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Archives >> 2011 Forecast Lounge

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MikeCAdministrator
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Emily Forecast Lounge
      #90810 - Thu Jul 28 2011 07:50 PM

This is for discussing the Central Atlantic wave (no invest numbering as of yet, but is P10L under the pouch system).

With the first outlook giving it a 20% chance of development, we open the lounge. If this were to be named by Sunday we would have had 5 named storms before August.


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Ed DunhamAdministrator
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Re: Central Atlantic Wave Lounge [Re: MikeC]
      #90812 - Thu Jul 28 2011 07:56 PM

Wave is located near 10N 40W at 28/00Z moving to the west at about 15 knots. Slow development is possible over the next couple of days and the development chances should improve (less shear) on Sunday.
ED


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cieldumort
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Invest 91L Becoming Better Organized [Re: MikeC]
      #90823 - Fri Jul 29 2011 01:57 AM Attachment (143 downloads)

The central Atlantic tropical wave is now being tracked as Invest 91L, and has been steadily getting better organized so far tonight, with increasing convection, and an improving low level circulation.

91L consists of a large surface circulation with a stretched center, and tonight there are now some hints of some mildly curved inflow banding, with deeper convection blowing up near or over the center of circulation . (See image below)




I have also uploaded a 7/28 2345Z (7:45 PM EDT) ASCAT pass (wind analysis), which shows an incipient low level circulation center located roughly 8.2N and 39.8W, at that time. The image is somewhat large, so please click the Attachment link above to view.


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MikeCAdministrator
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Re: Central Atlantic Wave (Invest 91L) [Re: MikeC]
      #90825 - Fri Jul 29 2011 08:19 AM

The GFDL model is picking this up well. It seems pretty 'bullish' on the development of the wave, takes it near Puerto Rico and the northern Leeward islands of the Caribbean probably want to think about preparations for later if this takes off.

Most of the globals slam it into Hispaniola, but if it misses, odds currently only slightly favor out to sea beyond the Caribbean, but that will probably change.

The HRWF avoids the Caribbean entirely, and keeps the system generally out to sea.

Either way, once passed the Caribbean...

With a trough probably setting up along the East coast, odds slightly favor this system staying out to sea beyond the Caribbean . But it's still worth watching to see what, if anything, changes.

With the NAO pattern like it is this year (fairly similar to last year), it means that most storms coming from the east/Cape Verde have odds that favor them staying out to sea. The things to watch for are any exceptions to the general rule.

In that case it's still a bit too early to tell with the system, so we watch, but odds still are odds.

The GFDL/HRWF can been viewed Here

Edited by Ed Dunham (Fri Jul 29 2011 09:24 AM)


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MikeCAdministrator
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Re: Central Atlantic Wave (Invest 91L) Lounge [Re: MikeC]
      #90827 - Fri Jul 29 2011 06:48 PM

91L hasn't changed much during the day, it appears to be two areas of convection, one more dominant than the other, that may merge or combine into something later. This fact right now is keeping it about the same today, so development chances probably will remain around 30-40% at 8PM.

The models are suggesting that it approaches the Leeward Islands, and later Puerto Rico. Those along the northeast and northern Caribbean will want to keep a close eye on it. Assuming it moves north of the Caribbean, odds are still in favor of recurving before approaching the Bahamas/United States. The trough forecast is really too strong for it to miss, the only way it could slip under is if it were to remain weak.

I'll be watching it the long haul though, regardless.


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MikeCAdministrator
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Re: Central Atlantic Wave (Invest 91L) Lounge [Re: MikeC]
      #90835 - Sat Jul 30 2011 07:02 AM

Long term on 91L is still interesting, the Euro model slams the wave into Hispaniola and destroys it, or more correctly splits it, if that happens it'll likely move the moisture toward Florida, but without the storm along with it, while another piece goes out over the Bahamas and out.

The GFS has it over northeastern puerto rico then staying to the northeast of the Bahamas, and in prime area for recurve.

Most of the other models have it going over or near Puerto Rico, a few of them keep it more westerly into Hispaniola, a few keep it away. But models generally agree until about the time it approaches Puerto Rico.

If it does approach Hispaniola it will likely get ripped apart, if it stays northeast or just over puerto rico and heads into the Altantic, it most likely recurves. If it stays south,it's likely to continue westward for a while. HRWF keeps it northeast of the Islands the entire time

The near/over Puerto Rico and recurve appears to be the most likely based on conditions, second most likely is slamming into Hispaniola, least likely is for it to stay south of the islands and continue west.

As for Bahama/US impact, chances are against it, but if it were to split the difference between Hispaniola/PR, then it possibly could, but this is not likely.

Personally, I'd lean toward the further south scenario (probably staying in the Caribbean perhaps the entire time), especially if development doesn't happen today which despite the front page title (which isn't just me) we put up, I think may hold off. However, If it gets up close to PR though and up through there, I see way more things keeping it away from the US than things that bring it closer. That trough is just going to be too much.

I don't expect it to bother the east coast US based on what I see right now.



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danielwAdministrator
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Re: Central Atlantic Wave (Invest 91L) Lounge [Re: MikeC]
      #90836 - Sat Jul 30 2011 09:17 AM

This is Friday's Recon Plan of the Day for Sunday. An updated plan should be out in a few hours.

CARCAH, National Hurricane Center, MIAMI, FL.
1005 AM EDT FRI 29 JULY 2011
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 30/1100Z TO 31/1100Z JULY 2011
TCPOD NUMBER.....11-059 AMENDMENT

I. ATLANTIC REQUIREMENTS
1. NEGATVIE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY:
A. INVEST SUSPECT AREA AT 31/1800Z NEAR 14.0N 54.0W. (Sunday 2 PM EDT )
B. ADDED....A G-IV MISSION FOR 01/0000Z. ( Sunday 8 PM EDT)
3. REMARK: P-3 MISSIONS FOR 29/1200Z AND 30/0000Z
CANCELED BY NHC AT 28/2345Z.


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Ed DunhamAdministrator
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Re: Invest 91L Lounge [Re: Ed Dunham]
      #90839 - Sat Jul 30 2011 09:38 AM

I'm not yet ready to jump on the 'rapid development' bandwagon for this system. I realize that NHC increased the 48-hour development probability to 70% last night but, from what I can observe on satellite, thats at least 20% too high. The tropical wave is elongated along a west northwest to east southeast axis and still has no well-defined center. NHC suggests a 1008MB low (up from 1007) near 11N 45W at 30/10Z which may have reorganized near 11.5N 46.3W at 12Z, however there are other convergence points within the wave. On the plus side, during the night the wave lifted out of the ITCZ but cyclonic organization still has a long way to go. I think that it will get there - its just going to take some time.

Until the centerpoint becomes established its difficult to develop a future track, however a west northwest movement toward the northern Leeward Islands seems likely - perhaps even slightly north of the Islands. As the wave lifts further north it will encounter westerly windshear which is why I'm leaning toward a slower development process. This shear zone should decrease west of the Islands.
ED


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MikeCAdministrator
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Re: Invest 91L Lounge [Re: Ed Dunham]
      #90848 - Sun Jul 31 2011 07:31 AM

This mornings models are gravitating toward Hispaniola. If this system were to move over the island which contains the Dominican Republic and Haiti, the high mountains there would rip the system to shreds, and probably cause extremely heavy rainfall in Haiti, which would likely bring heavy potentially deadly mudslides to the area.

It would open it up to get closer to the Bahamas, but as a very torn up, weak system. Some fairly well developed systems have disintegrated over the island before.

The split storm possibility still exists (See the ECMWF model) , meaning one area of convection stays in the Caribbean moving west, and the other split off and heads north through the islands. This keeps both extremely weak, and is a good possibility, and based on what I see this morning is probably what I'd go with.

The probability of this system affecting the US East coast is still very very low, like under 2% low, (but this is slightly higher than yesterday)-- overall not likely.

This split dynamic, and westward motion confuses things greatly so it will have to be watched closely over the next several days regardless since there are so many differing possibilities based around intensity and consolidation. It will likely keep the system weak, thus staying westward in the Caribbean maybe all the way to Nicaragua unless one takes over the other. Ie, what the FIM model shows.


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Ed DunhamAdministrator
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Re: Invest 91L Lounge [Re: MikeC]
      #90876 - Sun Jul 31 2011 03:59 PM

I was tempted to title this post 'The Mess Called 91L - Either One, Take Your Pick'. Anyway, I decided to put this here so that it could survive being EDited by myself

The right/east half of 91L has a mid to high level circulation, well defined but weakening, located at 15N 52.3W at 31/18Z. This center is moving slowly west.

The right/east half of 91L has a weak LLCC located at 13.5N 52.5W at 31/18Z which is also moving west.

The left/west half of 91L has its most predominant center (there are others - which is not bad for a so-called wind surge) located at 12N 58W at 31/18Z and it is also moving west. Both halves were evident yesterday - they were just in closer proximity to one another.

The left/west half has a better environment for development while the right/east half has better overall organization. I believe that recon is heading toward this right/east half but someone else can confirm that either way. The current best candidate for eventual tropical cyclone designation is the left/west half - but it will take awhile to get there.

At 31/12Z, the GFDL was initialized at 12.9N 51.5W - which is useless if the right/east half falls apart.
At 31/12Z, the HWRF was initialized at 13.1N 51.5W - which could also become useless for the same reason. (Note that the initialization points are approximations.)
The 31/18Z NHC Tropical Suite was finally published using 13.5N 52.8W, so all of the model marbles are rolling on the right/east half.

To add a little spice to the soup, there is also another piece of energetic development near 18N 62.5W.

Given the luck that NHC (and us) have been suffering with this bi-polar system, I fully expect the right/east half to soon be designated as a TD. Twelve hours later the TD will fall completely apart and the left/west system will be designated a TS (humor intended).
ED


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LoisCane
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Re: Invest 91L Lounge [Re: Ed Dunham]
      #90877 - Sun Jul 31 2011 04:04 PM

Good discussion, very good. About as good as it gets. Now...if we could get recon from the plane that would be good.

Models will have to be run over and over with the new data...so for now I'd put a hold on any previous model output.

--------------------
http://hurricaneharbor.blogspot.com/


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hogrunr
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Re: Invest 91L Lounge [Re: LoisCane]
      #90887 - Sun Jul 31 2011 05:40 PM

Wow...one of the more confusing situations that I remember seeing in recent years. From satellite imagery, it really looks like the Eastern half of the wave has developed into a TC of some kind, whether depression or storm, who knows. One important thing to notice is that the wave (or two halves) still seem to be moving west, right along 15N (maybe slightly south of the line). This, as others have said, pretty much throws the models out for now. Even though recon won't be going out until Monday morning, I have a feeling the weather stations in the islands will provide enough data for them to pull the trigger on it.

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WesnWylie
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Re: Invest 91L Lounge [Re: hogrunr]
      #90888 - Sun Jul 31 2011 06:02 PM

I think the models still pretty much hold for the developing Tropical Cyclone (the true 91L or the eastern half). They seemed to have analyzed the approx. location of the developing center of circulation pretty well with the 18Z runs. I don't see this system moving north of Hispaniola, though. My guess is that it could very well run aground if it moves over Hispaniola in a few days as a couple models suggest. It'll be interesting to see what happens, that's for sure.

--------------------
2011 Season Forecast: 16/09/04
2011 Systems: 10/01/01


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danielwAdministrator
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Re: Invest 91L Lounge [Re: hogrunr]
      #90889 - Sun Jul 31 2011 06:09 PM

"Twelve hours later the TD will fall completely apart and the left/west system will be designated a TS (humor intended)."

"Models will have to be run over and over with the new data...so for now I'd put a hold on any previous model output."

Let me see if I got this right. East meets West and becomes 91 Least. And I agree we need to run over the models.
I'm trying to summarize. Not poke fun at the above posts or members.

The buoys are still below 30 mph and NHC needs/ requires sustained 29 knot or 34 mph winds to pull the trigger.
If 91L east/right is a Tropical Depression the Islands will have to use their local Meteorological Services. Which they do to a certain extent anyway.

NOAA 49 Gulfstream high altitude dropsondes are due at 00Z or 8PM EDT, and I stand corrected on the Recon low level flight. It is scheduled to depart at 04Z or Midnight EDT.

FLIGHT THREE -- TEAL 71
A. 01/0600Z,1200Z
B. AFXXX 0305A CYCLONE
C. 01/0400Z
D. 15.2N 58.1W
E. 01/0530Z TO 01/1200Z
F. SFC TO 10,0000 FT

Edited by danielw (Sun Jul 31 2011 06:21 PM)


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MikeCAdministrator
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Re: Invest 91L Lounge [Re: danielw]
      #90893 - Mon Aug 01 2011 08:32 AM

West vs Recurve is setting up, this mornings GFS Run is included to illustrate (Please note this likely WILL Not happen)


That's part of the westward trend the models have been doing the last few days on this elongated system. I'm posting that to mention that it still hasn't formed, but it's worth watching. It still could head further west in the Caribbean, but model guidance suggests it may go over Hispaniola, if it misses Hispaniola to the east or west, a scenario like that could happen. But again it's not likely, if it were to make it north of the islands, the odds still favor the out to sea scenario, the classic "get really close but recurve" routine, which tends to drive hype up to extreme levels (and can have a potentially even more dangerous cry wolf side effect if nothing occurs). We'll try to avoid that, and keep it as matter of fact as we can, but even then if you haven't read the NHC's advisories first before looking at the rest of the internet, you are wasting your time.

What do I think will happen? It'll continue west for a while and recurve, but I have no idea when (it may still make it to Central America first), so it will be monitored. The best way to handle analyzing things like this is to take a historically common scenario, say recurve, then find all the reasons why something like that would occur, and search for that in the current system. The less of them you find the more likely it would not. Going into looking for reasons for it to go further west is usually the wrong approach, do the opposite, the lack of reasons for recurving will be more telling. I'm going to do that analysis probably tonight.

That said, it may not develop enough for advisories today, so speculation will continue.


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WeatherNut
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Re: Invest 91L Lounge [Re: Ed Dunham]
      #90896 - Mon Aug 01 2011 09:48 AM

Well, It looks like things are consolidating on the eastern part, and the western part is no more. I am also seeing a more northward component to the 'due west" movement as of late. This looks to be in a favorable spot so if we have a LLC (recon has not found that as of yet) I'm thinking straight to Emily

--------------------
Born into Cleo (64)...been stuck on em ever since


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MichaelA
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Re: Invest 91L Lounge [Re: WeatherNut]
      #90899 - Mon Aug 01 2011 10:12 AM

I don't think it will go directly to a named system just yet. There are some rather interesting scenarios playing out in the models with a couple doing an Andrew-esque situation late in the forecast periods. Of course, it's way too early to place much confidence in the runs until we get a solid, defined system for initialization.

EDIT: A special outlook has just been posted by the NHC: 10:25 AM ET

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

Edited by MichaelA (Mon Aug 01 2011 10:39 AM)


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metwannabe
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Re: Invest 91L Lounge [Re: MichaelA]
      #90901 - Mon Aug 01 2011 10:39 AM

Well no closed LLC just yet but they did find winds near tropical storm force.....so I will be surprised if we don't have a TD by 5pm if not Emily. Especially condsiering it looks very well organized in the mid levels and it's proximity to the Islands.

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Hurricane Season 2010: 15/8/4


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danielwAdministrator
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Re: Invest 91L Lounge [Re: metwannabe]
      #90918 - Mon Aug 01 2011 04:15 PM

Quick look at the CSC hurricane database. Using the current Center location and 1004 to 1010 mb for the storm strength.
Nearly the same as the current model suite... All over the place.
The results look like this:



data and image courtesy of NOAA Coastal Services Center


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weathernet
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Re: Invest 91L Lounge [Re: danielw]
      #90927 - Mon Aug 01 2011 05:53 PM

Been out of town and somewhat out of touch, and have taken a good part of today to analyze ( and mostly catch up on last couple days of developments, models, etc ) for 91L. Quick thoughts for the moment are:

1) Am and have been really concerned about the heat over the S.E. US,, with regards to overall ridging.
Furthermore, the latest 12Z run of the Euro seems to indicate ridging that is building westward along with time.
2) Though environment for 91L has shown a good amount of dry air to its north, a surge of moisture seems to be catching up from the ITCZ.
3) There is no doubt, an abundant extent of vorticity assocated with the overall envelope of this sizeable wave.
4) I believe we might see significant deepening of this system once "Emily" ( not yet officially named ) gets its act together. This may prove to be one of those more rare examples where significant developing occurs in the Eastern Caribbean
5) Will refrain from specific details or guess at this time, however have real concerns regarding a Southeast U.S. impact, and am more concerned over this possibly developing into a major hurricane.

Good news is that most of the models have not been carrying this as a consistantly strong developed system, but rather have been up and down with their forecasts......

Bad news is that all prior model data can be soon thrown out the window, and perhaps only now ( or soon ), given a potentially "true" developed system can the more reliable models be viewed with potential accuracy.

Overall, I think the slower development of 91L, may have really created the element of delay which might prove more crucial in the systems overall threat of not recurving.


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