Isaac remains disorganized

By: Dr. Jeff Masters , 8:29 PM GMT on August 23, 2012

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Tropical Storm Isaac has strengthened slightly, data from the hurricane hunters show, but the storm remains disorganized and difficult to forecast. If you have to make decisions based upon what Isaac will do, I highly recommend that you wait until at least Friday morning to make a decision, if at all possible, as the forecasts then should be of significantly higher accuracy. Isaac continues to have a large area of light winds about 50 miles across near its center. This makes the storm subject to reformations of the center closer to areas of heavy thunderstorms that form, resulting in semi-random course changes. Until Isaac consolidates, the lack of a well-defined center will make forecasts of the storm's behavior less accurate than usual. An Air Force Reserve hurricane hunter aircraft is in Isaac this afternoon, and has found that surface tropical storm-force winds on the east side of the storm, south of Puerto Rico, have undergone a modest expansion. These winds were mostly in the 40 mph range, with a few areas of 45 mph winds. The surface pressure remained fairly high, at 1004 mb. Infrared and visible satellite loops show that Isaac has fairly symmetric circular cloud pattern, with developing spiral bands that are contracting towards the center, which suggests intensification. However, the storm has a very clumpy appearance, and is a long way from being a hurricane. Given the storm's continued reluctance to organize, Isaac is unlikely to reach hurricane strength before encountering Haiti and Cuba. An analysis of upper level winds from the University of Wisconsin CIMSS shows an upper-level outflow channel well-established to the north, and an intermittent outflow channel to the south. Radar imagery from Puerto Rico shows some weak low-level spiral bands that haven't changed much in intensity or organization this afternoon. NOAA buoy 42060 reported 1-minute mean winds of 35 mph and a wind gust of 40 early this afternoon. At St. Thomas in the Virgin Islands, wind gusts up to 45 mph were observed early this afternoon. Isaac's rains caused major flooding last night in Trinidad and Tobago, the southernmost islands of the Lesser Antilles chain, according to the Trinidad Express. Isaac's rains have not been heavy enough today to cause flooding problems on other islands.


Figure 1. True-color MODIS image of Isaac taken at 1:40 pm EDT August 23, 2012. Image credit: NASA.

Latest model runs for Isaac
The latest set of 12Z (8 am EDT) model runs have shifted to the west compared to the previous set of runs. The models continue to show a west-northwestward track to a point on the south coast of Hispaniola, then across eastern Cuba and into the Florida Straits between Florida and Cuba. A trough of low pressure is then expected to pull Isaac to the northwest and then north, towards the Florida Panhandle. The big news in this model cycle is that both of our top models--the GFS and ECMWF--predict that 5 - 6 days from now, the trough of low pressure pulling Isaac to the north may not be strong enough to finish the job. These models predict that the trough will lift out and a ridge of high pressure will build in, forcing Isaac more to the west. The GFS predicts this will occur after Isaac makes landfall in the Florida Panhandle, resulting in Isaac moving slowly to the west over land, from Georgia to Alabama. The ECMWF predicts the westward motion will happen while Isaac is in the northern Gulf of Mexico, resulting in an eventual landfall near the Louisiana/Texas border on Thursday. There are some huge issues to resolve to make an accurate long-range track forecast for Isaac. Where will its center consolidate? How will the interaction with the mountains of Hispaniola and Cuba will affect it? Where will Isaac pop off the coast of Cuba? Hopefully, the data being collected by the NOAA jet this afternoon will give us a more unified set of model forecasts early Friday morning. For now, pay attention to the cone of uncertainty. If you're in the cone, you might get hit.



Figure 2. Predicted 5-day rainfall total ending at 8 am EDT Tuesday August 28 from Tropical Storm Isaac. Graphics were generated from the 12Z (8 am EDT) August 23, 2012 run of the HWRF model (top) and GFDL model (bottom). The heaviest rainfall is expected to occur in a 50 - 80 wide wide swath along and to the right of where the center tracks. Amounts in excess of 8 inches (yellow colors) are predicted for portions of the Dominican Republic and Haiti from the HWRF model, but not the GFDL model. Given the current disorganization of Isaac, these rainfall amounts are probably at least 20% too high. Image credit: Morris Bender, NOAA/Geophysical Fluid Dynamics Laboratory.

Jeff Masters

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Quoting Seflhurricane:
were are you at ???


Ruidoso, New Mexico
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Quoting StormTracker2K:
Where's FL. Now all the ensembles have shifted back east and are covering the whole state of FL. Concensus is right up the west coast of FL.



Given the current synoptic situation I just can't see Isaac moving as far West as Lousianna. The models had to come back East a bit, especially the Euro, which it did last night.
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Quoting Jedkins01:



That's for sure! I'm completely thrown off by how physics problems are worked, entirely word problems with many different ways to look at them. I always avoided word problems from the baby stages of College algebra to Calculus 3 last semester because I never get tested on them really. I'm regretting that now. However we are assigned a massive load of homework so I'll acquire the pattern soon enough as long as I put a lot of work into it. I've found my learning pattern is that I often struggle badly at new things for some time with seemingly slow progress but once I break through "the fog" I learn very fast and it becomes easy. I have a strange mind that way.
Not to get too much off topic but you're learning the sciences which I would guess is always on topic, but with all the higher mathematics and sciences, make sure you thoroughly understand each step as you go along because more often than not, it will build upon itself. Found that by merely just completing assignments, reading a little ahead, helping others (One of the best ways to learn is to teach.), and limiting distractions which there are way too many on campus, it all became a pleasurable routine full of great experiences and now memories.
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4070. Brock31
http://www.goes.noaa.gov/HURRLOOPS/huecvs.html

Interesting feature off the SC coast.
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Quoting kmanislander:


I am. Playing golf 7000 feet up in the mountains. Isaac trying to ruin my last day LOL.
were are you at ???
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Quoting CJ5:


A glance at the satellite loop would tell you that, but the outflow is becoming excellent on the SW side, and recon is finding an intensifying cyclone.
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Quoting BahaHurican:
Comments like this worry me, because my instinct is that the RNC's problem in Tampa is not tied to a landfall in Tampa. A close pass by a strong storm, or as we saw in June, a heavy rainfall event triggered by a meandering storm, could have similarly disastrous effects. The best forecast track I've seen recently for Tampa is the one with Isaac moving away towards Mobile at a pretty fast clip. Anything close to the FL coast or moving slowly is a serious problem.


Most models now have this very close to Tampa. Infact Tampa would be on the most dangerous right side of the storm. Everyone needs to look outside of the center point as the worst weather in a tropical cyclone is on the eastside. Basically all of FL would get whacked from Issac.

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4065. Grothar
Quoting Drakoen:
I see the models have shifted back east some over the FL panhandle. Will be interesting to see if they maintain this philosophy as the time frame closes.


I saw it first :)
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Quoting Seflhurricane:
hope you are having a good time, the G-IV plane samples the area last night and the models have come into agreement in a path towards eastern/central cuba , then across the florida keys and into the eastern gulf after that is were things get tricky does the high build back west and push it into louisiana or does a weakness remain longer and it moves into northern florida , but the confidence in south florida has increased


I am. Playing golf 7000 feet up in the mountains. Isaac trying to ruin my last day LOL.
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Quoting Floridaweathergirl:
I live in Miami and my co worker is telling everyone she thinks it's a zagger. She says it's going to be zig zagging his way through. she showed me a link where you see his path from the start.

http://abclocal.go.com/wtvd/feature?section=weath er/hurricanes&id=6372208

you have to look at the average path and tropical systems do not follow a sraight line they will jog back and forth but you must look at a consistency
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4062. WxLogic
12Z NAM is running and ingested quite a bit of RECCO Data:



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All I see looking at the steering is Isaac going west north west.



Isaac is starting to feed on the high OHC. With Hot towers popping in the storms in the western side.


The red box is the area of high OHC which corresponds with the below image


It is likely we will see Isaac continue to strengthen due to the high OHC.
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Quoting ltlurker:



Is that WunderKid?


No, he is referring to me. I replied to his post but not sure he saw it.
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Quoting kmanislander:


Good Morning

I have been following the blog but not posting as I am traveling and on my IPad.

Watching this storm very carefully. It has been exceedingly difficult to forecast and exceptionally stubborn. The position far South and inability to ramp up sooner raises questions as to whether the trough can pull it up before bypassing the system.

Debby has already demonstrated what can happen with the track when a system defies the models. I do not have acces to my links so not able to post in detail but today is a make or break as to whether it finally follows the NHC forecast or continues essentially due West.

hope you are having a good time, the G-IV plane samples the area last night and the models have come into agreement in a path towards eastern/central cuba , then across the florida keys and into the eastern gulf after that is were things get tricky does the high build back west and push it into louisiana or does a weakness remain longer and it moves into northern florida , but the confidence in south florida has increased
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4057. Grothar
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Quoting StormTracker2K:
Where's FL. Now all the ensembles have shifted back east and are covering the whole state of FL. Concensus is right up the west coast of FL.

Looks like most models see a shortwave picking up the storm and taking it NE. Yesterday looked like steering was becoming weak in the North gulf.
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I live in Miami and my co worker is telling everyone she thinks it's a zagger. She says it's going to be zig zagging his way through. she showed me a link where you see his path from the start.

http://abclocal.go.com/wtvd/feature?section=weath er/hurricanes&id=6372208

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Quoting pottery:
Anyone seen KMan ?



Is that WunderKid?
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Quoting StormTracker2K:
Where's FL. Now all the ensembles have shifted back east and are covering the whole state of FL. Concensus is right up the west coast of FL.



The stronger Isaac is, the farther East he goes. The worst situation is a close ride all the way up the coast, which is looking more and more likely.
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4052. pcbfla
I have a question, does any one know if you see any thing north of the United States coast may influence Isaac?
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4051. GetReal
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I agree. Carl Parker said this morning that the GFS has shifted a little more back to the east.

Did anyone else pickup on this ?
Beachman42

Thanks.
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Quoting MTWX:


I'm gonna stick with my prediction from yesterday morning:

going to pass over Jamaica and the western tip of Cuba, then strengthen to finally cause it to turn and make final landfall somewhere between New Orleans and Pensacola as a Strong Cat.1 to Cat 2...

(Already took the crow out of the freezer to defrost, if I'm wrong) ;)


Looking at satellite loops, I dont see much northward movement yet. I dont think the center is defined enough for the models to do a good job yet.
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Quoting wxchaser97:
Good morning everyone, Isaac looks to be organizing and tightening up.


The southern outflow is awesome. Very low shear. This boy could ramp up quite a bit today.
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4047. MahFL
er looks like an eye clearing out, which surely can't be true ?
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Quoting CJ5:
I think some of getting ahead of themselves. He does look better and seems to be consolidating, but he still is very thin on the N side. The convection is three sided right now.
I saw the 3 distinct areas. It seems like it's almost breaking up. The outflow in the west in south is healthy
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Quoting Drakoen:
I see the models have shifted back east some over the FL panhandle. Will be interesting to see if they maintain this philosophy as the time frame closes.


Yeah I would imagine there will be some shift back to the right.
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NWS is Melbourne is saying a track up the West Coast of FL means this.

SUN-TUE...FORECAST FROM LATE WEEKEND INTO NEXT WEEK DEPENDS HEAVILY
ON THE TRACK AND INTENSITY OF ISAAC...WHICH AT THIS TIME REMAINS
QUITE UNCERTAIN. IT IS STILL UNCLEAR HOW MUCH THE INTERACTION WITH
CUBA WILL DISRUPT THE SYSTEM AND HOW MUCH ISAAC STRENGTHENS AS IT
MOVES BACK OVER WATER. THE 00Z GFS HAS THE CENTER OF ISSAC EMERGING
FROM CUBA FASTER THAN THE 18Z RUN...LEADING TO A STRONGER SYSTEM.
RUN TO RUN MODEL TRACKS ALSO CONTINUE BETWEEN THE GFS AND ECMWF...
BUT A BETTER CONSENSUS BETWEEN THE TWO ARE DEVELOPING.

THE LATEST OFFICIAL TRACK FROM THE NHC HAS ISSAC EMERGING FROM CUBA
AS A TROPICAL STORM AND MOVING NORTHWEST TOWARD THE KEYS/SW FLORIDA
COAST SUNDAY EVENING. IT IS THEN EXPECTED TO STRENGTHEN TO A
HURRICANE AS IT CONTINUES NORTHWEST INTO THE EASTERN GULF MONDAY
THROUGH TUESDAY. THIS TRACK WOULD BRING INCREASING RAIN CHANCES...
MAINLY IN THE FORM OF SQUALLS PRODUCING GUSTY WINDS...LOCALLY HEAVY
RAIN AND THE POTENTIAL FOR RAINBAND TORNADOES SUNDAY AFTERNOON INTO
EARLY NEXT WEEK.
PERSONS SHOULD CONTINUE TO CLOSELY FOLLOW THE
LATEST FORECASTS FOR ISAAC OVER THE COMING DAYS AS ADJUSTMENTS IN
THE TRACK AND INTENSITY WILL LIKELY OCCUR.

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4043. Grothar
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Long Key, FL, already gusting into the 40's. This storm has a big circulation...

Link
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4041. centex
Quoting wunderkidcayman:
what kida fustrates my is HH RECON saying the LLCOC is at 15.6N 70.4W and NHC decides to change it and put it at 16.0N 70.3W
Right, I don't remember them ever ignoring the HH.
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Another View of the same data as post 4033...
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Quoting SouthTXWX:
I just dont see this making landfall on the west coast of FL, i see a Panhandle event now. Not to say their wont be some wind and rain on the west coast but isaacs wrath could very well stay off shore. Looks like the RNC may be spared for the time being. Surf will definitely increase and low lying areas may have flooding issues are Isaac rides up the coast close to FL.
Comments like this worry me, because my instinct is that the RNC's problem in Tampa is not tied to a landfall in Tampa. A close pass by a strong storm, or as we saw in June, a heavy rainfall event triggered by a meandering storm, could have similarly disastrous effects. The best forecast track I've seen recently for Tampa is the one with Isaac moving away towards Mobile at a pretty fast clip. Anything close to the FL coast or moving slowly is a serious problem.
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Quoting FLWeatherFreak91:
omg run on sentence if I've ever seen one. I tried reading it out loud, but almost died because there were no periods so I ran out of air.


I lost my coffee on that one. Haha!

I said yesterday tha I had a funny feeling that Isaac would explode in 12-36 hours, aaaaand it looks as though he may be on the verge of doing so. There is literally nothing in the way now, he's fully aligned and in a very low-shear and moisture-laden environment.

Today will be interesting, to say the least.

And can Joyce even be considered even remotely tropical anymore? I wouldn't even call that a TD.
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4036. CJ5
Quoting CJ5:
I think some are getting ahead of themselves. He does look better and seems to be consolidating, but he still is very thin on the N side. The convection is three sided right now.
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4035. Grothar
Quoting ProgressivePulse:


I keep hoping one day I'll click my saved link to the old SFWMD site and it will magically appear. I really miss having the forecast verification and recon fixes plotted.


Gee, maybe you might have another site that does that. Have you looked carefully?????????

What was the old link to the SFWMD?
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4034. GetReal
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From the 0z soundings:

A)Midlevel height weakness noted over the plains states and east of the rockies.
B)Weak midlevel ridging nosing out over FL into the east gulf.

As A) moves downstream the weak 700mb ridging currently N of Cuba should dimininsh, IMO.
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4032. Drakoen
I see the models have shifted back east some over the FL panhandle. Will be interesting to see if they maintain this philosophy as the time frame closes.
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Where's FL. Now all the ensembles have shifted back east and are covering the whole state of FL. Concensus is right up the west coast of FL.

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Looking forward to this storm going to be interesting on Marco, Today we are preparing at marco river marina. I allways dread that charley right hook! #westcoastcruiser
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4029. CJ5
I think some of getting ahead of themselves. He does look better and seems to be consolidating, but he still is very thin on the N side. The convection is three sided right now.
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4028. Grothar
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Good Morning everyone! I live in Jackson County Miss about a 1/8 mile from the gulf and my house is trying to be taken over by ants. After many years of reading this blog I have heard that ants seem to sense tropical storms. Is that true? If so Isaac may very well be on his way to South Miss and or somewhere very close.
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Quoting Maineweatherguy20023:

SW quad looks good


He is flexing his muscles. Get into the Gulf and watch it go.
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Good morning everyone, Isaac looks to be organizing and tightening up.
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Quoting TropicalAnalystwx13:

That loop is huge, lol.


Bigger is Better...:D
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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