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

[wxsmwhrms]

If it drives across Hispaniola I would agree. However, I am assuming that will do more of a skirt of the SW corner of the island as the forecast shows. And I will admit I still tend to agree with LEK, until I see the actual convective mass and circulation driving it gaining a lot of latitude, I don't think it's inconceivable much of the system ends up skirting or missing Hispaniola.

Just to add to this, the NHC forecast is actually to the right of the GFS, and it only goes across the SW portion of the island. The 18Z GFS never actually takes the MSLP center across anything but the absolute western tip of the SW peninsula.

[HKY_WX]

That eddy north of cuba looks like a good starting point for intensification.

[turtlehurricane]

If it drives across Hispaniola I would agree. However, I am assuming that will do more of a skirt of the SW corner of the island as the forecast shows. And I will admit I still tend to agree with LEK, until I see the actual convective mass and circulation driving it gaining a lot of latitude, I don't think it's inconceivable much of the system ends up skirting or missing Hispaniola.

Ernesto 2006 skirted SW of the island, which is probably the best case scenario for Isaac at this point. It was still crippled for days, I remember being in the center of Ernesto and we had 20 mph gusts with scattered clouds, only notable thing was it strongly smelled like the ocean even though we were well inland. Of course Cuba played a role too, but Isaac is likely to hit those mountains as well. I simply can't be optimistic about this.

[wxsmwhrms]

Ernesto 2006 skirted SW of the island, which is probably the best case scenario for Isaac at this point. It was still crippled for days, I remember being in the center of Ernesto and we had 20 mph gusts with scattered clouds, only notable thing was it strongly smelled like the ocean even though we were well inland. Of course Cuba played a role too, but Isaac is likely to hit those mountains as well. I simply can't be optimistic about this.

Don't get me wrong, I don't think it's going to do much of anything until it gets to the Gulf. My point is simply that the a broader circulation is not going to see much "weakening" when it's not organized, tight or strong in the first place.

[Superstorm93]

I wouldn't expect any sig' intensity changes anytime soon. Even if the center doesn't pass over Hispanola it will disrupt the inflow and limit it for the next day or two. As you stated the euro doesn't ramp it up till it crosses cuba and hits the high TCHP/low shear environment.

Exactly.

I trust the EURO's physics much more than I do any other model, and it seems that the model has some topographical influence regardless of a landfall or not. That could be enough to halt, if not weaken this.

[wxmeddler]

GFS output should be starting shortly... Ingested 40 dropwinsondes from the G-IV, P-3 and a few from the Air Force flight.

[Superstorm93]

I don't like the Ernesto comparison all that much.

As others have stated, it was undergoing extreme south-westerly shear at the time and Hispaniola only exacerbated it's unfavorable environment.

(IMO of course)

[HKY_WX]

Anyone have a list of canes hitting la/ms/al moving from SE to NW? That could be an interesting list to see.

[Superstorm93]

HOWEVER IT SHOULD BE NOTED

THAT THERE IS SIGNIFICANT UNCERTAINTY IN TROPICAL CYCLONE INTENSITY

PREDICTIONS AT 3-5 DAYS.

[ALhurricane]

Anyone have a list of canes hitting la/ms/al moving from SE to NW? That could be interesting to see.

Frederic is the first that comes to mind.

http://www.wunderground.com/hurricane/at19796.asp

[HKY_WX]

Frederic is the first that comes to mind.

http://www.wundergro...ane/at19796.asp

Yep. There would be a lot of big names on that list.

[e pluribus unum]

Anyone have a list of canes hitting la/ms/al moving from SE to NW? That could be an interesting list to see.

Elena eventually did that.

[hm8]

00z GFS further east and deeper through 48hrs...

[Superstorm93]

GFS has a whopping 24 hours of land interaction for Hispaniola and Eastern Cuba combined. Not bad.

Shoots it north of Cuba and looks to be heading WNW afterwards while strengthening a bit by 54 hours.

Should still be a GOM run.

[airmarci]

Don't get me wrong, I don't think it's going to do much of anything until it gets to the Gulf. My point is simply that the a broader circulation is not going to see much "weakening" when it's not organized, tight or strong in the first place.

I happen to agree with turtlehurricane here. While Isaac is unorganized, the circulation strength is ultimately a function of the oceanic heat flux. If that flux is cut off or weakened due to interactions with topography in Hispaniola and Cuba, the circulation becomes susceptible to other environmental factors that will weaken its strength. Although the current circulation is not strong, as you mentioned, it is still very likely it will weaken a fair bit.

[wxmx]

Anyone have a list of canes hitting la/ms/al moving from SE to NW? That could be an interesting list to see.

[turtlehurricane]

GFS has a whopping 24 hours of land interaction for Hispaniola and Eastern Cuba combined. Not bad.

Shoots it north of Cuba and looks to be heading WNW afterwards while strengthening a bit by 54 hours.

Should still be a GOM run.

I find it odd how it doesn't weaken the storm much over the mountains, just kind of steady state if not strengthening over eastern Cuba once it touches water. I guess that's what you get with 27 km horizontal resolution.

[Superstorm93]

Significant intensification offshore of Tampa by 93 hours. This would be a very favorable track for strengthening, verbatim.

Heading WNW

[HKY_WX]

Interesting. Odds are good that this will have a very favorable upper atmosphere once entering the strait till landfall. So the list can give an idea of possible outcomes.

[andyhb]

Recent microwave image:

[Cheeznado]

As suspected, the GFS is heading for a landfall somewhere between BIX and AQQ. Still think the Euro is OTL, we will see what the 00Z run does....

EDIT: landfall 18Z Tues PNS/MOB area

[DopplerWx]

Recent microwave image:

The center looks south enough to miss the worst of hispaniola even if it maintains a WNW trajectory. best case scenario is if isaac can thread the needle between cuba and hisp. and maintain a decent structure as it enters the straits.

[Superstorm93]

Extreme western Panhandle/MS landfall on the 00z.

Wouldn't be surprised to see the ECM to correct near MSY or east of there.

[wxmx]

That last MW image pretty much confirms that the northern vortex is weak...it's now under strong shear from the outflow which is centered over the convective mess around ~15.3N. The night visible tells the story

[Ian]

Extreme western Panhandle/MS landfall on the 00z.

Wouldn't be surprised to see the ECM to correct near MSY or east of there.

The GFS handles the system more reasonably than the Euro IMO. I guess if you give it a bit more spacing from FL you have room for a stronger sys.. tho the Euro seems bomb crazy.. too erratic from run to run in track as well. I'd probably lean left as there's no indication that realtime trend is over yet.

[HKY_WX]

Good news is well be able to follow this on radar starting saturday till landfall lol.

[Superstorm93]

In my days, when you have -92C tops near or over a ML center, it's possible for things to work down a bit or at least strengthen.

The whole convective pattern still looks like it's driven by the ML low, which is not heading WNW (at least to my eyes)

(11pm center position is the red square)

We'll see what happens.

[Dunkman]

End result from the 0z GFS was a little stronger and about 100 miles east. What I found interesting was that the 18z at 96h and the 0z at 96h were at basically the same spot. From there the 0z accelerates into the panhandle while the 18z went NW towards Biloxi. The 100 miles isn't a big shift at 120h, but I found the fact that all of the separation occured during the last day to be interesting...obviously the weakness was much stronger.

[wxsmwhrms]

End result from the 0z GFS was a little stronger and about 100 miles east. What I found interesting was that the 18z at 96h and the 0z at 96h were at basically the same spot. From there the 0z accelerates into the panhandle while the 18z went NW towards Biloxi. The 100 miles isn't a big shift at 120h, but I found the fact that all of the separation occured during the last day to be interesting...obviously the weakness was much stronger.

To me what I take out of today's model runs is just basically that we're looking at a very likely scenario of a WNW-NW track near Cuba followed by a continued WNW-NW, possibly bending more NNW-N, track over the Gulf toward an eventual landfall somewhere on the central Gulf Coast in about 5-6 days. Given that we are still debating tonight where exactly the center is now and is going to form, and the fact that very subtle differences in the strengths/orientations of the ridge/weakness features that are not forecastable with any strong accuracy at that time, I don't think there's any way to pin down with any kind of certainty where on the northern Gulf Coast the eventual landfall point will be. The last three runs of the GFS have given Mobile/Pensacola (00Z), Pascagoula (18Z), and Destin (12Z) and anywhere in that range stretched out a bit farther west and east from there seems pretty reasonable to me right now (say maybe MSY-PAM).

What may be a bigger question to me right now is how much does Isaac affect S FL and the Keys, and in what state is Isaac when it gets there. How much interaction occurs with Hisp and Cuba, what affect it has on it, and the ultimate track given the EC on the left side and GFS on the right during that time frame, should yield an interesting situation. The other 00Z runs will be interesting to see.

[deltadog03]

hmmmm...looks like the GFS clearly sees a weaker ridge...Lets see if the euro follows it