ATL: ISAAC - Models

[Pearl River]

Let's see if the 12z Euro moves west too. Like I said yesterday, I noticed that the 0z Euro runs east and the 12z runs west, let's see if that does hold true.

[meriland23]

if this thing crawls up the gulf.. so slowly, wouldn't that (if it were maj hur in gulf) help in weakening it substantially before it centers land cause of how slow it moves vs being major and going fast?

[deltadog03]

so, it looks like the gfs is a bit west with the landfall, but the biggest difference is with what happens after that....it slows and crawls north. instead of heading off to the NE

[meriland23]

so, it looks like the gfs is a bit west with the landfall, but the biggest difference is with what happens after that....it slows and crawls north. instead of heading off to the NE

looks like them steering currents have caused it to slow into the gulf again

[SunnyThoughts]

What is so unique about this, is the fact that most cyclones, when they are headed to the gulf coast like this..aren't just slowly moving as they come ashore..they are usually gaining speed as they come in and sweep through fairly quickly. This is really starting to worry me now, and I've been through a LOT of canes in my lifetime.

[Jevo]

12z Early Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)



12z Early Dynamic Models

[deltadog03]

Agreed!

[timmeister]

Landfall btwn hr90-96 and STRONG!!! Landfall near Pensacola....

Strong as in Cat 2, 3??

GFS has Isaac coming ashore @ 99HRS with a pressure of 979.8 mb which is a weak CAT 2 and onshore @ 102 HRS with a pressure of 980.0 mb which is a CAT 1 storm. But as we all know, the models cannot predict intensity because technology hasn't got there yet.

[Dean4Storms]

What is so unique about this, is the fact that most cyclones, when they are headed to the gulf coast like this..aren't just slowly moving as they come ashore..they are usually gaining speed as they come in and sweep through fairly quickly. This is really starting to worry me now, and I've been through a LOT of canes in my lifetime.

That's usually because the westerlies are getting involved, it looks like the GFS is depicting ridging from the Plains clear across the TN, Ohio valleys so in other words becoming blocked!

[meriland23]

What is so unique about this, is the fact that most cyclones, when they are headed to the gulf coast like this..aren't just slowly moving as they come ashore..they are usually gaining speed as they come in and sweep through fairly quickly. This is really starting to worry me now, and I've been through a LOT of canes in my lifetime.

I 'think' that, a slower moving means less intensity by landfall vs a BAM.. could be wrong, take my opinion for a grain of salt. The real issue would be the CONSTANT rain.. just never ending crud.. that is a good day and a half of practically being stationary on gfs new model. I don't want to use Katrina as a example, but it was more of a flood issue.. due to the levees. I wouldn't be surprised if something like would happen due to the stationary movement and emmense rain. I am NOT saying this will be a katrina, not implying at all, just saying..wouldn't surprise me cause the flooding.. will be a very real issue.

[cheezyWXguy]

if this thing crawls up the gulf.. so slowly, wouldn't that (if it were maj hur in gulf) help in weakening it substantially before it centers land cause of how slow it moves vs being major and going fast?

It could, but this likely going to be a situation that we won't be able analyze well until it is actually happening. Often times, storms approaching the northern gulf coast are picked up by troughs, which impose increasing wind shear on them as they approach the trough and are eventually shunted quickly NE. This, however, does not appear to be the case since it will only be meandering. It will probably be a complicated situation because there are so many small variables that have big impacts on the landfalling strength, including angle of movement, size, the storm's surrounding environmental conditions, and whether it decides to really slow down on or off the coast.

An example of this might be Ike, which if I remember correctly, maintained intensity or strengthened slightly up to landfall, despite its rather slow motion and large size.

[SunnyThoughts]

We have had SO much rain here already the last 2 weeks...wouldn't take much more rain to weaken the roots of trees so much, that hurricane force winds for any extended period of time..would just topple trees left and right. Flooding will definitely be an issue as well.

[USTropics]

if this thing crawls up the gulf.. so slowly, wouldn't that (if it were maj hur in gulf) help in weakening it substantially before it centers land cause of how slow it moves vs being major and going fast?

The GOM is pretty shallow, and looking at the TCHP map, upwelling due to a slower speed won't be much of an issue. As far as momentum and its correlation with strengthening, there just really isn't much of an influence there. Of course, we've seen tropical waves have issues with formation due to forward speed in excess of 20 knots, but this just won't be the case. In fact, in this scenario a slower speed means more time over water which leads to further strengthening.

[Jevo]

G-IV Afternoon flight plan for 0z model Data

[Dean4Storms]

If it moved too slow before reaching the coast it could upwell the seas and take a little off it, but I wouldn't look for much unless it completely stalled.

Actually a system moving between 10-15 mph are more apt to be vertically stacked providing no strong wind shear is present. We need to hope that the ULL expected to be over the Gulf puts dry air into this storm!

[meriland23]

Well guys, I mean.. okay for example.. you have a cat 4 hurricane running up the gulf at a slow 10 mph (or slower), first little bit of the center or even a bit before center reaches land.. hurricane goes "oop that there is land.." and start slowing before the full center reaches instead of "I was just over the water a few moments ago, now I am on land" If you catch my lame brain drift there .. lol. Kind of like.. if you were playing baseball and you swung and missed cause the ball was going too fast, but if you slowed time way down while that ball was being thrown, you would be able to hit it easily. Does that make.. any sense? sounds so overly simplified lol.

[PTrackerLA]

Quite a shift with the 12z GFS @ 2nd landfall. That would likely prompt the need to evacuate New Orleans...

[cheezyWXguy]

Well guys, I mean.. okay for example.. you have a cat 4 hurricane running up the gulf at a slow 10 mph (or slower), first little bit of the center or even a bit before center reaches land.. hurricane goes "oop that there is land.." and start slowing before the full center reaches instead of "I was just over the water a few moments ago, now I am on land" If you catch my lame brain drift there .. lol. Kind of like.. if you were playing baseball and you swung and missed cause the ball was going too fast, but if you slowed time way down while that ball was being thrown, you would be able to hit it easily. Does that make.. any sense? sounds so overly simplified lol.

Im having a little trouble with the baseball analogy haha, but your scenario for the northern gulf coast actually sounds even more devastating. If the center of a cat4 is just offshore or partially onshore and stalls, that puts the right-front quadrant of the eyewall on land, and over the same area for an extended period of time. Regardless of how much it would weaken stalling offshore in such a situation before making "official" landfall, that would likely spell a disaster for anyone in that right front quadrant.

[Jevo]

12z HWRF Initialized

[gboudx]

Quite a shift with the 12z GFS @ 2nd landfall. That would likely prompt the need to evacuate New Orleans...

The east bank of New Orleans, including all of St. Bernard parish. If what the 12z projected verified we would see surge on the east bank with east winds piling water onto St. Bernard and into Lake Pontchartrain. Then north winds would pile water in the lake on the south shore.