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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96 hrs and 120 hrs points will probably be shifted east. Everything before then will likely remain the same.
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4273. LargoFl
Quoting interstatelover7165:
T-MINUS 14 PAGES TO 100 PAGES.
lol justwait til it nears florida..then BOOM..doc will have to make new blogs every couple of hours lol
Member Since: August 6, 2011 Posts: 5 Comments: 50660
I'm not expecting major shift for 11 am. Maybe slight right, but that's it.
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So it's looking good for those of us that live along the TX/LA border as far as Isaac goes???
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good morning all watching Isaac this morning here in Florida Panhandle and waiting.
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Quoting 7544:
ok will the cone shift right or left at 11 am ?


Right
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track will shift east at 11am
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Quoting 7544:
ok will the cone shift right or left at 11 am ?


RIGHT
Member Since: September 2, 2008 Posts: 0 Comments: 744
Quoting GeoffreyWPB:
Beetleguise, Beetleguise, Beetleguise



And a ?. What does the feathering effect of clouds on Isaac's west flank mean is happening?


That is an excellent display of nearly perfect outflow.
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4265. LargoFl
Quoting midgulfmom:

Local met discounted as moving west and poofing. Just saying.
here on the west coast, they dont, as of right now, dont want to scare all those cash spending folks away from the convention, they have been counting on making big bucks for a long time now,they may live to regret it in not seriously enough..warning people of the possible real danger coming right during the convention..we shall see..if it does happen..they all should sanctioned
Member Since: August 6, 2011 Posts: 5 Comments: 50660
One of the best satellite loops to view Isaac..
Link
Member Since: July 8, 2005 Posts: 259 Comments: 24975
Quoting weathermanwannabe:
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.

Looking like we (Bahamas, Florida and Gulf Coast) will have to wait a little longer into the weekend and get a better picture of what he looks like going into Cuba and coming off the North end of the Island. That does not leave a lot of time for preparation in the Keys/South Fl/Bahamas if complacent folks are going to wait it out until the last minute to "see what happens".

If he is able to ramp up to a stronger TS or Hurricane level as he approaches Cuba, it will be time to consider evacuation of portions of the Keys. It does not look like there is going to much interaction of the coc with Haiti at this point.

Have to see what the 11:00 am update looks like as they try to get a fix on what is going on with the coc as they refine the track and intensity projections.

One of the toughest forecast challenges I have seen recently.
It seems to me the NHC has mastered the Hurricane forecast tracks... the TC tracks seem to create masses of more problems, because the models still can't seem to figure out the small changes that influence intensification prospects. Some of this is the resolution, but I can't help but feel a lot of it is "something" we're missing in the TC development process...
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Nice banding on the Southesat side, an looks to be wraping around the Northeast side around the so called DRY slot. Looks like it's making a run to hurricane Cat 1 strenght before land fall with Hati.
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4261. wn1995
Quoting GeoffreyWPB:
Beetleguise, Beetleguise, Beetleguise



And a ?. What does the feathering effect of clouds on Isaac's west flank mean is happening?


It just has pristine outflow on its westward side.
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4260. kwgirl
Quoting KeyWestwx:
I have a kayak, kwgirl. Look for me in those proverbial newspaper or news coverage photographs of "guy kayaking down the street after storm'!
If you are on Front St., I will be the one wading barefoot through the water to get to the Pier House:)
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T-MINUS 14 PAGES TO 100 PAGES.
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4258. hamla
if it stays on west track to jamicia then turns nw we in ms/la could b in trouble imo
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While the winds are stronger, and the outflow is impressive. The LLC is still well NE of the mid-level center, and it appear that the LLC may remain dominant...

Continues to be a tough forecast though!
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Isaac has definitely strengthened and is starting to become a dangerous storm. Still a couple problems though.

1. The central core remains a bit disorganized. He has been working on this though and it is slowly becoming less of an issue.
2. Most of the deep convection has remained south of the center. This has been a persistent problem and is probably the biggest thing working against him right now.

Member Since: February 11, 2012 Posts: 88 Comments: 8311
Quoting guygee:
Jeff Masters should entitle his next blog entry: "Isaac remains disorganized - Day 2".

If you plop 1,000 dropsondes down into a unpredictable disorganized blobby monster like Isaac, does it really improve the model forecasts?


Given that Isaac has strengthened from 40mph to probably 60mph in the klast 12 hours, I wouldn't exactly call it disorganised or a blobby mess.
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4253. 7544
ok will the cone shift right or left at 11 am ?
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Quoting GeoffreyWPB:
Beetleguise, Beetleguise, Beetleguise



And a ?. What does the feathering effect of clouds on Isaac's west flank mean is happening?


Ike looked just like that only all the way around. Always wondered what it was.
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Vis loop

Isaac appears to be traveling NW, and is right on track with the NHC fct plot.
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4250. LargoFl
Quoting StormTracker2K:


Yeah this upper trough over FL with a low off SC will make Issac's track very interesting. I wouldn't even rule out a strike on Miami or FL right now based on this.

NHC will have to shift the track back east at some point today.

..looks like issac would have to go right up the middle of them, right into florida
Member Since: August 6, 2011 Posts: 5 Comments: 50660
Quoting GeoffreyWPB:


How far up the east coast do you suspect T.S. Watches will be issued? If at all.



Cape Canaveral. I think issac is going to be right on the FL west coast or very close and I even wouldn't rule a SE FL landfall either.
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Quoting LargoFl:
..see that blob in the western gulf..met last night said That..was going to keep issac from going westward..we'll see

Local met discounted as moving west and poofing. Just saying.
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Quoting ChaseyChasinStorms:
Good morning all. :) Slidell, LA here getting nervous.........
I am at the Al line, north of I-10.....already nervous.......
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Quoting StormTracker2K:


Yeah this upper trough over FL with a low off SC will make Issac's track very interesting. I wouldn't even rule out a strike on Miami or FL right now based on this.

NHC will have to shift the track back east at some point today.



?
Member Since: July 8, 2005 Posts: 259 Comments: 24975
lol
Quoting CybrTeddy:


Didn't even notice we have 97L.

AL, 97, 2012082412, , BEST, 0, 127N, 232W, 25, 1007, DB, 34, NEQ, 0, 0, 0, 0, 1010, 225, 100, 0, 0, L, 0, , 0, 0, INVEST, S
Member Since: May 23, 2012 Posts: 0 Comments: 5004
Quoting CajunCrawfishhunter:


Lafayette too


Opelousas three
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4242. LargoFl
Quoting Thing342:
Has anyone noticed that we have had Invest 97L since about 5AM yesterday?
yes it was at 30% this morning
Member Since: August 6, 2011 Posts: 5 Comments: 50660
Quoting Michfan:


Best to use 37ghz Color to pick out the low level features. This is from 3 hours ago on Windsat. Very good banding on the south quadrant. Once that starts to wrap around on the northern side we should start to see an eyewall try to form.
A hallmark sign on the 37 GHz of a rapidly intensifying storm is a cyan ring around the center. It is often a precursor to an eyewall. Keep an eye out for that feature today when looking at 37GHz imagery.
Member Since: August 12, 2007 Posts: 11 Comments: 2449
Quoting drg0dOwnCountry:

TWC and Wunderground have merged. And there is a lot of good coverage from what i could say from what they do on the web.


I remeber an incident in Myrtle Beach with TWC in the early-mid 1990's.

It was either Hurricane Bertha or Bonnie. Whoever was doing the live remote was standing between two of the high rise hotels to get the higher windspeed due to the Bernoulli Principle. We were watching the coverage at the EOC and noticed what appeared to be chunks of buildings blowing past the reporter. A police car was dispatched. Turned out the cameraman was throwing chunks of styrofoam that they had brought with them. It was their first hurricane and I guess they were trying to make things look "dramatic". They were told they had two choices--keep the styrofoam in the truck, or they could report the rest of the storm from inside the city jail.

Also, TWC is owned by NBC, so ratings are going to eventually drive things. I hope and pray no adverse changes come here.
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Quoting GeoffreyWPB:
Beetleguise, Beetleguise, Beetleguise



And a ?. What does the feathering effect of clouds on Isaac's west flank mean is happening?


LOL! Issac has a small head.
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From 6Z GFS ENSEMBLE
Member Since: May 23, 2012 Posts: 0 Comments: 5004
4237. guygee
Jeff Masters should entitle his next blog entry: "Isaac remains disorganized - Day 2".

If you plop 1,000 dropsondes down into a unpredictable disorganized blobby monster like Isaac, does it really improve the model forecasts?
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Quoting stoormfury:
97L has a broad areaof low pressure with two distinct area of convection. the northern half is moving wnw and the southen part is at 10n 30w . this part of the system looks like what will become the dominant one ,as the system moves west.


Didn't even notice we have 97L.

AL, 97, 2012082412, , BEST, 0, 127N, 232W, 25, 1007, DB, 34, NEQ, 0, 0, 0, 0, 1010, 225, 100, 0, 0, L, 0, , 0, 0, INVEST, S
Member Since: July 8, 2005 Posts: 259 Comments: 24975
4235. LargoFl
Quoting Catgypsy:


The guy is clueless. The convention center is 4 feet above sea level. High winds collapsed some of their tents last night. And that was a small storm. Time will tell.
yes they are counting on the big bucks all these arrivals will spend this week and dont want to scare people off..i sure hope issac dont hit here..60 thousand people unfamiliar with the excape routes, clogged roadways, flooded streets..a recipe for diseaster..and he smiles?
Member Since: August 6, 2011 Posts: 5 Comments: 50660
Has anyone noticed that we have had Invest 97L since about 5AM yesterday?

Link
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Quoting StormTracker2K:
Looking at the sat. loops it appears Issac is moving more NW now. Also notice the low off GA and SC. There is a lot going on right now that is pointing a a storm track up the FL west coast maybe even further east based on this. Pretty strong low forming off the SE US coast this morning.


Link


How far up the east coast do you suspect T.S. Watches will be issued? If at all.
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Quoting BeanTech:


I'm not surprised.
Word on the street is that Tampa hired Ray Nagin as an independent disaster management consultant.
Hahaha...that is the real disaster!
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Quoting LargoFl:
..see that blob in the western gulf..met last night said That..was going to keep issac from going westward..we'll see


Yeah this upper trough over FL with a low off SC will make Issac's track very interesting. I wouldn't even rule out a strike on Miami or FL right now based on this.

NHC will have to shift the track back east at some point today.

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4230. Mikla
Something to remember... no matter where Issac goes or the cone is shown it is very likely that SE FL (and North) will be in the NE quadrant where wind and rain are at the worst... flooding is likely to be an issue...
e.g., 06Z GFS:
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Quoting GeoffreyWPB:
Beetleguise, Beetleguise, Beetleguise



And a ?. What does the feathering effect of clouds on Isaac's west flank mean is happening?
Great cirrus outflow channel to the SW provided by an upper-level anticyclone. That favors intensification.
Member Since: August 12, 2007 Posts: 11 Comments: 2449
Quoting GeoffreyWPB:
Beetleguise, Beetleguise, Beetleguise



And a ?. What does the feathering effect of clouds on Isaac's west flank mean is happening?


Excellent outflow is what is happening.
Member Since: July 8, 2005 Posts: 259 Comments: 24975
97L has a broad areaof low pressure with two distinct area of convection. the northern half is moving wnw and the southen part is at 10n 30w . this part of the system looks like what will become the dominant one ,as the system moves west.
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4226. HrDelta
Quoting BeanTech:


I'm not surprised.
Word on the street is that Tampa hired Ray Nagin as an independent disaster management consultant.


Okay, I have heard of some stupid things, but I find it hard to believe someone would be that stupid.
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Beetleguise, Beetleguise, Beetleguise



And a ?. What does the feathering effect of clouds on Isaac's west flank mean is happening?
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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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