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HanKFranK
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Reged: Mon
Posts: 1841
Loc: Graniteville, SC 33.56N 81.82W
Delta... why not?
      #63879 - Tue Nov 22 2005 02:26 PM

Have you ever watched one of those B-horror flicks where the monster/evil thing keeps getting supposedly done in, but returns a scene or two later no matter how dead it's supposed to be?

Don't you start wondering when the danged thing will just quit trying and wait until the sequel? Well, for those of you watching the 2005 hurricane season, you're probably starting to feel that way about how things are going.
Right now the system being tracked as invest 95L south of the Azores is, as the NHC puts it, 'acquring tropical characteristics'. The satellite analysis algorithms used by NRL and SSD think it's a sort of tropical cyclone, as NRL has it rated as a 40kt gale center with a 988mb central pressure... and SSD has it rated subtropical 2.5, or roughly a 35-40kt hybrid tropical cyclone. The 1:05 PM EST tropical discussion issued by the NHC notes it as a special feature 985mb low, as part of an occluded frontal system... the language says that it's acquiring tropical characteristics and could become a tropical storm at any time.

Last night Clark passed along that numerous global weather models are analyzing it as warm core. During the late season occasionally cut-off lows that occlude in the subtropics will go through the usual process that it's species of low does... after occlusion they will slowly acquire a warm core, and the convective processes that a tropical system usually needs will be sustained by the relative difference to their environment... even if the sea surface temperatures are running below that normal 27C/80F threshold usually considered necessary.
Forecast models take this low southward, stall it, and give it a variety of eccentric paths from there by the weekend as the big blocking high to the north (upstream of the deep trough currently in the Eastern U.S.) keeps it more or less in the middle of nowhere. Based on the current appearance it is quite likely that the NHC will upgrade the system to Subtropical or Tropical Storm Delta this evening... so if it follows one of the various forecast paths and lingers as projected, this system could be wandering around past Turkey Day.
Elsewhere there are a couple of convective complexes in the Caribbean.

Gamma's remnants have slid south along the coast of Nicaragua, while a small low pressure north of Panama is firing a little bit of convection. Upper winds are not supportive in the area.. but you guessed it.. may become favorable for development around the end of the week, if anything lingers. There's a small disturbance/wind shift line south of Puerto Rico, but conditions there are also generally unfavorable.
I've put up an early 2006 season forecast thread in the forum. It's just for fun... take your best shot at how active the coming hurricane season will be, based on what little we can tell about next year from here. In May we'll do an update where we can all make better stabs at it.

Alrighty, y'all have a good one.

HF 1926z22november


Edited by MikeC (Tue Nov 22 2005 02:55 PM)


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Rich B
British Meteorologist


Reged: Sat
Posts: 498
Loc: Gloucestershire, England, UK 51.81N 2.51W
Re: Delta... why not? [Re: HanKFranK]
      #63880 - Tue Nov 22 2005 02:37 PM

Agree with you totally on 95L, HF. Given the language coming from the NHC's products - namely the latest TWO and TWD - it would seem as if they are ready to classify this as Delta. However, given as there is no immediate land mass under threat, classification will likely wait until the normal 2100z package. Satellite imagery on this one has been showing a continually improving and organizing system. It appears to be detatching from the larger frontal cloud and structure, and taking on its own identity. With estimates putting winds in excess of 35 knts, it is likely that when (if) classified it will go straight to Storm strength, and miss out on depression status. Still, with the 2100z packages likely to come out within the next hour or so, we will see if it gets called now.

Regards

--------------------
Rich B

SkyWarn UK


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Rabbit
Weather Master


Reged: Sat
Posts: 511
Loc: Central Florida
Re: Delta... why not? [Re: HanKFranK]
      #63885 - Tue Nov 22 2005 03:46 PM

it appears this year has something else in common with last hurricane season--the NHC seems to be deciding lately not to name tropical storms that form late in the season

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Rich B
British Meteorologist


Reged: Sat
Posts: 498
Loc: Gloucestershire, England, UK 51.81N 2.51W
Re: Delta... why not? [Re: Rabbit]
      #63887 - Tue Nov 22 2005 04:20 PM

I wouldnt say that was a trait just from last year! Look how long it took them to classify Vince earlier this year.

With NRL still listing the system as 95L, and nothing on the NHC site, it looks like we wont see Delta just yet. The next likely time for a classification would be at 0300z. But seeing as they havent classified it now, it wouldnt be a surprise if they wait til visible imagery is available tomorrow and then go from there. However, visible imagery from earlier showed a well developed system, and the latest IR imagery continues to do so. Still, i guess they must have their reasons for classifying or not!

Regards

--------------------
Rich B

SkyWarn UK


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ltpat228
Storm Tracker


Reged: Tue
Posts: 201
Loc: Port Saint Lucie FL 27.20N 80.30W
Re: Delta... why not? [Re: Rich B]
      #63889 - Tue Nov 22 2005 04:37 PM

Thank you Rich B for your experienced Meteorlogical expertise.

Pat W.


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Rich B
British Meteorologist


Reged: Sat
Posts: 498
Loc: Gloucestershire, England, UK 51.81N 2.51W
Re: Delta... why not? [Re: HanKFranK]
      #63890 - Tue Nov 22 2005 05:28 PM

Well the 530PM TWO is out, and it looks like we dont have Delta... just yet. I would guess that NHC are waiting for the system to generate persistent and deep convection. It has been generating convection during today, but most of this has been relatively shallow. Recent IR imagery would suggest that this may be changing though, with an area of intense cold topped convection having formed to the immediate west of the centre, and now wrapping around the southern and eastern quadrants. If this continues then it has a decent shot. I would also imagine that NHC are waiting for it to break free totally from the frontal system to its northeast. Given how it is moving away from the front, and the continually improving convective patterns, we could see this upgraded within the next 6 to 12 hours.

Regards

--------------------
Rich B

SkyWarn UK


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Margie
Senior Storm Chaser


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Posts: 1191
Loc: Twin Cities
Re: Delta... why not? [Re: Rich B]
      #63891 - Tue Nov 22 2005 06:03 PM

Rich, from the NHC definition of a Tropical Cyclone:

Tropical Cyclone:
A warm-core non-frontal synoptic-scale cyclone, originating over tropical or subtropical waters, with organized deep convection and a closed surface wind circulation about a well-defined center.

If you look at the latest 85Hz scan (from about 3pm) from the NRL site, there is only a very small area of significant deep convection just to the ESE of the center that only covers about from 75 to 135 deg...barely a quarter of the way around, and barely any other convection present.

Even Gamma had more convection than this when classified (wrapping about 200 deg around the center...it was at about T2.5).

Edit: and the 2311Z pass doesn't show any deep convection at all.

--------------------
Katrina's Surge: http://www.wunderground.com/hurricane/Katrinas_surge_contents.asp

Edited by Margie (Tue Nov 22 2005 07:22 PM)


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typhoon_tip
Meteorologist


Reged: Wed
Posts: 568
Re: Delta... why not? [Re: Rich B]
      #63893 - Tue Nov 22 2005 06:29 PM

Quote:

Well the 530PM TWO is out, and it looks like we dont have Delta... just yet. I would guess that NHC are waiting for the system to generate persistent and deep convection. It has been generating convection during today, but most of this has been relatively shallow. Recent IR imagery would suggest that this may be changing though, with an area of intense cold topped convection having formed to the immediate west of the centre, and now wrapping around the southern and eastern quadrants. If this continues then it has a decent shot. I would also imagine that NHC are waiting for it to break free totally from the frontal system to its northeast. Given how it is moving away from the front, and the continually improving convective patterns, we could see this upgraded within the next 6 to 12 hours.

Regards




..Whether HPC has pulled the trigger on this at 5pm or not, I believe the after thought of most tropical Mets is that it has already acquired sub-tropical characteristics - check that, IS a nameable system at this time. Not sure with the overwhelming signal we are getting from heat channels what the hold up is, but I suspect it may have something to do with the actual meteorology of what is going on out there... I'll eat crow if wrong, but I suspect this is an internal policy decision because of certain meteorological observations that need to be atoned for; they will soon enough! (*I cast no aspersion at HPC for any policies they have and frankly believe they are completely necessary for a few reasons I won't broach here..)

For example, we do still see a tendency for a subtended baroclinic field between the remnant mid-lvl trough N, and the system its self, W of 30 longitude. However, there are no current large scale synoptic suggestions/reasonings that connote "Delta" will effectively be re-captured by the westerlies therein. Normally, when observing a tropical system so close to a baroclinically forced SFC trough you immediately think "..Oh, NNE motion along/ahead of that boundary.." - Nope, not this time.

I'm sure you are much agreed with this stuff already...But, in fact, quite the opposite as the continued separation from said attenuating trough is certain and already underway... This "monster" (for you HF ) is taking on more independent structure in tandem with that trough N losing its own present in the N Atlantic... It is filling and will be totally gone from the regions along 30W soon as the exertion of the -NA0 is coming into prominence. The -NAO will provide for a nice deep layer ridging there much sooner over later. This will effect/incur a S drift to "Delta", as HF has been intimating and follows quite logically...

Lastly, it is intriguing that in the -NAO phase we typically do see the amplification of the Azore's Low... I find it interesting that the counter part variant for this particular NAO seem to be an evolving tropical phenomenon... You have to find that awesome?

--...bold and or highlighted meteorology reference-able sections are for the general reader... I should also add a caveat that the SSTs are a slightly less that 26C....so we are certainly not talking explosive development!
TT

Edited by typhoon_tip (Tue Nov 22 2005 06:33 PM)


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Bloodstar
Moderator


Reged: Mon
Posts: 397
Loc: Georgia Tech 33.78N 84.40W
Re: Delta... why not? [Re: Margie]
      #63894 - Tue Nov 22 2005 07:05 PM

Looking at the latest imagry on delta, what is catching my attention the most is how the storm is now operating in isolation, there doesn't seem to be any attached fronts. I would argue the storm is more tropical in nature than sub tropical at this point, but it's still got a big windfield, Seeing some rain flagged 50Kt winds near the center. hmmmm, Personally I'd have classified, it, but they'll probably wait until an eyelike feature develops (which seems to be happening).

for an example of a similar storm. Olga in 2001 comes to mind. the cloud tempratures never got really cold, in fact I think the current invest has tempratures as cold as olga ever had, even when it had a well defined eye.

http://www.nhc.noaa.gov/2001olga.html

-Mark

--------------------
TD/TS/HU/MH
19/18/0905 <- My prediction (2013 Predictions)
01/01/00/00 <- Year Totals

http://blog.bloodstar.org


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Clark
Meteorologist


Reged: Wed
Posts: 1710
Loc: Great Lakes 45.95N 84.55W
Re: Delta... why not? [Re: Margie]
      #63896 - Tue Nov 22 2005 07:48 PM

Just as an aside, Margie, the 85GHz channel on the satellite products available on the NRL's site isn't directly a measure of deep convection. That channel, through various physical processes, is sensitive to ice content at upper levels. Higher ice content leads to lower brightness temperatures (what those images are displaying); note that a brightness temperature isn't an actual temperature, but instead deals with some of the radiative properties of an object.

Generally yes, deep convection will have relatively high ice content...but you'll see moderate to deep convection occasionally appear that does not have very high ice content. In the case of an extratropical cyclone trying to become a tropical cyclone, it's probably better to use the microwave imagery to try to discern developing banding or even eyewall structures and infrared imagery to actually sense the organization of the convection. A lot of this harkens back to these systems primarily being found in the midlatitudes and not the tropics and the properties of convection normally seen here.

In soon-to-be Delta's case, infrared imagery has hinted at a developing eyewall all afternoon, much as was seen with Vince immediately prior to classification, and the microwave image you referenced seems to confirm that with hints of a banding-style eye forming. It's getting close to classification and I would not be surprised to see it classified at 10p ET.


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Old Sailor
Storm Tracker


Reged: Mon
Posts: 293
Loc: Florida
Re: Delta... why not? [Re: Clark]
      #63897 - Tue Nov 22 2005 07:58 PM

Maybe more as a TD from latest sat's.

22/2345 UTC 29.8N 40.9W T2.0/2.0 95
22/1745 UTC 30.9N 40.4W ST2.5/2.5 95
22/1145 UTC 31.3N 39.9W ST2.5/2.5 95
Dave


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vineyardsaker
Weather Guru


Reged: Wed
Posts: 133
Loc: New Smyrna Beach, FL 29.03N 80.93W
Re: Delta... why not? [Re: HanKFranK]
      #63898 - Tue Nov 22 2005 08:11 PM

Skeetobiteweather.com (weird name, no?) does not have the models for 95L. Could it be headed for the US?

--------------------
Motto: chown -R linux:GNU *
Distros: Debian, Xubuntu, Mint
http://vineyardsaker.blogspot.com/
Charley(eyewall), Ivan, Jeanne, Dennis, Wilma


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Clark
Meteorologist


Reged: Wed
Posts: 1710
Loc: Great Lakes 45.95N 84.55W
Re: Delta... why not? [Re: Old Sailor]
      #63899 - Tue Nov 22 2005 08:54 PM

I concur...probably quite a bit more than that, too. Check the 37GHz satellite product from the TRMM Microwave Imager (TMI) at the NRL site. Note that the 37GHz product is sensitive to liquid water content and rainfall -- thus, the image you're seeing can be viewed as somewhat akin to a poor man's radar image. That depiction is not unlike what you see with many strong tropical storms or weak hurricanes and not terribly unlike that seen with Vince. The wind field is certainly there, per QuikSCAT, for a moderate tropical storm at least. The satellite appearance of this one continues to improve, both on infrared and microwave imagery, and has done so to the point that I will be quite surprised not to see Delta at 10p.

And to answer the follow-up question -- no threat at all to the US or any other land mass. Maybe in a week to 10 days, whatever is left of it will be part of some extratropical system impacting the Azores or Europe, but that's not likely to be anything more than they typically see from midlatitude weather systems.


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HanKFranK
User


Reged: Mon
Posts: 1841
Loc: Graniteville, SC 33.56N 81.82W
Re: Delta... why not? [Re: Clark]
      #63900 - Tue Nov 22 2005 09:04 PM

sailor, because of the shallower than typical convection and ragged look the storm has under a less-than-normal anticyclonic flow aloft, the satellite algorithms don't see a tropical storm. however, if you look at cloud motions and the fact that it has an eye and partial convective ring, the idea that it's a depression is nuts. remember, those t-ratings run low when you've got a sheared or hybrid system.
with the tropical rating and gale force quickscat vectors, the NHC not classifying the system at the next advisory cycle would be prepostorous. almost certain they will. if it goes straight to tropical, it begets the question: why have a subtropical system classification? they rarely use it for hybrid systems.. usually waiting until the system is obviously tropical to start advisories on it. case and point--vince earlier this year, otto last year, peter in 2003, karen in 2001... the post-analyzed subtropical storm of 2000. really hope the NHC takes a more active stance on classifying subtropical cyclones when they're active, as opposed to after the fact.
been looking at the SST fields out there, and along the expected track they run pretty much in the upper 70s. 80F gets quoted as the threshold all the time, but a tropical storm or hurricane in a colder than normal, baroclinic, or high-than normal slp environment doesn't always need that number. when dealing with late season hybrids, the usual barotropic rules are out the window.
okay, 'nuff of that.
HF 0204z23november


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Old Sailor
Storm Tracker


Reged: Mon
Posts: 293
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Re: Delta... why not? [Re: Clark]
      #63901 - Tue Nov 22 2005 09:06 PM

A little history here guys, more ships and life lost were do to gales then hurricanes in our history, so one shouldn't be so fast with the one Hurricane as being the biggest killer..

Dave


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HanKFranK
User


Reged: Mon
Posts: 1841
Loc: Graniteville, SC 33.56N 81.82W
Re: Delta... why not? [Re: Old Sailor]
      #63903 - Tue Nov 22 2005 09:31 PM

well, maybe that's 'cause a lot of shipping historically has stayed out of the tropics. i'd bet if you compared the volume of shipping traffic in the mid latitudes to the volume of shipping traffic in the tropics, and normalized the casualty rates to the amounts.. they'd be a lot closer.
HF 0231z23november

note: as of 9:30 EST, NRL hasn't changed the track on 95L. that suggests that NHC may not upgrade this cycle. somebody is asleep at the switch. -HF

Edited by HanKFranK (Tue Nov 22 2005 09:34 PM)


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Old Sailor
Storm Tracker


Reged: Mon
Posts: 293
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Re: Delta... why not? [Re: HanKFranK]
      #63904 - Tue Nov 22 2005 09:53 PM

Hank:

I was also talking about landfall systems, Nor'Easters etc, just check your history on both at Sea and Land fall.

Dave

guess i'll have to. you're the sailor here. -HF

Edited by HanKFranK (Tue Nov 22 2005 11:43 PM)


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HanKFranK
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Reged: Mon
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Loc: Graniteville, SC 33.56N 81.82W
Re: Delta... why not? [Re: Old Sailor]
      #63905 - Tue Nov 22 2005 11:51 PM

alright alright, it's still a 'strong, non-tropical low'. with an eye and CDO and no frontal attachment, of course.
it's inevitable that they'll upgrade it. may get to hurricane if the convection deepens some, based on the level of organization.
maybe it's just that i've been waiting for this thing since.. hang on let me check. sunday, november 14th was the first mention. yeah, i'm tired of waiting. now i have to wait for the NHC guys to decide that a system that meets their criteria is a tropical cyclone.
so anyway, delta is out in the east atlantic. to be named tomorrow? knabb must have something against nonconformists.
HF 0451z23november


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Margie
Senior Storm Chaser


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Posts: 1191
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Re: Delta... why not? [Re: HanKFranK]
      #63906 - Wed Nov 23 2005 12:24 AM

But it doesn't look like the tropical storms I've been seeing and learning about all season. It doesn't look very tropical. On the water vapor the temperature of the center isn't all that warm, the convection doesn't look the same like I'm used to seeing, and there's some kind of lack of, I'm not sure how to put it, but the band doesn't seem like a feeder band, with a force driving the convection into the center. It's more like a group of clouds that are all moving around the center, but only because of the rotation, like they're all just sitting in place, like a record on a turntable; staying the same, static. It seems like there is some dynamic that is missing.

Unbelieveably, the Circulation that Wouldn't Die is still spinning and now pulling along some convection as it heads into Central America at the border of Panama and Costa Rica.

see if you can find that paper on hurricane karl of 1980. a lot of the ET-T transition events happen where a hurricane forms within a large deep layer low. -HF

Edited by HanKFranK (Wed Nov 23 2005 03:28 AM)


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danielwAdministrator
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Posts: 3444
Loc: Hattiesburg,MS (31.3N 89.3W)
Re: Delta... why not? [Re: Margie]
      #63907 - Wed Nov 23 2005 01:21 AM

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST WED NOV 23 2005 (edited~danielw)

SPECIAL FEATURE...
CENTRAL ATLC 982 MB LOW IS CENTERED NEAR 30N41W DRIFTING SOUTHWARD. CONVECTION CONTINUES TO WRAP AROUND THE CENTER TONIGHT WITH A DISSIPATING OCCLUDED FRONTAL SYSTEM TO THE NORTH
WITH A DISSIPATING COLD AND WARM FRONTS FROM A TRIPLE POINT NEAR 33N34W.
STORM WARNING IS IN PLACE FOR WINDS OF AT LEAST 50 KT WITHIN 360 NM OF THE LOW IN THE SW QUADRANT.
ALTHOUGH THIS LOW IS CURRENTLY NON-TROPICAL...IT IS GRADUALLY ACQUIRING TROPICAL CHARACTERISTICS AND COULD BECOME A TROPICAL CYCLONE..."DELTA"... OVER THE NEXT DAY OR SO.
SCATTERED MODERATE CONVECTION IS WITHIN 175 NM OF THE CENTER IN THE E SEMICIRCLE. HEAVIER CONVECTION IS ASSOCIATED WITH THE FRONTAL BOUNDARIES.
punctuation and spacing edited for ease of reading and emphasis~danielw


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