't in a hurry to move fully inland, and has slowed down to a crawl this evening. This will give the storm the opportunity to keep its center mostly over water a few more hours, and maintain hurricane strength into the early morning on Wednesday.
Figure 1. Radar reflectivity image from New Orleans as Isaac made landfall at 6 pm CDT August 28, 2012.
A dangerous storm surge event underway
Isaac is bringing large and dangerous storm surge to the coast from Central Louisiana to the Panhandle of Florida. At 10 pm EDT, here were some of the storm surge values being recorded at NOAA tide gauges:
6.2' Waveland, MS
9.9' Shell Beach, LA
3.0' Pensacola, FL
4.4' Pascagoula, MS
3.4' Mobile, AL
The 9.9' storm surge at Shell Beach, which is in Lake Borgne 20 miles southeast of New Orleans, exceeds the 9.5' surge recorded there during Category 2 Hurricane Gustav of 2008. Research scientists running a Doppler on Wheels radar located on top of the 16' levees in Plaquemines Parish near Port Sulphur, LA, reported at 8:30 pm EDT that a storm surge of 14' moved up the Mississippi River, and was just 2' below the levees. Waves on top of the surge were cresting over the west side of the levee. Needless to say, they were very nervous. Over the past hour, the surge has retreated some, and waves were no longer lapping over the top of the levee. This is probably due to the fact that we're headed towards low tide. A storm surge of 9.5' has moved up the Mississippi River to the Carrrollton gauge in New Orleans. This is not a concern for the levees in New Orleans, since the storm surge has now brought the river up to 2.5' above its normal water level, which was 7' low due to the 2012 U.S. drought. The highest rise of the water above ground level will occur Wednesday morning over much of Southeast Louisiana, Mississippi, Alabama, and the western Florida Panhandle, when the tide comes back in. It is clear now that this storm surge event will be as dangerous as that of Category 2 Hurricane Gustav of 2008. One piece of good news: NWS New Orleans successfully launched their 00Z balloon. However, their discussion noted the atmosphere is "saturated or nearly saturated" all the way up to 470mb, or 20,000 feet. Precipitable water was 2.76 inches, which will be ripe for extremely heavy rainfall.
Figure 2. Tide gauge data from Shell Beach, located on the south shore of Lake Borgne, just east of New Orleans. The green line shows the storm surge. The red line is the storm tide, the height of the water above Mean Sea Level (MSL.)
Portlight disaster relief charity responds to Issac
The Portlight.org disaster relief charity, founded and staffed by members of the wunderground community, have mobilized resources in advance of the arrival of Hurricane Isaac. Their crew, including 2 EMTs, is at the Biloxi Special Needs Shelter, and will be caring for shelter dwellers and doing rescues of people who call for help. Another team will be surveying all the shelters in the area to ensure that they are accessible to all people. You can donate to Portlight's disaster relief fund here.
I'll have more in the morning. Hunker down, New Orleans. It's going to be a long night.
Jeff Masters
Reader Comments
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Im interested to know if he was at home or a command center..because if he was at home riding the storm out, then how can one expect the town to evacuate if their own leadership is not following the evacuation orders...
I dont know the story just speculating here..
Not responding to you directly, but more the general sentiment...
It is human nature to search for a reason to not care. We all do it to some degree or other. It's comforting to believe that the good and bad things that happen in life occur for a reason. In my opinion, our ability to reject this is a excellent measure of our worth, both as individuals and as a society.
Hope you do OK through it all, H98. If they can get your power restored in three days, you're doing good. It was 12 days in AL due to Ivan. Isaac seems to have been at least as bad, in terms of rain, in its outer rain bands as it has been in the center of the storm. Mobile s up to over 4.5 inches over the last two days, and I know there are areas of Florida with much more than that. Isaac is going to be studied for a long time.
It's psychology really. We humans are a reactive species, not a proactive species by nature. It's always going to happen. In everything we do. It's "close the barn door after the horse runs out."
I have to admit that BadMonkey's comment caused me to create my first blog! I'm not taking credit for the comment ... but I COULD NOT resist doing it because I didn't want to see it "disappear" into thin air.
Lindy
He had been in the command center and when reports of issues with one of the levee was near overtopping he responded with Corp Engineer leadership. Regarding knowing his home was damaged, he went home to change into dry clothing when he discovered the piece of missing roof and the collapsing wall and water damage.
He has been a well respected hands on leader for that parish and a strong advocate against BP and the Fed Govt after the spill in 2010.
Nungesser has a good reputation outside of SE Louisiana.
Profound.... thank you!
Mine went out on the early run.
Evacuation and the decision to do so is a complex process.
Nola was told to Shelter in place.
The reason to leave, if at all, is also very often a financial decision.
Projected to be a Cat 1, but has a Cat 2 surge.
and many people were expected to come back to work on Thursday, so they are hestitant to evac, or cannot since they have a job to do.
It is expensive for gas to arkansas and a hotel for 6 plus people, and to find one that takes dogs over 100lbs is difficult at best. Or they have cattle or other responsibilities.
If you have never been there, perhaps it is best not to judge others until you have walked in their shoes.
Try to look for the good in people first.
Thats my point!
The American alligator exists naturally in virtually all of the state of Louisiana, most especially the southernmost part.
In fact, not many people know this but it is Louisiana, not Florida which has the highest concentration of alligators per capita (number of alligators vs. humans living in the designated region).
New Orleans was asked to ' Shelter in Place" by the Mayor... No evacation was called. They are fortunate that the storm did not intensify
Is this valid?? Doesn't look good.. lake coming in?? http://mesonet.agron.iastate.edu/sites/site.php?st ation=OACL1&network=LA_COOP
Anyone that works on the water would agree. Anything over 48 knots is a storm and is treated as dangerous. Over 64 knots and it is a matter of survival.
The categories are really more to gauge potential damage, but people take them to mean how "safe" it is to be in the storm.
A lot of the mets on here come from there. Please pray for them!
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