Katrina is looking pretty damn good on infrared

[jax]

I see a drift lately to the WSW...anybody notice this? Maybe just a wobble.

yep... i wouldn't be surprised if she passes below Miami...

[gatorcane]

some models are showing it passing south of Miami still. Max Mayfield said there is great uncertainty in the track with this one...

[Scorpion]

It wont pass south of the Palm Beach/Broward line.

[gatorcane]

It wont pass south of the Palm Beach/Broward line.

Look at the wobble though it is move WSW....but maybe it will resume back to the W or WNW shortly.

[skysummit]

SOUTH of Miami? Hmm....I doubt it will go that far south, but I do also see heading a tad south of due west in the last few frames.

[Scorpion]

Likely just a wobble. Will continue to the W or WNW and hit around WPB-Boynton. Im gonna be in the northern eyewall.

[gatorcane]

if it goes South of Miami that would be a surprise but hey this is what Andrew did right...

[WindRunner]

Why are we posting NWS radar images? I'm sure everyone knows where they are.

speak for yourself, i appreciate it

Exactly, it saves time if you can bring everything together in one place, and it makes people much more likely to look at it if it's right in front of them.

[Air Force Met]

Diffluence is the spreading out of air. Remember a Hurricane (and other low pressure systems) are places where air comes rushing in at the surface (convergence). All that air has to go somewhere...or the low pressure would quickly become high pressure because all that air "fills it up".

So the low needs a mechanism to get rid of that air rushing in. In the case of a tropical system, it establishes outflow aloft--air that comes into the low goes up and out--diverging--or creating diffluence--aloft.

Divergence aloft alone acts to lower surface pressures--air rushing away aloft means that more air has to converge at the surface to keep things in "balance". So divergence/diffluence aloft means surface pressures are dropping.

Write back if you want more clarification. It's not quite so simple as I've laid out here, but hope it helps.

Let me do a little clarification on your explaination...which was good..BTW....but to help answer the ? completely.
1) Tropical systems do establish outflow...but are usually established under a favorable area first...and as they develop...they develop the outflow aloft further through laten heat release of condensation...which adds heat to the atmopshere and builds high pressures aloft and lowers sfc pressure.
2) Divergence aloft doesn't necessarily mean sfc pressures are dropping. There are plenty of examples right now on the map where there are good amounts of divergence in the upper levels and there are no pressure falls. If boundry layer convergence is greater than the divergence aloft...then pressures can remain stable or rise. In cases such as this blob SE of Kat...I wouldn't expect sfc pressure to drop that much because of divergence aloft and thunderstorms due to the shear. What happens is all that latent heat released by the convection is transported away from the system before it can lower pressures and raise upper level heights. It's kinda like filling a hot air balloon in a 50 kt wind. You get a lot of energy released from the burning propane...but most of it gets blown away before it can make it into the balloon....so that you never fill it.

[gatorcane]

it's continuing to wobble WSW!

[skysummit]

Why are we posting NWS radar images? I'm sure everyone knows where they are.

speak for yourself, i appreciate it

Exactly, it saves time if you can bring everything together in one place, and it makes people much more likely to look at it if it's right in front of them.

Okie doke....sorry about that. I'm just a little grouchy this morning.

[rockyman]

Here are 2 links...the first shows areas of low-level convergence...the second is upper level divergence:

http://cimss.ssec.wisc.edu/tropic/real-time/atlantic/winds/wg8conv.html
http://cimss.ssec.wisc.edu/tropic/real-time/atlantic/winds/wg8dvg.html

[gatorcane]

heading towards Miami right now...could be a wobble but it looks pretty definitive.

[Scorpion]

Miami? Katrina won't be near Miami. At its current trajectory it would hit Ft Lauderdale. But it will bend back W and then WNW.

[wjs3]

AFM:

Thanks--I really appreciate the note back. This is this board at its best, IMO.

I forgot to add the "divergence aloft must exceed convergence at the surface" caveat. So to repeat: Surface pressures fall when there is more exiting an air column aloft than what's coming in at the surface...right?

Most of what I've learned about divergence aloft and the role in creating surface lows is in a mid latitude setting...I study Tropical systems next in courses I'm taking...so I still have much to learn.

You really clarified things with your latent heat explanation. Totally get how shear can remove the height building mechanisms by removing the warmer air that would do the dirty work of building heights, and, ultimately creating outflow.

Thanks a ton!

[caneseddy]

BocaChris,

IF this is a definitve movement to the WSW and nt a wobble the farthest it can go will be South Broward; now as Scorpion said, Andrew wobbled east of the Bahamas which gave it a lot more room to pass south of Miami

It's just to close to the coast to make a definite hit in Miami or south of there

Now I hate to see a WSW motion because i\'d be closer to the eyewall

PS: Channel 4 meterorologist (not Norcross) said that there is a wobble to the WSW but they talked to the NHC and they are not sure yet if its a wobble or definite motion

[gatorcane]

well look what so many hurricanes have done when they near the coast....and we want to concentrate on the line but the cone puts it as far South as the FL Keys...so anything is possible here. Look at what Charley did...

[Scorpion]

Charley did so because of an exceptionally strong trough.

[krysof]

But Charley was already quite strong before its rapid intensification- Category 2.

[gatorcane]

she is starting to slow down now folks....