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Tropical Storm Ana Moving Away From Main Hawaiian Islands. Watching Invest 93L in Southern Gulf of Mexico.
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typhoon_tip
Meteorologist


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Subtropical Gabriel, no longer 99L; still some concern for East Coast
      #77744 - Sun Sep 02 2007 12:23 PM

We have what appears to be a book-end vortex attempting to develop in the vicinity of the NC/SC Coast. Both satellite and radar are beginning to show a cyclonic turning amid the on-going convection that has been lingering there for the past 18 to 24 hours.

Radar: http://radar.weather.gov/radar.php?rid=CLX&product=N0Z&overlay=11101111&loop=yes
Satellite: ...See below

This feature was originally triggered by a stalling frontal zone. Originally a baroclinic system altogether, this now appears to be entering a phase-transition because the air mass north to south through the axis of weak rotation is becoming less differentiable. This, while convection persists, needs to be monitored so long as we have a general southwest wind field beneath the axis of frontalysis and east-northeast wind above, which provides a natural cyclonic convergence in the low levels.

Two key factors:
  • Shear remains low in the deep layer analysis. Moreover, the upper level winds are somewhat divergent while being light in that area. This can be seen using
    http://www.ssd.noaa.gov/goes/east/nwatl/loop-avn.html ..and clicking the radial button that states, HDW-High, which overlays the wind field on the image. There is no floater assigned to this feature but NHC has given it a mention in the 11am so perhaps an Invest is in the works. Given to some cyclonic presentation emerging a circulation is likely in the process of forming and an Invest would have more success at that time.

  • Oceanic heat content; ample availability in the area as is suggested via:
    http://www.erh.noaa.gov/box/maps/sst/2007090200_sst_AB.png Additionally, we all know the Gulf Stream is in that area and that supplies an artery pumping rich fuel directly into any fledging system. Sometimes if there is an offshore component, cooler shelf water can upwell along the immediate Coast in that vicinity. That does not appear to be the case now as buoy data indicates temperatures ranging between 81 and almost 90F!


Whatever develops there it is likely to move very slowly and be there for awhile. The larger scale synoptic evolution does not provide for very many steering signals. There is a ridge tending to develop surface and aloft, moving off the Mid Atlantic and New England states and into the NW Atlantic, from day-3 through day-6. That should help pin whatever is there in place, or perhaps even push it SE or SW. Some of the models actually do suggest that occurring, showing a slow but gradual development only drifting around in that area.

First step...get a system going.

Edited by typhoon_tip (Sat Sep 08 2007 01:11 AM)


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orlandocanewatcher
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Reged: Thu
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Loc: E Central Florida
Re: Region of interest just off the SE U.S. Coast [Re: typhoon_tip]
      #77769 - Sun Sep 02 2007 04:20 PM

So basically we could have a system develop and meander around for a while and then either curve back into Florida or further north towards S.Carolina?? Does that seem to be the basic idea?? What are the chances that this become a hurricane? Or are we looking at closer to a tropical storm??

Edited by orlandocanewatcher (Sun Sep 02 2007 04:21 PM)


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StrmTrckrMiami
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Loc: Manchester, NH
Re: Region of interest just off the SE U.S. Coast [Re: orlandocanewatcher]
      #77772 - Sun Sep 02 2007 04:26 PM

Looking at the current radar system of the storm system off of Georgia, it looks as though to be the reason for the severe storms that are currently in Georgia's Coast and also in Northern Florida. This storm system is causing severe thunderstorms and strong winds in areas over Northern Florida (Daytona Beach is under a watch) Looking at the radar, it looks as though it is trying to form into a depression or a storm system, and it now appears to be rotating the way a hurricane would, not a cyclone (however I could be wrong) But it looks to be an overall healthy system that is forming. We will just have to keep a close watch on this storm systym over the next few days.

http://radar.weather.gov/radar.php?rid=CLX&product=N0Z&overlay=11101111&loop=yes

--------------------


Tracking Storms Since 2004
Miami, Cocoa, Fort Myers and Jacksonville
Currently Reside in New England

Edited by StrmTrckrMiami (Mon Sep 03 2007 12:39 AM)


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Loudest Tundra in Florida
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Re: Region of interest just off the SE U.S. Coast [Re: orlandocanewatcher]
      #77773 - Sun Sep 02 2007 04:30 PM

This seems to remind me of "Jeanne" IIRC in 04. How it just circled around for some time. No telling what this thing is gonna do EDIT: Watching the loop, and trying to find a C.O.C somewhere, I see that it is def. drifting SE.

Edited by Loudest Tundra in Florida (Sun Sep 02 2007 04:35 PM)


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nc_tropical_wx79
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Re: Region of interest just off the SE U.S. Coast [Re: Loudest Tundra in Florida]
      #77789 - Sun Sep 02 2007 07:15 PM

Been at work all day but how is the system off of the southeast coast doing? is it still going strong or has it weakened and also will it come under high shear in the upcoming future? (Sorry for all the questions).

--------------------
W.D. Duncan


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Loudest Tundra in Florida
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Loc: "Rivertucky" FL
Re: Region of interest just off the SE U.S. Coast [Re: nc_tropical_wx79]
      #77808 - Sun Sep 02 2007 09:14 PM

It looks as if it is encountering quite a bit of rather unfavorable conditions right now.

(Forecast Lounge material was removed.)

Edited by Ed Dunham (Sun Sep 02 2007 10:59 PM)


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typhoon_tip
Meteorologist


Reged: Wed
Posts: 570
Re: Region of interest just off the SE U.S. Coast [Re: Loudest Tundra in Florida]
      #77838 - Mon Sep 03 2007 12:49 AM

Quote:

It looks as if it is encountering quite a bit of rather unfavorable conditions right now.

(Forecast Lounge material was removed.)




Nothing has changed in terms of the deep layer analysis. The shear is still generally low. Oceanic heat content is of course high. There are some new convective elevments presently erupting near the southern aspect of what appears to be an emerging cyclonic circulation.

Unfortunately, we don't have a Floater assigned at this time. There may be data sources out there but I have been using: http://www.ssd.noaa.gov/goes/east/gmex/loop-avn.html ...and then clicking the HDW-high radial button to show the upper level winds, which are divergent over the area -- i.e., favorable.

The models are suggesting this as still quite plausible but they take a long time to do so. Important to remind folks that the models are not really well-performed during genesis phases of TCs. So, they may belay this until they are better initialized. That may occur when a system becomes better defined and enters the initialization array.


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typhoon_tip
Meteorologist


Reged: Wed
Posts: 570
Re: Region of interest just off the SE U.S. Coast [Re: typhoon_tip]
      #77865 - Mon Sep 03 2007 02:34 PM

Update...

Convection persists in associating with the area of disturbed weather situated along the tail end of a slowly decaying frontal boundary, which extends seaward from approximately 50miles east of the central Georgia Coast. Nestled in this vicinity is a region of slightly improved cyclonic organization.

The general parameters are essentually unchanged for now:

    Oceanic heat content is large in that vicinity -- positive
    Upper air analysis suggests evolving divergent vectors in the 200mb level -- positive
    Pressures remain high in that region -- negative


Forecast models:
They are showing trends toward a converged opinion as of the 12Z run this morning, that this region will likely continue to evolve and eventually lead to a Tropical Depression. Models typically will not perform stellar during the genesis phase of any given TC (Dean was a startling exception rather than the rule), so timing the birth of this feature is inherently going to be low skill. The general consensus of the models is to drift a beta low toward the east-southeast where it will slowly gather purer tropical characteristics. By 72-84 hours, the NAM has a depression centered near 70/30. (*The NAM is a low skill predictor for tropical weather phenomenon) This is intriguing because the GFS also places a similarly defined system at that location and time; from that point forward in time, it then shows a west movement with some implications for development as it approaches the Eastern Seaboard by as near as 120 - 132 hours. The most glaring solution is that of the CMC, which shows also this similar solution through 84 hours as the GFS and NAM, but then it does something interesting: It bombs this into an intense hurricane and has it moving due N about 50 to 100 miles east of Cape Hatteras, NC, by 132 hours. (*The CMC is also a low skill predictor for tropical weather phenomenon, tending to over-production). The 12Z ECM is also now developing this system close to the same location as the NAM, GFS and CMC, and in similar timing. It also shows it moving back west and at least implies intensification. I have not seen the 12Z UKMET.

Visible imagery is showing a general albeit weak for now, cyclonic motion, with some indication of a mid-level circulation displaced east of the weakly discernable broad low level rotation. However, given to:

    The persistence of convection and on-going phase transition from barolcinic to barotropic
    The favorable parameters discussed
    The emerging model consensus


slow development is quite plausible if not likely. Can never be certain about these things.


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typhoon_tip
Meteorologist


Reged: Wed
Posts: 570
Re: Region of interest just off the SE U.S. Coast [Re: typhoon_tip]
      #77866 - Mon Sep 03 2007 03:22 PM

Area of interest off the SE U.S. Coast is officially declared an Invest. Floater assigned:

http://www.ssd.noaa.gov/goes/flt/t3/loop-vis.html

Now that the closer inspection avails, it does appear there is some light to moderate westerly UL shear in the area that was not readily discernable from the other vantage points. This is another reason to assume slow intensification.

Edited by typhoon_tip (Tue Sep 04 2007 05:03 PM)


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ltpat228
Storm Tracker


Reged: Tue
Posts: 201
Loc: Port Saint Lucie FL 27.20N 80.30W
99L [Re: typhoon_tip]
      #77873 - Mon Sep 03 2007 04:55 PM

Here is the link for a NRL visual on 99L; then another link for the computer model.

NRL visual:
http://www.nrlmry.navy.mil/tc-bin/tc_hom...s/microvap/dmsp

Computer model:
http://www.weatherunderground.com/tropical/tracking/at200799_model.html


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nc_tropical_wx79
Weather Guru


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Re: 99L [Re: ltpat228]
      #77898 - Tue Sep 04 2007 01:06 AM

is 99l still attached to the front or is it a low on it's own yet?

--------------------
W.D. Duncan


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typhoon_tip
Meteorologist


Reged: Wed
Posts: 570
Re: 99L [Re: nc_tropical_wx79]
      #77900 - Tue Sep 04 2007 01:52 AM

Quote:

is 99l still attached to the front or is it a low on it's own yet?




It appears I am the only Met frequenting this thread...

The answer is no. The recent analysis is that the stationary boundary has washed out and we now have a low with a surface trough subtended S approximately 77W/30N.

This is encouraging for this system's genesis phase as it means the phase-transition is becomeing more purely barotropic and less baroclinic.

Moreover, another encouraging sign is that there is new convective elements exploding close to the center of circulation.

There is still shear impacting the area, however, so this is not in any rapid intensification by a long shot.

Models are still indicating development off the 00Z runs. The GFS has a TC suggestion and the the oft' over-zealous CMC still tries to develop a significant TC. The NAM still suggests steady development while drifting the vortex ESE to the eastern Bahamas.

I have a funny feeling this system will make headlines! There is way more model support than not for this to spin up and the key for me is the evolving favorable UL wind field together with way more oceanic heat content than knows what to do with. At that time, about 66+ hours out, this is probably going to develop stronger than models in keeping with the usual 'gets deeper and more intense than expected' bias that pervades results of both machine and man expectations as of late.

Edited by typhoon_tip (Tue Sep 04 2007 01:53 AM)


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Hurricane29
Weather Guru


Reged: Mon
Posts: 148
Loc: Miami Florida 25.77N 80.25W
Re: 99L [Re: typhoon_tip]
      #77913 - Tue Sep 04 2007 08:01 AM

Quote:

Quote:

is 99l still attached to the front or is it a low on it's own yet?




It appears I am the only Met frequenting this thread...

The answer is no. The recent analysis is that the stationary boundary has washed out and we now have a low with a surface trough subtended S approximately 77W/30N.

This is encouraging for this system's genesis phase as it means the phase-transition is becomeing more purely barotropic and less baroclinic.

Moreover, another encouraging sign is that there is new convective elements exploding close to the center of circulation.

There is still shear impacting the area, however, so this is not in any rapid intensification by a long shot.

Models are still indicating development off the 00Z runs. The GFS has a TC suggestion and the the oft' over-zealous CMC still tries to develop a significant TC. The NAM still suggests steady development while drifting the vortex ESE to the eastern Bahamas.

I have a funny feeling this system will make headlines! There is way more model support than not for this to spin up and the key for me is the evolving favorable UL wind field together with way more oceanic heat content than knows what to do with. At that time, about 66+ hours out, this is probably going to develop stronger than models in keeping with the usual 'gets deeper and more intense than expected' bias that pervades results of both machine and man expectations as of late.




Question...

How far south do you think 99L will move?Is there any chance of a Katrina like track.Right now i see it drifting SE.


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allan
Weather Master


Reged: Thu
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Loc: Palm Coast, Florida 29.55N 81.20W
Re: 99L [Re: Hurricane29]
      #77922 - Tue Sep 04 2007 11:10 AM

Well Hurricane29, it depends on how the high drifts west and how strong it gets. If the high is strong as of what now most models are showing, this will be a remembered strom for folks in the Northeast. If the high is weak, the storm will push through it and head out to sea affecting nothing but the fish. I put more confidence in the reliable models that show this storm "Gabreille" a threat to the USA. EVERYBODY on the east coast needs to watch this storm, Typhoon is right, this will make headlines. This storm reminds me ALOT of Gustav in 2002
http://www.wunderground.com/hurricane/at20027.asp

If I remember, I believe Gustav was pushed by a strong High and then caught up with a front saving my butt from a strike in NY at the time. Anyways getting back on topic, it appears that 99L (Gabrielle) will become subtropical later today, looks good, outflow is good, and the center is right next to that bloom of convection. We'll have to see what happens in time with it.

--------------------
Allan Reed - 18,9,5


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orlandocanewatcher
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Re: 99L [Re: typhoon_tip]
      #77923 - Tue Sep 04 2007 11:12 AM

I see that a few of the spaghetti models still have this thing moving to Cen Fla...how accurate are those models?? I know that it is harder for them to pick up on a developing system....just curious what you think the chances are?? What is the set up with the high and any troughs coming through? I am not a met, only read a lot of what you guys post...so thanks so much for all your help!! Also, what kind of time frame are we looking at??

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Lamar-Plant City
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Re: 99L [Re: orlandocanewatcher]
      #77924 - Tue Sep 04 2007 11:45 AM

Not only are the models all over the place as far as direction, they are also FAR apart in speed of that movement (Clark's models show time intervals). The two models that show it moving in my direction have it in my vicinity either 72 or 120 hours from now....that is a HUGE window. I think we are going to have to wait until more models have a solid fix on this system and that won't likely occur until it shows signs of better organization than it has now. Maybe by the 5th model run, we will get more of a concensus (hopefully).

--------------------
If you don't like the weather, wait 5 minutes...
2014 Season Prediction: 14/4/2


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Lee-Delray
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Re: 99L [Re: orlandocanewatcher]
      #77925 - Tue Sep 04 2007 11:47 AM

It is way too early to tell when of if this system will develop or where it is going. None of the models seem to have a grip on it, it could be anywhere from Central Florida to NY or out to sea at this time. The system is under about 20 knots of shear now, so its development will be slow if at all. My guess is it won't be until late Thursday or Friday before we know what (if) is happening.

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typhoon_tip
Meteorologist


Reged: Wed
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Re: 99L [Re: Hurricane29]
      #77926 - Tue Sep 04 2007 01:26 PM

Quote:



Question...

How far south do you think 99L will move?Is there any chance of a Katrina like track.Right now i see it drifting SE.




It is impossible to say with any certainty...as you well know.

Possibilities, assuming this does succeed in developing, range from slow eastward component drift, to then resuming a north motion well-enough offshore to not be a significant impactor beyond surf, to eastward component drift, to then retrograding west (perhaps even after performing a loop) as a more serious eventual threat.

Most guidance show solutions at or in between these themes, but ALL develop this at this point in time. The NAM's 06Z and 12Z solutions blended together with the 00Z CMC would spell some signficant trouble for New England.

One additional concern for me is that warm SST anomalies that are currently aligning along most of the Coastal waters and extending eastward to beyond 70W. The following link elaborately shows this, and some phenomenal sigma values along and the preceived path of this would-be system:
http://www.coaps.fsu.edu/~maue/sst2.png

The integrated heat content is obviously no especially high once we get N of the Gulf Stream recurving latitudes (roughly 37N), but the shelf waters have been as high as almost 80F -- even as far N as the New York bite waters:



Currently, we see they are not, but the 80F isotherm is abeam of the Del Marva latitudes and if a TC were to evolve with the ferocity of the CMC/NAM blend, it would have a healthy fuel source to considerably high latitude; then enters the concern for how quickly it is moving and if the shelf waters can have enough time to assert very important weakening in time. Bob is an example of this, as he was still deepening slightly even after crossing the gradient from the Gulf Stream to the shelf waters S of Long Island.

Confidence is high in the overall larger-scale synoptic evolution, and confidence is growing that there will indeed by a TC to monitor. To pick each concern apart:

    NAO teleconnector has entered a period of upward rising values. That means the tendencies to lift the exit latitudes of the westerlies from off the N/A continent is present. Therefore, seeing the operational models converged on a ridge amplfication first along the Mid Atlantic and New England areas, then bulging seaward toward the east-northeast is increasingly plausible relative to this teleconnector signal. This also enhances the plausibility for trapping features in the regions surrounding 30N/70W.

    TC: Currently NHC has advertised this as a non-tropical area of low pressure. I find that interesting because my own evaluation late last night had this as pretty well entered into a symmetric phase transition in terms of environmental conditions. The trouble is, shear I think is masking some of this. However, the frontalysis that was in that vicinity had completed by evening last night, such that DPs north to south across the axis of apparent cyclonic circulation had become homogenized. Nevertheless, whether it is or is not more or less tropical is probably less important at this hour. Shear continues to impact this and will continue to do so in the shorter terms. Once said ridge development gets underway, this will weaken this NW shear markedly and we'll see the deep layer field lurch rather abruptly into a more favorable regime. That will probably take place in the 30 hour time range and onwards. Until then, this will probably (but not certainly) remain a fledging interest with lots of modeling debate. The TCs best hope in surviving this first day or so of shear assault is to bodily move east-southeast such as to tap into a lower "relative" shear result. ...Ironically, a more important threat to the EC may require moving away...



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scottsvb
Weather Master


Reged: Mon
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Re: 99L [Re: typhoon_tip]
      #77927 - Tue Sep 04 2007 02:27 PM

Well this has been a easy forecasting hurricane season so far. 99L might be alittle more difficult but still I feel straight forward. Lets look at it:


Right now its a LLC inbeded from a decay frontal trough. The center has picked up enough Tropical Characteristics to be at least subtropical in nature. Inhibiting factor so far on this is the shear. Models feel this will slow down and turned NW after meandering for a day...some say it will head back to florida. Lets look at why this wont come back to florida. 1 foremost is the ridge will not lie over the midatlantic...its more over the NW atlantic...moreso the ridge will slide to bermuda and have a SE-NW orientation with it. Now in the Nowcasting side of things we have a trough digging in just north of the system...this should swing 99L in the near term more NE later tonight into Weds....and as this trough weakens the Ridge should develop over the NW atlantic thru the end of the week and migrate south towards bermuda taking anything NW. I think NC has the best chance of getting brushed by this then SE N.E. but another cold front and stronger will slide into N.E. and probably keep the main center off shore. This is though more then 5 days out and anything really more then 3 days is unclear. Its not certain that this will move into the Outerbanks directly. As the 0Z runs come out later tonight and more data is collected things will be more clearer tomorrow. If that Nowcast shortwave was just a few deg ahead of 99L ...99L would of been more S and SE and would of posed more of a threat to Florida and SC. Right now.. its just not .

scottsvb


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doug
Weather Analyst


Reged: Mon
Posts: 835
Loc: parrish,fl 27.53N 82.44W
Re: 99L [Re: scottsvb]
      #77929 - Tue Sep 04 2007 05:28 PM

Looking at the 5p.m. sats...I don't see any thing to be concerned about here...to be sure there is a low level, but nothing above that.. shear from the NW is pronounced and dry air wrapping in too...Its direction now seems to be north. I give it less than 3 to develop.

--------------------
doug


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