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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3924. CJ5
Isaac looks a little better this am. Seems to be getting a little stronger. It also appears he is trying to consolidate, thought we looked for that all day yesterday without any results. Shear ahead looks marginal. There is a little bit of dry air ahead but I don't see that as much of an issue. His speed seems to have slowed slightly and he is still producing plenty of convection. I don't think he is completely stacked yet, but much better than last evening. It appears the models have shifted to the west and I think if he struggles all day today, like yesterday, we will see a movement by the models even further west. To get a good storm, he is going to have to consolidate today.
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Considering the distance to land, NHC will likely issue a special advisory with the updated intensity.
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Quoting RTSplayer:


It's west, and probably drifting S...

...or will wobble south significantly again during the next 6 to 12 if steering holds.

So the further south Isaac goes, the less chance of a Haiti hit and more west in the GOM Isaac will be.
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3921. Grothar
Quoting StormHype:


Yeah... I hear ya. Surprised how many still think if the 'center line' doesn't run over your house, you're in the clear. Even my wife said last night "looks like it's going offshore and will miss us." I said "Honey, it's a 200+ mile diameter storm, not a fishing boat."


I don't usually write this, but LMAO!
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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.
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3919. nolajet
Quoting JasonRE:
So even the MS and LA coast are 'within the cone of uncertainty' this thing is now for sure heading into AL? I understand that there is still uncertainty, but didn't I read that by today it would be more exact on where it would go by today or tomorrow? I'm in LA here so just wondering after last night's models and cone was further West almost towards us. Thanks


If you are in the cone of uncertainty, then there is no reason to think that it isn't at least possible for it to come your way. That outlook is for Wednesday at 2am, there's a lot of time in between for models and tracks to adjust to.
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65 mph seems likely at 11 am.
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Quoting weatherguy03:


Yeah, I was thinking if anything maybe 15.5 to 16.0, somewhere in there. Not gonna make much difference in the overall long term track. Haiti and the D.R are still gonna get blasted with heavy rain unfortunately especially if Isaac keep growing and getting stronger. Will be interesting to see how much land interaction it does have with Hispaniola.


Yes and still lots of possible surface center jogs and wobbles as it attempts to consolidate and as frictional forces begin to affect it as it gets closer to Hispanola.
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Quoting LightningCharmer:
Wilma did something similar to the Florida Keys. Pushed the water away, and then it came back, and somebody forgot to tell it to stop at the shoreline. Have heard some great Donna stories from the Keys and SW Florida.
yup! 1/2 of key west was under water due to wilma's storm surge. Some homes had 6 ft of water...many vehicles were destroyed . And it all happened after wilma passed north of the island, moving east.
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LATEST ON TROPICAL STORM ISAAC
__________________________________________

NNOTE: the white line inside the path is my best bet...
add or take 5 mph from current wind intensities...

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3914. Grothar
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Quoting indianrivguy:


That scenario would be awful for Tampa. A near miss would tend to empty the bay and as the center passed a tidal bore of storm surge could blast up the bay.


Don't forget, we're going to be close to a full moon by the time Isaac comes ashore as well. That will further influence storm surge.
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Quoting pottery:
I would love to see what Dr. Masters has to say, right now.

New Blog Time !

He seems to start a new blog when the current one gets around 4000 comments.
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Willing to bet that Isaac is a 60mph (50kt) storm, if not 65mph (55kt).
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Flight level winds support a stronger TS.
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Quoting ProgressivePulse:


Mention the GOM and people get tunnel vision. Who cares if it has to cross Haiti, Cuba, "FLORIDA" Keys and Potentially SFL on it's way darn it, it's going into the GOM.

In other news, I about had a heart attack seeing this mornings NHC position after last nights recon...


Yeah... I hear ya. Surprised how many still think if the 'center line' doesn't run over your house, you're in the clear. Even my wife said last night "looks like it's going offshore and will miss us." I said "Honey, it's a 200+ mile diameter storm, not a fishing boat."
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3908. MTWX
Quoting RTSplayer:


Well, I'm going to paint a broader brush because I'm just not sure at this time.

It may still hook hard after passing the W. Tip of Cuba, so I'll say as far east as possibly Panama City.

We'll go with Texas/LA border for the west side of my cone for now.

For now, most likely is probably between NOLA and Pensacola as you've said though. I just don't want to look too silly later on.

So basically I'm shifting the official forecast westward by about half a circle radius.

But because the storm will be taking a much more circuitous route than the official cone, it will likely be 12 to 24 hours slower.


I don't mind looking silly!! LOL!! This is the first storm where I actually posted my personal forecast on the blog... So we will see how I do!!

One thing I have learned over the years is to never even try to forecast a landfall location until it is, at the max, 5 days out!! ;)
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3906. scott39
We are really going to realize the size of Isaac once in the GOM. He will have a far reach from the center.
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AL, 09, 2012082412, , BEST, 0, 159N, 704W, 45, 1000, TS, 34, NEQ, 160, 90, 60, 120, 1008, 250, 60, 0, 0, L, 0, , 0, 0, ISAAC, D,

12Z models might be the best run yet.
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3904. bwi
Looks like the Air Force mission is ascending. Seems to me between the drops and and the flight measurements, they've found a pretty solid center south of 16n with about 1000mb pressure and strong tropical storm winds. we'll see how NHC interprets at the 11am update!
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3903. Michfan
Quoting Elena85Vet:


But they did weigh the GFS more. When the GFS adjusted they followed suit.

I would think the NHC has the dropsonde data from the burmuda high last night into their system at the 8am this morning. I don't know that for sure, just assuming. If their next advisory has a similar cone I'll be a pretty solid buyer of landfall on the N. Gulf coast.

The only thing that would change my mind is if Isacc were to somehow achieve hurricane status here in the next 24-36 hours.


They do. 40 Dropsondes were inputted into the 00Z models last night.
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Quoting AussieStorm:
Is Isaac still heading west or is it west north west now?


It's west, and probably drifting S...

...or will wobble south significantly again during the next 6 to 12 if steering holds.
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Quoting WPBHurricane05:
Wonder if we'll see a special update. Could put the hurricane warnings back up for Haiti too.
dont think so maybe cuba but thats going to be a close call
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3900. pottery
I would love to see what Dr. Masters has to say, right now.

New Blog Time !
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Quoting Jedkins01:


Might as well call the national guard ahead of time while you're at it, make sure to alert the NHC to adjust the path to a directly over Tampa as a category 2 because that one model run is definitely without a doubt going to be the outcome ;)


I guess I'm doom if I don't evacuate the Tampa Bay area by tomorrow, wait where's my coffee?
Prognosticating before the first cup of coffee is a bad idea... lol

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3898. TBPauly
Quoting washingaway:


That looks like about a 100 mile jump east or so, on average...
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Quoting JasonRE:
So even the MS and LA coast are 'within the cone of uncertainty' this thing is now for sure heading into AL? I understand that there is still uncertainty, but didn't I read that by today it would be more exact on where it would go by today or tomorrow? I'm in LA here so just wondering after last night's models and cone was further West almost towards us. Thanks
i would not be concerned until it leaves the cuban coast lots of things can happen
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Quoting atmosweather:


Microwave puts it at around 15.4-15.5...NHC says 16N based on dropsonde data (which actually did verify for the last 2 vortex fixes), RECON says 850 mb center is around where microwave depicts. So honestly I'm not sure, it just doesn't seem to be organized in there at all, yet RECON are finding hurricane strength winds at 5,000 feet. Really strange!


And if both the low level center estimate by RECON and the data showing increasing winds and deepening are true, then Isaac is basically intensifying without being ANYWHERE NEAR "well-organized". If so...anyone in the SE-ern United States truly need to be hoping for as much land interaction as possible in the next 48 hrs because he's going to make quick work of deepening when he aligns himself vertically.
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Wonder if we'll see a special update. Could put the hurricane warnings back up for Haiti too.
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Quoting floridaboy14:
the HH found the center at 15.7N they show it moving at 275 degrees which is just north of due west. i dont understand why the nhc has it bending NW over hati and cuba just because the models do. if they open their eyes, they can see he is trying to shoot the gap between hati jamaica and cuba. your thoughts?


I have been saying the last few days it was gonna slip just South of Haiti, especially given its weaker state the last few days. Right now its gonna be close depending on the ramp up today, if it happens. If he suddenly explodes today he could make that jump towards Haiti, if not he moves just South of Haiti. Its all about organization.
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Quoting kwgirl:
Good morning all. Here in the Keys we are getting ready for this storm....Maybe I should buy a kayak :) Get ready Gulf Coast. This is coming your way. Hopefully it will not get it's act together.


You buy that kayak and you may end up in Apalachicola next week :)
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3891. scott39
Quoting BahaHurican:
In that sat picture you can see the bands of Isaac in front of it starting to "fan" out better. That is the signs of a developing TS. He has some more dry air to deal with, but once he passes 75W we should continue to see Isaac develope. The strength of Isaac for the gulf Coast, is going to be how long will Isaac be over Cuba and how fast will he move in the GOM until landfall.
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Quoting MTWX:


I'm gonna stick with my prediction yesterday morning:

going to pass over Jamaica and the western tip of Cuba, the 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) ;)


I can buy this...unless he actually makes a 3 before landfall
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based on recon info it appears likely we have a 60 mph TS at 11am and if trends continue a hurricane watch may be needed for cuba
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3888. emguy
Quoting yonzabam:


It'll still collapse the eye wall, and it probably won't have time to get it back. Happened to Gustav, among others.


Gustav traversed the entire length of Cuba...by the time is reached western Cuba, it just couldnt hang on any longer. It ran out of gas. This kind of path affected Ike too.

Storms that cross western Cuba on any level of south-north route do pretty good. I should know...Hurricane Charley got me. Otherwise, the western 2/3 of Cuba less one mountain, generally do not hinder hurricane core's much.
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Quoting Abacosurf:
I have heard that during Donna in Naples the bay almost emptied out with the offshore winds and then within minutes of the eye passing to the north the water surged 12 feet within 30 minutes. My house has a water line behind the walls that shows the water was chest deep out side. I am 1/2 mile to the ocean and 1/4 mile to the bay.
Wilma did something similar to the Florida Keys. Pushed the water away, and then it came back, and somebody forgot to tell it to stop at the shoreline. Have heard some great Donna stories from the Keys and SW Florida.
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3886. JasonRE
So even the MS and LA coast are 'within the cone of uncertainty' this thing is now for sure heading into AL? I understand that there is still uncertainty, but didn't I read that by today it would be more exact on where it would go by today or tomorrow? I'm in LA here so just wondering after last night's models and cone was further West almost towards us. Thanks
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Quoting WxLogic:
Good Morning:

Now this is a deep TROF in the GOM:



No wonder Isaac is acquiring a WNW to NW track as depicted by the HH fixes.


Maybe why the GFS and GFDL have went back east some. The Ensemble Mean is right over Tampa at 84hrs as a hurricane. Something to watch as the day goes on to see if the Euro responds to this trend as well. So far the CMC, GFDL, and GFS all carry Issac right up the FL west Coast to a final landfall just east of Panama City.
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Quoting mikatnight:

Real nice... except the center isn't at 17.3N. Start the models again at even 16N and see what they come up with.
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3883. icmoore
Quoting indianrivguy:


That scenario would be awful for Tampa. A near miss would tend to empty the bay and as the center passed a tidal bore of storm surge could blast up the bay.


Yes it would and I wish his WOW!!! didn't seem so happy ... it's just me LOL going in for extra coffee this morning.
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Is Isaac still heading west or is it west north west now?
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Quoting atmosweather:


Microwave puts it at around 15.4-15.5...NHC says 16N based on dropsonde data (which actually did verify for the last 2 vortex fixes), RECON says 850 mb center is around where microwave depicts. So honestly I'm not sure, it just doesn't seem to be organized in there at all, yet RECON are finding hurricane strength winds at 5,000 feet. Really strange!


Yeah, I was thinking if anything maybe 15.5 to 16.0, somewhere in there. Not gonna make much difference in the overall long term track. Haiti and the D.R are still gonna get blasted with heavy rain unfortunately especially if Isaac keep growing and getting stronger. Will be interesting to see how much land interaction it does have with Hispaniola.
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impressive outflow to the south,sw,se of the storm
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Quoting MTWX:


I'm gonna stick with my prediction yesterday morning:

going to pass over Jamaica and the western tip of Cuba, the 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) ;)


Well, I'm going to paint a broader brush because I'm just not sure at this time.

It may still hook hard after passing the W. Tip of Cuba, so I'll say as far east as possibly Panama City.

We'll go with Texas/LA border for the west side of my cone for now.

For now, most likely is probably between NOLA and Pensacola as you've said though. I just don't want to look too silly later on.

So basically I'm shifting the official forecast westward by about half a circle radius.

But because the storm will be taking a much more circuitous route than the official cone, it will likely be 12 to 24 hours slower.
Member Since: January 25, 2012 Posts: 33 Comments: 1520
Quoting ProgressivePulse:


Mention the GOM and people get tunnel vision. Who cares if it has to cross Haiti, Cuba, "FLORIDA" Keys and Potentially SFL on it's way darn it, it's going into the GOM.

In other news, I about had a heart attack seeing this mornings NHC position after last nights recon...


lol, so true man, that is because the GOM has the 3 big freak out hurricane cities, Houston, New Orleans, and Tampa.
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3877. FOREX
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.


Maybe he is an auctionairre when not blogging.
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Quoting washingaway:


Interesting. I should have picked up on this last night when the GFS showed Isaac drifting NW toward Panama City. I wouldn't be surprised to see a shift to the NE in upcoming model data at around 84 hours. Depends on the strength of the second trough (currently sitting over New Mexico).
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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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