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]

There is a ship at 16.5N, 70.8W reporting an ENE wind of 35 kt and a pressure of 998.8 mb. Center must be just south of that.

[deltadog03]

HR30...GFS is over E Cuba... 12z GFS

[deltadog03]

HR42 is just off shore near North Central Cuba...moving WNW to NW.

[Superstorm93]

GFS is even further NE this run.

Just SE of SW Florida by 54 hours and heading WNW. Could make landfall there.

EDIT: Main 850 vort is over south Florida by 60 hours.

[phil882]

GFS is even further NE this run.

Just SE of SW Florida by 54 hours and heading WNW. Could make landfall there.

EDIT: Main 850 vort is over south Florida by 60 hours.

Here is the really strange part... the GFS is actually stronger with the ridge. Most of the major E shift is due to the fact that is has a stronger vortex so it moves further north when the ridge is weaker in the early part of the forecast post-Hispaniola.

[deltadog03]

This run looks like a first strike over SW FL, then just offshore and a 2nd hit prolly near PCB to Big Bend....

[Superstorm93]

Basically we're back to the old runs where this makes landfall in SFL and scrapes the whole west coast thereafter. Looks decently weaker than the 0z due to land interaction with Florida.

At least we'd be able to track the whole system on radar

Personally, I'd wait for the EURO.

[IsentropicLift]

Basically we're back to the old runs where this makes landfall in SFL and scraps the whole west coast thereafter.

At least we'd be able to track the whole system on radar

Personally, I'd wait for the EURO.

Wasn't the Western solution (Euro) based on a weaker disorganized stystem until it got past Cuba? The GFS could be responding to the fact that Isaac has been getting its act together today.

[Sunny and Warm]

This run looks like a first strike over SW FL, then just offshore and a 2nd hit prolly near PCB to Big Bend....

Is there a chance Isaac is pulled further inland across FL peninsula than being depicted by the 12z GFS due to frictional effects if indeed it takes a track like that? I'm not talking wholesale right movement, but is this a potential case where land effects could pull it further east and have it end up further east on second landfall?

[packbacker]

GFS sure does track this over a lot of land, the most time it has in the water is after Cuba and before Miami, I wonder if it could even gain hurricane strength during that period which is only about 24 hours.

[phil882]

Even though the 500 hPa heights are higher over the eastern US, the GFS splits a weak trough in the mid-west, with one piece dangling in the mid-south. This actually helps to create some southerly mid-level flow which is enough to keep Isaac from getting far enough west. This feature is presently a pretty potent upper level feature over Colorado, and one should pay attention to its evolution over the next few days.

[Dunkman]

Wasn't the Western solution (Euro) based on a weaker disorganized stystem until it got past Cuba? The GFS could be responding to the fact that Isaac has been getting its act together today.

0z Euro was 991mb at 8pm tonight. So, no, it wasn't based on a weak system at all.

[turtlehurricane]

I put a detailed forecast on my blog. http://weather.schematical.com/

Calling for Isaac to be a 60-70 mph tropical storm at landfall in Haiti since it still seems to be having organization problems, though the consolidated circulation is a good step forward. I still think the 1-2 punch of the mountains in Hispaniola and Cuba could end Isaac or at least cripple it for a long time. I don't think this will be more than a tropical storm by the time it reaches the Keys, but it's better to wait and see what happens with the land interaction than make a call for the Keys and the rest of the Gulf.

[icebreaker5221]

Looks like downsloping off Hispanola is already causing Isaac some issues, even with the center several hundred km south of the island. If Isaac had a smaller, tighter circulation, he would have to be much closer for this to have been an issue. Microcanes ftw.

[wxsmwhrms]

GFS sure does track this over a lot of land, the most time it has in the water is after Cuba and before Miami, I wonder if it could even gain hurricane strength during that period which is only about 24 hours.

I completely disagree with this. This GFS track has Isaac going over about the least amount of land possible between where it is now and when it gets to S FL. It pretty much shoots the gap between Haiti and Cuba, just barely grazing the SW tip of Haiti and the SE tip of Cuba. The center basically spends a few hours over SW Haiti and about 6 hours over SE Cuba in the model, and that is about it. It is actually a few MB deeper when it gets to S FL on this run. I am not saying it is right, and I am not saying that the fact that the eastern part of the storm would be going over Hisp won't hurt it - just pointing out that this track actually has much less land interaction than some of the earlier runs that had it more going WNW over Cuba.

[wxsmwhrms]

I completely disagree with this. This GFS track has Isaac going over about the least amount of land possible between where it is now and when it gets to S FL. It pretty much shoots the gap between Haiti and Cuba, just barely grazing the SW tip of Haiti and the SE tip of Cuba. The center basically spends a few hours over SW Haiti and about 6 hours over SE Cuba in the model, and that is about it. It is actually a few MB deeper when it gets to S FL on this run. I am not saying it is right, and I am not saying that the fact that the eastern part of the storm would be going over Hisp won't hurt it - just pointing out that this track actually has much less land interaction than some of the earlier runs that had it more going WNW over Cuba.

12Z UK is quite a bit farther left of the GFS. Has it hugging the north coast of FL and heading WNW SW of EYW at 72 hours.

Correction: obviously meant the N coast of Cuba, not FL.

[thewxmann]

If model trends continue, I can't even rule out the possibility of a FL Peninsula or E Coast scenario. We had a similar situation with Ernesto in 2006 right? ULL's that unexpectedly steer TC's have been the bain of models for years; models never catch them right (until they start ingesting Gulfstream data ).

[phil882]

12Z UK is quite a bit farther left of the GFS. Has it hugging the north coast of FL and heading WNW SW of EYW at 72 hours.

Does the UKMET ingest the same G-IV dropsondes that both the GFS and ECMWF use? It would be curious to see if the rightward shift in guidance is partially related to the new observations that were obtained yesterday.

[PSUBlizzicane2007]

Does the UKMET ingest the same G-IV dropsondes that both the GFS and ECMWF use? It would be curious to see if the rightward shift in guidance is partially related to the new observations that were obtained yesterday.

It should from what I remember... I don't see why it would not.

[am19psu]

UKMET I'm looking at has landfall 12z Wednesday near Fort Walton Beach

http://www.meteociel.fr/modeles/ukmo2.php?nh=1&carte=1021&ech=72&archive=0

[packbacker]

I completely disagree with this. This GFS track has Isaac going over about the least amount of land possible between where it is now and when it gets to S FL. It pretty much shoots the gap between Haiti and Cuba, just barely grazing the SW tip of Haiti and the SE tip of Cuba. The center basically spends a few hours over SW Haiti and about 6 hours over SE Cuba in the model, and that is about it. It is actually a few MB deeper when it gets to S FL on this run. I am not saying it is right, and I am not saying that the fact that the eastern part of the storm would be going over Hisp won't hurt it - just pointing out that this track actually has much less land interaction than some of the earlier runs that had it more going WNW over Cuba.

I didn't word that correctly. But in the short term yes it's less direct land interaction, but after it flirts around with Haiti/Cuba as you pointed out, it has about 24 hours of relatively clean water to work with before it hits Florida and spends about 24 hours over parts of Florida and than it hits the gulf again and has maybe 6-12 hours to work with, not a recipe for a strong hurricane or even a hurricane at all. I would have rather it stayed SW and had more land interaction with Cuba in the short term but than hit the open gulf and had a couple of days to strengthen.

[PSUBlizzicane2007]

12Z UK juts Isaac to the NNE/NE into Pensacola at 144 after being in the central Gulf south of MS/AL.

Edit: Pensacola 144, central Gulf 120.

[SN_Lover]

Looks like downsloping off Hispanola is already causing Isaac some issues, even with the center several hundred km south of the island. If Isaac had a smaller, tighter circulation, he would have to be much closer for this to have been an issue. Microcanes ftw.

no kidding. i know water vapor imagery only catches the upper levels, but you can already see the impact with convection and water vapor drastically diminishing.

[Derecho!]

12Z UK is quite a bit farther left of the GFS. Has it hugging the north coast of FL and heading WNW SW of EYW at 72 hours.

Correction: obviously meant the N coast of Cuba, not FL.

After that the UKMET looks essentially Identical to 0Z - ends up in Apalachicola, though it looks like it does this by swinging west a bit and recurving.

Canadian is back to the East coast of Florida.

[dtk]

Does the UKMET ingest the same G-IV dropsondes that both the GFS and ECMWF use? It would be curious to see if the rightward shift in guidance is partially related to the new observations that were obtained yesterday.

We have data sharing agreements in place and the obs get sent over the GTS. Here is an example plot showing that the reccon observations made their way into the ECMWF system last night for the 00z cycle (obviously the green dots):

I'm 100% certain that the UKMO at least receive these (and I'd be shocked if they didn't assimilate them).

[am19psu]

0z GFS EnKF T878 is farther right than any of the other 0z guidance from last night...

And the 0z GEFS EnKF ellipses are very similar to a 12z op GFS type track

[PSUBlizzicane2007]

UKMET I'm looking at has landfall 12z Wednesday near Fort Walton Beach

http://www.meteociel...ch=72&archive=0

http://meteocentre.com/models/explorateur.php?lang=en&map=na&run=12&mod=ukmet&stn=PNM&hh=144&comp=1&runb=12&mod2=ukmet&stn2=PNM&hh2=120&fixhh=1

I see it a bit further west?

After that the UKMET looks essentially Identical to 0Z - ends up in Apalachicola, though it looks like it does this by swinging west a bit and recurving.

Canadian is back to the East coast of Florida.

Apalachicola? I don't see that at all.

[MarkSC]

12Z Canadian is right of 0Z--nearly up the FL east coast. It does seem like there is pretty good consensus now on a NE turn at some point.

[Weathergun]

Even though the 500 hPa heights are higher over the eastern US, the GFS splits a weak trough in the mid-west, with one piece dangling in the mid-south. This actually helps to create some southerly mid-level flow which is enough to keep Isaac from getting far enough west. This feature is presently a pretty potent upper level feature over Colorado, and one should pay attention to its evolution over the next few days.

The 0z Euro last night, started picking up on this trough split over the Midwest. as well. Probably why it shifted Issac east too:

[am19psu]

http://meteocentre.c...hh2=120&fixhh=1

I see it a bit further west?

Not to my eyes, but really, at T+120 we're within the margin of error