EXTREMELY weak nhc analysis

[Brent]

Google news links are reporting "minimal" damage... that is not what I am hearing out of Miami/Hollywood/etc.

I've heard of no structual damage(outside of the bridge collapse), so I guess that could be considered "minimal".

[Eyes2theSkies]

I have always had faith in the NHC but i don't know what they are thinking.

[gatorcane]

Your NOT missing anything the HP pressing down on it has Lifted slightly allowing the Outflow to kick off plus the Big Jog to the South has put alot of the Core over the Everglades and theres enough hot water in the glades to Keep the storm a cane till she reaches the Gomex.

That is not what the NHC thinks, TS of 45K

[wxmann_91]

Yes, I believe that the NHC's recent forecast is a bit farfetched, but you must remember that the NHC is going through a hurricane right now. I think power is out at the NHC and they are going through backup. So one must realize that they are really in a rush right now. (just like I am, so no disco from me tonight - JFYI)

[Brent]

Yes, I believe that the NHC's recent forecast is a bit farfetched, but you must remember that the NHC is going through a hurricane right now. I think power is out at the NHC and they are going through backup. So one must realize that they are really in a rush right now. (just like I am, so no disco from me tonight - JFYI)

I'm pretty sure they can function just fine, storm or no storm. The building is made to withstand a Cat 5...

If they cannot issue advisories, then have the backup HPC(isn't that right?) issue them... they made it through Andrew, they can make it through this.

[gatorcane]

Why would the NHC be in Miami? That doesn't make sense to me. They can do just a good of job in Alaska with high-speed internet and the tools we have now.

[Brent]

Why would the NHC be in Miami? That doesn't make sense to me. They can do just a good of job in Alaska with high-speed internet and the tools we have now.

I was thinking about this earlier this evening... I don't think it would be as fun for them. It's kinda like having the SPC in Oregon... at least in Oklahoma they are in tornado alley.

[jwayne]

The only feasible solution: make Stewart work 24 hours a day when there is a hurricane. Sleep is overrated anyway.

[Wthrman13]

my 7 year old could have done better than that. Weaken to 45 mph when obvious on radar it's more than holding it's own and only 3 hours to water?no discussion of impact of sw movement and possible west shift? Avila needs to get with it or get out.

It's called friction, which starts from the ground up (even the Everglades create more friction than a pure water surface). A hurricane may still look decent on radar, even maintaining an eye structure, for quite a while after moving inland, even though the surface winds may drop below hurricane strength due to friction with the surface. Think of a glass of tea with tea leaves in it. If you stir the tea with your spoon, what happens? The tea leaves "bunch up" near the bottom of the glass, while the circulation of the tea in the middle and near the top of the cup persists for quite a while longer. The friction with the bottom of the glass causes the tea to flow inwards toward the center, and at the same time weakens the circulation there. The same thing, essentially, happens with a hurricane when it moves over land. The friction near the surface causes the surface winds to flow in toward the center, reducing the rotation rate and at the same time slowing the surface winds down. However, higher up, the circulation still has not "felt" this effect. Turbulence will eventually cause the friction effect from the surface to propagate upwards, eventually weakening the entire circulation, but this takes longer. The mid and upper-level structure of the hurricane can remain intact for quite a bit longer. (The main thing about landfall that really weakens a hurricane significantly is not so much the surface friction, but the loss of moisture and heat flux from the warm ocean, but this is probably not as big of a factor with Katrina as it is with other hurricanes, given it's relatively short duration over land). Thus, in the case of Katrina, the mid and upper-level structure (as revealed by the radar) will likely remain mostly intact, while the surface winds near the center may actually decrease below hurricane force.

The short of this long-winded explanation is that no, Avila is not on crack, it is quite possible that despite the maintenance of structure on radar, the surface winds may drop to tropical storm force, which is what really matters in the classification of a tropical cyclone. That said, I wouldn't be surprised if the storm doesn't weaken as much as he said, given that it doesn't have that much longer over land.

[dhweather]

MY gut feel is that they are going to stay with the "package" until 5AM
and see what happens.

Then, at that point, they may make a significant change in their forecast.
Katrina has already made bad things happen with the forecasts, the trough isn't digging south, the ridge isn't moving much. If all that stays so
overnight, well then they basically have to re-do it all.

[FritzPaul]

45kts in 12 hrs.......

Maybe when the eye was passing over, Avila took a peek outside and was accidently struck by a tree branch. When he did the 11 update, he then accidentally blended the earlier forecast that took Katrina over a larger portion of S. FL.

[Ivanhater]

45kts in 12 hrs.......

Maybe when the eye was passing over, Avila took a peek outside and was accidently struck by a tree branch. When he did the 11 update, he then accidentally blended the earlier forecast that took Katrina over a larger portion of S. FL.

haaaaaaaaaaa

[gatorcane]

MY gut feel is that they are going to stay with the "package" until 5AM
and see what happens.

Then, at that point, they may make a significant change in their forecast.
Katrina has already made bad things happen with the forecasts, the trough isn't digging south, the ridge isn't moving much. If all that stays so
overnight, well then they basically have to re-do it all.

Well, they did handle the system well up until it hit land but then after hitting land they were not correct...., however, I give them credit for this as this is a very complex storm to forecast.

[Eyes2theSkies]

nice explanation wrthrman

[JTD]

What is the most interesting thing at this point is what will Katrina max out as in the GOM.

I see no reason why we shouldn't see rapid deepening ala Dennis and Emily, none at all, unless Florida is doing things to the core and structure that we don't understand.

Please note the little part in the NHC discussion about the ECWMF dropping Katrina's pressure to 961 mb in the GOM. That is highly significant.

[jasons2k]

MY gut feel is that they are going to stay with the "package" until 5AM
and see what happens.

Then, at that point, they may make a significant change in their forecast.
Katrina has already made bad things happen with the forecasts, the trough isn't digging south, the ridge isn't moving much. If all that stays so
overnight, well then they basically have to re-do it all.

That concerns me DH

[jwayne]

my 7 year old could have done better than that. Weaken to 45 mph when obvious on radar it's more than holding it's own and only 3 hours to water?no discussion of impact of sw movement and possible west shift? Avila needs to get with it or get out.

It's called friction, which starts from the ground up (even the Everglades create more friction than a pure water surface). A hurricane may still look decent on radar, even maintaining an eye structure, for quite a while after moving inland, even though the surface winds may drop below hurricane strength due to friction with the surface. Think of a glass of tea with tea leaves in it. If you stir the tea with your spoon, what happens? The tea leaves "bunch up" near the bottom of the glass, while the circulation of the tea in the middle and near the top of the cup persists for quite a while longer. The friction with the bottom of the glass causes the tea to flow inwards toward the center, and at the same time weakens the circulation there. The same thing, essentially, happens with a hurricane when it moves over land. The friction near the surface causes the surface winds to flow in toward the center, reducing the rotation rate and at the same time slowing the surface winds down. However, higher up, the circulation still has not "felt" this effect. Turbulence will eventually cause the friction effect from the surface to propagate upwards, eventually weakening the entire circulation, but this takes longer. The mid and upper-level structure of the hurricane can remain intact for quite a bit longer. (The main thing about landfall that really weakens a hurricane significantly is not so much the surface friction, but the loss of moisture and heat flux from the warm ocean, but this is probably not as big of a factor with Katrina as it is with other hurricanes, given it's relatively short duration over land). Thus, in the case of Katrina, the mid and upper-level structure (as revealed by the radar) will likely remain mostly intact, while the surface winds near the center may actually decrease below hurricane force.

The short of this long-winded explanation is that no, Avila is not on crack, it is quite possible that despite the maintenance of structure on radar, the surface winds may drop to tropical storm force, which is what really matters in the classification of a tropical cyclone. That said, I wouldn't be surprised if the storm doesn't weaken as much as he said, given that it doesn't have that much longer over land.

I understand land's effect on tropical systems. Here's the point: it ain't going from 70mph to 50mph in two hours (time before over gulf). The end.

[NorthGaWeather]

What is the most interesting thing at this point is what will Katrina max out as in the GOM.

I see no reason why we shouldn't see rapid deepening ala Dennis and Emily, none at all, unless Florida is doing things to the core and structure that we don't understand.

Please note the little part in the NHC discussion about the ECWMF dropping Katrina's pressure to 961 mb in the GOM. That is highly significant.

EURO was dropping it sub 940mb.

[Wannabewxman79]

So some of you think it is strengthening over land huh? Talking about someone on crack, that would defy the laws of physics and that really doesn't happen if I recall correctly. Anyway, the NHC was off on the track once it hit land but they also made mention that it could follow the path set forth by the GFDL which was the outlier. Hince forth they were wrong but said they could be wrong and that you probably should watch the GFDL model since it has handled T.C.s well this year.