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

[Baroclinic Zone]

Euro ensembles at hr 66 have Isaac at the mouth of the MS delta in LA.

So that puts them W of the OP?

[Sunny and Warm]

It is sort of the opposite...but models are models and they don't always have to behave the way we think they may. It's possible the euro and its resolution may be picking up the tendency for lower heights down that way, but that is just a WAG. I'm just getting back from being away, so perhaps someone else who has looked at this a lot more in detail can answer.

Thanks for your insight regardless. I never would have thought to look that high up. It gives a greater impression to the hobbyist as to what you guys/gals go through before you even think of speaking one word of a forecast. Humbling really to be able to converse with you guys on such a heady subject as a possible cat 2/3 heading for the gulf coast.

Feel free to delete this post, but felt I needed to say it. This is one of the best tropical threads I've ever seen for its pure meteorology.

[CoastalWx]

So that puts them W of the OP?

Yeah looks like it. More like SW of the op at the same time...hr 66.

[CoastalWx]

PSU is this what you meant? I only see 00z.

[CoastalWx]

So that puts them W of the OP?

They then crawl north and a little spread develops. Looks like anywhere from near NOLA to eastern MS by hr 84.

[Baroclinic Zone]

Yeah looks like it. More like SW of the op at the same time...hr 66.

I'll also add that that would seem to be in line with the 12z GFS Ensm mean as well. Looking at h60 on Raleigh's maps.

[PSUBlizzicane2007]

PSU is this what you meant? I only see 00z.

Thanks for posting this... while I haven't seen this *exact* product before, it is very helpful to see what the EnKF (I always mix up the caps on this) version of the GFS shows.

I know it runs later than the normal GFS times, so 00Z should be the only one available. I find it intriguing that, compared with the 00Z hybrid operational GFS and the Euro solutions, the full EnKF exp GFS is closer to the Euro.

[Sunny and Warm]

They then crawl north and a little spread develops. Looks like anywhere from near NOLA to eastern MS by hr 84.

If memory serves, that's two runs in a row where the Euro ENS mean was closer to the GFS ENS mean than the Euro operational. In fact, if I were forecasting, I might blend the two ensembles means and leave the operationals on the sidelines. That would give a Katrina-like landfall clipping the delta and landing on the MS coast just east of Lake Ponchatrain neading nearly due north.

[Uncle Bobby]

I think it's worth noting that there has apparently been zero tornado activity in FL thus far.

[Snow_Miser]

The overall presentation of Isaac on the Visible and Water Vapor imagery looks substantially improved from this morning. You can see that it is trying to form a symmetric CDO with more convection flaring up to the eastern flank of Isaac's circulation.

Also note the expandng outflow, which indicates a very benign environment in terms of wind shear.

[CoastalWx]

Like CUMet said...the overall cirrus canopy is spread out better..especially on the west side. Probably a sign the ULL to the SW is moving out of the way.

[LakeEffectKing]

Here's the 06z:

[PSUBlizzicane2007]

Here's the 06z:

Thanks! What's interesting about this one is how it predicts the weakness to be strong enough to pick up Isaac versus the operational hybrid GFS which has it following the Louisiana coast.

[Dsnowx53]

Be careful with ensemble means when there are two separate clusters of tracks. The mean might split the difference, even though synoptically, a split might be tough to come by.

[Ed Lizard]

The center is somewhat obvious, I wonder if we'll get a clear eye while in BYX radar range.

[Sunny and Warm]

Be careful with ensemble means when there are two separate clusters of tracks. The mean might split the difference, even though synoptically, a split might be tough to come by.

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.

[dan11295]

202330 2403N 08158W 8430 01437 9923 +207 +182 133014 019 026 003 00

Am guessing pressure is down to ~991 mb now.

[LakeEffectKing]

Thanks! What's interesting about this one is how it predicts the weakness to be strong enough to pick up Isaac versus the operational hybrid GFS which has it following the Louisiana coast.

Yeah, I'm not sure what to make of it....a lot of times, these differences in tracks, intra-model or between models is a result more of the speed of the storm (at these type leads), but I'm not seeing anything that is overwhelmingly different speed wise.

This must just be one sensitive steering environment that is progged.

I'm LEANING to a JUST west of NO hit at this time...but most certainly not sold at all!!! Hoping, as you, that 00z can tighenten up the envelope.

What % numbers would you put at Isaac reaching cat 3 or higher during it's lifetime?? I'd go with 30-40%....

[PSUBlizzicane2007]

Yeah, I'm not sure what to make of it....a lot of times, these differences in tracks, intra-model or between models is a result more of the speed of the storm (at these type leads), but I'm not seeing anything that is overwhelmingly different speed wise.

This must just be one sensitive steering environment that is progged.

I'm LEANING to a JUST west of NO hit at this time...but most certainly not sold at all!!! Hoping, as you, that 00z can tighenten up the envelope.

What % numbers would you put at Isaac reaching cat 3 or higher during it's lifetime?? I'd go with 30-40%....

I'd say it's fairly likely it reaches cat 3. Percentage wise, I'm not sure, but the trends on the models... especially the Euro... for intensity are very concerning.

[Ginx snewx]

Yeah, I'm not sure what to make of it....a lot of times, these differences in tracks, intra-model or between models is a result more of the speed of the storm (at these type leads), but I'm not seeing anything that is overwhelmingly different speed wise.

This must just be one sensitive steering environment that is progged.

I'm LEANING to a JUST west of NO hit at this time...but most certainly not sold at all!!! Hoping, as you, that 00z can tighenten up the envelope.

What % numbers would you put at Isaac reaching cat 3 or higher during it's lifetime?? I'd go with 30-40%....

Yikes. Most unsettling has been the tendency of a deeper broader storm being portrayed by the Euro. With the consensus slowly consolidating on a LA to Miss landfall, intensity and forward speed will be what the emphasis will turn to. Model depictions are consistently ramping up and slowing down. Very disconcerting.

[Indystorm]

Hooray! We can finally say we have an obvious center compared to multiple rotating gyros of the past few days south of Hispaniola. I do think tonight's Dmax will be very interesting and of course the 00z model suite. The storm is improving in satellite presentation, is quite large, and I am becoming quite concerned for the LA/MS coastal area.

[jconsor]

The agreement of a good number of the GFS EnKF ensembles with the 12Z Euro ensemble mean on a track 50 miles either side of the mouth of the Mississippi lends more confidence to the forecast track.

Also, the fact that Isaac continues on a WNW (~285-290 degree track) despite model projections of a ~300 degree track is interesting. Current recon puts Isaac already about 30 miles south of the 15Z NHC forecast track.

[LakeEffectKing]

Hooray! We can finally say we have an obvious center compared to multiple rotating gyros of the past few days south of Hispaniola. I do think tonight's Dmax will be very interesting and of course the 00z model suite. The storm is improving in satellite presentation, is quite large, and I am becoming quite concerned for the LA/MS coastal area.

I think we still have a solid 12-18 hours of organizational tasks to take care of before we entertain rapid/robust/significant intensification. We have essentially 1 spiral "snake" that needs more feeder bands to effectively utilize the theromodynamic energy of the oceanic surface. Most models indicate that the entire footprint/circulation envelope will moisten up considerably over the next 12-18 hours....then.....we watch to see a fuse lit......and what fireworks is at the end...

[Ginx snewx]

THE HURRICANE WATCH IS CHANGED TO A HURRICANE WARNING FOR THE

NORTHERN GULF OF MEXICO COAST FROM EAST OF MORGAN CITY LOUSIANA TO

DESTIN FLORIDA...INCLUDING METROPOLITAN NEW ORLEANS...LAKE

PONTCHARTRAIN...AND LAKE MAUREPAS.

[N. OF PIKE]

Anyone ,What is the radius of tropical storm winds as well as hurricane force winds FOrecast to be by tuesday pm. Getting very concern'd regarding storm surge,esp if this starts crawlin late tuesday. Thanks. To me it seems this storm has really not been given the chance in the last several days to show us just how large he really is.

[dan88]

000

URNT12 KNHC 262059

VORTEX DATA MESSAGE AL092012

A. 26/20:24:50Z

B. 24 deg 00 min N

082 deg 01 min W

C. 850 mb 1368 m

D. 42 kt

E. 036 deg 35 nm

F. 118 deg 46 kt

G. 039 deg 57 nm

H. 992 mb

I. 17 C / 1511 m

J. 21 C / 1524 m

K. 18 C / NA

L. NA

M. NA

N. 12345 / 8

O. 0.02 / 2 nm

P. AF309 2109A ISAAC OB 18

MAX OUTBOUND AND MAX FL WIND 52 KT NW QUAD 20:37:20Z

[hm8]

Hurricane Warning for New Orleans, track shifted west...

[SnowGoose69]

Anyone ,What is the radius of tropical storm winds as well as hurricane force winds FOrecast to be by tuesday pm. Getting very concern'd regarding storm surge,esp if this starts crawlin late tuesday. Thanks. To me it seems this storm has really not been given the chance in the last several days to show us just how large he really is.

This is a storm that would have potential for TS wind radius around 250-300 miles and hurricane maybe 80-100 in the worst case situation. The good news possibly with Isaac is that even if it does become a major hurricane it may do so late enough that the surge may be lagging a bit much as was the case with Charley in 04 which had nothing even resembling a cat 4 as far as storm surge since the storm had only become a cat 4 hours before landfall.

[EasternUSWX]

I think we still have a solid 12-18 hours of organizational tasks to take care of before we entertain rapid/robust/significant intensification. We have essentially 1 spiral "snake" that needs more feeder bands to effectively utilize the theromodynamic energy of the oceanic surface. Most models indicate that the entire footprint/circulation envelope will moisten up considerably over the next 12-18 hours....then.....we watch to see a fuse lit......and what fireworks is at the end...

The last few frames on radar actually form some of those feeder bands you mentioned. Pretty neat.

[turtlehurricane]

The shear must be getting to it since the circulation is staying at the very southern edge of the convection. We'll see if the next recon pass shows it's holding the same intensity, that might be the case considering Doppler velocities haven't increased. Pretty much agree that this needs another 12 hours or more of organizing as well as a decrease in shear.