Hurricane Irene (Significant U.S. Threat)

[Fred Gossage]

The 12Z Euro ensemble mean is a hit very close to New Orleans...

Early afternoon thoughts....
 
The chances of this being an East Coast or recurver are highest if the system gets north of the big Caribbean islands prior to 144 or so hours from the 12Z runs today. This puts it ahead of the first trough that will be exiting the eastern United States early to middle of next week. If not, it doesn't get picked up by that trough, and gets influenced by ridging that builds in behind it. A lot of things can change... but with this convective blow-up being almost completely on the north side of the circulaton today... with that placement of the circulation, and the structure as it's approaching the Caribbean, I think the odds are increasing that this may go south of Hispanola. If we do get the system to miss next week's trough.... history has shown us over and over again that the westward building of ridging north of a tropical cyclone is almost always underdone in the models, especially when the tropical system is an intense one... and there is the potential for "ridge pumping" with the latent heat being released through the northern outflow channel. All nothing more than speculation right now, but it's things to keep in mind if we don't get this to go north of the big islands.

[Fred Gossage]

Cyclonic, if you look at visible satellite and low-level vorticity plots... the low-level center is not under that convection... it's on the south side of it. closer to 12 deg N.

[Cyclonicjunkie]

Cyclonic, if you look at visible satellite and low-level vorticity plots... the low-level center is not under that convection... it's on the south side of it. closer to 12 deg N.

The convection is showing signs of bending towards the south. which leads me to believe that the center may be reforming underneath or at least that's what the convection is tricking my eyes to believe.

[Fred Gossage]

The convection is showing signs of bending towards the south. which leads me to believe that the center may be reforming underneath or at least that's what the convection is tricking my eyes to believe.

That's what the convection is tricking your eyes into believing. It is becoming banded... and banding toward the low-level vorticity. But that vorticity is centered near 12-13 N. That area in the east side that has kinda cleared out... is the dry air wrapping back in... not a new center forming. The overall circulation envelope is large; so, the circulation can redevelop SLIGHTLY after convection is firmly established... but it's too early for that. The low-level vorticity is co-located under the mid-level vorticity (a good sign), but that's all located on the southern side of the big convective blowup. Still, as you've mentioned, to see this kind of blow-up and banding... in the middle of the day, and in the presence of this much dry air... with the upper-outflow expanding toward the dry air.... is a very ominous sign.

[Fred Gossage]

Here's you a visual aid...



Note the structure of the low-level clouds south of all the convection...

[Cyclonicjunkie]

Here's you a visual aid...



Note the structure of the low-level clouds south of all the convection...

Yeah that seems to be about right, I pictured it just a hair north of there but you know how hard a exact center can be to locate on such a weak system. Anyways, when I came in from work, didnt expect convection to be as widespread as it is until at least tomorrow due to all the dry air. I imagine conditions will only get better for development from here on out..with the only possible hurdle being the mountain ranges on the islands of Hispaniola and Cuba...

Will be the most interesting system to watch this season thusfar.

[Cyclonicjunkie]

Looks like the center of circulation has reformed  near 15-16 north / 51 west, not sure if it has worked itself all the way down to the surface yet, but it's definately trying. As you can tell, dry air is still doing it's best to inhibit convection but this will escape the dry air sooner or later.

[Fred Gossage]

It's much closer to the 13-14N region.



Note the arcing bands on both sides that converge near 14N.

[Cyclonicjunkie]

I was just estimating, there may be some competing vorticies going on here. At any rate the NHC does list it at 13N in their discussion but its clearly a little north of there on IR.

As I said earlier its really difficult to pinpoint the exact location on weaker systems that lack alot of convection due to the ascat, windsat and microwave not being able to pick up on a well established center point of organized convection.

It may be more of a mid level center closer to 15N and a low level center further south near 13N...There is one thing that is certain, it has my attention. I cant get over how consistent the GFS has been at putting a well developed hurricane near S FL.

It will be interesting to see if it survives those Islands if and when it forms.



0Z Models have South FL in their crosshairs if you chase Hurricanes Key West seems to be as good a spot as any

[Cyclonicjunkie]

97L is starting to work the dry air out, and is quickly becoming better organized. A upper level Anticyclone is nearby and trying to become stacked overhead, when that happens this will more than likely become a very organized tropical storm rather quickly.



After that, eyes will turn to where this is headed, and that depends on ALOT of different factors, with strength of storm probably being the most influential aspect IMO.

This is going to become a well developed tropical cyclone at some point but it's hard to say how quickly it does this. If it doesn't do it really quickly, the threat to the U.S will become more likely. It's going to head in a general direction of FL due to steering currents.



Now it seems a little further north than it should be to my eyes which may keep it away from the gulf of Mexico. If it goes north of the islands it would be more likely to effect the Bahamas and the eastern coast of FL and possibly the Carolina's or none of the US mainland and this scenario would probably play out if the storm becomes a monster real fast like.

If it stays south of the islands it will probably be Gulf of Mexico bound and one beast of a Hurricane. If it tracks over the islands it will likely weaken a bit before landfalling on the southern tip of FL.

So there is still alot at play here





Alot of the 12z ensembles take this south of Hispaniola

[ajatwister]

Going to be a tropical depression anytime now. Recon reporting tropical storm force winds.

[Cyclonicjunkie]

18z NAM misses Hispaniola to the south...if that happens it really gives this a better chance of a Major hurricane in the GOM

[Cyclonicjunkie]

A upper level Anticyclone is nearby and trying to become stacked overhead, when that happens this will more than likely become a very organized tropical storm rather quickly.

The upper level anticyclone has done it's dirtywork and the NHC best track has this skipping Tropical depression and is going straight to Tropical storm Irene. This one is really getting it's act together fast and at this rate it wont be too long before this is Hurricane Irene.

Probably be a special advisory issued by the NHC anytime now or they may just wait til 8pm EST.

EDIT: It's official now

[harlequin]

This is going to be such a tricky path.

[Cyclonicjunkie]

This is going to be such a tricky path.

Yeah, I would hate to be in the NHC's shoes right now, trying to forecast the track and intensity.I wouldnt even want to attempt it. The slightest shifts to the west or east will have huge impacts on a forecast.

Updating infared satellite



18zGFDL misses all the islands to the south and sends it toward the central Gulf of Mexico at 921Mb
That would suggest a Category 4 Hurricane, but this particular model has not been too accurate this year IMO.





Only one ensemble member is on the east side of FL now..it's hard to ignore such a gathering of ensembles.




But the COC of the cyclone still appears to be north of the NHC placement. I'm not sure if the MLC is still north of the LLC, but that would be the only explanation of the COC being further north than the NHC's placement of the TC. Also the storm appears to be heading more NNW than W, but trying to pinpoint centers and motion from satellite can be quite tricky.