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Tropical Storm Isaac, Part 1: Moving Through The Eastern Caribbean Sea


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Man that thing is bombing the freak out, then again it's hard not to imagine with the hot tub water sitting in the Gulf if it does make it there (although that would be really bad for gas prices). :wub:

Despite issues with outside influences (other vort maxes, the TUTT, etc.), one cannot deny that these verbatims are churning out some interesting tracks.

really hoping that bombing track into the GOM doesn't verify.... highly doubt houston would get back to normal in a week for when I'm heading down to visit friends.. not to mention Gas prices would jump faster than Usane Bolt can run the 100 meters... interesting tracks the models are pointing out tho...

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Here at home all I have is what I can see on the web, so I don't have that kind of detail. My point really just was that the previous few runs have had more of a strung out wave looking feature, while this runs has more of a look of intense vorticity center indicative of a TC. While I am definitely in the camp of believing that the global models are an excellent tool in forecasting tropical cyclone intensity trends, I just did not want to leave the idea that just because the low center is only 1008 mb that means it's not showing much development. I think it is better to look at the vorticity, its trends, and how aligned it is vertically. Gordon was a good example of that.

I totally agree with ya ;) Plus this far out there is no point in put much faith in that kind of detail of the 500mb...I'm sure that feature will be gone with the next run.lol. I was just relaying why I thought the model produced the crappy sfc winds and organization during that time.

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I'm going to take a guess and say that the multiple vort maxes at 500 mb at 156 hrs is to blame for the lack of sfc and wind organization on the Euro. during that time frame. Having two regions fighting for center of circulation dominance I would assume would induce areas of convection that would interfere with one another hindering a nice area of central organization that would promote intensification. Later on at 180 the vort max consolidates at 500 mb though. post-3697-0-32808700-1345405134_thumb.pn

Given the upper air pattern over the Western Caribbean, the ECMWF is definitely low balling the intensity in my opinion. I continue to be skeptical of its solution in the medium range in terms of intensity.

Here at home all I have is what I can see on the web, so I don't have that kind of detail. My point really just was that the previous few runs have had more of a strung out wave looking feature, while this runs has more of a look of intense vorticity center indicative of a TC. While I am definitely in the camp of believing that the global models are an excellent tool in forecasting tropical cyclone intensity trends, I just did not want to leave the idea that just because the low center is only 1008 mb that means it's not showing much development. I think it is better to look at the vorticity, its trends, and how aligned it is vertically. Gordon was a good example of that.

Agree somewhat... its worth mentioning that the ECMWF had no representation of Ernesto in the Western Caribbean until 24 hours before its robust development as it slowed down. Again given its poor performance with previous systems in this particular area, I am not putting much confidence in the ECMWF intensity long term. The upper level environment should be favorable so its unknown why there isn't more development.

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Given the upper air pattern over the Western Caribbean, the ECMWF is definitely low balling the intensity in my opinion. I continue to be skeptical of its solution in the medium range in terms of intensity.

Agree somewhat... its worth mentioning that the ECMWF had no representation of Ernesto in the Western Caribbean until 24 hours before its robust development as it slowed down. Again given its poor performance with previous systems in this particular area, I am not putting much confidence in the ECMWF intensity long term. The upper level environment should be favorable so its unknown why there isn't more development.

Yup...Euro just hasn't been up to par this season in track or intensity in the long range. GFS seems to be laying it down so I will continue to roll with it until it gives me reasons not to.

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Yup...Euro just hasn't been up to par this season in track or intensity in the long range. GFS seems to be laying it down so I will continue to roll with it until it gives me reasons not to.

And to be fair, the GFS isn't overly agressive with the intensity of Invest 94L either. I'm thinking we see this as a moderate to strong tropical storm before it makes it to the Lesser Antilles. One thing that has changed today is that its no longer developing as strong of a mid-level reflection with the TUTT that was located SW of bermuda. This has resulted in a stronger ridge that does not pick up Invest 94L when its in the greater Antilles. Thats the feature worth watching in the modeling over the next few model cycles to see if we get a Caribbean Cruiser track vs. an East Coast threat.

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Yup...Euro just hasn't been up to par this season in track or intensity in the long range. GFS seems to be laying it down so I will continue to roll with it until it gives me reasons not to.

I think the euro so far is a bit better in handling this system if you look back about three days ago.

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Unlikely. Whereas a path like Charley can cut across Cuba in pretty much the shortest way possible with the core pretty much intact, the 18Z GFS gives 94L a 48 hr tour of Cuba which would be very hard to recover from.

Wouldn't analyze it in detail at this range, but your expert analysis is appreciated (no sarcasm). I'm guessing the GFS is responding to its ensembles in a sense, will be interesting to see where the model trends take us.

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Continues to get better organized...

000

ABNT20 KNHC 192340

TWOAT

TROPICAL WEATHER OUTLOOK

NWS NATIONAL HURRICANE CENTER MIAMI FL

800 PM EDT SUN AUG 19 2012

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SHOWERS AND THUNDERSTORMS CONTINUE TO SHOW SIGNS OF ORGANIZATION

ASSOCIATED WITH A TROPICAL WAVE AND A LOW PRESSURE AREA LOCATED

ABOUT 1400 MILES EAST OF THE LESSER ANTILLES. ENVIRONMENTAL

CONDITIONS APPEAR CONDUCIVE FOR A TROPICAL DEPRESSION TO FORM

DURING THE NEXT DAY OR SO. THIS SYSTEM HAS A HIGH CHANCE...80

PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS

AS IT MOVES WESTWARD AT 20 TO 25 MPH.

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Wouldn't analyze it in detail at this range, but your expert analysis is appreciated (no sarcasm). I'm guessing the GFS is responding to its ensembles in a sense, will be interesting to see where the model trends take us.

No offense to anyone (seriously, not trying to be obnoxious) but talking about whether or not something is going to hit Hispaniola or Cuba at this point, and how it would disrupt the core, is not very productive. Those islands really are not that big of targets in the grand scheme of things, and even in the near term there have been times when the thought was the time over them would disrupt a system greatly and the system recovered, and vice versa. Considering we are dealing with an undesignated disturbance that is still around 40W, this is just really not much meaningful that can be said

00Z TWD has the low center near 14N, 39W. Certainly looks to continue to improve in organization.

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latest satellite fix. hasn't strengthened, but 0.3º South of the last fix

19/2345 UTC 14.3N 39.8W T1.0/1.5 94L -- Atlantic

Healthy spread, as would be expected, in 18Z ensemble perturbations at 8 days, with a split, some sort of like the op 18Z into the Caribbean than Northwest, some missing the Caribbean to the North, forming what looks like two distinct clusters on the ensemble means, but none suggests a Northwestern Gulf threat at this time.

ETA:

CIMSS shear, and aligned vorticity, look like pluses for development. large size, competing convection may slow it. IMHO. MIMIC TPW loop shows dry air Northwest of 94L trying to circulate in, but with weak shear not blasting dry air into the center, a lot of convection, and a large circulation giving dry air plenty of time to modify, I'm just seeing any major negatives for development in the short term, IMHO.

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Beautiful anticyclone, dry air looks like the main problem right now. I have my doubts about this thing becoming classified before it reaches the Caribbean due to the large amount of dry air... every time a convective complex forms it will easily choke itself out with cold downdrafts.

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At this point it sure seems to be headed to the eastern Caribbean. I would be surprised to see the models go back NW after trending south-ish for a few runs in a row. I don't think the exact location of center formation matters that much (in terms of the future direction), it is a rather large area of circulation and unless there is some massive convective flareup away from the current center area, it shouldn't move its location very much.

As others have mentioned, it is impossible to know whether it will interact with the islands, stay south of the islands, or make a quick turn to the N like the GFS is showing. Considering it is getting close to peak season and the environment ahead isn't horrible, it almost certainly will form. But so much can change, it was just Friday afternoon that it was looking like it would be a well developed storm when it reached the islands.

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Wouldn't analyze it in detail at this range, but your expert analysis is appreciated (no sarcasm). I'm guessing the GFS is responding to its ensembles in a sense, will be interesting to see where the model trends take us.

No offense to anyone (seriously, not trying to be obnoxious) but talking about whether or not something is going to hit Hispaniola or Cuba at this point, and how it would disrupt the core, is not very productive. Those islands really are not that big of targets in the grand scheme of things, and even in the near term there have been times when the thought was the time over them would disrupt a system greatly and the system recovered, and vice versa. Considering we are dealing with an undesignated disturbance that is still around 40W, this is just really not much meaningful that can be said

00Z TWD has the low center near 14N, 39W. Certainly looks to continue to improve in organization.

Yeah, sry, I'm usually pretty good at not doing something like that. Guess 94L just didn't do much today so I got caught up responding to some outlandish hypotheticals. :wacko:

Back to reality, looks like 94L is walking a thin line. Shear and very dry air near that TUTT, but low shear and very moist just to the south.

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At this point it sure seems to be headed to the eastern Caribbean. I would be surprised to see the models go back NW after trending south-ish for a few runs in a row. I don't think the exact location of center formation matters that much (in terms of the future direction), it is a rather large area of circulation and unless there is some massive convective flareup away from the current center area, it shouldn't move its location very much.

As others have mentioned, it is impossible to know whether it will interact with the islands, stay south of the islands, or make a quick turn to the N like the GFS is showing. Considering it is getting close to peak season and the environment ahead isn't horrible, it almost certainly will form. But so much can change, it was just Friday afternoon that it was looking like it would be a well developed storm when it reached the islands.

Considering its current motion, the south trend doesn't look that farfetched right now.

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From what I can tell from the trends tonight, Invest 94L is not really getting better organized. If anything, it looks like the mid-level vortex and low-level vortex are still somewhat decoupled, with the low level circulation northwest (around 15N 40.5) ahead of the mid-level circulation center which has been moving wsw over the last few hours. The system still appears to be having some difficulty tapping into the moister air to the south in the ITCZ. While the storm is still likely to develop over the next 24-48 hours, I don't think we are going to see a very organized system before it reaches the Lesser Antilles.

6ykrac.jpg

One other thing I'd like to discount. Some people were mentioning the ECMWF has been preforming better than the GFS with regards to the curtailment in development. I wouldn't really agree. Both the ECMWF and GFS were pretty agressive with the genesis of Invest 94L and robust development in this range. The ECMWF might have backed off a run before the GFS followed suit but its still markedly weaker with the forecast of 94L in comparison to the GFS, which I think is not going to turn out to be correct.

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I understand that if this was a snowstorm forecasted to impact the Super Bowl in New York, it'd be fair game for discussion, and that the Republican National Convection is a big deal nationally, but let's just leave comments about it out of this thread, please. It's too easy for the thread to start going off track quickly. Thanks.

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