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#96L 's remnants now consolidating into a compact well-defined Low over the Bahamas. May head towards Bermuda eventually.
Days since last H. Landfall - US: Any 38 (Michael) , Major: 38 (Michael) Florida - Any: 38 (Michael) Major: 38 (Michael)
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Archives 2000s >> 2007 News Talkbacks

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HanKFranK
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subtropical storm andrea [Re: cieldumort]
      #74625 - Tue May 08 2007 09:58 PM

that's probably what is out there right now, like mr. deathsky says. my prediction about the NHC being first dismissive and then speculative about its possible transition for a while is right so far. they're obviously interested in it, and it fits enough of the subtropical cyclone criteria (in fact it's a poster child for why the term exists) that everybody is wondering why they don't go ahead and name it. the NHC response is the most predictable thing when we have a really good hybrid system like this... it fits the criteria listed in all but the most semantically exclusive way, but that just happens to be the one they use. i do wonder why the NHC bothers with the term subtropical cyclone since they apply it so narrowly that it's irrelevant.
the subtropical system does have deeper convection than earlier today, but not by much. it doesn't seem to be quite there yet, for the NHC to give in. if it blew some really deep convection the argument would suddenly become that it's a tropical storm, since recon would then of course find a more pronounced warm core aloft. what happens probably also depends somewhat on what forecaster is in charge. i bet ya that beven is all twitchy over this thing, for instance. unlike most of the subtropical candidates we fuss over, this one is actually going to thump the coast some... and the NHC will have to listen to a lot more people than usual wonder aloud why they mince words over these things every time.
anyhow, we might have us a subtropical storm tomorrow or we might not. if we don't there's a good chance it will end up being subtropical storm one, in a post-analysis. either way it's essentially like a dry, slow moving tropical storm buffeting the coast. better news out of this thing is that it's starting to push showers on shore, which should help some with the fires. might end up being a boon. the wind, on the other hand, could make it not worth the benefit.
HF 0258z09may

Edited by HanKFranK (Tue May 08 2007 09:59 PM)


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dem05
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Re: could there be a storm surge from this system?! [Re: MikeC]
      #74626 - Tue May 08 2007 10:11 PM

Refence to the GFDL in a recent post was excellent. Also excellent was a recent post on "Post Season Analysis". I've been thinking the same thing throughout the day so I got a kick out of it. More or less, I've seen less interesting subtropical systems getmore attention...and I've definately seen less impressive tropical systems get a designation. I agree with your statements that subtropical storms do typically exibit more uniform cloud activity around the center. However, they also have cloud activity that is generally shallower than we are seeing tonight. I consider this an offset and I really look forward to reading some post system analysis and reasoning. I am also puzzled why NWS frontal analysis shows an occluded front in the system, when that front is not connected to any Cold Fronts and/or warm fronts. It seems to me that they should be identifying this as a trough instead of an occluded front.

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dem05
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Re: subtropical storm andrea [Re: HanKFranK]
      #74627 - Tue May 08 2007 10:17 PM

FYI...As of 10:15PM, the Special Tropical Disturbance Statement on the NHC home website is gone. That may mean something (New STDS or advisories for an STS) or it will mean nothing at all. I guess we'll know with time.

EDIT: Disregard...the 4PM STDS is back now...Sorry!

EDIT: I will now get the official nickname of forum pscytzo, but that 4PM STDS is gone again...and I refreshed the page sevel times to make sure. Sorry about the craziness gang!

Edited by dem05 (Tue May 08 2007 10:33 PM)


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Doombot!
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Re: subtropical storm andrea [Re: dem05]
      #74629 - Tue May 08 2007 10:47 PM

<dusts off user ID for a new season>

It seems to still lack any form of core; I doubt this one is gonna get the bump up from NHC.


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BillD
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Re: subtropical storm andrea [Re: dem05]
      #74630 - Tue May 08 2007 10:48 PM

You are not crazy. I've seen that before. I think they have multiple, load balanced, servers and for some reason their content is not always in sync.

My guess is that the NHC, right or wrong, is not going to name this system at this point unless there is some major increase in intensity which I don't think is going to happen. This is one of those borderline systems that is hard to define. What I don't understand is why a non tropical system is not considered dangerous.

Bill


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dem05
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Re: subtropical storm andrea [Re: BillD]
      #74635 - Tue May 08 2007 11:21 PM

As a follow up to your comment, thank you for your redemption! An update STDS has been posted by the NHC, but the news isn't all that new. I expect they will wait for that morning recon flight...but the system is getting it's act together even more tonight. I'd be surprised if a flight is cancelled.

http://www.nhc.noaa.gov/text/refresh/MIADSAAT+shtml/090312.shtml?


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Hugh
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Re: subtropical storm andrea [Re: BillD]
      #74636 - Tue May 08 2007 11:24 PM

Quote:

You are not crazy. I've seen that before. I think they have multiple, load balanced, servers and for some reason their content is not always in sync.

My guess is that the NHC, right or wrong, is not going to name this system at this point unless there is some major increase in intensity which I don't think is going to happen. This is one of those borderline systems that is hard to define. What I don't understand is why a non tropical system is not considered dangerous.

Bill




The NHC pulled the Special Tropical Disturbance Statement shortly before 5pm as well, but only to update it and replace it a few minutes later. They did the same thing at 11pm. As far as the consideration of this thing being dangerous or not, that's not the issue - no one is questioning that it is dangerous, which is why the National Weather Service offices have issued various high wind warnings, gale warnings, etc. The NHC is not issuing advisories because it's not their job to warn the public about a non-tropical entity.

Now, as for the debate about whether NHC *should* consider this a tropical or sub-tropical entity, that's a matter for some debate. Right now it does not look very tropical to me, but six hours ago, I was thinking NHC would pull the trigger by now.

--------------------
Hugh

Eloise (1975) - Elena and several other near misses (1985) - Erin & Opal (1995) - Ivan (2004)


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dem05
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Re: subtropical storm andrea [Re: Hugh]
      #74637 - Tue May 08 2007 11:47 PM

Respectably, I must disagree. This system looks a lotmore subtropical/tropical that it did 6 hours ago.

IR Loop: http://www.ssd.noaa.gov/goes/flt/t4/loop-avn.html
Shortwave Loop: http://www.ssd.noaa.gov/goes/flt/t4/loop-ir2.html

At this point, I can only say that this agressive low has done everything anyone could ask to earn a name. If it keeps this up and doesn't cross land before recon, it more than desrves it too. NOTE: While watching the floaters, I invite you to click "NWS Fronts" on the menu. This has been updated and shows a 1mb pressure drop from 1001 to 1000mb. Also, you will note that the occluded front signature is now gone from the heart of the system and has been replaced by a distant trough line to the north and a Stationary Front that is disconnected and far to the east. This system is an independant Low Pressure system now.

Edited by dem05 (Tue May 08 2007 11:49 PM)


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BillD
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Re: subtropical storm andrea [Re: Hugh]
      #74639 - Wed May 09 2007 12:04 AM

Just to clarify what I meant, but not to belabor the point (this is not the right place for this discussion, and given past history could go on for hundreds of messages and get nowhere). The fact that gale warnings have been issued is not the same as the NHC issuing TS warnings. All I am saying is that it should be the same. There should be no difference based on the type of storm or which entity issued the warning, but the average person (and the media at large) is only going to pay attention to warnings from the NHC.

As far as this system, I think it looks more "tropical" than it has all day, but it is very disorganized, weak, and will likely not strengthen.

Bill

Edited by BillD (Wed May 09 2007 12:05 AM)


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Bloodstar
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Re: subtropical storm andrea [Re: BillD]
      #74640 - Wed May 09 2007 12:10 AM

Maybe I'm strange, but I don't see this as Named storm yet. The biggest issue I have with it is the obvious lack of centralized convection and and equally obvious lack of a eyewall. so it's like a big eye like feature that isn't contributing to the growth of the storm, either it needs to fill in the central convection or it needs to get the outer bands to create an eyewall and transition itself over.

Depending on how the storm is moving, it looks like it could have another 48 hours to develop, and it's certainly possible it could break through and develop either one of those features.

Let's see some more organization first.

--------------------
M. S. Earth and Atmospheric Sciences, Georgia Tech - May 2019.


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Clark
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Re: Is the Offshore Storm Subtropical? [Re: MikeC]
      #74641 - Wed May 09 2007 12:11 AM

Yikes, I've been slipping on posting for this one, especially since it's right up my alley!

From the outset, I gave this one about a 30% shot of getting to the subtropical level and 10% to the tropical level. My reasoning was mostly guided by the cyclone phase space analyses, as I have been following severe weather much more so than anything tropics-related lately, but was governed by the various model solutions for the storm in the phase space. Basically, they were (and still are) very similar to my mental set of "null case" tropical transition cases, where the cold core representation goes very close to a low-level warm core but sorta fades away. It showed a tightening of the wind field but ultimate decay of the storm, whereas the case of systems that completed tropical transition would more or less maintain themselves but go back cold-core in the phase space. It's tough to get across in words without having any pictures to help, but I don't have access to old phase space analyses of Epsilon (2005) -- probably the best case -- to really show this that well.

This system has and had many of the parameters necessary to complete transition but lacked the vertical temperature differential to get the tropical transition process started. Basically, part of the theory on how tropical cyclones develop is based upon a "heating efficiency" based on the difference in temperatures from the ocean's surface to the upper atmosphere, with a greater difference being better. There is a threshold for getting the engine going, to coin a term, and I don't think that it has been met here.

Satellite analyses show that the storm has never quite separated from its frontal structures nor has it shed the markings of an extratropical low. In particular, a cold front-type boundary is still evident to the east of the storm (http://www.ssd.noaa.gov/goes/east/nwatl/avn-l.jpg -- time sensitive) and a descending dry air jet is present south and west of the storm (http://www.ssd.noaa.gov/goes/east/nwatl/wv-l.jpg -- also time sensitive). These are both hallmarks of extratropical systems. Convection in the inner core has become better organized over the past day or two but is still not very well organized nor present near the center of the storm. The splotchy nature of it suggests that it is more of a slightly deeper form of the open cell (dubbed because of how it looks like numerous scattered cells) convection common with extratropical cyclones.

Essentially, while it has taken many of the steps toward becoming a subtropical or tropical system, it hasn't quite completed them all. The radius of maximum winds has tightened, perhaps in response to the slightly better convective organization -- particularly that ring evident about 200 miles from the center of the storm in the images above --and the system may have briefly developed a lower level warm core. But, it never developed that aloft, thanks to not getting organized enough convection-wise (as I believe HF alluded to) and now is more likely in the filling, or weakening, stages of its lifecycle. SSTs cool from here to the coast and land is just ahead.

It basically is an oddly-traveling occluded mid-latitude cyclone (say that three times fast!) that will go down as an interesting oddity and early precursor to what could be an active 2007 season.

Hope everyone's ready for the ride!

--------------------
Current Tropical Model Output Plots
(or view them on the main page for any active Atlantic storms!)


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cieldumort
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Re: Is the Offshore Storm Subtropical? [Re: Clark]
      #74646 - Wed May 09 2007 01:11 AM

I think Clark makes the "company" argument not to name 90L extremely well, and those of us wondering if NHC may get around to bumping 90L would be remiss not to consider his words.

On the other hand

The front to 90Ls east is really no longer married to 90L, at all, but rather just a part of the very large cyclonic circulation. (90L being, IMHO, a subtropical storm embedded and birthed from within a much larger extra-tropical feature. And the older warm seclusion which took place is now probably just a bit of a trof, at best.

Also, many people mistakenly assume or demand that to be "subtropical" there must be a warm core. This is simply not so. Nor must there be strongest winds close to the "eye". In fact, quite the opposite of each is most often the case, and simply more correct. Certainly 90L, as a subtropical cyclone, stands far slimmer odds of ever transitioning over to warm-core, tropical, than, say, an Epsilon. That is undeniable. But the core has probably been just either side of neutral throughout the day, and that is classic subtropical. Also, the _very_ symmetrical wind field (I would recommend to anyone to glance this time-sensitive Scatterometer, while it is still valid, to see this first-hand, has tended to have an equally symmetrical core radius of maximum sustained winds roughly 100+ miles from the center. Again, truly subtropical.

I have probably mentioned this here before, and I'm sure I'll mention it somewhere again, that it is at least this individuals observation that NHC is usually extremely reluctant to name legitimate subtropical storms as such unless they have a better than 50-50 chance of transitioning to fully tropical, and right now, and all day long, that has not been the case with our 90L.

On the other hand, following the golden rule above, if there should be a decent flareup closer to the center overnight and/or before or during recon tomorrow, and especially if recon does find even a decent smidgen of warm core, then the official naming of (Andrea) before landfall still seems to me to be entirely possible.

It will be interesting to see how long it can last in at least it's current state, now that the clock is ticking, and it is currently on a course with dry land, and perhaps more dry air entrainment, as well. While I am not writing 90L off for a recon flight entirely, if it doesn't flare up overnight, I suspect NHC might leave this one for post-season. We've all seen this before.


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scottsvb
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Re: Is the Offshore Storm Subtropical? [Re: cieldumort]
      #74647 - Wed May 09 2007 01:42 AM

Clark spelled it out correctly with his take on this. Also this storm couldnt vent intself. Tropical systems need a outflow...and its been vertically staked. 500mb and 850 is Baroclinic still. Its kinda like needing help breathing. It just cant do it unless it gets rid of the mid cyclone....and thats still there. Still there is a chance there could be a subtropical cyclone in the morning after recon checks it out. Winds are there.. center is there..but is it worth a name??? Well if it was moving away from land...probably not...but since its close and will bring coastal flooding and pressure of 1003-1005mb by Thurs morning landfall near St Aug-Fl/GA boarder they might go ahead with it.
It should move SW thru florida into central florida as it feels the ridge over the NE gulf.

Edited by scottsvb (Wed May 09 2007 01:43 AM)


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Bloodstar
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It's trying, it really is.... [Re: scottsvb]
      #74648 - Wed May 09 2007 02:22 AM

it's trying... it really is...
09/0545 UTC 30.9N 78.8W ST3.0/3.0 90L

up to 3.0 on the Dvorak classification, and the convection is starting to get colder compared to last night, and it is starting to creep into the center just a hair more. but it still got that 30 miles of clear space around the center that remain devoid of storms.

The storm does still appear to be tightening up, I was hoping to peek at CIMSS's ADT product, but it's not tracking the storm at the moment, at least not that i could find.

But... I'd give it even odds at this point in the next 24 hours. maybe I'm too optimistic, but it's doing better than I expected. let's see if the trend holds up.

--------------------
M. S. Earth and Atmospheric Sciences, Georgia Tech - May 2019.


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cieldumort
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Re: It's trying, it really is.... [Re: Bloodstar]
      #74649 - Wed May 09 2007 02:58 AM

I am >90% certain that if NHC doesn't name it -at some point *during* it's life cycle- 90L will be added during reanalysis as an unnamed storm.

As Bloodstar mentions above, the structure is indeed improving tonight. In fact, it is now looking like it is gradually taking on a little more *tropical* than just subtropical characteristics, especially with significantly deeper convection - as opposed to the mostly shallow convection early on - now starting to legitimately close in around the center at this hour.

In keeping with the headline of this thread, the question posed is not whether 90L is an extra-tropical storm or tropical storm, it is whether or not it is a *sub* tropical storm. For this, I would strongly suggest one reads the Glossary of NHC's Terms


This is exciting, of course! Would become the first named May storm since 1981 if bumped, yes?


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MikeCAdministrator
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Re: It's trying, it really is.... [Re: cieldumort]
      #74650 - Wed May 09 2007 07:17 AM

Recon is around in there now, but hasn't sent back a full report (Vortex message), but the system still doesn't have all that much convection wise around the center. We'll probably know fairly shortly.

Nothing all that much new so far this morning.

From what I can tell so far winds are around 50 knots (Ie 55MPH)




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Hugh
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Re: It's trying, it really is.... [Re: MikeC]
      #74651 - Wed May 09 2007 07:58 AM

Quote:

Recon is around in there now, but hasn't sent back a full report (Vortex message), but the system still doesn't have all that much convection wise around the center. We'll probably know fairly shortly.





I thought that was the main difference between a subtropical and tropical system - the fact that in a subtropical storm the convection is largely separated and out from the LLC - that plus the cold core in a subtropical system.

Regarding my earlier comments - things are changing with time with this system. Earlier this morning it looked less impressive to me, but now it's back to getting its act together - VERY rapidly. In fact, it looks more impressive now than ever, particularly in the 1115z image, which is the latest I'm seeing.

Edit: Just pulled up the Jacksonville radar. The center of circulation is clearly visible as a very large eye-like feature on the long range radar. Maybe it's just that the radar loop is not very long - but I also notice this on the AVN loop now that I look at it closer - but I don't think "Unnamed/Andrea" is moving very fast, if at all. Given that the LLC is sitting over or very close to the Gulf stream waters... not good.


--------------------
Hugh

Eloise (1975) - Elena and several other near misses (1985) - Erin & Opal (1995) - Ivan (2004)


Edited by Hugh (Wed May 09 2007 08:08 AM)


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dem05
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Re: It's trying, it really is.... [Re: Hugh]
      #74652 - Wed May 09 2007 08:30 AM

Well, we talked a whole lot about African Dust last year... Morning visible shows 90L is sucking up one heck of a lot of smoke from across the Florida Penninsula...Pretty amazing view actually.

http://www.ssd.noaa.gov/goes/flt/t4/loop-vis.html

Any thoughts on if the smoke has a similar affect as dust? I'd imagine that it could hamper development somewhat.


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cieldumort
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Re: It's trying, it really is.... [Re: dem05]
      #74653 - Wed May 09 2007 08:45 AM

That's something you don't see every day. And interestingly enough, it does appear to be affecting the cyclone like dry air, in a way. I am not very well versed on what the effects should be, but it certainly seems to be at least a slight inhibitor, in that general area of ingestion, if nothing else.

Noticed that FNMOC has pulled "90L". We wait...

Eh. There it is again. (I was considering the possibility that it was being replaced with noname)

Edited by cieldumort (Wed May 09 2007 08:54 AM)


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cieldumort
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Subtropical Storm Andrea [Re: cieldumort]
      #74654 - Wed May 09 2007 09:07 AM

SPECIAL TROPICAL DISTURBANCE STATEMENT
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
905 AM EDT WED MAY 9 2007

SATELLITE IMAGERY AND PRELIMINARY REPORTS FROM AN AIR FORCE RESERVE
RECONNAISSANCE AIRCRAFT THIS MORNING INDICATE THAT THE AREA OF LOW
PRESSURE CENTERED ABOUT 150 MILES EAST OF JACKSONVILLE IS ACQUIRING
THE CHARACTERISTICS OF A SUBTROPICAL CYCLONE. THE SYSTEM CONTINUES
MOVING GENERALLY WESTWARD AT ABOUT 5 MPH. IF PRESENT TRENDS
CONTINUE... ADVISORIES ON SUBTROPICAL STORM ANDREA WOULD BE
INITIATED LATER THIS MORNING.

DANGEROUS SURF CONDITIONS CONTINUE ALONG THE COASTS OF THE
CAROLINAS... GEORGIA... AND NORTHEASTERN FLORIDA. INTERESTS IN
THESE AREAS SHOULD CONTINUE TO MONITOR PRODUCTS ISSUED BY LOCAL
NATIONAL WEATHER SERVICE FORECAST OFFICES. ADDITIONAL INFORMATION
ON THIS SYSTEM CAN ALSO BE FOUND IN HIGH SEAS FORECASTS ISSUED BY
THE NATIONAL WEATHER SERVICE... UNDER AWIPS HEADER NFDHSFAT1 AND
WMO HEADER FZNT01 KWBC.


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