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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Isaac looking a bit better on satellite imagery...but we all know that means nothing.
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Quoting Joanie38:
Hi everyone.....

I have been lurking for a few hours now..I have noticed a trend to the west...I am in Louisiana, keeping a close watch on Isaac, my parents say there is nothing to worry about that it not going to trend this way that it is going to FL. How can I convince them that it is a great possibility that it can and we should be prepared??? TIA!!! LOVE reading yall's post BTW!!! :):):)


Just show them the models and the cone from this very website.
http://www.wunderground.com/tropical/

There is little certainty, but it bears watching.
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72 hrs. crosses over the Keys.

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Quoting Hurrihistory:
I think the NHC will probably drop Isaac to a Tropical Deppression at 8:pm. This system cannot overcome the dry-air. It's a very sick system at the current time!


Lol
Member Since: June 2, 2010 Posts: 0 Comments: 1404
Quoting Tazmanian:




i think Isaac's center could be re fourm under that deep convection

I wouldn't rule it out. If so the track would probably shift further west and it may strengthen quicker since it would have the convection on top of it.
Member Since: February 11, 2012 Posts: 84 Comments: 8049
Quoting Joanie38:
Hi everyone.....

I have been lurking for a few hours now..I have noticed a trend to the west...I am in Louisiana, keeping a close watch on Isaac, my parents say there is nothing to worry about that it not going to trend this way that it is going to FL. How can I convince them that it is a great possibility that it can and we should be prepared??? TIA!!! LOVE reading yall's post BTW!!! :):):)
You've got 2 choices. 1) Tell them the truth, no one knows at this point and we need to keep an eye on it. 2) Tell them the underground tropical experts (don't have any restrictions on what they say) Say it's going to be further west than NHC currently saying and maybe as far west as LA/MS. If you decide #2 and correct they will come back to you for future forecast. It's up to you if you want to take the leap of faith. Not really serious.
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Quoting Tazmanian:




i think Isaac's center could be re fourm under that deep convection


It can but I don't think it will happen quite yet
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Quoting Joanie38:
... How can I convince them that it is a great possibility that it can and we should be prepared???


Perhaps you can communicate to your family that they should be prepared at all times and that now is as good a time as any to at least make a plan and stock up on basic supplies (before the stores sell out of everything if it does head there).

Later isn't better when it comes to preparation...
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Quoting HimacaneBrees:
We just got the word to evacuate the rig. We'll start rig down procedures and getting non-essential personnel off Saturday AM. The rest of us will be off by no later than noon Monday.
Hey Himi, where are you located, we are in Miss. Canyon and havent made official decision yet, but know it is coming..Thanks
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West for the HWRF?
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714. yoboi
Quoting HimacaneBrees:


We are in South Marsh Island right now.



that sucks i live in swla....
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Quoting HimacaneBrees:
We just got the word to evacuate the rig. We'll start rig down procedures and getting non-essential personnel off Saturday AM. The rest of us will be off by no later than noon Monday.


Time to top off my tank.
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Quoting wxmanjarod:
Plenty of TCHP downstream across the western half of the Caribbean if Isaac can stick around in some form or fashion until then. Right now, I can't see him making a strong NW turn until he's better organized. However, that 280-295 jaunt is definitely plausible.

I've been a lurker/ocassional poster on here for a long time, and I've seen the chit-chat get more malicious each year. Let's remember this folks, this should be a place where we can throw out ideas and opinions. Try to receive everyone's thoughts with some level of respect. Personally, I come on here to help my forecasting abilities by looking at things from other peoples' points of view... the ol' "two heads are better than one" addage.

There's always different ways of looking at forecasting and analysis. None of us are perfect meteorologists/weather observers/forecasters. Weather forecasting is an imperfect science. Let's just enjoy the ride.
Well said but it is hard to convince prima-donna's of that
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711. yoboi
Quoting aislinnpaps:


well, I sure hope he's wrong as I lost my house to a fire a year and a half ago and I sure as heck don't want to lose the new one to a hurricane! Cat 1, 2 or 3, it'd survive, but a 5???

I don't think anyone wants to hear someone saying a Cat 4 or 5 this far out.


he likes to hype storms the more he hollas the more he gets paid...
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Quoting MAweatherboy1:

How many more of these comments are we going to be forced to read. This comment, and all those like it, aren't adding anything more to the discussion on the blog than the things the trolls are saying.

Isaac's deep convection seems to be remaining mostly south and west of the center:





i think Isaac's center could be re fourm under that deep convection
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Quoting yoboi:


what block ya work???


We are in South Marsh Island right now.
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Quoting Hurrihistory:
I think the NHC will probably drop Isaac to a Tropical Deppression at 8:pm. This system cannot overcome the dry-air. It's a very sick system at the current time!

There's no evidence to support a downgrade, and dry air isn't a problem. Multiple vortices that are having a hard time consolidating is.
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Quoting wunderkidcayman:


ok but Taz I did not say Cayman at all and this dude and about 2 others on here are driving me to insanity about this thing




why not you put the ones that are bugging with too marh on Ignore and let it go and move on
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Quoting PcolaBob:
It seems as if the western soultions are being under estimated for some reason. For days the experts have said a weaker storm would not move north as quickly (as the euro model predicts) and this has been the case. In fact, in between two of the earlier reports they showed the center moving just south of due west between 16 north and 15.5 north now back to 16 north.For more than 24 hrs the center has hardly budged north but the model still show a sharp move with minimal change to the 5 day outlook... ???
I have noticed this as well - I think this is do from the pissing match between Euro & US Mets!! LOL How this storm can possibly hit any part of Hispan is beyond me at this time!
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Quoting MAweatherboy1:

How many more of these comments are we going to be forced to read. This comment, and all those like it, aren't adding anything more to the discussion on the blog than the things the trolls are saying.

Isaac's deep convection seems to be remaining mostly south and west of the center:


...And it's not like it is that hard to scroll through them.
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Based on the latest aircraft data. I expect Isaac to be a 50 MPH storm with a pressure of 1000 mb at 8pm.
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Damn look at the GFS.
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Quoting HimacaneBrees:
We just got the word to evacuate the rig. We'll start rig down procedures and getting non-essential personnel off Saturday AM. The rest of us will be off by no later than noon Monday.


important thing is to be safe. and as you predicted Gas prices are rising, 15 cents in the past 2 days here.
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Member Since: July 5, 2005 Posts: 592 Comments: 29708
I think the NHC will probably drop Isaac to a Tropical Deppression at 8:pm. This system cannot overcome the dry-air. It's a very sick system at the current time!
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Quoting cluelessthunder:
WOW I have never seen the blog like this, where is administration. It's so frustrating to scroll through all this BS. This used to be so informative.

How many more of these comments are we going to be forced to read. This comment, and all those like it, aren't adding anything more to the discussion on the blog than the things the trolls are saying.

Isaac's deep convection seems to be remaining mostly south and west of the center:

Member Since: February 11, 2012 Posts: 84 Comments: 8049
Quoting Tazmanian:




your going too get bannd for saying thing like this



ok but Taz I did not say Cayman at all and this dude and about 2 others on here are driving me to insanity about this thing
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Hwrf seems weaker and faster.
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18z HWRF 66 hrs.

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695. yoboi
Quoting HimacaneBrees:
We just got the word to evacuate the rig. We'll start rig down procedures and getting non-essential personnel off Saturday AM. The rest of us will be off by no later than noon Monday.


what block ya work???
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For those of you saying that the forecasts have been terrible might want to go back and look at the original cone. Every single point of Isaac so far has been inside the ORIGINAL 5 day cone. For those of you that do not know what the cone represents, check out this site: About NHC Cone

Here is most of the definition: "The cone represents the probable track of the center of a tropical cyclone, and is formed by enclosing the area swept out by a set of circles along the forecast track (at 12, 24, 36 hours, etc). The size of each circle is set so that two-thirds of historical official forecast errors over a 5-year sample fall within the circle."

"Based on forecasts over the previous 5 years, the entire track of the tropical cyclone can be expected to remain within the cone roughly 60-70% of the time."
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Quoting Tazmanian:




the nhc dont update the winds at 8p they olny update the winds at 5pm 11pm 5am 11am

that is not true at all.

they don't update the track but they most certainly change winds speeds during intermediate advisories.
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Quoting JLPR2:


I don't see the quote post anymore so I would recommend deleting the quote, just in case.




thanks post been re moved



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Quoting Tazmanian:




the nhc dont update the winds at 8p they olny update the winds at 5pm 11pm 5am 11am


Taz...that's not true.
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690. GoWVU
Learning more each day what is the G-IV data?
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Quoting Joanie38:
Hi everyone.....

I have been lurking for a few hours now..I have noticed a trend to the west...I am in Louisiana, keeping a close watch on Isaac, my parents say there is nothing to worry about that it not going to trend this way that it is going to FL. How can I convince them that it is a great possibility that it can and we should be prepared??? TIA!!! LOVE reading yall's post BTW!!! :):):)


Crap, I can't get my wife worked up yet about Isaac, and I live just outside of Pensacola. She thinks it'll go to La. / Tx. So, I don't know how you can convince your parents, especially this far out and with models shifting hourly.
Member Since: March 9, 2012 Posts: 0 Comments: 150
Quoting RTSplayer:
GFS goes west.




Hunker down buddy!
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Still disorganized:

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Quoting Hurricane1956:
Once again this system is not going near the Cayman Island!!!!!!!!!.

Would you bet a nickel against a bucket of cow manure!

Quoting Tazmanian:




your going too get bannd for saying thing like this



Why would that cause a ban Taz? He said nothing wrong!
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Quoting ChaseyChasinStorms:


End of line........LOL. TRON

Yep! TRON ;)
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684. JLPR2
Quoting Tazmanian:




your going too get bannd for saying thing like this



I don't see the quoted post anymore so I would recommend deleting the quote, just in case.

Also, to not waste a post, Isaac might be disorganized, but it keeps developing some decently strong convection.
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WOW I have never seen the blog like this, where is administration. It's so frustrating to scroll through all this BS. This used to be so informative.
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.
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Quoting stormpetrol:
I think the NHC will probably up Isaac winds to 45-50 mph.at 8pm




the nhc dont update the winds at 8p they olny update the winds at 5pm 11pm 5am 11am
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Starting with Ernesto and now with Issac, the Eastern Caribbean "graveyard" notion that is tossed around frequently, until the systems move further West in the Caribbean, is holding true. A little hard to fathom how weak Issac has remained the past 48 hours in spite of working out some dry air issues, and, slowing down which were the main impediments to Ernesto in the same general vicinity.
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We just got the word to evacuate the rig. We'll start rig down procedures and getting non-essential personnel off Saturday AM. The rest of us will be off by no later than noon Monday.
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Plenty of TCHP downstream across the western half of the Caribbean if Isaac can stick around in some form or fashion until then. Right now, I can't see him making a strong NW turn until he's better organized. However, that 280-295 jaunt is definitely plausible.

I've been a lurker/ocassional poster on here for a long time, and I've seen the chit-chat get more malicious each year. Let's remember this folks, this should be a place where we can throw out ideas and opinions. Try to receive everyone's thoughts with some level of respect. Personally, I come on here to help my forecasting abilities by looking at things from other peoples' points of view... the ol' "two heads are better than one" addage.

There's always different ways of looking at forecasting and analysis. None of us are perfect meteorologists/weather observers/forecasters. Weather forecasting is an imperfect science. Let's just enjoy the ride.
Member Since: Posts: Comments:
Hi everyone.....

I have been lurking for a few hours now..I have noticed a trend to the west...I am in Louisiana, keeping a close watch on Isaac, my parents say there is nothing to worry about that it not going to trend this way that it is going to FL. How can I convince them that it is a great possibility that it can and we should be prepared??? TIA!!! LOVE reading yall's post BTW!!! :):):)
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Quoting Tazmanian:




your going too get bannd for saying thing like this



... and that would be a good thing.
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675. 900MB
Quoting MAweatherboy1:
Not sure what some of you are seeing to think Isaac is looking better... He looks the same or worse than a couple hours ago.



Just from the looks of those tops, some could see some decent convection, but, what concerns me most is that Isaac could miss much of the mountains of Hispaniola and spend more time in a toasty Gulf.
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It seems as if the western soultions are being under estimated for some reason. For days the experts have said a weaker storm would not move north as quickly (as the euro model predicts) and this has been the case. In fact, in between two of the earlier reports they showed the center moving just south of due west between 16 north and 15.5 north now back to 16 north.For more than 24 hrs the center has hardly budged north but the model still show a sharp move with minimal change to the 5 day outlook... ???
Member Since: Posts: Comments:

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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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