http://www.wunderground.com/blog/JeffMasters/show.html<snip>
I've been criticized by some for recommending people evacuate New Orleans, since that's not my job, and for saying "it's not natural" to live in a city that lies partially below sea level. I apologize for my remarks, they could have been phrased better. We had to build New Orleans where it is, and it is a great city that needs to be protected.
The fact remains that New Orleans is highly vulnerable to storms like Gustav. Gustav is capable of bringing a storm surge to the city that will overwhelm the levees. Pre-Katrina wisdom suggested that the city needed 72 hours to evacuate. With the population about half of the pre-Katrina population, that lead time is about 60 hours. With Gustav likely to bring tropical storm force winds to the city by Monday afternoon, that means it's time to leave. I'm not an emergency manager, but I am a hurricane scientist. I understand the danger this storm poses better than most. The risk of staying in New Orleans is unacceptable. This is a huge and dangerous storm that has already killed a lot of people. The projected track and strength of Gustav is very close to that of Hurricane Betsy of 1965, the Category 3 hurricane that overwhelmed New Orleans' levees, and killed 76 people. It's time to get out of New Orleans.
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Gustav has expanded significantly in size, and will be a large and dangerous hurricane the remainder of its life. But will it rival Katrina in size, bringing an enormous Katrina-like storm surge to the coast? Well, our ability to predict size changes in hurricanes is poor. We do know that as storms move further from the Equator, they grow in size. This is because the Coriolis force increases as you move away from the Equator. An increased Coriolis force provides more spin to the storm, and the hurricane responds by growing in size. Thus, expect Gustav to grow in size as it approaches landfall along the Gulf coast. Hurricanes also tend to grow in size as they intensify. These two factors are taken into account when NHC makes a wind radius forecast. NHC is forecasting that Gustav's current diameter of tropical storm force (about 300 miles across) will remain about the same at landfall. This is about 70% as wide as the 440 mile-wide region of tropical storm force winds Hurricane Katrina had at landfall (5 am August 29, 2005).
A wind field of this size in a Category 4 hurricane traveling NW over the Gulf of Mexico is capable of carrying a 13-15 foot high storm tide to the coast in central Louisiana. NNW-moving storms bring the highest surge to this region of coast. Storm tide is the storm surge, adjusted upwards by 2 feet in case the storm hits at high tide.
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Masters has been right many times before. It's time to get out of New Orleans and the Gulf Coast NOW.
No schadenfreude gloating here. This is a very dangerous situation.