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Models “cluster” on near-worst-case track
Posted by on Friday, August 26, 2005 at 9:56 pm

The 10:00 PM discussion of Hurricane Katrina is pretty much all bad news. Let’s start with the new forecast track, which has once against shifted to the left, and is now very, very close to being the doomsday scenario for New Orleans:

Here’s a closer view. This is pretty much the very track that disaster planners have feared for years, the one that features a major hurricane “moving in from due south of the city” with the eye passing “next to New Orleans but just to the east,” thus literally blowing the overflowing Lake Pontchartrain into the city, turning the Big Easy into a modern-day Atlantis. (Here’s what it might look like. Here are some maps.)

Here’s my (entirely unofficial) rendering of a close-up of the NHC’s track, using Google Maps, and based on the forecast latitude and longitude points for 48 and 72 hours (and a conservative estimate of recurvature):

Compare and contrast with Camille and Betsy, both of which were further from New Orleans than this would be.

This is not good, people. And it gets worse:

It is worth noting that the guidance spread has decreased and most of the reliable numerical model tracks are now clustered between the eastern coast of Louisiana and the coast of Mississippi. This clustering increases the confidence in the forecast.

Great… a high-confidence forecast for a track that could kill 100,000 people and utterly destroy a major American city.

Oh, and another bad thing: after leveling off this afternoon and evening, Katrina is strengthening again. She’s up to 105 mph now. The official forecast brings her to 130 mph at landfall, with 160 mph gusts. One computer model thinks she’ll have sustained winds of 140 mph. Another says 150 mph. Barring some unexpected intervening force, this thing is going to be a monster. The water out there is very warm and very deep, and the atmosphere is very conducive to strengthening. There’s nothing standing in Katrina’s way except, well, the Gulf Coast.

I expect Hurricane Watches and massive evacuations tomorrow.

If I can glean any good news out of this discussion, it might be this: “Katrina continues to move stubbornly toward the west-southwest or 250 degrees at 7 knots along the eastern side of a very strong deep-layer mean high centered over Texas.” I like that word “stubbornly,” because when hurricanes are moving “stubbornly,” it often means the forecasts will continue to be wrong because the computer models really are not understanding the dynamics of what’s going on. In this case, that might mean Katrina will continue to move further west than expected, and perhaps New Orleans will be spared as landfall occurs west of the city, in the central parishes. This is actually my personal forecast, but bear in mind, I’m not a meterologist, I just play one on the Internet.

Bottom line… New Orleans is in serious trouble if Katrina follows the NHC’s projected path.

CAVEAT: Hurricane forecasting is an inexact science. 72-hour predictions have a substantial margin of error. The entire northern Gulf Coast should be keeping a very close eye on Katrina. I am focusing on New Orleans because a direct hit there would be catastrophic in a way that no other scenario would be, NOT because other areas are safe. If you live anywhere from western Louisiana to the central Florida panhandle, you should be watching Katrina closely.

P.S. Charles Fenwick writes: “Residents of coastal southeast Louisana, Mississippi, and western Alabama need to start taking action tomorrow morning to prepare for the arrival of what will be a dangerous hurricane. Due to the warming of the Gulf of Mexico that has taken place throughout the summer, there is far more fuel for the hurricane as it approaches the coast. Dennis ran out of gas as it were during his last hours [over the water]. This is much less likely to be the case for Katrina as deep warm waters extend almost all the way to land.”

3 Comments on “Models “cluster” on near-worst-case track”

  1. Andrew Says:

    Wouldn’t the water be significantly cooler south-southeast of New Orleans, as the Mississippi freshwater rolls out into the Gulf?

  2. Andrew Says:

    I tried answering my own question by looking at the NOAA’s sea temperature sat image but it’s not enough detail in the Gulf to tell.

  3. Brendan Loy Says:

    As you indicated elsewhere, this map seems to answer your question, and the answer apparently is: yes. However, that’s not the direction Katrina is expected to approach from. Instead, she’s expected to track over the massively warm spot almost due south of New Orleans. I fear a 150+ mph landfall.

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