forecasting eyewall replacement cycles

[Nimbus]

Looks like the only thing that could drop Katrinas intensity at landfall is an eyewall replacement cycle.

Is there any data or history available concerning monster annular hurricanes with large eyes?

Subjectively it seems as though storms with smaller eyes sometimes go through replacemaent cycles when they hit more favorable conditions and outgrow the ventilation capabilities of the smaller eye.

Would a monster storm like Katrina with a huge eye be more likely to go through an ERC if she started having proximity to land or shear issues that made her environment slightly less than ideal?

I realize we are only talking a couple catagories of strength but the difference between the destruction caused by a cat 5 VS a cat 3 is amazing.

[Mac]

Well, there are other factors which could likewise affect her strength...upwelling, low overall heat content (hot SSTs, but shallow), etc. Regarding ERCs, unfortunately, annular hurricanes do not undergo as many ERCs as non-annular hurricanes. They don't need to, they are nearly structurally perfect already.

[Nimbus]

They don't need to, they are nearly structurally perfect already.

Exactly.
Annular hurricanes usually occur under ideal conditions.
It requires a perfect symmetry with no dry air infringment or outflow restrictions to support the ventilation rate of a huge eye.

[weatherwindow]

still believe another cycle is in the offing prior to landfall....a good clue to the possibility of another ERC is a steady reduction in the diameter of the eye. ..normally precedes the development of a concentric wall with a outer wind max. unfortunately, i havent seen any reduction in the diameter as of yet. here's hoping

[TPACane04]

I want to go back and look at "Mitch" stats on this topic...he was very similar in size and strength, see how long he sustained max power.

[TPACane04]

OK ...two recent Cat 5's:

Mitch (1998) only stayed at 905 mb for 6 hours, then "weakened" back into 920 range

Isabel (2003) stayed 915-920mb for 24 hours out in the Atlantic.

Certainly, neither were Gulf storms, and I have not found any Climo yet for Camille as far as length of time she sustained herself, but suffice to say Camille was not weakening when she hit MS.

[Jim Hughes]

Well, there are other factors which could likewise affect her strength...upwelling, low overall heat content (hot SSTs, but shallow), etc. Regarding ERCs, unfortunately, annular hurricanes do not undergo as many ERCs as non-annular hurricanes. They don't need to, they are nearly structurally perfect already.

Or you can pray for a strong solar wind shock to occur...This would bring along a higher solar wind speed. The conditions that I have continually spoken about were in place the prior 24-36 hours and look how Katrina has bombed out.....quicker than what the models were forecasting at this time frame.


Jim

[Air Force Met]

still believe another cycle is in the offing prior to landfall....a good clue to the possibility of another ERC is a steady reduction in the diameter of the eye. ..normally precedes the development of a concentric wall with a outer wind max. unfortunately, i havent seen any reduction in the diameter as of yet. here's hoping

I've noticed that too...the ERC hasn't started yet...which means it will get stronger before it gets weaker.

[wjs3]

TPACane:

Awesome research. Let us know what you find on Camille. I know that all the advisories for Camille are archived at the NHC:

ftp://ftp.nhc.noaa.gov/pub/storm_archiv ... 9/camille/

(Hope I did that URL right!)

An incredible read.

[storms in NC]

still believe another cycle is in the offing prior to landfall....a good clue to the possibility of another ERC is a steady reduction in the diameter of the eye. ..normally precedes the development of a concentric wall with a outer wind max. unfortunately, i havent seen any reduction in the diameter as of yet. here's hoping

I've noticed that too...the ERC hasn't started yet...which means it will get stronger before it gets weaker.

Do you still think NOLA is going to get hit?

[Air Force Met]

still believe another cycle is in the offing prior to landfall....a good clue to the possibility of another ERC is a steady reduction in the diameter of the eye. ..normally precedes the development of a concentric wall with a outer wind max. unfortunately, i havent seen any reduction in the diameter as of yet. here's hoping

I've noticed that too...the ERC hasn't started yet...which means it will get stronger before it gets weaker.

Do you still think NOLA is going to get hit?

Yes...and I think most of NOLA will be in the western eyewall...which is the only good news.

[storms in NC]

what is the bad news for NOLA. sorry I have never dealed when a storm this big

[TPACane04]

The bad news for NOLA is that unless Katrina gets far enough east (ie Biloxi direct hit) per the current forecast path, the N and NE winds will have a horrific impact on Lake Ponchatrain and all land masses south of the Lake. go to nola.com and look for their special report "The Big One"...it is stunning.

[Nimbus]

The Lake Pontchartrain scenario theorized winds from a western eyewall of a major hurricane would surge the lake over the levee flooding the city to the south?

They felt this might happen with a cat 4 or larger cane IIRC.

The western eyewall of Katrina will be passing over Lake Pontchartrain however the sustined wind speeds may not go over cat 2 if we are lucky.

The way the wind couples with the lake surface makes the slosh effect non linear.

A cat 4 hurricane might have wind speeds 30 or 40 percent higher than a cat 2 but the slosh effect due to wind coupling with the water surface would double (or something like that).

Any news about the lake level or levee system yet?

[Myersgirl]

The eye appears to be getting much smaller now
http://radar.weather.gov/radar/loop/DS. ... kmob.shtml