Eye of the Storm

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Sunday, August 28, 2005

Katrina's winds now at 175 mph

...POTENTIALLY CATASTROPHIC HURRICANE KATRINA...EVEN STRONGER...HEADED FOR THE NORTHERN GULF COAST...

At 10 AM CDT, the center of category five Hurricane Katrina was at 26.0 North 88.1 West, 225 miles south-southeast of the mouth of the Mississippi River. Maximum sustained winds are 175 mph and minimum central pressure is 907 millibars (26.78"). Hurricane force winds extend up to 105 miles from the center.

Hurricane Katrina Advisory Number 23

"Katrina is comparable in intensity to Hurricane Camille of 1969 only bigger." Fluctuations in strength are likely, however, "we see no obvious large-scale effects to cause a substantial weakening (of) the system and it is expected that the hurricane will be of category 4 or 5 intensity when it reaches the coast".

There is no change in the track forecast, which is in the center of model guidance. Due to the average errors in a 24 hour forecast, Katrina could strike anywhere from southeastern Louisana to the Missippi coast. Destructive weather extends well beyond the eye, so focusing on the exact point of landfall is not necessarily productive.

Hurricane force winds are expected to last for up to 150 nautical miles (172.5 statute miles inland)

Hurricane Katrina Discussion Number 23

Official track forecast with warning areas

Alternate view of track forecast

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A couple of days ago, I wrote about the average track error in the NHC's forecasts last year. I went back and looked at the forecasts for the two hurricanes last year that featured a synoptic situation roughly similar to this, namely Charley and Ivan.

In the case of Charely, the forecast that took place 24 hours before landfall was off by about 40 nautical miles and the forecast 12 hours before was off by 29 nautical miles. Both were too far to the left, meaning that Charley turned harder than forecast.

For Ivan, the error at 24 hours out was 42 nautical miles, and the 12 hour error was 26 nm. Again, the forecast was too far left as it hit further east than forecast.

If a similar error to occur in this case, then the resulting landfall position would be comparable to that of Camille. However, due to the greater size of Katrina, effects in New Orleans would be worse than they were for Camille.

No guarantees however, as if we will see a repeat of this type of error. After all, it is quite possible that the forecaster has already factored it into his forecast (i.e. shifted it say, 20 miles to the right of where he normally placed it).

The Gulfstram-IV jet flew this morning to feed upper-air data from the Gulf of Mexico to the 12Z global models, which just started crunching the numbers. Forecasts will be coming out from them over the next two hours, and any changes in their tracks would affect a change in the 5 PM advisory package.

Intensity forecasting at this stage is nothing more than speculation with regards to whether Katrina will maintain her strength. It is fairly certain however, that if she were to weaken some, the bottom would probably be at the high end of the category four range (i.e. 145-155 mph winds).

If you are under evacuation orders now is the time to leave. Time for preparations to secure property is expiring. Remaining in your present location longer reduces your chances of making it to a shelter or other refuge in a safe manner. Conditions will quickly detoriate this evening.

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