2005 Atlantic Tropical Cyclone Reports Discussion Thread

[Pearl River]

Maximum 700 mb flight-level winds were still 130-135 kt east of the eye around that time and were the basis for the operationally assessed intensity of 120 kt at the Buras landfall and at 1200 UTC. NWS Slidell WSR-88D radar data confirmed the strength of these flight-level winds, but the center of the hurricane was much too distant for the radar to provide concurrent near-surface wind estimates close to the eye.

CindyUsing a standard reduction factor of 0.90 yields an approximate surface wind speed of 60 kt, which compares well with the Doppler radar surface wind speed estimate of 60 kt for that area.

They don't look like they say the same thing to me.

[Audrey2Katrina]

NHC used the Slidell radar in the same manner for both Cindy and Katrina. They used it to measure wind speeds ALOFT, and then use these aloft wind speeds to estimate corresponding surface winds using a determined reduction factor. The type of radar data used by NHC is the same for both storms.

But the application of the data was "Inconsistent" no matter how one plays with the words.

A2K

[jazzfan1247]

Maximum 700 mb flight-level winds were still 130-135 kt east of the eye around that time and were the basis for the operationally assessed intensity of 120 kt at the Buras landfall and at 1200 UTC. NWS Slidell WSR-88D radar data confirmed the strength of these flight-level winds, but the center of the hurricane was much too distant for the radar to provide concurrent near-surface wind estimates close to the eye.

CindyUsing a standard reduction factor of 0.90 yields an approximate surface wind speed of 60 kt, which compares well with the Doppler radar surface wind speed estimate of 60 kt for that area.

They don't look like they say the same thing to me.

Ok, so I guess I have to really spell this one out for you. They do indeed say the same thing, and let me try to explain again.

NWS Slidell WSR-88D radar data confirmed the strength of these flight-level winds, but the center of the hurricane was much too distant for the radar to provide concurrent near-surface wind estimates close to the eye."

This means that the radar cannot DIRECTLY measure surface wind speeds (because it is too far away), and this is what they mean when they say they can't "estimate" surface winds. They DON'T mean that they can't use any reduction factors to estimate surface winds based on the flight-level winds recorded by radar. They simply mean they can't DIRECTLY MEASURE these surface winds.

Using a standard reduction factor of 0.90 yields an approximate surface wind speed of 60 kt, which compares well with the Doppler radar surface wind speed estimate of 60 kt for that area.

Here, when they say "Dopper surface wind estimate of 60 kt"...they do NOT mean DIRECT Doppler data, they mean the surface wind speed derived from the assumed 90% reduction from the ACTUAL radar data of wind speeds ALOFT. In other words, they really mean the EQUIVALENT surface wind speeds. This is made clear in the sentences before with the phrases:

Instead, the wind swath depicts a region of Doppler velocities that, WHEN APPLYING THE 0.90 ADJUSTMENT FACTOR, yields an approximate region of 64-kt or greater equivalent surface wind speeds...

A couple sentences later:

"However, Doppler velocity CONVERSIONS...indicated a EQUIVALENT surface wind of 60 kt...

To sum up the Cindy report, they use the Slidell radar to confirm winds ALOFT (since it cannot directly measure surface winds), and use other observations to determine which reduction factor to use to determine the surface winds.

I really don't know how else to spell this out, honestly

[jazzfan1247]

NHC used the Slidell radar in the same manner for both Cindy and Katrina. They used it to measure wind speeds ALOFT, and then use these aloft wind speeds to estimate corresponding surface winds using a determined reduction factor. The type of radar data used by NHC is the same for both storms.

But the application of the data was "Inconsistent" no matter how one plays with the words.

Just because the reduction factors are different doesn't make the usage of the data "inconsistent".

The NHC used the Slidell radar velocity data in the same manner. They used it to determine the wind speeds ALOFT for both Cindy and Katrina, and determined a reduction factor for surface winds in each storm. The raw radar data is of the same type for both storms (winds aloft). The reduction factors just happened to be 90% in Cindy, and 80-85% in Katrina. Just because the reduction factors came out different, does NOT mean the radar data was used in different ways.

[Audrey2Katrina]

NHC used the Slidell radar in the same manner for both Cindy and Katrina. They used it to measure wind speeds ALOFT, and then use these aloft wind speeds to estimate corresponding surface winds using a determined reduction factor. The type of radar data used by NHC is the same for both storms.

But the application of the data was "Inconsistent" no matter how one plays with the words.

Just because the reduction factors are different doesn't make the usage of the data "inconsistent".

The NHC used the Slidell radar velocity data in the same manner. They used it to determine the wind speeds ALOFT for both Cindy and Katrina, and determined a reduction factor for surface winds in each storm. The raw radar data is of the same type for both storms (winds aloft). The reduction factors just happened to be 90% in Cindy, and 80-85% in Katrina. Just because the reduction factors came out different, does NOT mean the radar data was used in different ways.

Umm sorry; when you use .9 for one, and .8 for the other over the same terrain, same area, ... you are using data inconsistently by the very definition of the term.

A2K

[jazzfan1247]

Umm sorry; when you use .9 for one, and .8 for the other over the same terrain, same area, ... you are using data inconsistently by the very definition of the term.

A2K

lol

Do you know what the statement "No two storms are the same" means? Of course they aren't gonna have the same reduction factor.

[WindRunner]

NHC used the Slidell radar in the same manner for both Cindy and Katrina. They used it to measure wind speeds ALOFT, and then use these aloft wind speeds to estimate corresponding surface winds using a determined reduction factor. The type of radar data used by NHC is the same for both storms.

But the application of the data was "Inconsistent" no matter how one plays with the words.

Just because the reduction factors are different doesn't make the usage of the data "inconsistent".

The NHC used the Slidell radar velocity data in the same manner. They used it to determine the wind speeds ALOFT for both Cindy and Katrina, and determined a reduction factor for surface winds in each storm. The raw radar data is of the same type for both storms (winds aloft). The reduction factors just happened to be 90% in Cindy, and 80-85% in Katrina. Just because the reduction factors came out different, does NOT mean the radar data was used in different ways.

Umm sorry; when you use .9 for one, and .8 for the other over the same terrain, same area, ... you are using data inconsistently by the very definition of the term.

A2K

You have to remember that the conversion factor for each altitude in each storm will have its own value; there will be typical values that most storms adhere to, but some storms have conversion values that are rather extreme, I believe Bret back in 1999 had a conversion value of 1.1 to 1.2 at one point, meaning that the surface winds were actually stronger than the winds aloft. We must also remeber that these conversions are no precise nor accurate measurement, only estimates. Very rarely will such a rounded number yield perfect conversions, and the chances that the conversions would be the same for two storms (even in the same/similar locations) is practically zero.

[Audrey2Katrina]

No disagreement with anything you've stated WR, and the operative word is indeed "estimates" which by its very definition has a margin of error. The only point I was attempting to make is that there was an inconsistency however one may attempt to justify it, in the application of the data.

A2K

[jazzfan1247]

No disagreement with anything you've stated WR, and the operative word is indeed "estimates" which by its very definition has a margin of error. The only point I was attempting to make is that there was an inconsistency however one may attempt to justify it, in the application of the data.

A2K

There is no inconsistency in the APPLICATION of the data. It was used in the same manner to determine equivalent surface winds, as I have mentioned before. The reduction factor was different in both cases, but that doesn't mean NHC applied the data any differently. The radar velocity data played the same role in each case; it was the other factors (different reduction factor determined from sondes, SFMR, obs) that made the result different.

[WindRunner]

No disagreement with anything you've stated WR, and the operative word is indeed "estimates" which by its very definition has a margin of error. The only point I was attempting to make is that there was an inconsistency however one may attempt to justify it, in the application of the data.

A2K

I see your point, and the only explanation for it is the fact that WSR-88D velocity data only goes up so high, and is probably rather inaccurate in itself at such velocities as would be measured in Katrina, as well as being at a height that we don't have conversion factors for. The radar beam for measuring velocities at the first LA landfall would have put the Slidell beam between 10,000 and 14,000 feet, and would have been between 3,000 and 5,000 feet for the MS landfall. Neither of these values (except for the 10,000 foot height) are typical values that we have conversion values for, and so the NHC tried to keep its analysis to actual data instead of interpolations, and errored on the low end. The other problem with the Slidell radar's location is that in order to get to the appropriate area of the storm, the beam would have to have gone through the eyewall at both landfalls, which usually ends up providing bad data on the low end, as the beam is scattered by the large volume and high speed of the particles in such a powerful eyewall.

I'm sure the NHC could have done a little interpolating (and probably did internally), but then we'd be arguing about that, right?

[Audrey2Katrina]

Jazzfan:
There is no inconsistency in the APPLICATION of the data.

I beg to disagree.

WindRunner:
I see your point,

Glad someone could

I'm sure the NHC could have done a little interpolating (and probably did internally), but then we'd be arguing about that, right?

Absolutely!

A2K

[jazzfan1247]

There is no inconsistency in the APPLICATION of the data.

I beg to disagree.

What difference is there in how NHC used the radar data in both Cindy and Katrina? You claimed earlier that the NHC used the radar for Cindy, but threw it out with Katrina, but this has been proven false. So why do you still disagree?

[Audrey2Katrina]

What difference is there in how NHC used the radar data in both Cindy and Katrina?

The difference is how they applied it? Do I really have to explain that any further?

You claimed earlier that the NHC used the radar for Cindy, but threw it out with Katrina, but this has been proven false.

Actually to resort to the kind of legalese this discussion has descended to, that's what's known as either proving or disproving a minor point. In my initial post I simply stated they didn't deem the Slidell radar as "worthy" in the Katrina report, while they did in the Cindy. This vaguary on my part was clarified in the very next post. It wasn't a question of whether or not they referenced the Slidell radar, as clearly anyone capable of reading could see that they did. The "worthiness" of the "data" is what I was referencing and I made that patently clear in every post since that. The inconsistency is in how they interpolated the data from one upward and the other downward, and any cursory review of semantics would allow that this is tantamount to an inconsistency, however one may try to explain or justify it--A point which I gratefully acknowledged at least one other party in here seemed to grasp.

So why do you still disagree?

See above.

A2K

[Pearl River]

Slidell radar went out 46 minutes prior to 2nd landfall. Something else omitted from the Katrina report.

[jazzfan1247]

The difference is how they applied it? Do I really have to explain that any further?

Yes you do. There is no difference in how they applied the data. The DATA ITSELF was different in each case, which is why they came up with different results and different reduction factors. For instance, data other than radar (dropsondes, SFMR, onboard doppler, etc) indicated that the reduction factor was 90% in Cindy, and 80-85% in Katrina...hence the DATA ITSELF was different. But the radar wind velocities were used in the same manner in that they took those wind velocities and multiplied it by each given reduction factor (determined by the other data), and they did this process for BOTH Cindy and Katrina. How is there ANY difference in the two cases? The data determining the reduction factor was different...the application of the radar data the same. It played the same role. How you can see otherwise is beyond me...

Actually to resort to the kind of legalese this discussion has descended to, that's what's known as either proving or disproving a minor point. In my initial post I simply stated they didn't deem the Slidell radar as "worthy" in the Katrina report, while they did in the Cindy. This vaguary on my part was clarified in the very next post. It wasn't a question of whether or not they referenced the Slidell radar, as clearly anyone capable of reading could see that they did. The "worthiness" of the "data" is what I was referencing and I made that patently clear in every post since that. The inconsistency is in how they interpolated the data from one upward and the other downward, and any cursory review of semantics would allow that this is tantamount to an inconsistency, however one may try to explain or justify it--A point which I gratefully acknowledged at least one other party in here seemed to grasp.

The worthiness of the radar data was equal in both cases. The NHC confirms this fact by saying: "Max. 700 mb flight level winds were still 130-135 kt...NWS Slidell WSR-88D radar data confirmed the strength of these flight-level winds..." The only thing is that the radar data seems to get less fanfare in the Katrina report than the Cindy report, which just maybe leads you to believe in the whole "unworthiness" idea. BUT, this is only because there were actually planes and flight data gathered at the Katrina landfall, while there wasn't during the Cindy landfall.

[Derek Ortt]

Umm sorry; when you use .9 for one, and .8 for the other over the same terrain, same area, ... you are using data inconsistently by the very definition of the term.

Please learn about vertical momentum transport and come back and debate then, because you apparantly do not grasp this concept. A hurricane that does not have high vertical velocities means that the strongest winds will be located above the top of the boundary layer. Katrina had weaker VV's than did Cindy; thus, Cindy was better able to transport its momentum down to the surface than was Katrina

[Audrey2Katrina]

Umm sorry; when you use .9 for one, and .8 for the other over the same terrain, same area, ... you are using data inconsistently by the very definition of the term.

Please learn about vertical momentum transport and come back and debate then, because you apparantly do not grasp this concept. A hurricane that does not have high vertical velocities means that the strongest winds will be located above the top of the boundary layer. Katrina had weaker VV's than did Cindy; thus, Cindy was better able to transport its momentum down to the surface than was Katrina

Please learn a little about not sounding so insufferably arrogant in responding to another's post, because you apparently do not grasp this concept, and I'll come back whenever it pleases me or the powers that be deem otherwise. Ok? I don't really care about all the technicalities and intricacies of momentum with which I am quite familiar despite your condescension to the contrary--there are 10,000 ways one can spin data this way or that, and I will hold my position as stated regardless of those whose hubris is only exceeded by their inability to apply courtesy when disagreeing with another in dialogue.

Have a momentous day

A2K

[Derek Ortt]

then dont come crying to me when a real cat 4 hurricane hits you, because you will not grasp the data that beyond a reasonable doubt indicates Katrina was a 3.

Please, everyone on the hurricane coast know, Katrina showed just how bad a category 3 hurricane is. Please do not take a cat 3 lightly. It does not take a 4 or a 5 to level a region, as Cat 2 Isabel showed at Cape Hatteras

Based upon some of the comments here, I am going to be posting much less, since the stress of talking to a wall and having people say that the data is wrong, when it is not and over inflating storms and getting people to believe that a 3 cannot level a major city is really wearing on me... to the point where it is affecting me as a person

[Audrey2Katrina]

Yes you do.

Actually, I do not. Look we've beaten this dead horse over and over, and no matter what spin you put on it, I'm going to maintain there is an inconsistency, and you're going to counter that there isn't. We will simply have to agree to disagree. I'm not budging an inch, er mm, and it is quite apparent neither are you. So be it.

A2K

[Extremeweatherguy]

then dont come crying to me when a real cat 4 hurricane hits you, because you will not grasp the data that beyond a reasonable doubt indicates Katrina was a 3.

Please, everyone on the hurricane coast know, Katrina showed just how bad a category 3 hurricane is. Please do not take a cat 3 lightly. It does not take a 4 or a 5 to level a region, as Cat 2 Isabel showed at Cape Hatteras

Based upon some of the comments here, I am going to be posting much less, since the stress of talking to a wall and having people say that the data is wrong, when it is not and over inflating storms and getting people to believe that a 3 cannot level a major city is really wearing on me... to the point where it is affecting me as a person

I know what you mean about talking to a wall sometimes, especially when you have all the evidence on your side. I think your points are valid though, but people just do not want to believe that a life-changing storm to hit their area was ONLY a category 3. They don't realize that a Cat. 3 can level a town, and immediately assume that it must have been a 4 or 5.