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Azores #96L fails to complete transition into a Sub-Tropical Storm. Elsewhere, weak low pressure in Caribbean may linger into next week.
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Archives >> 2012 Forecast Lounge

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WeatherNut
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Re: Tropical Storm Isaac Forecast Lounge [Re: mcgowanmc]
      #93384 - Thu Aug 23 2012 01:20 PM

I think the next recon is going to find the center a little south of the previous fix. Its looking like the convection is finally starting to wrap around one center, although it is really hard to determine. If the center is close to where I think it is, it is well south of the NHC's forecast point.
Recon is starting to drop down from their cruising altitude so it wont be much longer before they are there

--------------------
Born into Cleo (64)...been stuck on em ever since

Edited by WeatherNut (Thu Aug 23 2012 01:23 PM)


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doug
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Re: Tropical Storm Isaac Forecast Lounge [Re: WeatherNut]
      #93392 - Thu Aug 23 2012 02:45 PM

I am amazed at the appearance of this system. If you watch the WV it seems the moisture is just evaporating especially in the vicinity where one would expect a convective core to be developing. From the visible, I would actually peg the center at 15.6 or so and not 16. This is the issue all along, the lowest point of pressure may be at 16, but the cloud presentation suggests some other point.. What shear is effecting this system? It seems some southerly shear may be part of the problem too. Still very disorganized...no evidence of consolidation or intensification.

--------------------
doug


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ralphfl
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Re: Tropical Storm Isaac Forecast Lounge [Re: doug]
      #93398 - Thu Aug 23 2012 03:30 PM

And i think even more of a west track will be in the 5pm update.It may not be much of a movement west but i see it going to happen this next update.

But like some have said it has to wait till we get a real center before we can say what it will do.


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Ed DunhamAdministrator
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)


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Re: Tropical Storm Isaac Forecast Lounge [Re: doug]
      #93399 - Thu Aug 23 2012 03:57 PM

Many of you have made excellent observations on the problematic center fixes over the past 24 hours. I realize that multiple vortices within a general circulation area is the prime suspect, but there seems to have been a bad-luck tendency to pinpoint the wrong one - which becomes frustrating because the real track, forecast track, and model track are seldom in sync. At 18Z I would have put the center at 14.8N - perhaps 15.2N to allow for some consistency. The18Z Advisory stated that a WNW movement had started, but I just don't see any sign of that - at least not yet. Maintaining a nebulous center around 16N will yield bad data input for the various models. Isaac remains a poorly organized system, so realize that the details of the model outputs for both track and intensity will be suspect until Isaac develops and maintains a firm center.
ED


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berrywr
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Re: Tropical Storm Isaac Forecast Lounge [Re: Ed Dunham]
      #93400 - Thu Aug 23 2012 04:00 PM

Earlier today, aircraft recon had a vortex message with a 14.8N; as of 23/2000Z, I have the center near 15.5N 66.5W...there is a slight donut hole there, not an eye.

--------------------
Sincerely,

Bill Berry

"Survived Trigonometry and Calculus I"


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berrywr
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Re: Tropical Storm Isaac Forecast Lounge [Re: doug]
      #93401 - Thu Aug 23 2012 04:08 PM

Dry Saharan air is filtering into the system disrupting convective activity near the center; I had said aircraft recon posted a vortex message just before 12Z this morning at 14.8; actually it was 14.5; tops later in the morning have warmed but it was cooking pretty good at 14.5. Right now I have a center fix near 15.4N...15.5N and 66.5W and Issac is following the south side of the track envelope for the time being.

--------------------
Sincerely,

Bill Berry

"Survived Trigonometry and Calculus I"


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stormtiger
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Re: Tropical Storm Isaac Forecast Lounge [Re: berrywr]
      #93407 - Thu Aug 23 2012 05:30 PM

Issac continues to represent what the 2012 season has become, a season of storms that have not seemed to catch the genie in a bottle to become a traditional, full blown hurricane.

Dry air, East Carribean graveyard, fast motion or whatever is the main cause; it is playing havoc with the models and forecasters.

48 hours ago Issac was predicted to be at 16.6 and at 66.3 with 75 mph winds. Just 24 hours ago Issac was predicted to be at 16.7 and at 66.7 with 60 mph winds.

Right now the NHC has Issac pegged at 16.0N and at 67.1West with 40 mph winds.
And that position is sort of a compromise so they can provide a point on the map which represents a best "average" of several vortices in a larger area.

The point here is that until Issac gets better organized he could do almost anything once he organizes. Right now models are trending westward which means exactly nothing except that maybe people in Hispanola, Cuba and S Florida may let their guard down when in fact Issac could still wind up hitting Miami.

Issac is a dangerous storm. Not because of what it is, but what it could become. A weak storm, a storm not really getting its act together crossing Cuba and then suddenly intensifying in 88 degree plus GOM waters and then moving on a fast track to NO, Mobile, or Tampa before many have prepared or evacuated is a worst case scenario.

Let's hope this doesn't happen, but on a weekend people need to remain vigilant because the danger is ever present because a weak storm like Issac gaining strength rapidly in the GOM can in a sense be more dangerous than a larger storm on an obvious path.


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CoconutCandy
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Re: Tropical Storm Isaac Forecast Lounge [Re: stormtiger]
      #93408 - Thu Aug 23 2012 06:27 PM

Quote:

"... The point here is that until Issac gets better organized he could do almost anything once he organizes. *Right now models are trending westward, which means exactly nothing* ...

Issac is a dangerous storm. Not because of what it is, but what it could become. A weak storm, a storm not really getting its act together ... and then suddenly intensifying in 88 degree plus GOM waters and then moving on a fast track to NO, Mobile, or Tampa ... " - Storm Tiger



Quote:

"I realize that multiple vortices within a general circulation area is the prime suspect, but there seems to have been a bad-luck tendency to pinpoint the wrong one - which becomes frustrating because the real track, forecast track, and model track are seldom in sync. ... Isaac remains a poorly organized system, so realize that the details of the model outputs for both track and intensity will be suspect until Isaac develops and maintains a firm center." - Ed Dunham




Very nicely summed up. And I tend to agree that far too much is made of the long range model runs (3 to 5 days out) when systems are still in their formative stages, or experiencing significant deterrents of one form or another, as Isaac has now for the last few days.

Although the model runs are, of course, very interesting and useful tools, we should use heed their solutions with objectivity, even skepticism (speaking especially of the extended forecasts), until the storm is well formed, where they can initialize in a more meaningful manner and generate a more realistic prognostication.

--------------------
Prepare or Despair. Above all ...
"Don't Get Stuck on Stupid" - General Honore, following Hurricane Katrina




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doug
Weather Analyst


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Re: Tropical Storm Isaac Forecast Lounge [Re: CoconutCandy]
      #93410 - Thu Aug 23 2012 06:43 PM

Nice discussion and certainly salient points.
I am obviously not SOId on this system. I do not see any west component in the circulation envelope that is associated with a center. There are three little clusters of convection building in the 16+ 67 vicinity where NHC want to place a center, but...no w-e component there. Otherwise there is evidence of a sharp wind shift in the south but again no true west component... we will see if the convection near 16+ can maintain and take control. I find it very strange to have a "tropical storm" with this poor organization, to wit: no true circulation center.

--------------------
doug


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OrlandoDan
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Re: Tropical Storm Isaac Forecast Lounge [Re: ftlaudbob]
      #93411 - Thu Aug 23 2012 06:48 PM

From Water Vapor, at 18:47 EDT, I got this baby pegged at 68W 15.5N. Anyone have a different opinion?

--------------------
Keith (1988), Charley (2004), Frances (2004) , Jeanne (2004), Fay (2008), Mathew (2016), Irma (2017)


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CaneTrackerInSoFl
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Re: Tropical Storm Isaac Forecast Lounge [Re: OrlandoDan]
      #93412 - Thu Aug 23 2012 07:19 PM

Quote:

From Water Vapor, at 18:47 EDT, I got this baby pegged at 68W 15.5N. Anyone have a different opinion?




I think so too. It would be nice if this system is going to be an issue down the line, to get its act together tonight so we all can have a better idea to prepare. It looks like its giving it the old college go again this evening as the sun sets. Some very intense convection but again, lots of dry air. This is easily the oddest tropical system I can think of in a while.

--------------------
Andrew 1992, Irene 1999, Katrina 2005, Wilma 2005



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danielwAdministrator
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Re: Tropical Storm Isaac Forecast Lounge [Re: OrlandoDan]
      #93415 - Thu Aug 23 2012 07:51 PM

From radar I got 68W and 15.6N... Very close, 6 miles difference.

New Advisory has Center at 16.2N/ 67.8W

Edited by danielw (Thu Aug 23 2012 08:01 PM)


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CoconutCandy
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Re: Tropical Storm Isaac Forecast Lounge [Re: CaneTrackerInSoFl]
      #93418 - Thu Aug 23 2012 08:02 PM

Although it's entirely conceivable (and even likely) that there remain two competing centers of circulation, my impression, based on the last few hours of the unenhanced IR animated satellite loop, is that the increasingly predominate LLCC now appears, to me, closer to 15 N, perhaps even as low as 14.8, as clearly evidenced by significant low level turning amongst strong, developing thunderstorms immediately surrounding that locus of activity.



Which bodes worse, perhaps, for a strong GOM event, due to a weaker system initialized further south of previously thought, perhaps bypassing the detrimental run up the spine of Cuba entirely, and simply crossing the narrow, relatively flat, western end of Cuba in a somewhat more perpendicular fashion (thus lessening time spent over land), ending up entering the Gulf much more intact and better able to respond quickly (aka: rapid intensification) in the very warm waters of the gulf with it's currently rather high oceanic heat content.

Also quite telling is the curvilinear 'banding' structures of moderate thunderstorms now beginning to flare up north of Hispaniola and farther NW'ward towards the Turks and Caicos and SE'ern Bahamas and also the rapidly increasing convection streaming in from Venezuela, all of which support the idea of a large circulation envelope remaining, and are perhaps the harbingers of a final 'push' to consolidate the LLCC and begin a cycle of rapid intensification.

In any event, I think we'll see significant intensification during the overnight hours tonight, perhaps dramatically so, should 'Isaac' decide to finally consolidate about one of it's myriad LLCC's.


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CaneTrackerInSoFl
Storm Tracker


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Re: Tropical Storm Isaac Forecast Lounge [Re: CoconutCandy]
      #93419 - Thu Aug 23 2012 08:08 PM

It's so difficult because I see the same center too on the unenhanced IR, but at the same time, the vortice that the NHC has pegged and the one which several of us have already stated earlier is also there. At this point, it's a battle of which center wins out.

But at least since Isaac is deciding to stick around, he looks to be finally consolidating and will give us a better idea of a forecast.

--------------------
Andrew 1992, Irene 1999, Katrina 2005, Wilma 2005



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MikeCAdministrator
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Re: Tropical Storm Isaac Forecast Lounge [Re: CaneTrackerInSoFl]
      #93422 - Thu Aug 23 2012 08:21 PM

Tomorrow should be the start of a clearer picture, at least I hope so, since time will run out if it stays disorganized tomorrow. Things I'm looking for overnight is how much latitude it gains (or doesn't) and if the recon finds a decent center or not.

Models have shifted west during the day, from a concentration along the west coast of Florida (except Euro) to more west of Floirda toward the western Panhandle. Euro moved more west back toward Louisiana, but the lack of a definite center really keeps me from trusting any of these. (Either west or east, which is still a possibility) The recon fix around 15.5N 67.5W is what's (Barely) dominating now it seems. Another split system tearing itself apart.

Tomorrow night it may be close enough to force watches up along the keys.


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WeatherNut
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Re: Tropical Storm Isaac Forecast Lounge [Re: MikeC]
      #93423 - Thu Aug 23 2012 08:33 PM

It also has been said that if the initialized center is not the dominant center...than the models aren't going to be reliable because they dont initialize properly. Also, is anyone noticing that there are vast swaths of data missing from the recon flights...its been maddening to try and follow, and its been both aircraft that sample at lower altitudes. Pressure readings are all over the place...and I still dont see any significant west wind either.

--------------------
Born into Cleo (64)...been stuck on em ever since


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ftlaudbob
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Re: Tropical Storm Isaac Forecast Lounge [Re: MikeC]
      #93424 - Thu Aug 23 2012 08:34 PM

As of 8pm pressure is down to 1002 and max wind is up to 45.If this trend continues overnight things maybe come clearer.

--------------------

Survived:
Gloria,Bob,Katrina,Wilma and a bunch of tropical storms.


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MikeCAdministrator
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Re: Tropical Storm Isaac Forecast Lounge [Re: ftlaudbob]
      #93425 - Thu Aug 23 2012 08:38 PM

The next (0z) model runs (some of the early cycles will be out soon, and late cycles starting around 11:30) have some the Gulfstream IV data in them. Special Balloon launches are starting tomorrow as well, so there will be a good deal more data points for the models and hurricane center tomorrow. The "center" mentioned above probably will change again, last night I said the northern one looked more healthy, and it wound up being the opposite.

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mcgowanmc
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Re: Tropical Storm Isaac Forecast Lounge [Re: danielw]
      #93426 - Thu Aug 23 2012 09:06 PM

Land Interaction. I don't see how these models 'model' that.

And no Recorded Hurricane has traversed Hispaniola, Cuba and gone up the West side of Fl.
as a Hurricane.

The Drought. And MS has been wet. Along with Tallahassee.

Quote:

The unusual drought conditions are the result of a weather pattern known as the death ridge, said Prescott Bishop, an atmospheric science graduate student from San Antonio, Texas. “It stretches from the Rocky Mountains to the East Coast,” Bishop said. “It’s even larger than last summer’s.”

Bishop said the death ridge is a warm, high pressure weather system that has covered the Great Plains since April.
“High pressure makes the weather warmer and drier, which makes the high pressure stronger, causing even more warmth and dryness,” said Garrett Black, an atmospheric science senior from Hutchinson.

So far, no other weather pattern has broken the death ridge, which is unusual, Black said. Black did have hope that weather systems moving into the region this week could begin to curb the drought conditions.




http://kansan.com/news/2012/08/22/death-ridge-causes-drought-raises-food-prices/

So, just like Ernesto. If there's a chance of Sabine River to Morgan City,
Isaac will take it.

IF the EMCWF is correct and

http://www.meteo.psu.edu/~gadomski/ECMWF_12z/ecmwfloop.html

Triangulates Isaac between Cuba, Jamaica and Western Haiti. the Euro will really
start looking good.

And a Cat 4 would kill the Death Ridge.

Edited by mcgowanmc (Thu Aug 23 2012 09:20 PM)


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danielwAdministrator
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Re: Tropical Storm Isaac Forecast Lounge [Re: MikeC]
      #93427 - Thu Aug 23 2012 09:08 PM

Ships model is showing a possible RI event. 36% chance.
Prob of RI for 25 kt RI threshold= 36% is 2.8 times the sample mean(12.8%)
Prob of RI for 30 kt RI threshold= 17% is 2.0 times the sample mean( 8.4%)

I've never paid much attention to the parameter below. If those numbers are Helicity in m2/s2, that's some major spinning going on. Which is what we have been seeing on the sats.
850 MB ENV VOR 83 77 87 89 95 80 88 82 100 90 74 50 45

http://tropic.ssec.wisc.edu/real-time/wi...zoom=&time=

Edited by danielw (Thu Aug 23 2012 09:13 PM)


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