WTF Isaac?

Isaac is still not a hurricane. It will be one within 24 hours. Right? Right?

Either way, Isaac is big, wet, and windy and long before it makes landfall it will start to cause flooding and wind damage ashore, within the next 24 hours or so. There is a pretty good chance that the storm will be upgraded to hurricane status just before that. Maybe. Well, frankly, I no longer trust Isaac so I’m not making any commitments. I’m tired of these relationships when the other person storm never does what they are expected to do.

Lately the problem has been dry air intruding into the storm, which interferes with the process of getting all round and organized and stuff.

The track has been adjusted slightly to the west. At this point, details matter a great deal. If the center of the storm shifts far enough to the west, a severe storm surge may be avoided for Lake Pontchartrain. Yesterday, the predicted track (and this is just an estimate) went right through NOLA, now it goes just to the west. The big lake is to the east.

Comments

  1. #1 Jared Cormier
    United States
    August 28, 2012

    It’s not really that big nor wet anymore; a large portion of the moisture was lost after it passed over Florida. Three weeks ago, we had over 7 inches of rain over a period of three days; that’s slightly more than is expected for this tropical storm (4-6″). It’s being way overblown.

    I’m going make myself a hurricane now…

  2. #2 Greg Laden
    August 28, 2012

    Well, Jared, that’s actually all pretty much inaccurate. Isaac did not pass over Florida. A tropical cyclone sitting over the Gulf for several days does not really lose moisture. A significant storm surge is expected. The total rainfall in the hardest hit areas are predicted by the National Weather Service to be 7 – 14 inches (over a fairly large area) with local areas of 20 inches, not 4-6″.

    I’m not sure where you are located but if it is near the coast near NOLA or east of it you may want to revise your thinking a bit!

    Accuweather is predicting 4.5 inches of rain in NOAL today, and another 6.5 tonight, then more tomorrow. Even Pensacola Florida is predicting 3-4 inches over the next day and a half.

    As this large wet storm moves inland it will continue to sweep moisture into the lower Mississippi basin.

  3. #3 Jared Cormier
    August 28, 2012

    …didn’t you just talk about the fallacy of “landfall”and you’re accusing me of inaccuracies regarding the storm’s path? The largest band of the storm did, in fact, pass over Florida; it then continued up the coastline.

    I’m in between Baton Rouge and New Orleans. We’re talking about two different numbers. Even 6 inches of rain over a 24 hour period isn’t unheard of here, 12 inches in 2 days is rare, but still not unheard of. It’s usually associated with tropical storms, but not always. That number you just spouted is through Friday morning; 4 days, 5″ per day, which is well under the drainage rate in most areas. The rainfall rate is more important than the total rainfall.

    Two inches of rain in two hours causes flooding while four inches over ten hours won’t. The pumps in New Orleans can handle an average of 1/2″ of rain per hour indefinitely–about 10″ per day, but if that whole 4″ falls in two hours, it won’t be able to keep up.

    Quit watching the news coverage of this storm, it’s a lot of media hype without much in the way of background information.

  4. #4 Greg Laden
    August 28, 2012

    Well, now we can write a post about the storm’s path. Yes, part of the storm “went over” florida but the storm’s path did not go over the Florida mainland. It did go over the keys, of course.

    Your comment was irresponsible and inaccurate. Anyone living in the area would have read that Isaac is not really an issue. It is an issue.

    I am not watching any news coverage of the storm. My information comes from the hurricane prediction center as well as directly from meteorologists who produce commercial models.

    We will talk after the storm is past. If there was any flooding you will apologize to the people of Louisiana and Mississippi. If there was no flooding you can have my blog. How’s that sound?

  5. #5 Jared Cormier
    August 28, 2012

    Look at the satellite images from Sunday and Monday, you will see the dry air entering the storm is because of dry sheer winds separating a large section of the feeder band from the main circulation. This feeder band then shifted north along the eastern coastline (South Carolina right now)

    I never said there will be “no” flooding; there will be flooding, as there is for any thunderstorm in this area. My point is that this is no worse than any large non-tropical weather system we get here in late summer and that the vast majority of the drainage systems can cope with this quantity of rainfall. It should be prepared for like any other hurricane, if I gave any sense that people shouldn’t, then I apologize.

  6. #6 Vikki Frederick
    North of NOLA
    August 28, 2012

    Ya, Jared you definitely gave me the impression you felt that the storm was nothing to worry about and that this would be like any other week in New Orleans and surrounding, and seems like you still are saying that when you say that this is just like any thunderstorm in this area. I think you probably now that Isaac is larger than a thunderstorm and mean “like any thunderstorm in the area but the size of Texas.”

    New Orleans weather TV says 10 inches of rain between now and morning.