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

[mattmfm]

Buoy SW of Key West reporting 63mph sustained http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=MKRAU

[samdman95]

Has to get better organized soon . Next 12 hours are key. If its stil stuck as a ts, it's a launch fail. Gfdl wins

The NWS has it as a TS for the next 24 hours, and it strengthens to a cat 2 before landfall. RI may not be for another day or so (if at all), but if you wake up tomorrow and its still a TS, it still has a chance of strengthening significantly and causing major damage.

[Dsnowx53]

I think you might be commenting on my post. I haven't seen the individual Euro members, but the GFS ensemble members were tightly clustered to landfall, at which time they deviated somewhat. I agree with what you say, but I wanted to just put that out there that the GFS package essentially had one solution with outliers not too far away. It would be interesting to see the Euro members and if they diverge from each other.

I wasn't necessarily responding to anyone directly, but yeah it would certainly be helpful to see the individual Euro ensembles. The GFS individuals certainly had a lot more continuity as you said, so my post might not directly apply--though there were a few right "strayers"...maybe a tiny little gap near the mouth/just east of NO, though that might be stretching it a bit.

I'm also leaning towards a landfall a bit to the SW of New Orleans at this point. I think if the weakness wins out, it would turn NE a bit earlier towards the MS/AL border, and if it doesn't win out, and the ridging dominates, which is what the data has been slowly trending towards, and which is what I favor, then Issac should still turn a bit more WNW before making landfall. I don't like the idea of threading the needle, so to speak.

[OKpowdah]

Per IR and WV, seems like Isaac is dealing with some light SW shear

[turtlehurricane]

Beautiful sunset rapid scan imagery, big convective burst going up. http://www.ssec.wisc.edu/~rabin/goes14/loop_srso.html

You can tell there's shear since the southern edge of the tower quickly goes from anvil to clear air, but the water is super warm under the storm so lots of energy to work with regardless.

[WeatherMimmi]

I wasn't necessarily responding to anyone directly, but yeah it would certainly be helpful to see the individual Euro ensembles. The GFS individuals certainly had a lot more continuity as you said, so my post might not directly apply--though there were a few right "strayers"...maybe a tiny little gap near the mouth/just east of NO, though that might be stretching it a bit.

I'm also leaning towards a landfall a bit to the SW of New Orleans at this point. I think if the weakness wins out, it would turn NE a bit earlier towards the MS/AL border, and if it doesn't win out, and the ridging dominates, which is what the data has been slowly trending towards, and which is what I favor, then Issac should still turn a bit more WNW before making landfall. I don't like the idea of threading the needle, so to speak.

Can anyone comment on the weakness and the signs to look for?

[eyewall]

It looks to me the LLC Is still slightly displaced from the mid level center but it is trying to stack up now.

[LakeEffectKing]

Can anyone comment on the weakness and the signs to look for?

A rule of thumb (sometimes) is to see if you can identify any "oval" or "protrusion" in the mid level circulation pattern of the storm (not always easy to do via IR). Many times a weakness will "show" itself in the orientation of said oval....i.e. a line drawn through the major axis of the oval...

Again....a very rough rule of thumb...use caution.

[turtlehurricane]

Radar indicates that the center is at 24.05 °N, 82.25 °W, almost 20 miles due west from the last recon position. My chances of chasing this are diminishing since I'm not going into the swamps of Louisiana.

[EasternUSWX]

Convection is increasing nicely this evening. Best this storm looked in over 24hrs.

[Dsnowx53]

The 18z GFS shows a very similar track to 12z. However, it is a tad faster, which is a good thing for New Orleans. Additionally, its faster progged speed means that it also stalls a bit further WNW, so the prolonged flooding scenario wouldn't be as prolific as it was on the 12z.

[DaculaWeather]

Looks like it might be trying to develop a core

[CooL]

Big time thunderstorms over the center and Isaac is getting much more symmetrical. It looks way more healthier than it did 12 hrs ago.

[David Reimer]

-83C cloud tops with the blowup west of Key West.

[Derecho!]

P-3 Dropsonde at 992 mb with a 24 kt surface wind - actual pressure probably something like 990-991.

Or maybe not - dropped another one 3 minutes later with 992 mb, but 7 kts.

[Buckeye05]

Am I the only one seeing circulation within the actual precip. on radar? Maybe I have been watching radar/satellite loops too long.

[Superstorm93]

I'm pretty surprised that this is still not strengthening. I would have thought it would have been able to build an inner-core by this time at the very least.

Regardless, if it does not so so within the next 12-18 hours, the stronger intensity models will more than likely bust too high.

[David Reimer]

Am I the only one seeing circulation within the actual precip. on radar? Maybe I have been watching radar/satellite loops too long.

Precipitation will rotate around the center of circulation, so you are indeed seeing the circulation on radar. As the southern semicircle fills in, you'll be able to notice it even more.

[DeltaPilot]

Looks to me that the latest burst of convection coupled with those cold tops is the first sign of what a lot of the models are showing towards strengthening and better organization.

[WeatherMimmi]

Can someone comment in laymens terms on what is causing one track to be to the West of the cone and one to the East. and what we are looking for to see what track actually pans out?

[Buckeye05]

Precipitation will rotate around the center of circulation, so you are indeed seeing the circulation on radar. As the southern semicircle fills in, you'll be able to notice it even more.

Not what I am saying, I thought I was seeing a closed circulation in the precip shield. I think I am hallucinating. Time for a break.

[dan88]

Not what I am saying, I thought I was seeing a closed circulation in the precip shield. I think I am hallucinating. Time for a break.

That likely would be the mid level circulation, which appears to be separated from the low level circulation off to the South.

[andyhb]

I'm pretty surprised that this is still not strengthening. I would have thought it would have been able to build an inner-core by this time at the very least.

Regardless, if it does not so so within the next 12-18 hours, the stronger intensity models will more than likely bust too high.

Pressure is dropping, so it does look to be intensifying/organizing better than previously, considering the winds will lag behind due to the storm's size.

[thewxmann]

The map that Superstorm posted indicates about 10-20 kt of southerly shear. However, this was well-captured by the models so it is not surprising by any means. Southerly shear should decrease in the next 24 hours, after which intensification can begin in earnest.

[Geos]

Can someone comment in laymens terms on what is causing one track to be to the West of the cone and one to the East. and what we are looking for to see what track actually pans out?

I know one thing at least is the interaction with the ULL that is off the Yucatan Peninsula. Which is tugging it to the west more.

[Superstorm93]

Pressure is dropping, so it does look to be intensifying/organizing better than previously, considering the winds will lag behind due to the storm's size.

I doubt we will see any substantial wind increase until the system becomes aligned (I feel like a broken record saying this throughout the storms life)

[HKY_WX]

The outflow channel is really starting to expand over the east coast. This should really start to help CDO growth and the appearance as we head through the night.

[David Reimer]

Just a reminder for everyone, but if the pressure continues to drop don't be surprised if we see a sudden reaction with the winds. The same thing happened with Katrina for about 24-36 hours after it moved into the Gulf of Mexico. Although Katrina's pressure fall was on a much larger scale, it serves as a good example.

[QVectorman]

I'm pretty surprised that this is still not strengthening. I would have thought it would have been able to build an inner-core by this time at the very least.

Regardless, if it does not so so within the next 12-18 hours, the stronger intensity models will more than likely bust too high.

It's interesting to see that the models with the lowest error on intensity forecasts generally are keeping below 60 knts for the next 48 hrs and avg. max intensity is 61 knts at 72 hours. Not saying that they will verify just interesting contrast to the 85 kt forecasts from NHC

[CoastalWx]

Can someone comment in laymens terms on what is causing one track to be to the West of the cone and one to the East. and what we are looking for to see what track actually pans out?

Well basically one set of models say that this will continue to be steered by a ridge to the north with it acting like a wall and little chance for it to move north. Another set of models say that there will be just enough of a weakness in the mid and upper levels such that the flow within these levels will help turn the storm north towards MS and AL. The weakness is basically an extension of the upper level trough over the southeast.