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Archives 2000s >> 2006 Forecast Lounge

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Registered User

Reged: Sat
Posts: 1
Recurvature Model Bias
      #51022 - Sat Aug 27 2005 10:06 PM

I believe Katrina will come inland east of current projections of SE LA. I have noticed previous storm projections on storms that are in the beginning of the recurvature process tend to have a left bias. This may be partially due to persistance, and partially due to missing the exact moment the storm beginning their turn poleward. The storms are big ships and take a while to turn, but once they turn, they do so more than expected.

I believe model runs after 00Z will begin to shift right. I also believe the storm will predominately spend it time to the right of the current forecast path. Ultimately landfalling between MS/AL border and Pensacola(again).

As for intensity, I believe there will be a rapid intensification period in the next 12 to 24 hours. There is a small window when the approaching troph creates an ideal environment as outflow is enhanced and shear is minimal. Then as quickly as these conditions appear, the troph gets too close, impenges on the outflow, and returns strong shear. This also is a recurvature event that is misunderstood. This is often blamed on eyewall replacement cycles, however many storms undergo these cycles and maintain a constant (but fluctuating level). These storms actually weaken from external, noy internal forces. Classic example of this would be Opal. However, we need not look any further back than Dennis, and to some extent, Ivan.

Katrina may reach as high as a weak Cat 5 and scare some people to death, and then back off before landfall a Cat or two. Still a strong and dealy beast, but there will be a bit of a let down for the media.

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Veteran Storm Chaser

Reged: Fri
Posts: 1236
Loc: South Florida
Re: Recurvature Model Bias [Re: jrkelly]
      #51066 - Sat Aug 27 2005 10:59 PM

Until the models differ a bit (if they do) it's hard to go against them. And, yet she went against them with her sudden track to the SW over Miami. And, the biggest difference was not the track but the timing. Worried the timing is off again for a few reasons.. staring at water vapor and she can be deceptive. Watching.


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Weather Analyst

Reged: Fri
Posts: 387
Loc: Opelika, AL
Re: Recurvature Model Bias [Re: jrkelly]
      #51069 - Sat Aug 27 2005 11:06 PM

Your observations are correct and there has been a left bias in the models as there were last year too. It is important that everybody understand despite what a series of satellite images show, the NHC does not radically jump from previous reasoning unless forced to do so, such was the case yesterday when a radical revision was made to the forecast track of a land fall near Panama City to near Houma, LA. The public reads these discussions just like we do and NHC knows that, thus continuity prevails unless reasoning and data points them in another direction opting for subtle adjustments whenever possible. The storm has begun it's turn to the right, and like you said, what isn't known whether it will bend all the way around and take a NE heading prior to landfall and if that shortwave is as strong as they say it is, it can't be ruled out.

New Orleans is vulnerable to a storm approaching from this angle and any deviation to the east exaberates the situation considerably. Strong east and southeast winds will pull water into Lake Ponchatrain and as the center goes by, winds come around and push it into the city over the sea wall and there is a scenario that could flood the entire city given on track trajectory.


Bill Berry

"Survived Trigonometry and Calculus I"

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Re: Recurvature Model Bias [Re: jrkelly]
      #51074 - Sat Aug 27 2005 11:19 PM

i agree with all of this. it seems that the storm has more english on it than the track allows.

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Verified CFHC User

Reged: Sat
Posts: 17
Loc: Kansas
Re: Recurvature Model Bias [Re: gregoryb]
      #51564 - Sun Aug 28 2005 03:04 PM

since there she will have to hit land sometime and significant weakening doesn't seem likely given the high water temp and the fact it began warming along the coast, I hope you're right. I'm not sure NO could survive a direct hit by a storm that essentially is already off the scale. I don't just mean damage in NO, I mean there could be a question of whether it could be rebuilt or would have to be relocated.

Almost only counts in horseshoes, hand grenades and hurricanes.

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