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

[Superstorm93]

Interesting tidbits from the disco:

-DESPITE THE GENERAL

WESTWARD SHIFT...THE HWRF AND CANADIAN MODELS STILL CALL FOR ISAAC

TO MOVE UP THE FLORIDA PENINSULA.

-HOWEVER...THE ENVIRONMENTAL CONDITIONS

ARE FAVORABLE FOR RAPID INTENSIFICATION...WHICH COULD OCCUR IF THE

CYCLONE DEVELOPS A WELL-DEFINED INNER CORE.

[Amped]

Taking a big step back... The system looks less organized on IR imagery than it did yesterday or last night. Even when recon was having trouble locating a center, it still looked good and had that spectacular outflow pattern. Totally it looks a bit more scrambled, in my opinion.

One little Tstorm that presists near the center is actually better than a big blobs for the development of a TS , rapidly expanding convection is a sign that the ciculation can't control the bands. TCs need to start in first gear and work their way up slowly.

[turtlehurricane]

I don't think they "aborted" the mission. They flew all the way from Miami, so there probably was limited time to complete additional passes. It looks like they are flying back in that direction as well.

Something weird definitely happened since they're flying back towards Isaac now. Never seen that before.

Maybe they're trying to sample upper level winds around the storm??? Still above 30k feet.

[Derecho!]

Interesting tidbits from the disco:

-DESPITE THE GENERAL

WESTWARD SHIFT...THE HWRF AND CANADIAN MODELS STILL CALL FOR ISAAC

TO MOVE UP THE FLORIDA PENINSULA.

-HOWEVER...THE ENVIRONMENTAL CONDITIONS

ARE FAVORABLE FOR RAPID INTENSIFICATION...WHICH COULD OCCUR IF THE

CYCLONE DEVELOPS A WELL-DEFINED INNER CORE.

I like Beven and all, but the HRWF and CMC actually kept him from moving the track further left? (as implied by the wording) Seriously? Of course avoidance of windshield-wiping, etc. are other reasons as well, but still.

[Superstorm93]

USAF Plane is heading back for Isaac

NOAA P-3 jet is in the lower right hand corner

[CUmet]

Ah, cool! So you think the center is near 15N-- not further N?

I don't think it's that far south, but it is definitely south of the 16.0N estimate given in the latest advisory. Of course the question is whether this is the "real" LLC or just a small vorticity center rotating around a larger, broad one. I will say, though, that we haven't seen such a strong, well-defined low level circulation in flight-level and surface data for quite some time, and this will likely take over as the "main" circulation center if it hasn't already.

[dan88]

Something weird definitely happened since they're flying back towards Isaac now. Never seen that before.

Maybe they're trying to sample upper level winds around the storm??? Still above 30k feet.

When they left, communications seemed to have been having problems for a while and there was a 30 minute period without anything coming from recon, an issue which appears to have since been fixed.

[Ginx snewx]

Euro Ens like Louisiana, NHC slowly moving west and increasing intensity.

[LakeEffectKing]

I'm kinda surprised the NHC hasn't altered their track near Cuba much....the Euro has been rock steady with that part of the track (along or just off the southern shore) vs. most other models that have been over or to the north of Cuba.....and many have trended south. I'd give Isaac about a 70% chance of missing D.R./Haiti and a 50% chance of it missing Cuba.

[Superstorm93]

12z ECMWF EPS Control is a carbon copy of the OP.

Seems like the 12z ECM wasn't too crazy with it's shift west since the ensembles like it as well.

[phil882]

Something weird definitely happened since they're flying back towards Isaac now. Never seen that before.

Maybe they're trying to sample upper level winds around the storm??? Still above 30k feet.

Yea strange flight path...

In other news, one of the mesovorticies rotating around this system is just off the coast of Puerto Rico. Does not seem like the main center though which is much broader and rotating these disturbances within its broad envelope.

[CUmet]

The circulation has become better defined in the low-levels, but conversely, it still looks like dry air is intruding into the circulation, which is resulting in the degraded satellite appearance. Soundings from the ABC islands in the Netherlands Antilles clearly show dry air still being advected into the circulation.

How much is the air recovering due to surface fluxes off the ocean before it gets to the inner core, though? I don't know the answer to that question, and I'm too lazy to do the calculations, but it is something to consider.

[turtlehurricane]

When they left, communications seemed to have been having problems for a while and there was a 30 minute period without anything coming from recon, an issue which appears to have since been fixed.

I'm wondering if this is some sort of joint mission between the P-3 and the G4, both are sampling the upper levels simultaneously in different spots right now. The fact that the P-3 released a dropsonde at upper levels is another thing that makes me think that.

[phil882]

How much is the air recovering due to surface fluxes off the ocean before it gets to the inner core, though? I don't know the answer to that question, and I'm too lazy to do the calculations, but it is something to consider.

That's true, I am sure there is some recovery time, but the rather chaotic pattern witnessed on satellite and microwave imagery argues that the dry air is making it into the inner core.

[MGorse]

I'm wondering if this is some sort of joint mission between the P-3 and the G4, both are sampling the upper levels simultaneously in different spots right now. The fact that the P-3 released a dropsonde at upper levels is another thing that makes me think that.

From the NHC 5 PM discussion:

THE NOAA G-IV JET AND AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT ARE CURRENTLY CONDUCTING A SYNOPTIC SURVEILLANCE MISSION AROUND ISAAC. THE DATA WILL BE AVAILABLE FOR THE 0000 UTC MODEL RUNS.

[PSUBlizzicane2007]

I'm kinda surprised the NHC hasn't altered their track near Cuba much....the Euro has been rock steady with that part of the track (along or just off the southern shore) vs. most other models that have been over or to the north of Cuba.....and many have trended south. I'd give Isaac about a 70% chance of missing D.R./Haiti and a 50% chance of it missing Cuba.

You're kidding, right? There is pretty much no way this misses Cuba unless it goes as far east as the spine of Hispañola (very unlikely) or threads the needle in the windward passage after going over Haiti.

[HurricaneJosh]

One little Tstorm that presists near the center is actually better than a big blobs for the development of a TS , rapidly expanding convection is a sign that the ciculation can't control the bands. TCs need to start in first gear and work their way up slowly.

I wasn't talking abo the big blobs-- I was talking about the overall symmetry, the apparent banding, and the outflow pattern. Anyhoo...

[LakeEffectKing]

You're kidding, right? There is pretty much no way this misses Cuba unless it goes as far east as the spine of Hispañola (very unlikely) or threads the needle in the windward passage after going over Haiti.

Euro has had this brushing the southern coast for days....so no, I'm not kidding!

Edit: I should clarify, it should miss the eastern 3/4's of Cuba.....the mountainous part....of course it will cross over at least the western tip....

[PSUBlizzicane2007]

Euro has had this brushing the southern coast for days....so no, I'm not kidding!

The 12Z Euro has it passing over western Cuba and has had it passing over Cuba for multiple runs. I'm not sure what you're looking at.

[Ginx snewx]

I wasn't talking abo the big blobs-- I was talking about the overall symmetry, the apparent banding, and the outflow pattern. Anyhoo...

Troy Landry and Lizbeth might have a room for you on the bayou. Conditions look pretty sweet after emergence. This started out for me as a meh, but it is getting synoptically interesting and looks to be a huge threat down the road, based on current upstream predicted environmental conditions. Initial west side shear and dry air might at first delay RI , but if the modeling is correct...JMHO

[wxmeddler]

About the recon. Here is the flight plan for the G-IV and since the C-130 came from Biloxi, it looks like they made a quick center fix before going up higher (saves fuel too) and drop a few sondes to help out the work that the G-IV is doing before turning for St.Croix. The P-3 is doing its own mid-level thing with the radar mission.

[wxsniss]

Comments on lack of an inner core?

Plenty of southwesterly wind readings on recon southwest of the last center fix:

[phil882]

Time to do some global model fact checking with the mid level ridge... lets compare the NOAA G-IV mission to the forecast 18z GFS heights at 500 hPa.

At Sounding Closest to 22N 70W

G-IV: 5900 m

GFS: 5893 m (8 m too weak)

At Sounding Closest to 24N 75W

G-IV: 5900 m

GFS: 5898 m (2 m too weak)

At Sounding Closest to 26N 67W

G-IV: 5910 m

GFS: 5917 m (7 m too strong)

At Sounding Closest to 26N 78.5W

G-IV: 5890 m

GFS: 5891 m (1 m too strong)

Based on the obs so far, the 18z GFS seems to be capturing the ridge pretty accurately with only minor errors both on the stronger and weaker side depending on what sounding you look at.

[phil882]

Comments on lack of an inner core?

Plenty of southwesterly wind readings on recon southwest of the last center fix:

They are flying at 500 hPa in which the circulation is displaced well to the south of the low-level circulation center.

[turtlehurricane]

Comments on lack of an inner core?

Plenty of southwesterly wind readings on recon southwest of the last center fix:

Note that they are at 15k-30k feet where the SW winds south of the center are, in the outflow layer so winds spiral anticyclonically outwards from the center as observed.

[wxmx]

Comments on lack of an inner core?

Plenty of southwesterly wind readings on recon southwest of the last center fix:

I guess you meant southeasterly winds. The reason is that it's a very shallow vortex, 850mb and below, and recon is flying above that, where there is a strong easterly flow. If you look at the dropsonde you will see the SW winds there.

[neweathereye]

I am wondering if we have an over zealous Euro with its track towards NO...and what about this upper level parked in the GOM and the upper level low center just ahead of Issac,it seems as though these two systems may just pull Issac more northwards into Fla then westwards and eventually onto the East side of Florida..I am just not seeing it. The movement has been more WNW all afternoon then westwards,so be it that it is pulled across Cuba,it will have ample time to juice up and intensify once it nears the Keys...Maybe I'm not making sense here,,and I don't post often here,its just a observation. We shall see what happens tonight with the new model runs.

Thanks for reading

Craig

http://northeastweathereye.com

Augusta Maine

[andyhb]

18z GFS going west, looks like a Biloxi landfall.

[Superstorm93]

NOAA P-3 plane confirms that the 700mb low is south of the weak LLC.

1002 mb extrapolated surface pressures for a long stretch.

Here is the twitter feed for the NOAA Jet.

HRD/AOML/NOAA ‏@HRD_AOML_NOAA

#NOAA42: At our Initial Point winds at flight-level very weak, surface winds strong, suggesting storm still disorganized

[wxmx]

NOAA P-3 plane confirms that the 700mb low is south of the weak LLC.

1002 mb extrapolated surface pressures for a long stretch.

Here is the twitter feed for the NOAA Jet.

The difference now is that the lowest pressure coincides with the wind shift....if this vortex takes over...I'll let it at that.