Ex-Dorian Attempting a Comeback off the Florida Coast

By: Dr. Jeff Masters , 1:44 PM GMT on August 02, 2013

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After a long trek over the Atlantic Ocean from the coast of Africa, the remains of Tropical Storm Dorian (now called Invest 91L) have finally arrived at the shores of North America. Ex-Dorian is nearly stationary, and is situated over the Northwestern Bahama Islands, just off the coast of Southeast Florida. Satellite loops and Melbourne, Florida radar images show that ex-Dorian has only a limited amount of heavy thunderstorms, which are not well-organized. There does appear to be a surface circulation center trying to form just north of the storm's heaviest thunderstorms, about 70 miles east of Vero Beach, Florida. However, dry air to the northwest, as seen on water vapor satellite loops, is inhibiting development. WInd shear is moderate, 10 - 20 knots, but is expected to rise to the high range, 20 - 30 knots, by Saturday morning. Ex-Dorian is expected to move slowly northwards and then north-northeastwards on Saturday. This motion will get ex-Dorian tangled up with a cold front that extends from Northern Florida northeastwards, just offshore from the Southeast U.S. coast. Before it merges with the front, ex-Dorian has some potential for regeneration into a tropical depression, and in their 8 am Friday Tropical Weather Outlook, NHC gave ex-Dorian a 30% chance of becoming a tropical cyclone by Sunday. Ex-Dorian will likely bring heavy rains to the Northwest Bahamas on Friday, and these heavy rains may also clip the coast of Southeast Florida. However, the bulk of ex-Dorian's rains should stay offshore.


Figure 1. Morning radar image of ex-Dorian from the Miami radar.

Jeff Masters

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A slight bend to the West b4 heading NNE doesnt seem out of the question.. Anyone agree?
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Quoting 1422. KoritheMan:
If that's the low-level center racing ahead of the convection, literally every single surface observation and scatterometer pass up to this point has been terribly wrong.

Doesn't seem likely to me, but you never know.


Buoy 41012, located 40 miles ENE of St Augustine is reporting WSW winds right now
Member Since: March 19, 2010 Posts: 0 Comments: 1147
Camille33 taking this to Wilma status would be the fastest RI in the history of any storm. Shear is only going to be moderate though and being over the Gulf Stream, annular, and increasing quickly; this could RI to 60-70mph TS. Anyway you see this making it to landfall on the OBX Kori? Front should make that an impossibility, right?
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1425. sar2401
Quoting flsky:
I guess it looks like it's forming an eye. Whadda you think?
Link
No, it's not forming an eye. You're seeing a hot tower on the IR satellite, a thunderstorm with a top higher than others around it. Look, this thing might be a 45 mph TS, and I'm not even convinced of that. It's an area of some concentrated convection, but even that is somewhat scattered. These kind of features don't form eyes. If it gets to be a 75 mph hurricane, then start looking for eyes.
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Quoting 1414. VR46L:
Getting pretty intense




Yeah, you should see the lightning out there right now. Glad I am not on a vessel out there. A lot of lightning flickering to my east right now is association with that blob of nastiness.
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1423. VR46L
I am wondering now that it appears as though its going out to see and was a storm in cooler waters would that mean he could become quite a fish in the cooler North Atlantic and turn Extrop later than usual ?

(a selfish question I know!!)
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If that's the low-level center racing ahead of the convection, literally every single surface observation and scatterometer pass up to this point has been terribly wrong.

Doesn't seem likely to me, but you never know.
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Quoting 1416. yankees440:
What is that spin being ejected out to the North of the convective mass?


You see that too, huh?
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Quoting 1416. yankees440:
What is that spin being ejected out to the North of the convective mass?


That's not the low-level center, because the synoptic flow is still weak; the system can't outrun itself like it did a week ago.

Without carefully examining it, I'm not really sure. I know there's some explanation, but it's darn near 3:00 AM and I'm getting tired, lol.
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Quoting 1411. VR46L:


If you look at its North east Quad on Radar ...It is looking like a wholly tropical entity it would appear as though the thunder storms are gathering there .


The deepest convection that I see on radar is on what would be located on the south/southwest side of the circulation. Those storms are not moving, nor rotating around the core. NE of the deepest convection, those are moving N. If I was to pinpoint where the LLC was based on radar, which mind you is difficult to do from a radar that is nearly 100 miles away, I would say it is east of the Volusia County coast. When I look at the satellite loop, I see a low cloud swirl in the neighborhood of 29N 80W (perhaps 79W, even), moving N.

Honestly, I think the LLC is now leaving the convection in the dust.
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1418. flsky
I guess it looks like it's forming an eye. Whadda you think?
Link
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Quoting 1415. Camille33:
91 l is about to do a Wilma on us. There is a clear rapidly rotating llc bunched up along the north side of an expanding mass of deep and slanted upward convection. In this situation given the forward movement being under 10 kt...this will suggest that the llc can get bounced under the vertical acceleration of the updrafts and take off.


So... 30 kt to 160 kt?

Hoo boy.
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What is that spin being ejected out to the North of the convective mass?
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91 l is about to do a Wilma on us. There is a clear rapidly rotating llc bunched up along the north side of an expanding mass of deep and slanted upward convection. In this situation given the forward movement being under 10 kt...this will suggest that the llc can get bounced under the vertical acceleration of the updrafts and take off.
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1414. VR46L
Getting pretty intense


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Still think it's gonna get closer to the OBX than what the 0z dynamical suite said. The subtropical ridge has temporarily restrengthened.
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1411. VR46L
Quoting 1401. ecflweatherfan:
In my opinion, if the NHC does not issue an advisory on 91L at 5am, the likelihood is that they will not at all. Just looking at the satellite imagery, I see a system that is "squashed" on its northern side, and once it gets to 29N, the shear will be too strong for it to develop. If the center is located at 28N 80W (Melbourne is at 28N, Cape Canaveral is approx. 28.5N), that gives it 60 nautical miles more miles to get to 29N, or esentially east of Daytona Beach.


If you look at its North east Quad on Radar ...It is looking like a wholly tropical entity it would appear as though the thunder storms are gathering there .
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What I see in satellite loop using the Shortwave IR2 channel, not the floater imagery as it is too difficult to tell, I see the low level swirl north of the convection, and moving north. In the vicinity of 29N 80W.
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Just wrote a late night blog. Check it out.
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Shear expected in 10-15kt range
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Convergence continues to increase
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1406. JLPR2
Quoting 1405. Tribucanes:
Recent increase in strong convection and some banding features, probably a TD at this point. If not, very very close, no chance at RI, but I've enjoyed following this persistent system. NHC seems very closely monitoring this, and by their wording, they'll probably upgrade this as soon as it warrants. Maybe even within the next two hours. Run of the mill 40-45mph TS, but He did make it back from the grave. And with no landfall expected, this is a win win. There's so few here, can tell members are Dorianed out.


Well it is 3am in the East Coast, that might have something to do with that, maybe...

XD
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Recent increase in strong convection and some banding features, probably a TD at this point. If not, very very close, no chance at RI, but I've enjoyed following this persistent system. NHC seems very closely monitoring this, and by their wording, they'll probably upgrade this as soon as it warrants. Maybe even within the next two hours. Run of the mill 40-45mph TS, but He did make it back from the grave. And with no landfall expected, this is a win win. There's so few here, can tell members are Dorianed out.
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Quoting 1400. Felix2007:


No not the kind that predicts the path of storms, I mean the one that predicts like 10 days out what the tropics might look like and if any storms will develop. The one that showed pressure readings and things like that.


I used to know it as the NCEP. Check on this site: http://mag.ncep.noaa.gov
There you will see a global map, select "model guidance", and then from there, select the region you want to see. It will give you the models available and their range of outlook.
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METEOSTAR IR LOOP

METEOSTAR WV LOOP
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1402. VR46L
I am thinking this is a tropical entity again

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In my opinion, if the NHC does not issue an advisory on 91L at 5am, the likelihood is that they will not at all. Just looking at the satellite imagery, I see a system that is "squashed" on its northern side, and once it gets to 29N, the shear will be too strong for it to develop. If the center is located at 28N 80W (Melbourne is at 28N, Cape Canaveral is approx. 28.5N), that gives it 60 nautical miles more miles to get to 29N, or esentially east of Daytona Beach.
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Quoting 1395. ecflweatherfan:


Here you go..

Link


No not the kind that predicts the path of storms, I mean the one that predicts like 10 days out what the tropics might look like and if any storms will develop. The one that showed pressure readings and things like that.
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1399. sar2401
Quoting yankees440:



I know that...obviously at its current state..Now,say it explodes into a cat3 (which obviously won't)then it would head West and not East, right?

I can't give you an answer to something which hasn't happened, since 91L turning into a cat 3 would take a complete turnover of the atmosphere in a way which just isn't physically possible in 24 hours. A cat 3 that's well developed can head pretty much where ti wants to, especially in the face of weak steering currents. It's kind of like asking if frogs had wings, could they fly? The answer is maybe but, since frogs don't have wings, there's no real answer to the question
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Quoting 1397. sar2401:

Yes, I do. Radar is a very poor tool to show feeder bands, even on a well developed system. You're seeing part of a thunderstorm's circulation that's at the outer edge of radar range. Use an IR satellite and match it up to the radar and see if you think it's still feeder bands.


You must be right, although it would be too early to distinguish a feeder band from the IR satellite at this early stage.

I think we will wake up to TS Dorian :)
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1397. sar2401
Quoting Surferdude:


I disagree - check the radar link and let me know if you still have the same opinion :)

Link

Yes, I do. Radar is a very poor tool to show feeder bands, even on a well developed system. You're seeing part of a thunderstorm's circulation that's at the outer edge of radar range. Use an IR satellite and match it up to the radar and see if you think it's still feeder bands.
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1396. sar2401
Quoting SunriseSteeda:


Ah yes. As it happens, I was contracting at Worldcom just as they were preparing to merge with MCI, and my last 9 months or so there was working on the Y2k stuff.

Most boring months of my life, albeit the richest (I was being paid a lot, and allowed to work as many hours as I wanted to beyond 40). It was boring because it was PHONE CALL data. Phone companies only care about Julian Day (of year), time of day, and day of week. Only places century appeared was on hard-coded report headings (which we fixed).

And you are right, various systems will begin to fail later because of the patches put in to remediate Y2k. Unfortunately (or fortunately), this will happen at various times over the next century.

For example, in 2000 I also worked for the company that produces the enterprise software used by about 800 of the top 1000 retailers (from Brookstone to Victoria's Secret to Tiger Direct to As We Change <-- this one is for Grothar). Their solution was to do handle dates like this:

For non-birthdates: If year is < 50, then century is 20, else it is 19.

For birthdates: If year is < 20, then century is 20, else it is 19.




There is a related problem looming. Remember that Unix epoch I mentioned? In the Unix operating system, the # of seconds since 1/1/70 is stored in a signed 32-bit integer variable, that can hold a value as big as 2,147,483,648 but no bigger. That's about 68 years. In 2038 these variables will "overflow" and wreak havok.

More money shall be made with the year 2038 problem, perhaps.





Ah, yes, the years of 1996 right up until New Years Day, 2000 were the best five years of income in my life. My work was on power generation and distribution equipment. Very little of it cared what year it was, only the day of the week and time of the day on the 24 hour clock. We knew this but had to test everything and document it for FERC. If we had done nothing, we would have lost 8 megawatts of generation. It would have taken Power Control about a half hour to notice it, since we normally generated about 950 megawatts. Thankfully, I was a consultant, so I just made money. When we were all called in on January 3, 2000, to explain what we had spent $13.5 million on, the answer was "Nothing". Within a month, almost every employee who worked on Y2K was fired. Strange times.

Sorry for the interruption. We now return you to breathless speculation about RI and which part of Florida may be flattened. :-)
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Quoting 1393. Felix2007:
Seeing as it now appears that you have to pay a subscription to see the models on the Raleigh wx site... is there anywhere else I can find the model runs?


Here you go..

Link
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Quoting 1379. yankees440:
A special advisory might just be in the cards for soon to be TS Dorian..And because of the proximity to land, the advisory would not be held till 5AM


Yeah they would wait, since TS force winds would be confined to open waters east of the CoC. And even if there were TS force winds on the west side of the system, it would really depend on the wind field. They would not issue a special advisory since it is not considered at this time to be a threat to land.
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Seeing as it now appears that you have to pay a subscription to see the models on the Raleigh wx site... is there anywhere else I can find the model runs?
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Quoting 1389. sar2401:

No, I think you're seeing the bands from the approaching trough that's going to capture 91L rather than feeder bands.


I disagree - check the radar link and let me know if you still have the same opinion :)

Link
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Shear is on the increase as well.

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Quoting 1385. sar2401:

Theoretically, no. The BAMD is a statistical model and works well on very deep, well developed cyclones. 91L is neither. The BAMD is probably the worst model to use in this circumstance. Rather than look at the one outlier, look at all the other models. When they are just about stacked on top of one another, that's a pretty good indication of where a storm is going.



I know that...obviously at its current state..Now,say it explodes into a cat3 (which obviously won't)then it would head West and not East, right?
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1389. sar2401
Quoting Surferdude:
Anyone else seeing the feeding band building from the north, following the gulf stream? Unreal if true.

No, I think you're seeing the bands from the approaching trough that's going to capture 91L rather than feeder bands.
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Quoting 617. sar2401:

Don't forget all those date windows we created to fix Y2K either. I think some of them start to run out in, what, 2017 or something like that. As I recall, Win 95 is one that will stop giving correct dates at the end of that window, and Microsoft said they have no intention of fixing it.

Source: Programmer who remembers when 8" floppy disks were the most amazing thing ever created. :-)


Ah yes. As it happens, I was contracting at Worldcom just as they were preparing to merge with MCI, and my last 9 months or so there was working on the Y2k stuff.

By far the most boring months of my life, albeit the richest (I was being paid a lot, and allowed to work as many hours as I wanted to beyond 40). It was boring because it was phone call data. Phone companies mostly only care about Julian Day (of year), time of day, and day of week. The only places throughout the system that the century appeared were by and large on report headings, which were almost always hard-coded for "19" if in MM/DD/CCYY format. These were the easiest to find and fix.

And you are right, various systems will begin to fail later as the years progress, in part because of the patches put in to remediate the initial Y2k problem. Unfortunately (or fortunately), this will happen at various times over the next century, instead of on one apocalyptic date.

For example, from 2000-2009 I worked for the company that produces the enterprise software used by about 800 of the top 1000 retailers (from Brookstone to Victoria's Secret to Tiger Direct to M&M Mars). Their solution was to do handle dates like this:

For non-birthdates: If the year is < 50, then century is 20, else it is 19.

For birthdates: If the year is < 20, then century is 20, else it is 19.

Works well for now. If you figure no one over 99 will be keying in their DOB, then 2020 will become a problem, but not a widespread one (since people age at varying rates). Otherwise 2050 will (a much more systemic problem will occur).


There is a related problem looming. Remember that Unix epoch I mentioned? In the Unix operating system, the # of seconds since 1/1/70 is stored in a signed 32-bit integer variable, that can hold a value as big as 2,147,483,648 but no bigger. That's about 68 years. In 2038 these variables will "overflow" and wreak havok.

More money shall be made with the year 2038 problem, perhaps. There's even a Wikipedia entry for it..


To tie this to the weather, here is a quote from and article in the Information Technology journal in 2000 about tropical models.

"Each computer model adds unique and valuable information, Mr. Williford adds. The Florida State global model, for instance, "has been tuned to the tropics," he says. The researchers are now studying whether a superensemble can have an optimal number of forecasts. They think, for instance, that each forecast has unique strengths and that removing any one of them weakens the ensemble forecast. Using statistical weighting techniques, the researchers try to minimize the effects of known flaws in a particular model's forecasting skills. "


(sr2401... I am looking at a diskette punch right now that geeks/hacks used to convert singled sided double density (SSDD) diskettes to DDDD (double-sided).
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Link
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freshly updated.

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1385. sar2401
Quoting yankees440:
Theoretically speaking, let's say XDorian puts on rapid intensification in the next 12 hours. Wouldn't he tend to follow Bam-d into west into Florida due to the steering at the 300-850 levels?

Theoretically, no. The BAMD is a statistical model and works well on very deep, well developed cyclones. 91L is neither. The BAMD is probably the worst model to use in this circumstance. Rather than look at the one outlier, look at all the other models. When they are just about stacked on top of one another, that's a pretty good indication of where a storm is going.
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Anyone else seeing the feeding band building from the north, following the gulf stream? Unreal if true.
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Link

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Doesn't look like it's waiting for anything either.
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The gulf stream is feeding Dorian with an endless supply of nice hot water.
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A special advisory might just be in the cards for soon to be TS Dorian..And because of the proximity to land, the advisory would not be held till 5AM
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SSD Moved the low back down to the NW tip of Grand Bahama
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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.