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

[tornadotony]

In the short term, the longer Isaac takes to organize, the MORE concerned I would actually be about the Gulf Coast. Given the likelihood of a significantly favorable environment in the Gulf, IMO, the longer that it takes to organize and begin a faster intensification, the lower the probabilities that Isaac would begin an ERC near landfall. Of course, given that we are about 66 hours to landfall, it could begin strengthening faster 24h from now and still have a good shot at an ERC. But IMO, each passing few hours shaves a small probability from that and slightly increases the stakes along the Gulf Coast. Now if we don't see decent organization by, say, tomorrow evening, then I would expect prospects for a major landfall to decrease. As of right now, though, I think the odds of a major hurricane strike on the Gulf Coast are rising, albeit slowly.

[EasternUSWX]

Given the visible and IR presentation I think Isaac is going to start an intensification trend soon.

Agree and radar looks like it as well. Recon on the way to see what we got going on.

[jasons]

Something to keep in mind...while Isaac may be getting better organized, be careful of using radar to draw conclusions. As the center gets closer to radar, the resolution is better, so the presentation will look better too.

[heavy_wx]

Something to keep in mind...while Isaac may be getting better organized, be careful of using radar to draw conclusions. As the center gets closer to radar, the resolution is better, so the presentation will look better too.

More importantly, the radar will be sampling closer to the surface and will give a better idea of the LLC.

[tornadotony]

Something to keep in mind...while Isaac may be getting better organized, be careful of using radar to draw conclusions. As the center gets closer to radar, the resolution is better, so the presentation will look better too.

This is a good point. Don't forget a few days ago with TJUA was picking up Isaac to the south. The MLC was clearly visible on radar but the LLC was still displaced well to the N at the time. Always check LLC position against any vortex a radar is picking up, especially if that vortex is far from the site and being sampled in the mid-levels.

[SN_Lover]

Given the visible and IR presentation I think Isaac is going to start an intensification trend soon.

that and the fact that this system is massive in size. outflow stretches far from the center already.

[HurricaneJosh]

Landfall near Biloxi with winds of 90 kt.

[HurricaneJosh]

New forecast barely makes Isaac a Cat 2.

Landfall point is Alabama.

Huh? They have it near Biloxi with winds of 90 kt, which is as high was it was before.

[wxmx]

This have been talked extensively in this thread, but I fear the GFS shift west is for real, as it becomes clearer the trough will completely bypass Isaac, and some ridging builds north. The Euro will probably confirm this in the 12z run. This reduces the risk for the FL panhandle and increases it for Louisiana. Also, the ridge is not that strong that far east, so it will probably be a slow mover from just before landfall to a bit after it, as the Central Plains ridge plays the role of a blocking high. It also looks as it will be a little bigger than an average cyclone to me.

Currently it looks it's organizing slowly but surely, and that will probably continue for the rest of the track up to landfall, with a better chance of slightly faster strengthening rate 24 hours prior to landfall.

[Superstorm93]

Huh? They have it near Biloxi with winds of 90 kt, which is as high was it was before.

My program was showing a cached forecast. My bad...

[HurricaneJosh]

The Discussion is really short and cryptic. I was hoping for more analysis of the model spread, the reasons, and why one solution might be better than the other.

[phil882]

Maybe a pro-met can chime in, but looking at Isaac's path the last few days, and his path of jumping north towards Haiti and then hugging the north coast of Cuba, could this be a case of the frictional effects on the winds 'pulling' the center towards the coast(s)?

A certain un-named met talked about this at length in his column years about when Isidore would not 'let go' of the Yucatan. The accelerating wind over water would hit land, slow down, and act to tug on the core and pull it inward back to the coast. Isaac's path resembles a weaker version of this Idisore-like land effect. Now Isaac is significantly weaker, so it may not hold water in this case, but is there any validity to it, or can this trend be solely attributed to the mid-upper steering currents?

There is a thread I made several days ago on this...

Again, a lee cyclone was produced on the SW part of Hispaniola and SE portions of Cuba, where the high terrain was located. It has since moved wnw into the Western Caribbean. Isaac has been rotating north of this feature and undergoing binary interaction, which is why we saw the shift from NW to WNW over the past 24 hours as Isaacs circulation both feels the effects of the strengthening mid-level ridge, and rotates counter clockwise around this larger circulation.

[phil882]

The large size of the storm in my opinion is going to hurt it intensity wise. The reason being is that the winds in advanced of the storm are already upwelling the waters well ahead of Isaac's inner core. You can see how in key west, water temperatures are falling a good 24-36 before Isaac makes its final approach.

[Dunkman]

pressure steady.

LLC is mia though, 24kts. of wind on the surface at the 850mb center.

edit: Or not, nice 6kt. winds on the dropsonde and 996mb. Looks like Isaac isn't doing so bad.

[Superstorm93]

LLC is mia though, 24kts. of wind on the surface at the 850mb center.

Still close to the Cuban coast

000

URNT12 KNHC 261544

VORTEX DATA MESSAGE AL092012

A. 26/15:27:10Z

B. 23 deg 38 min N

080 deg 57 min W

C. 850 mb 1393 m

D. 56 kt

E. 351 deg 56 nm

F. 058 deg 48 kt

G. 341 deg 61 nm

H. 996 mb

I. 19 C / 1401 m

J. 20 C / 1524 m

K. 16 C / NA

L. NA

M. NA

N. 12345 / 8

O. 0.02 / 5 nm

P. AF309 2109A ISAAC OB 06

MAX FL WIND 48 KT N QUAD 15:04:00Z

;

[Bostonseminole]

Still close to the Cuban coast

tracking south of the forecast cone, might miss the Keys, just nip the Dry Tortugas if it stays on that heading.

[okie333]

12Z GFS has it not moving much...

60:

72:

[eyewall]

Key West livestream: http://www.ustream.tv/channel/kev24k

[Sunny and Warm]

The large size of the storm in my opinion is going to hurt it intensity wise. The reason being is that the winds in advanced of the storm are already upwelling the waters well ahead of Isaac's inner core. You can see how in key west, water temperatures are falling a good 24-36 before Isaac makes its final approach.

Are we certain that the size of Isaac caused the water temp drop? The high/low yesterday in Key West was 82/73 with NE winds all day averaging 15mph with gusts to 40. The water temp dropped 4F yesterday. Upwelling certainly occurred and likely due to Isaac's circulation, but isn't that more an effect of Key West being surrounded by shelf water than anything else? Once over the open water of the gulf, Isaac's size shouldn't matter as much as long as it is moving forward. Otherwise, how do we explain Katrina's strenghening when it was easily the same size as Isaac?.

[Superstorm93]

Isaac crawls along the LA coast on the 12z GFS from 63-81 hours

Still going as well.

Most of the strengthening takes place when it nears the LA coast.

[Bostonseminole]

Key West livestream: http://www.ustream.tv/channel/kev24k

I will start a thread to put them in.

[phil882]

Indeed... GFS drifts the system westward on the Louisiana coastline as a formidable hurricane. The GFS continues to shift further west with each subsequent run. Verbatim this is a pretty substancial hit for the entire coastline of Louisiana.

[Derecho!]

12Z UKMET shifted W a decent amount - FL/AL border landfall, moving very slowly

[phil882]

Are we certain that the size of Isaac caused the water temp drop? The high/low yesterday in Key West was 82/73 with NE winds all day averaging 15mph with gusts to 40. The water temp dropped 4F yesterday. Upwelling certainly occurred and likely due to Isaac's circulation, but isn't that more an effect of Key West being surrounded by shelf water than anything else? Once over the open water of the gulf, Isaac's size shouldn't matter as much as long as it is moving forward. Otherwise, how do we explain Katrina's strenghening when it was easily the same size as Isaac?.

Katrina WAS NOT the same size as Isaac when it was in this portion of the Gulf of Mexico. If you remember, Katrina become much larger when it entered the Central Gulf of Mexico. Isaac already has a large swath of tropical storm force winds. In fact, Katrina didn't have a similar large radius of tropical storm force winds until it became a category 5 hurricane.

[phil882]

I will start a thread to put them in.

Thank you... lets try to keep this thread for meteorological discussion only. We have other threads set up for banter, and we can create one for real time obs.

[OUGrad05]

12Z GFS has it not moving much...

60:

72:

Hello fellow Tulsan

First as an FYI to fellow forum members, I work in the oil/gas industry, I would recommend filling up your cars today. IF it does move west upon landfall there will be a huge number of refineries impacted, additionally as this storm looks more and more likely to take a westerly track more oil and natural gas production will be significantly impacted then was thought 24 hours ago.

My 2 cents, take it for what its worth...

On the storm...

This ULL and interaction with the mountains in Cuba seem to be inhibiting development somewhat. Slow steady strengthening though, is all it takes for this storm to become a hurricane in the next 12 to 18 hours. The GFS and NAM have this thing at a strong TS and maybe barely hurricane strength when it makes landfall. So that is the good news...but models in many cases do a poor job handling intensification of tropical systems.

There's a few models bringing it onshore as a strong hurricane. Does anyone have any thoughts or experience with similar setups that can provide some analysis and input? The data is all over the place at the moment and I'm certainly not qualified to interpret in this type of situation with such divergence among the models.

Convection appears to be kicking up a notch or two the last few IR/Visible scans that I've seen.

[turtlehurricane]

Latest recon pass has 996 mb and 60 mph flight level winds 35 miles from the center (rather than 100+ miles away like most of yesterday). Winds gusting from 40-60 mph across the Florida Keys and SE FL.

[winterymix]

Hello fellow Tulsan

First as an FYI to fellow forum members, I work in the oil/gas industry, I would recommend filling up your cars today. IF it does

There's a few models bringing it onshore as a strong hurricane. Does anyone have any thoughts or experience with similar setups that can provide some analysis and input?

For your industry, I would be concerned with threshold swell heights and threshold sustained winds that would trigger mandatory evacuations of rigs. Try to predict when and where for mandatory evacuations based on forecast offshore conditions.

It hasn't really been thought that this would go much over 100 kts sustained. It will be a slow moving rainer.

For onshore interests, I'd be concerned with flashfloods, mandatory evacuations and tornadoes. Some spots such as Mobile Bay may get a test of levees during high tide and full moon amplified storm surges. Many make the mistake of worrying about winds when it is these other factors that matter more.

[BeauDodson]

The Discussion is really short and cryptic. I was hoping for more analysis of the model spread, the reasons, and why one solution might be better than the other.

I don't even read NHC discussions - the discussions in this thread beat anything else available. Of course you know that already.

[SN_Lover]

Meteorologist Brad Panovich just posted a video on youtube about the current synoptic setup and the potential synoptic setup. He said that Isaac will actually strengthen with the warm gulf waters.