Ivan Advisories

[senorpepr]

Remember... to save on the server... try to avoid posting entire advisories. Post links instead. There's a topic at the top of the Hurricane Hollow Forum that talks about this.

[chris_fit]

Well 145 is better than 160

[rtd2]

quote" ericinmia wrote:


The Bermuda High that was to keep Ivan more wnw over this period has been retrograding slowly over time, due to the low wraping around its southeastern periphery, disrupting the westerly steering currents above, and ahead of Ivan.
-Eric




I just read another thread where they said it was stronger than the models predicted and building. Geez, it can't be both"








Posted about this ridge this am..it looked strong then and just as strong now so I would say its not weakening!

[ColdFront77]

Remember... to save on the server... try to avoid posting entire advisories. Post links instead. There's a topic at the top of the Hurricane Hollow Forum that talks about this.

Lines of text tax the service... if that's the case, lenghty posts should be discouraged, too.

[mobilebay]

From the 00Z recon fix to the new 0600 recon fix Ivan has moved exactly one degree west, and a half a degree north. I believe that is a true 300 degrees. Correct me if I'm wrong...

[rtd2]

FELLOW LEFTY HERE! (West) I was a lefty on frances and now Ivan... Models are still doing a crappy job on ridge strength

[bahamaswx]

k i r now type shrt post

[ericinmia]

It may be obvious to you, but I'm still learning how to read this stuff so I rely more on what others say.
Then I go look at it and try to figure out what the heck they're talking about. It didn't look like it was weakening yet to me, but hey, what do I know?

Sorry i didn't mean to come across like that...

Here is about 6 hours ago...
http://cimss.ssec.wisc.edu/tropic/real- ... dlm5-2.GIF

Here is the current...
http://cimss.ssec.wisc.edu/tropic/real- ... g8dlm5.GIF

That shows it retrograding, especially on its southwestern periphery...
That also shows the high on the southeast of the bermuda high... and the effect it is having.
-Eric

[mobilebay]

FELLOW LEFTY HERE! (West) I was a lefty on frances and now Ivan... Models are still doing a crappy job on ridge strength

Agree. I will be very interested at the 0600 run of the GFS to see if goes further west for the sixth straight run.

[HurricaneBill]

I heard 8 of the inmates fled to public shelters. (Probably felt it was better to be safe than loose in a raging hurricane.)

[FungusMoldlyColdcuts]

Dang....it's not gonna give an inch, is it?

Huh?

The new Canadian just flopped from an Alabama landfall to a landfall in the Big Bend of Florida...that's a HUGE flop.

I think this thread and the links were posted before the 0Z fully updated; the models updates gradually.

Derecho do you ever make forecasts or compliment a post? I think you just post when you find something negative to say about someone else post.

does it make a difference? did you expect anything more?

In my opinion, the GGEM has infact shifted right about hundreds or thousands of miles the last 2 days. That is quite an east trend, indeed.

[Possum Trot]

How long does an ERC usually take, and what factors effect the length of the cycle?

[HurricaneBill]

It sounds like extortion too

::hits myself upside the head::

Oh, that's what I meant!

[Sean in New Orleans]

This is copied from a local web site, and I'm including a link to keep this legal, so credit goes to where credit is due:

http://www.wwltv.com/cgi-bin/bi/discuss ... apsed&sb=5

Keep in mind, this is from a local New Orleans met, so you're going to get an explanation as it pertains to New Orleans. The message is to those in the New Orleans metropolitan area.

*********************************************************



*Everyone from Louisiana to FL Needs to Monitor Future Track of Ivan

*Highest Risk Remains Over FL

*Very Complex Steering Pattern Makes Forecast Difficult and Uncertain Beyond 60 Hours

*Forecast Key Will be Decay of Ridge (High) Steering Ivan


Current Analysis:

Ivan has been fluctuating in intensity due to these “eyewall replacement cycles” whereby the eyewall will break down; weaken the storm, then reform, resulting in a stronger storm. Expect these cycles to continue, perhaps with another completing before Ivan reaches Jamaica, thus some strengthening is possible prior to a landfall there.

Outflow on Ivan remains excellent tonight in all areas around the storm. Motion remains WNW, but there has been a trend toward a more NW motion tonight, as expected. Ivan continues to ride on the southern flank of a ridge to his north, but has begun to slow a little. Forward speed was reported as 13 mph by NHC in their 10pm update. Expect that to continue to slowly come down. Maximum winds remain at 150 mph, but looking at satellite estimates tonight, that may be a bit high.

Forecast:

Over the next 48 hours, the forecast on Ivan is pretty straight-forward. It’s after that things get interesting. The ridge Ivan is riding is centered off the New England Coast and is going to break down as Ivan gets close to Cuba. At this point, the steering currents become very weak. Ivan will likely slow down a great deal by Sunday and could even stall just south of Cuba. The forecast key here will be the rate and extent this ridge breaks down. The factors making this happen are very complex.

The main thing we are watching is an upper low over the central Atlantic which is sliding SW along with an associated trough. As that low slides SW, it is going to weaken the SW part of the ridge Ivan is riding. We also have a trough (dip in the upper winds) over the East Coast which is eroding that ridge (and is actually being aided, I think, by what’s left of a Typhoon in the West Pacific). So in effect, this ridge is feeling the “squeeze play” from two systems which are trying to thin it down. At the same time, a new trough digging into the Pacific NW (which is being aided by what’s left of the Typhoon in the western Pacific too) will force a ridge to build under it. That ridge will extend as far east as Texas by Sunday. This leaves a general weakness from LA to FL for Ivan to travel into.

So, why do the models take him into FL and not LA then? Good question. The answer is because the weakness is forecasted to be weaker over FL than LA. Here’s why: As that ridge which Ivan is currently riding gets squeezed from our East Coast trough AND from the upper low over the Atlantic, it gets narrow and lifts north by Saturday. The center of the ridge then shifts NE as that aforementioned East Coast trough slides east and breaks it down. This leaves a distinct weakness to the north of Ivan probably by late Saturday or Sunday which he will begin to move into. As he moves into the weakness, he picks up speed and moves into FL. After that, ridging in advance of our Pacific NW trough forms north of Ivan possibly causing him to slow over FL late Tues into Wed. After that, the Pacific NW trough swings in and allows him to continue north faster. In addition to all that, the models are hinting at some trough splitting occurring which would settle a bit of a weak trough over the lower MS valley by the weekend. This would also tend to prevent Ivan from moving our way.

Now, all of that is an explanation as to why the models are doing what they are doing. The question that begs to be asked is “can he come any further west?” I think the answer to that is yes, but here’s what needs to happen:

1.) That upper low would need to be weaker and not move as expected.
2.) The East Coast Trough would need to be weaker than expected and lift out sooner than expected.
3.) The result of the two above situations would result in a stronger ridge, or a ridge that is not being broken down as quickly and would result in a motion further to the west, perhaps not as far as us, but too close for comfort.

What we need to watch for is what happens when Ivan gets to Cuba on Sunday night. It’s at this point the weakness to the north should be developing and a more northerly motion should begin. This is my “fork in the road” period. If he continues to move more NW then we know that ridge isn’t being broken down as fast and the track will be further west. I do suspect the trends in the models before then would let us know if that were going to be the case anyway.

I guess the bottom line here is that the scenario the models want to go with is encouraging for us, but we need to keep in mind this is a very complex steering situation with some of the highest levels of uncertainty I have seen in quite a while, all that, despite the model consensus. When steering currents become that weak, it gets me nervous… not really for us so much, but for a bust in the track, especially in the extended time periods.

I guess the good news is that Ivan will likely weaken as a move to the north takes place. Shear is also forecasted to increase over him, perhaps within 48 hours. Depending on the track, I don’t think Ivan will be nearly as strong as he is now when he hits the U.S., but he could still likely be a major hurricane.

That’s all for now. I’ll try to get something else up this afternoon.

John


John Gumm
Meteorologist
WWL-TV
1024 North Rampart Street
New Orleans, LA 70116

[BUD]

I feel sorry for everybody in his way, the worst one this year

[artinla]

eric

Excuse my ignorance, trying to learn. I took a look at the graphics, but they left me with more questions than answers.
It appears to me that the storm is moving too slowly and is too far south to get caught in the trough before the high presently over Texas moves into the eastern gulf. (It appears to be moving quickly toward the east) Would this not force Ivan further west before the northward turn?

[LaPlaceFF]

I'll be keeping my eye on Ivan for sure..

[crazycajuncane]

I think it has already shown signs of wanting to head more north than ever before. At this time, I don't see Louisiana as a threat. That can change in a heartbeat. I'm still watching this storm like everyone else, but the northern jog is already happening.

[TSmith274]

It seems to me that whenever someone puts his/her head to it instead of their computer to it, the more the track deviates from the model consensus. That said, I still agree with the models.

[ericinmia]

eric

Excuse my ignorance, trying to learn. I took a look at the graphics, but they left me with more questions than answers.
It appears to me that the storm is moving too slowly and is too far south to get caught in the trough before the high presently over Texas moves into the eastern gulf. (It appears to be moving quickly toward the east) Would this not force Ivan further west before the northward turn?

The high moving in from texas/mexico is a "Blocking High" It is not positioned above Ivan, but will be to the west of Ivan. It will act like a wall preventing Ivan from heading into the GOM theoretically depending on how strong, and east it builds.

High's like the "Bermuda High" are north of the tropical system, and its clockwise current flow would cause the westerlies north of Ivan to strengthen thus pushing him farther west.

This Bermuda high however is under the influence of a building low on its southeastern periphery. This low is weakening the clockwise strength of the high, especially at the lower latitudes... ie. over fla. The high is beginning to retrograde of diminish in this area, and also retreat more northerly.

This allows for the trough to strengthen, and due to storms natural nature to move poleward... eventually the storm will begin a more northward course.

WHERE/WHEN this occurs will mean the difference between the following:
a) The storm to go north through the bahamas and possibly out to sea, or a brush with the carolina's.
b) The storm may head north at about 82-80 west bringing it over south fla.
c) The storm could pass further west before its Northward turn, bringing it into the gulf... from fl, al, west to la.

Hope that helped some.
-Eric