Interesting Discussion from a New Orleans Met.
NEW INFORMATION - The FSU Super Ensemble Model Trends WEST.
Contacts tell me the FSU S.E. model (probably the best model out there) has trended west with the 7pm run from last night, now showing a landfall west of Pensacola, FL. It seems to be picking up on a ridge which is decaying less than what was previously thought. This means the panhandle is certainly still under the gun.
As stated in my previous discussion below, for this thing to do what the models are saying and go up FL proper, a bunch of variables will have to come together just right and the uncertainty remains pretty high that will happen, imo. NHC has their track right on top of the GFDL model now.
Based on this new information about the S.E. model, and my gut feelings all along, I feel as though this track may be too far east. Look for a possible shift in the track eventually if the FSU S.E. continues this trend.
What does this mean for us? Well, it means we are certainly not out of the woods altogether, nor have we been. However, *nothing* I have seen even suggests it will make it this far west and there is new model evidence to suggest that may be difficult. Like David said, the models are a little stronger on this little mini trough coming our way which would tend to keep Ivan away from us. But anywhere along the FL panhandle to Miami appears to be the highest risk at this point, with perhaps the risk increasing for the FL panhandle.
Even though it looks like a strike somewhere in FL is the best bet, there's still the posibility it could come far enough west to get everyone around here nervous.
I'll have more as time allows.
Previous Discussion Appears Below:
*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.
