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General Discussion >> The Tropics Today

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cieldumortModerator
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Perky Late Season Atlantic: 90L, 91L, 92L
      #89970 - Wed Oct 27 2010 03:21 PM

Mid-late October sometimes sees a brief, secondary upswing in activity, and we have already seen this with the formation of Hurricane Richard in the Caribbean.

Now, three interesting, late-season features are percolating out in the Atlantic this week - none currently with great odds for development in the near term, but conditions for development could be turning less hostile by the end of the week.

First up, Invest 90L. Originally this disturbance started out as a very late-season, vigorous Cape Verde wave, and very nearly had enough time to become a tropical depression while still way, way out by the Cape Verde islands. 90L has since morphed several times, now in its most recent incarnation as the centerpiece of a fairly well-defined, hybrid, subtropical low, having merged with a non-tropical upper-level low.

Upper-level winds are currently unfavorable for much development, but could become a little less hostile over the course of the next few days, and the National Hurricane Center currently gives this disturbance about a 30% chance of becoming a subtropical or tropical cyclone within the next 48 hours.

Steering currents suggest virtually less than zero threat to the U.S.

Invest 90L



Next up, Invest 91L. Another very potent, late-season tropical wave, and this one running fairly low latitude, so as not yet to be re-curved and/or ripped to shreds, Invest 91L keeps heading west to west-northwest, towards the northern tip of South America.

There is some chance that it stays partially, or even mostly over water, and upper-level winds could become less unfavorable for development over the next few days, and NHC currently gives 91L a slim 10% chance of becoming a tropical cyclone over the next 48 hours.

Steering currents suggest that 91L could be something to pay more attention to for those in the Caribbean over the coming weekend and/or into next week, should it stay over water, and there is actually some tepid model support for this feature, if it should get into the western Caribbean.

While 91L is a long shot for development in the near term, it is much closer to land, and is quite a vigorous wave. As such, it does bear some watching.

Invest 91L


Lastly, Invest 92L. Invest 92L seems to have grown out of some of the remnants of a fairly well-defined central Atlantic low, originally out near 13.5N and 42.5W before encountering detrimental wind shear, and another upper-level trough. This Invest is now situated somewhere around 25N 54W, and appears to be drifting west-southwest, at present.

There is a surprising amount of early model support for this feature, and while unlikely a direct threat to the U.S., it could bring some weather to Bermuda, should it develop. NHC currently gives 92L about a 20% chance of becoming a subtropical or tropical cyclone over the next 48 hours.

Invest 92L


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MichaelA
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: cieldumort]
      #89971 - Wed Oct 27 2010 06:47 PM

It's really interesting to have three invests in the Atlantic in the last week of October. Of the three, I'd lean toward 92L as having the best shot of developing into possibly a sub-tropical system. 90L still shows considerable shear and 91L is really far South. The northern portion of 91L may have some chance of developing in the Caribbean later, but I think the main body will just go inland in South America. Only time will tell, though. I guess this just shows that the 2010 Atlantic season is still alive and kicking.

--------------------
Michael
2014: 8/2/0
2014 Actual: 8/6/2


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MichaelA
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: MichaelA]
      #89972 - Wed Oct 27 2010 08:15 PM

8 PM EDT outlook has 90L and 92L at 30% and 91L at 20% probabilities. I'm still leaning toward 92L being the one to develop.

--------------------
Michael
2014: 8/2/0
2014 Actual: 8/6/2


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cieldumortModerator
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: MichaelA]
      #89976 - Thu Oct 28 2010 12:58 AM

Looks like we're probably going to be discussing these more - and in the main thread Mike just started.

I somewhat concur with you, in that 92L may actually the one closer to being "there" tonight. However, NHC seems all but ready to give 90L the bump any time now... which I can also understand. Also somewhat agree that 91L perhaps has the longer road ahead of it for any significant development. However, all three of these now appear to me to have quite unseasonably decent shots of developing this week, and I would give them all at least 40% chances for popping sometime between now and Tuesday.

A recent ASCAT of 90L (NHC just issuing a 50% chance on it) does show it to be embodied by a very well-defined LLC, with convection sheared and firing off to the east of the center. With shear relaxing, there is indeed an increasingly good chance of deep convection developing over the center.. and thus NHC suggests a tropical cyclone could form... practically at any time now.

Usually this would necessitate their using wording closer to a 70% to 90% chance of development within the next 48 hours... but, the question of just how well this convection will be able to build over the center is uncertain. However, if and when it does so, I would not be surprised to see 90L go strait to being named, skipping any TD or STD advisory.

Tonight's ASCAT Pass of 90L


With regard to 92L, if I were Head of NHC for a Day, I suppose I would probably already have a 50% or 60% up on this feature tonight. NRL and SSD identify 92L at either 22.9N 55.3W or 24N 54.4W, respectively. But I suspect that a more pronounced center of circulation may have been forming all afternoon and tonight in the mid levels, and may actually be drawing in the elongated LLC more into closer and more symmetrical alignment with it ... this mid-level center now being somewhere closer to 24.5N 56W.

Invest 92L


Where I guess we might see things less alike, perhaps, is that it now appears to me that all three of these features are more likely to become basically tropical, than subtropical. The main reason for this is that the process of shedding off their non-tropical origins (at least with respect to both 90L & 92L) are already well underway. And of course, 91L is a juicy, low-latitude tropical wave, to begin with.

All in all, a very impressive last week in any season's October.


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doug
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: cieldumort]
      #89977 - Thu Oct 28 2010 11:23 AM

Interesting! Re: 91L both GFS and ECMWF throw something into the south central Carribean at the end of their forecast runs...5-6 days. Based on these two models reasonable accuracy all season 91 L does bear watching.

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


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cieldumortModerator
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: doug]
      #89979 - Thu Oct 28 2010 12:32 PM

I agree - think 91L bears a great deal of watching, as not only is it an exceptionally vigorous tropical wave for the time of year, but also that conditions upstream, once it is "land-locked," look supportive of more development, and I could see tropical cyclogenisis occurring with this one potentially even before it crosses the Windwards, provided it stays over water.

Recon now tentatively scheduled to check out both 91L & 92L

1030 AM EDT THU 28 OCTOBER 2010
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 29/1100Z TO 30/1100Z OCTOBER 2010
TCPOD NUMBER.....10-149

I. ATLANTIC REQUIREMENTS
1. SUSPECT AREA (NEAR BERMUDA)
FLIGHT ONE -- TEAL 70
A. 29/1800Z
B. AFXXX 01JJA INVEST
C. 29/1400Z
D. 29.0N 65.5W
E. 29/1730Z TO 29/2100Z
F. SFC TO 10,000 FT

2. SUSPECT AREA (APPROACHING WINDWARD ISLANDS)
FLIGHT ONE -- TEAL 71
A. 29/1800Z
B. AFXXX 01KKA INVEST
C. 29/1530Z
D. 09.5N 57.0W
E. 29/1730Z TO 29/2200Z
F. SFC TO 10,000 FT

3. SUCCEEDING DAY OUTLOOK: BEGIN 6-HRLY FIXES ON SYSTEM
NEAR THE WINDWARD ISLANDS AT 30/1200Z NEAR 11N 62W.


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Lamar-Plant City
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: cieldumort]
      #89980 - Thu Oct 28 2010 03:46 PM

This might be a little off the topic of these three systems.....but looking out into the western GOM....is that the remnant energy from Richard starting to fire up on the western end of that frontal trough. There was NOTHING there yesterday and the west end of the trough looked very dry (so much so that our rain chances were predicted to be pretty low as it passes). Throughout the day there is a growing area out there with the appearance of a 'twist' in the clouds at a couple of points? Anything to be concerned about? If it brings some rain here (29 days in Tampa with no measurable) it would be GREAT!!

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


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cieldumortModerator
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: Lamar-Plant City]
      #89986 - Thu Oct 28 2010 07:02 PM

It does look as if some of the remains of x-Richard have been drawn into & energized an elongated N-S oriented surface trough, which has itself T'd with the progressive cold front pushing deeper into the GOM. Tropical cyclone development looks very unlikely in the GOM over the near-term, but together these features do look to be juicing things up in the there, and now into Florida. Go rain!

What may be more interesting, is that even if nothing comes of the x-Richard/trough/cold front trifecta, these features may serve to help put enough moisture into the western Atlantic that should 91L be something if and when in the Caribbean, it may now not have as much dry air to contend with.


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weathernet
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: Lamar-Plant City]
      #89987 - Thu Oct 28 2010 07:17 PM

Gonna be close as to which might be designated to T..D. first, between 91L and 92L, but my money is on 91L. Won't be as fast as I might had thought earlier to day due to convergence at such a low latitude, however because shear is still impacting 92L and 90L so significantly, I see 91L possibly gaining just enough latitude by late tomorrow along with its more favorable upper air conditions, that assuming that the other two systems take a while longer for the upper air conditions to improve, am guessing that 91L with all its convection will simply need show a little more significant banding features and given its overall size, potential need for watches for the islands......, perhaps a T.D. ( or even skip to T.S.? ) between noon and 5:00 tomm.

Though not really able to pay much reliable attention to downstream models yet ( at least until we have a true identified center and actual motion fix ), the concept of even looking to see if this could be any kind of downstream threat to the U.S. seems ludicrous. The fact that this is an approaching system from the east and being October 28, would cause one to imagine a typically immediate northward turn. Add to that the fact, that we have already had two fronts drop some very dry air into the west/central Caribbean, with an appearant long wave pattern looking like its going to set up shop over the Eastern U.S. seaboard. Just goes to show that during this period of seasonal transition, along with perhaps amplified ridging in the east, perhaps enhanced by a very strong La Nina....., you just can't quite know its over until the westerlies have really taken a firm hold in the lower latitudes.


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cieldumortModerator
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: weathernet]
      #89988 - Thu Oct 28 2010 07:42 PM

It's a cliff-hanger, if you're placing bets on which one gets the upgrade first. My money is still on 92L, but wouldn't it be something to see them both upgraded at the same time... in the last few days of an October! Sheesh!

My reasoning for 92L deserving an upgrade first is simple: I think 92L is basically already there, and could arguably go strait to being named, bypassing TD advisories, whereas 91L may just have a little further to go to develop a stable LLC core.

92L's developing LLC has apparently tucked further under the much more convectively active MLC, and the two have come into much better alignment, making for tightening and increasingly colocated mid and low level centers within a ball of deepening convection.

And pressures close to this center are really falling, with wind responding in kind, with the wind-pressure relationship classically characteristic of a tropical depression or storm.

For example, take a look at the current trends at Station 41049, located at 27.5N 63.0W: (LINK)

Only (current) hold up for 92L to get the bump, I think, is the possibility of some decoupling over the next few hours.

It will be very interesting to see what NHC does with each of these later tonight and by tomorrow morning.


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cieldumortModerator
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: cieldumort]
      #89990 - Thu Oct 28 2010 10:44 PM

Invest 92L is now Tropical Storm Shary, the 20th officiated, and 18th named tropical cyclone of the 2010 Atlantic Hurricane Season. Maximum sustained winds are currently estimated to be about 35 knots, and this could be conservative.

Shary is in a slightly favorable for environment for further development, and may bring very blustery weather and heavy rains to Bermuda soon, directly, or indirectly.


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MichaelA
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: cieldumort]
      #89991 - Thu Oct 28 2010 10:55 PM

Very small storm, but it is the one I thought had the best short term shot at developing. 91L is massive and looks like the bulk of it will get into the Caribbean now. 90L is still rather sheared, but some convection is trying to fire up nearer the LLC.

--------------------
Michael
2014: 8/2/0
2014 Actual: 8/6/2


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weathernet
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: cieldumort]
      #89992 - Fri Oct 29 2010 01:37 AM

Nice call. Well, looks like you guys have to split the $400,000! - LOL

Can't really argue with regards to Shary's LLC, which is really spinning, and though meager....., convection is truly firing from that point. Given the shear at hand, am still somewhat surprised on NHC's call, given near term course and near term upper air conditions perhaps soon to deteriorate further. 91L though massive as it may be, is just not even close to exhibiting the same tight LLC that Shary has.


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weathernet
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: weathernet]
      #89993 - Fri Oct 29 2010 02:55 AM

Wow, middle of the night and 91L is looking like it's tightening up a tad. Tops getting colder and hints of convective banding beginning. That, and taking a hard look at the 0Z GFS upper air data, and am really starting to worry about the potential of a major hurricane in the central Caribbean in just a few days. GFDL is finally on board as well, showing a distinct system trekking somewhat towards Jamaica ( or just east of there ). Regardless of exact forecast points at this time, an already large system further supported by a significant anticyclone overhead could create a devastating flooding risk for Jamaica, E. Cuba, Haiti, Dominican Republic and possibly P.R.

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cieldumortModerator
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: weathernet]
      #89994 - Fri Oct 29 2010 03:10 AM

Quote:

am really starting to worry about the potential of a major hurricane in the central Caribbean in just a few days




I'm right there with you on that. I would probably break down 91L's prospects roughly along these lines:

Top max sustained winds within 91L during the next 7 days (personal best guess odds):

Less than 39MPH: 5%
39 - 50 MPH: 10%
55 - 70 MPH: 25%
75 - 90 MPH: 15%
95 - 110 MPH: 25%
Over 110 MPH: 20%

Or put another way, 95% odds of becoming a named storm, 35% odds of then maxing out as a TS, 60% odds of actually becoming a hurricane, and even 20% odds of becoming a major hurricane, within the next 7 days.


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berrywr
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: cieldumort]
      #89995 - Fri Oct 29 2010 05:55 AM

Unfortunately while 3 tropical systems in the Atlantic our best candidate to become a late season hurricane has not been formally designated. This system has one chance in being a viable system and that is for the upper high currently over the system rides along and if it doesn't, it's game over as the system will ripped apart by shear which is 20 knots from the SW less than 100 miles to it's NW, 30 knots from the SW at less than 150 miles to it's NW. Shary is being covered by an upper low to it's SW and as separation occurs shear will become more pronounced and the progression of short-waves will spell the end of Shary being tropical in no more than a couple days. I don't doubt the Caribbean system looks impressive on satellite, but its days are numbered given the hostile atmosphere that lies ahead.

--------------------
Sincerely,

Bill Berry

"To work in the service of life and the living..." - John Denver

Edited by berrywr (Fri Oct 29 2010 06:09 AM)


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MichaelA
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: berrywr]
      #89997 - Fri Oct 29 2010 08:58 AM

I haven't looked at the model runs on 91L yet, since they are little better than conjecture until several runs of solid data are acquired. The shear in the Caribbean may relax as Shary moves away anyway. 90L looks like it will be history, since convection has diminished and the LLC has really broadened from what it was yesterday. Waiting to see if NHC pulls the trigger on 91L later today, since it looks fairly impressive in the latest vis pics this morning. I can't see if there is a closed LLC there yet.

--------------------
Michael
2014: 8/2/0
2014 Actual: 8/6/2


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cieldumortModerator
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: MichaelA]
      #89998 - Fri Oct 29 2010 10:11 AM

Well, the AVN shear forecast through Monday along 91L's most likely tracks can scarcely be called hostile, actually (LINK), and there is a fair to good chance that the upper-level anticyclone currently riding atop and along with the cyclone will continue to do so, more or less, for at least another day or two, and possibly quite a bit longer.

All in all, I think 91L has unusually strong prospects for more development, given the time of year.

91L's broader LLC looks just about centered with the obvious MLC.

1218Z Composite:


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doug
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: cieldumort]
      #89999 - Fri Oct 29 2010 11:25 AM

GFS blows this up quite a bit late in the forecast period and places it south of Haiti. What is scary is the weakness in the ridge over the SE US at that time. ECMWF has a system in the west central Carribean.
The satelite presentation says tropical storm now. The aircraft will give accurate data so the models can begin to grab it, and we should see a clearer picture tonight. Something this big and potentially powerful is worth watching carefully.

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


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florida central
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Re: Perky Late Season Atlantic: 90L, 91L, 92L [Re: doug]
      #90000 - Fri Oct 29 2010 12:00 PM

Wow just looking at the sat. images below, any one know if 91L is pulling all that moisture from the fae se to east of the main area? meaning from 20-45 long.
http://www.ssd.noaa.gov/goes/east/tatl/wv-l.jpg


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