ATL: ISAAC - Post-Tropical - Discussion

[meriland23]

safe to assume, the cone of 'error' should be about 1000 mi across lol

[KWT]

Well to be fair this one is out of the cone already, but thats to be expected given the NHC position was just a guess in the end.

I think this time we can be pretty sure where the systems center actually is, for the first time in 36-48hrs.

[Nimbus]

Surface pressure down to 1000 MB's and the circulation is so large that Haiti, Jamaica and Cuba shouldn't focus on the exact track. We have seen in the past that the mountains of Haiti sometimes tighten up the circulation of a developing tropical storm. Isaac has slowed down so they have time to update warnings in Jamaica if the NNW turn doesn't occur. The NHC usually clings to their forecasts for consistency sake so don't expect any changes at 11 AM.

Tonight if the models have shifted the track between Jamaica and Cuba with more ridging over the north gulf coast I might have to update my original prediction of a Florida panhandle landfall.

Most of the short waves and weaknesses have been dipping down to the gulf coast near Georgia stretched up the east coast as a front. A weak storm might stall south of the ridging and get shunted NE or east by the one of these weaknesses.

Stronger hurricanes build an anticyclone over themselves that often disrupts the prevailing upper air steering pattern.

[cycloneye]

Hey everyone. I'm in south florida near fort lauderdale. Just wanted to hear a few opinions on what I can expect from this storm and what you guys think about the current track. Thanks

Jordan

Welcome to Storm2k. So far that area will not be impacted directly by Issac,but as it moves thru the Keys,rain with some gusty winds may impact the area. But stay tuned as things can change.

[Shuriken]

The unofficial forecast below uses the 850mb fix as the center-point, and assumes an initial 280-degree heading. It otherwise follows a gently curving upglide more or less parallel to the NHC's current further-east track.

* Isaac will become a much bigger than average-sized storm with large radii of TS-force winds.
* Isaac will be a hurricane at landfall in Jamaica, and stay a hurricane traversing the island.
* If this track materializes, I expect a cat-4 or -5 storm in the northwestern Caribbean and/or over the Gulf loop-current.

[cycloneye]

TC update:

TROPICAL STORM ISAAC TROPICAL CYCLONE UPDATE
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
630 AM EDT FRI AUG 24 2012

AT 630 AM EDT...1030 UTC...THE GOVERNMENT OF JAMAICA HAS ISSUED A
TROPICAL STORM WATCH FOR JAMAICA.

$$
FORECASTER BRENNAN

[KWT]

Shuriken, I think intial motion is much more northerly than that, I'd hazard a guess at 290-300 but we will get a much better pass with the next pass through the center very soon.

[Shuriken]

Shuriken, I think intial motion is much more northerly than that, I'd hazard a guess at 290-300 but we will get a much better pass with the next pass through the center very soon.

Given that the mid-level center went over Martinique, and recon variously fixed 850mb centers at 15.1N and 15.3N this morning, I think I'm being generous INIT-ing a motion vector of 280 instead of 270.1.

[Blown Away]

Looks like Isaac has slowed way down?

[KWT]

Shuriken, I think intial motion is much more northerly than that, I'd hazard a guess at 290-300 but we will get a much better pass with the next pass through the center very soon.

Given that the mid-level center went over Martinique, and recon variously fixed 850mb centers at 15.1N and 15.3N this morning, I think I'm being generous INIT-ing a motion vector of 280 instead of 270.1.

I think recon is finding the system jogging pretty much to the NW, the first two passes came up with a motion of 310, I'm going to be interested to see where the center is this time. Thats why I mentioned the motion I did.

Next center pass should be soon, the wind field isn't quite as uniform on this pass as it has been before.

[meriland23]

Looks like Isaac has slowed way down?

he's stacking..

[tgenius]

If he's moving at 310 then the model tracks are going to all be off due to the init with the wrong COC right?

[meriland23]

If he's moving at 310 then the model tracks are going to all be off due to the init with the wrong COC right?

310? sorry, still learning

[meriland23]

wonder what the NHC will say when it passes south and west of hispanola completely.. cause that is how it is lookin right now..

[TheBurn]

If he's moving at 310 then the model tracks are going to all be off due to the init with the wrong COC right?

310? sorry, still learning

Degrees (just south of NW which is 315)

[tgenius]

310 is motion KWT is extrapolating. Due west would be 270 so 310 is a hair south of WNW

[meriland23]

aight, so is 310 its assumed motion? Cause this looks to be nothing but west to me looking at current loop

[KWT]

Recon not showing a perfectly shaped LLC despite a very impressive eastern quadrant, recon looks like they've pulled up to try and locate the center. There is a wind shift though it is weak. I guess we'll see what recon shows next time.

[jlauderdal]

aight, so is 310 its assumed motion? Cause this looks to be nothing but west to me looking at current loop

recon and visible the only sure thing to look at, IR not real good unless you have an eye..thanks for all of your hard work posting on isaac, you have been a real trooper

[Shuriken]

I think recon is finding the system jogging pretty much to the NW, the first two passes came up with a motion of 310

I'm inclined not to assume that they're the same center (which moved between passes) -- rather than an elongated axis.

-- A NW/SE-oriented line of CBs is marching into/under the CDO while the plane is making its passes, and the structure is evolving rapidly.

In any event, the mean vector of the convective blob has been moving steadily almost due west since east of the islands; and, given Isaac's behavior so far, I'm inclined to doubt any asserted movement otherwise until I actually see the convection trend in that direction as well.