Tropical Storm Isaac, Part 2: Isaac Moving Into The Gulf Of Mexico-Hurricane Warnings For Morgan City, LA/MS/AL & FL Panhandle To Destin, FL

[Ian]

Uh, "contaminated" by what, number one?

Number two, it's not just the Euro. The GFS, UK and EC (and their ensembles) are now all showing landfall somewhere from LA to near Mobile.

Number three, from a synoptic and climatological perspective, a landfall over the central Gulf coast makes a lot of sense. This system is being primarily guided by strong ridging without any significant trough. The models agree on a dominant ridge setting up east of FL during the day 3-6 period. That strongly suggests a WNW track toward somewhere on the northern Gulf Coast.

Unless something changes with the new data tonight it seems we should be pretty much there for a N GOM landfall. It's certainly not as tricky as if there was strong trough interaction at some point IMO. I guess there might be some room for either way still.. but seems harder to find... not sure I buy the far western idea at the moment anyway. I think the idea of some sort of rapid intensification over the Gulf makes sense given the setup tho hard to buy much with the storm still pretty infantile. Speed may end up important as some models are quite slow which might end up detrimental for landfall strength.

[turtlehurricane]

Fresh sonde, 1002 mb with 30 mph winds, so maybe a sub 1000 low. Recon heading due towards it and already experiencing flight level winds in excess of 45 mph 50+ miles from the center.

1002mb (29.59 inHg) Sea Level (Surface) 27.4°C (81.3°F) 25.2°C (77.4°F) 90° (from the E) 27 knots (31 mph)

[Ginx snewx]

Just a note that the GFS ensemble looks well clustered along the 18Z ops run. There are now no longer any members east of about the far eastern GOM - but there are also no members as far west as the op EC with it looking like the farthest west member being about SE LA.

EDIT: FWIW (and I know it's not much) HWRF has shifted from being east of the track to west. Has landfall as a minimal hurricane (literally 64 kt) over right over the bird's foot of SE LA at 120 hours. These GFS based models seem pretty fast which is why (at least partially) I am guessing they don't intensify the system quite as much as the EC would imply as they have quite a bit less time over the Gulf.

Today's GFS Ens runs from 0z to 18z near landfall time

[Connor McCrorey]

I don't know if this has been mentioned, but it looks like a sonde just measured 1002 mb likely a bit displaced from the center.

Edit - Whoops, looks like I got beat by a minute or so. I do think that Isaac has been consolidating all day and finally achieved the minimum organization necessary to start actually intensifying. Cloud tops have gotten very cold, especially over the western side of the cyclone, and I expect Isaac to begin steadily strengthening throughout the night.

[tmagan]

00Z Observations

[kwt]

NOAA plane just tweeted that the flight level center is south of where they are currently at. Whatever is present looks like its tilted a fair amount still.

[SN_Lover]

It looks like Brad Panovich is thinking the storm will not interact with high mountain peaks and make landfall on the narrow part of Cuba

He also added "Once Issac gets into the Gulf Of Mexico. There are 2 eddies in the loop current which have deep warm water with them. With light shear & humid air intensification could be rapid there. Something to watch closely as the track shifts west."

[HurricaneFrances04]

It looks like Brad Panovich is thinking the storm will not interact with high mountain peaks and make landfall on the narrow part of Cuba

He also added "Once Issac gets into the Gulf Of Mexico. There are 2 eddies in the loop current which have deep warm water with them. With light shear & humid air intensification could be rapid there. Something to watch closely as the track shifts west."

His circle isn't exactly the center of the storm.

[Ian]

It looks like Brad Panovich is thinking the storm will not interact with high mountain peaks and make landfall on the narrow part of Cuba

He also added "Once Issac gets into the Gulf Of Mexico. There are 2 eddies in the loop current which have deep warm water with them. With light shear & humid air intensification could be rapid there. Something to watch closely as the track shifts west."

i got the impression he was just making a wild guess with a wild line but maybe that's his forecast.

[Connor McCrorey]

His circle isn't exactly the center of the storm.

No, but I wouldn't be too surprised if he wasn't as far off as it seems. I get the impression that Isaac is just about done with all this nonsense and finally has a more organized LLC a bit farther south. Recon just turned back in, so we should finally know before too long.

Edit - Eh, looks like they're heading home after all.

[David Reimer]

0Z Early Suite Tracks

[Amped]

[DopplerWx]

Any strengthening will be short lived if it treks across the mountains of hisp. and traverses cuba as the early 00z model suite seems to show. will be tough to get a strong storm in the GOM after that land interaction.

[U_Thant]

Any strengthening will be short lived if it treks across the mountains of hisp. and traverses cuba as the early 00z model suite seems to show. will be tough to get a strong storm in the GOM after that land interaction.

On the other hand, it's pretty hard to significantly disrupt a core that is as sloppy as Isaac's.

[wxsmwhrms]

On the other hand, it's pretty hard to significantly disrupt a core that is as sloppy as Isaac's.

This.

As long as Isaac is as unorganized as it is now, land interaction is not the big concern.

[deltadog03]

I think the Northern CIRC/Vort will become the main one, that is certainly where the best Low Level Conv. There is also some very healthy storms firing there. IMO that bottom part of the big thunderstorm blob will shred off and weaken...

[Derecho!]

Any strengthening will be short lived if it treks across the mountains of hisp. and traverses cuba as the early 00z model suite seems to show. will be tough to get a strong storm in the GOM after that land interaction.

It's only the Southern Peninsula of Haiti now, realistically, and that's narrow and the mountains get lower the further west you go on it. Much less of a big deal than the center of Hispaniola.

[deltadog03]

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[wxsouth]

It's only the Southern Peninsula of Haiti now, realistically, and that's narrow and the mountains get lower the further west you go on it. Much less of a big deal than the center of Hispaniola.

I wouldn't be surprised if the land interaction (as long as its not too lengthy) actually helped focus and organize the low level structure with the help of a little frictional convergence.

[ALhurricane]

I wouldn't be surprised if the land interaction (as long as its not too lengthy) actually helped focus and organize the low level structure with the help of a little frictional convergence.

I was just about to post this very thing. We have certainly seen 'loose' systems aided by frictional convergence in the past.

[wxsmwhrms]

I think the Northern CIRC/Vort will become the main one, that is certainly where the best Low Level Conv. There is also some very healthy storms firing there. IMO that bottom part of the big thunderstorm blob will shred off and weaken...

I know what you're saying and don't disagree. But I would have to say that whatever the larger circulation is that is driving the movement of the convection does not look as though it could be any farther north than about 16N based on satellite. This would also be supported by the fact that there are easterly FL (700 mb) winds south of 16N on the latest recon.

[turtlehurricane]

This.

As long as Isaac is as unorganized as it is now, land interaction is not the big concern.

I would say less of a concern but still a significant concern, Hispaniola can destroy it if it gets caught up in the 2-3 km mountains like so many previous cyclones. Tons of dry air will be pumped into the circulation too as air condenses out on the mountains and compressionally warms on the backside.

Basically we may end up with a ragged mid-level vortex plagued by dry air when the encounter is over, I doubt there will be much of a low level reflection left if it hits the range as forecast.

[wxsouth]

Last several dropsondes and FL winds indicate a sfc center near 16.4N and 69.3W with the 700mb center closer to 15.5N and 68.2W. Roughly 85nm apart.

[wxsmwhrms]

I would say less of a concern but still a significant concern, Hispaniola can destroy it if it gets caught up in the 2-3 km mountains like so many previous cyclones. Tons of dry air will be pumped into the circulation too as air condenses out on the mountains and compressionally warms on the backside.

If it drives across Hispaniola I would agree. However, I am assuming that will do more of a skirt of the SW corner of the island as the forecast shows. And I will admit I still tend to agree with LEK, until I see the actual convective mass and circulation driving it gaining a lot of latitude, I don't think it's inconceivable much of the system ends up skirting or missing Hispaniola.

[Superstorm93]

Yeah, that's a healthy cloud pattern.

Given it's current center location and heading, this will be very close to Hispaniola by tomorrow. I highly doubt we see a significant change in intensity in that time. Same alignment issues that we have had for days now are still obviously occurring. 700mb low is driving the main convective mass while the LLC is way up at 16.7N.

For now, the ECM may have the right idea by keeping this weak until it gets into the GOM

[wxsmwhrms]

Last several dropsondes and FL winds indicate a sfc center near 16.4N and 69.3W with the 700mb center closer to 15.5N and 68.2W. Roughly 85nm apart.

That 700 mb center is what you can see in satellite as a center of circ. The surface center is SW of where NHC called it in the advisory. It's a tough system for them I'm sure, but it seems like overall what recon ends up find for centers is a bit south of what they are carrying in the advisories.

[jhamps10]

That 700 mb center is what you can see in satellite as a center of circ. The surface center is SW of where NHC called it in the advisory. It's a tough system for them I'm sure, but it seems like overall what recon ends up find for centers is a bit south of what they are carrying in the advisories.

could the NHC just be doing a rough compromise from the Satellite imagery and what recon is finding for continuity sake?

[wxsmwhrms]

could the NHC just be doing a rough compromise from the Satellite imagery and what recon is finding for continuity sake?

Probably, and I'm not saying I blame them, as I said it's a tough situation. But it could result in some later jumps due to relocations if/when it ever gets a more aligned center.

[Superstorm93]

That 700 mb center is what you can see in satellite as a center of circ. The surface center is SW of where NHC called it in the advisory. It's a tough system for them I'm sure, but it seems like overall what recon ends up find for centers is a bit south of what they are carrying in the advisories.

This.

I know they are taking a mean of SAT/BUOY/RECON since this is still broad, but that has been pretty much the case since last night.

Once this starts to interact with Hispaniola, I assume specifics will become somewhat more important.

[HKY_WX]

Yeah, that's a healthy cloud pattern.

Given it's current center location and heading, this will be very close to Hispaniola by tomorrow. I highly doubt we see a significant change in intensity in that time. Same alignment issues that we have had for days now are still obviously occurring. 700mb low is driving the main convective mass while the LLC is way up at 16.7N.

For now, the ECM may have the right idea by keeping this weak until it gets into the GOM

I wouldn't expect any sig' intensity changes anytime soon. Even if the center doesn't pass over Hispanola it will disrupt the inflow and limit it for the next day or two. As you stated the euro doesn't ramp it up till it crosses cuba and hits the high TCHP/low shear environment.