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

[EasternUSWX]

I swear I'm seeing the LLC move rapidly north to a position just SE of the clearing and very close to alignment with the MLC. You can clearly see two rotations occurring in the imagery as they align better.

I thought it looks like that too. Like it jumped from the previous position and quickly moved north to almost match the clearing area. Strange.

[turtlehurricane]

[LocoAko]

FWIW, 00Z Early Guidance:

Statistical Models:

Dynamic Models:

With a few exceptions, most models indicate a final track west of New Orleans now, with some even to the Lake Charles, LA area. Clear trend westward from 12Z but not so different than 18Z.

[Buckeye05]

I am fairly confused about what I am seeing on radar. Some are saying that the eye like feature is the COC, others are saying that it is the midlevel circulation and the real COC is further south. Others saying that the two are aligning. Any ideas?

[PSUBlizzicane2007]

It's not surprising that Isaac jogged westward as the momentum from the western side convection was strengthening and wrapping around. As this continues to strengthen and develop, including the formation of a complete eyewall with proper highest momentum on the NE side, we should continue to see a stair-step pattern, possibly through at least 24 hours, including with this recent northward jog.

[Jaguars]

I thought it looks like that too. Like it jumped from the previous position and quickly moved north to almost match the clearing area. Strange.

agree as well, sure it's just a jog but from this vantage point a clear northward nudge

http://radblast-mi.wunderground.com/cgi-bin/radar/WUNIDS_map?station=BYX&brand=wui&num=20&delay=15&type=N0R&frame=0&scale=1.000&noclutter=1&t=1346003151&lat=24.60408020&lon=-81.62238312&label=Key+West,+FL&showstorms=0&map.x=400&map.y=240&centerx=400&centery=240&transx=0&transy=0&showlabels=1&severe=0&rainsnow=0&lightning=0&smooth=1

[turtlehurricane]

Something really interesting just happened, mid-level circulation developed at 24.5 °N, 82.8 °W, over 20 miles NW of the clearing. This storm is now very tilted and it happened quickly. Velocity image is 1.3 ° tilt, reflectivity is the standard 0.5 °.

[thewxmann]

This guy's reasoning is terrible except for the part about the continental shelf waters. The fact that Isaac has been somewhat of an underachiever for most of its life doesn't have any bearing on its future, because the atmospheric conditions are so different and the vortex structure has undergone much change having traversed parts of two islands. There is dry air around the storm, but how is it going to get into the inner core if there's no shear?

I'll never get those 4 minutes of my life back...

Was thinking the exact same thing. Also, I've never seen you so frustrated CUmet

[phil882]

It looks like on radar that the center may be trying to relocate further to the north. Will be interesting to see if this actually transpires, so far no signs of a center relocation on the recon observations.

[Buckeye05]

Almost looks like two seperate circulations that can't quite align.

[turtlehurricane]

It looks like on radar that the center may be trying to relocate further to the north. Will be interesting to see if this actually transpires, so far no signs of a center relocation on the recon observations.

Recon was below the new mid-level center but it's undoubtedly there on doppler, I think it's going to take over quickly based on Doppler trends and the vigorous convection. Classic downshear center reformation.

[tmagan]

00Z Observations

[BeauDodson]

I noticed there has been a fairly significant increase in lightning near the center over the last hour.

[FredRed]

Obvious northward tilt from surface to 20K'. However, the upper level circulation is starting to work itself down to the surface. TR=0.5~4.5K', BL=1.5~10K', BR=3.5/20K'

[Superstorm93]

Definitely seeing a large increase in lightning like others have stated.

Still concerned about the mid level and low level centers not being aligned.

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[Uncle Bobby]

On second thought, I believe Recon got it right. Since I posted the last reflectivity image that so-called developing eye doesn't look so convincing. I now believe the center is about where I placed the little red square, which is about the same as Recon's fix.

[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.

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.

The early 00z model guidance shows what I was referring to pretty well (the one on Allan's site). There is a large cluster SW of New Orleans (what I'm currently favoring), a small cluster heading for the MS/AL border, and only one model that actually has a true in-between scenario of a track closer to Katrina's and what the NHC has. There are synoptic reasons behind this, which is why I'm not splitting the difference and instead am favoring the western cluster.

[dan11295]

Pretty clear from the Base Velocity loop that the the circulation has moved rather quickly north within the past hour.

[mattmfm]

Recon was below the new mid-level center but it's undoubtedly there on doppler, I think it's going to take over quickly based on Doppler trends and the vigorous convection. Classic downshear center reformation.

Didn't the same happen with Gabrielle in '01(ish?)

[turtlehurricane]

Increased lightning indicates there's more snow and ice aloft if I know my microphysics right, which is a result of deeper convection and cooler cloud tops. The sun going down probably helps too for cooler cloud tops.

[David Reimer]

0Z Early Cycle Guidance

[BeauDodson]

Sort of been glancing at the lightning data all day - seems like this is the most lightning strikes I have noted on the screen.

[Ground Scouring]

POPS / precipitable water over portions of SE FL appear to be exceeding local forecasts...locally, some areas have received more than eight inches of rain since sunrise today. Flood warnings will likely be issued for the FLL-PBI area in less than a few hours.

[Sunny and Warm]

0Z Early Cycle Guidance

Significant in that the early guidance now suggests that there are two paths opening for Isaac, but they are converging. One group is clustered through eastern LA and the other through central/western LA. Only two members are in AL and TX each. All others go through LA and MS. It appears that the models may be narrowing the effects of the troughing down to a roughly 100 mile influence 60 hours out.

[Nikolai]

Radar has shown a significant structural improvement in the last 30 minutes and the latest frames look like the centers are now consolidating or have consolidated, with an eye-like feature now apparent.

[WildFlower]

know I should post this in banter and it may get moved... BUT.. from what I can tell from Lighthouse Point FL.. the back half of this storm is more powerful.. no thunder/lightening all day.. then this evening more activity... thunder, wind and rain.

[Indystorm]

Emily, Rita, and Katrina all had significant amounts of lightning. Yet other large hurricanes have not. It does seem rather unusual for the lightning to be occurring during the formative stages for Isaac. Most hurricane winds are horizontal, so some deeper vertical convection (intensification?) might be happening at this time.

[wxsmwhrms]

Seems pretty clear in recon data that some sort of restructural organization is going on. Looks like kind of a broad center with multiple swirls trying to consolidate. Given increased convective organization on satellite will be interested to see what the rest of the overnight brings.

[Buckeye05]

Radar has shown a significant structural improvement in the last 30 minutes and the latest frames look like the centers are now consolidating or have consolidated, with an eye-like feature now apparent.

I'm not seeing any eye like feature now. Actually I thought it looked better earlier. It now does seem to have developed one single COC though.

[CoastalWx]

Emily, Rita, and Katrina all had significant amounts of lightning. Yet other large hurricanes have not. It does seem rather unusual for the lightning to be occurring during the formative stages for Isaac. Most hurricane winds are horizontal, so some deeper vertical convection (intensification?) might be happening at this time.

It's not that unusual for intensifying tropical systems. I mean if you think about it..intensification usually goes along with stronger updrafts and colder cloud tops...you are naturally gonna electrify the atmosphere a bit more. It also doesn't mean RI either. It's a blob of convection that is really going to town.