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Atlantic Tropical Action 2014


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Phil is there confidence in the overall Size of this circulation come Sunday, I.E small(compact) or larger circulation.

 

Well The system is already fairly large in size, and if the storm undergoes a substantial trough interaction (the further north and east solutions) the storm will likely only grow its wind field further. Most of the deterministic guidance I've seen keeps this as a fairly large tropical cyclone and I'd be inclined to agree barring any substantial environmental changes. 

 

 

Another point is there is some increasing southwesterly shear across the Central Caribbean in the wake of EPAC TS Marie exiting off to the WNW. Hispaniola is notorious for creating havoc when we have a disorganized disturbance tracking just N of the Coast. Where this disturbance exits and how close to Andros Island in the Southern Bahamas it actually ends up, will have significant impacts on where it will track and likely more westerly as it misses the trough. If we see the disturbance slip NW after passing Haiti toward the Turks and Caicos or further E, then the re-curve scenario would be favored. The faster track since yesterday has likely led to some of the shifts seen in some of the guidance. If this survives its encounter with Hispaniola, then a slow process of strengthening is possible. This part of the world is tricky to forecast. We can look back to 2005 and see some similarities with Rita for example.

 

That's a good point. It looks like the GFS though has had a reasonable handle on the southwesterly flow in the Caribbean related to Marie. On the other hand, the GFS thought 96L would be a good 5 degrees south and east of where the current broad low level circulation is right now

 

http://www.tropicaltidbits.com/analysis/models/gfs/2014082218/gfs_vort850_uv200_watl_comp0.html

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http://www.tropicaltidbits.com/analysis/models/gfs-ens/2014082218/gfs-ememb_lowlocs_watl.html

 

This is a fun animation of the 18z GEFS forecast normalized spread with MSLP minima overlaid (roughly where you would expect the position of future 96L to be in the ensemble members).

 

Three distinct camps oriented from southwest to northeast appear to emerge by 96 hours. The first camp is the furthest northeast just west of Bermuda (early and full capture of mid-latitude trough). The second camp doesn't make it as far northeast is in between the Bahamas and Bermuda (delayed or partial capture of mid-latitude trough). The final group is the one most of us have been focusing on because it maintains 96L on a slow wnw heading towards Florida and the southeastern coastline (trough does not produce large enough weakness to capture system).

 

While the GEFS still suggests the majority of its members are northeast of the deterministic run, keep in mind the ECMWF had more even spread with its ensemble members from southwest to northeast. Alot of the northern members are also suggesting 96L doesn't make it much beyond the longitude of Hispaniola before it starts moving significantly northward. Thus the short term forecast is quite important for this particular system, especially since the llc isn't well defined yet. 

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Remember Debby 2000...Hispaniola could do some weird things to the center, pulling the southern vortex into land (via orographic effects) and stretching vorticity from NE to SW. If that's the case, then 96L may slow down in the next 24 hours, allowing it to reform its center farther north, deepen more, and feel the trough to its north--a situation favoring recurvature. Tonight's 00Z ECMWF is the most important model to watch. If it holds with its path, then recurve off the East Coast is practically certain. If the southern vortex were to hold and continue WNW over the next 24 hours, then a hit in southern FL would be more probable.

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Remember Debby 2000...Hispaniola could do some weird things to the center, pulling the southern vortex into land (via orographic effects) and stretching vorticity from NE to SW. If that's the case, then 96L may slow down in the next 24 hours, allowing it to reform its center farther north, deepen more, and feel the trough to its north--a situation favoring recurvature. Tonight's 00Z ECMWF is the most important model to watch. If it holds with its path, then recurve off the East Coast is practically certain.

I don't know how you can say that with certainty based upon one model especially with the models trending to the left through the day today and the system's quick forward momentum to the WNW.

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Remember Debby 2000...Hispaniola could do some weird things to the center, pulling the southern vortex into land (via orographic effects) and stretching vorticity from NE to SW. If that's the case, then 96L may slow down in the next 24 hours, allowing it to reform its center farther north, deepen more, and feel the trough to its north--a situation favoring recurvature. Tonight's 00Z ECMWF is the most important model to watch. If it holds with its path, then recurve off the East Coast is practically certain.

Don't understand this post at all. The significant spread among the ECM ENS members indicates a low confidence forecast in track.

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Models can't really cope with global weirding,

( http://en.wiktionary.org/wiki/global_weirding )

 

The appearance of what is actually out there seems to show that it will drift west; once it is far enough west it can't exactly (re)curve ; it will depend if the ULL and trough entering the Pacific northwest part of the continent can move past the weeks-old stagnant Gulf block (that is the cause of bringing up the "global weirding" concept.)  It will be easier to see a possible course in the morning, thankfully. 

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The intensity is way off on 00z GFS. With that upper level environment to work with and very warm SST's this system should be exploding. It's north of 18z but way west of 12z and 06z.

The intensity on the 00z is significantly stronger than what the 18z was showing so it's a step in the right direction. Perhaps the 00z track further north is a result of a stronger solution.

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The intensity on the 00z is significantly stronger than what the 18z was showing so it's a step in the right direction. Perhaps the 00z track further north is a result of a stronger solution.

 

Here we are at day 5... the next trough is starting to dig into the the midwest, and there is only weak anticyclonic flow to the north of 96L at this point with a stronger mid-level ridge to its east steering it northward. Close but no cigar here.

 

gfs_z500_vort_watl_21.png

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Models can't really cope with global weirding,

( http://en.wiktionary.org/wiki/global_weirding )

 

I'd say "global weirding" is the dumbest term/concept I've ever heard of (unsurprising coming from a laughable hack like Friedman) were it not for the even sillier idea that models can't cope with it. Model tropical cyclone track forecast accuracy has steadily improved for the last 30 years.

There is nothing more utterly routine than 96L and it's track forecast uncertainty.

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Pretty substantial shift in the 00z GFS ensembles... very few early recurving members, most siding close to what the GFS was suggesting. Again the GFS ensemble is underdispersive so its likely not capturing the full PDF of solutions possible with 96L, but still the leftward shift and decrease in spread is notable.

 

gfs-ememb_lowlocs_watl_8.png

 

gfs-ememb_lowlocs_watl_11.png

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Fwiw nhc area discussion for key west, miami , and Melbourne write this off . I just went thru them all and i think Jacksonville is only one to even mention slight track uncertainty.

Miami disco updated to include a bit of uncertainty regarding the track of the tropical entity, Melbourne still writes it off. Seems like those people writing them didn't find it significant  to highlight the uncertainty of the ensembles.

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Miami disco updated to include a bit of uncertainty regarding the track of the tropical entity, Melbourne still writes it off. Seems like those people writing them didn't find it significant  to highlight the uncertainty of the ensembles.

They both mention uncertainty

 

MLB: NOTE: FCST WILL HINGE ON THE FUTURE TRACK AND DEVELOPMENT OF THE   

TROPICAL DISTURBANCE N OF HISPANIOLA AND MAY BE SUBJECT TO SIG   
CHANGES.    
 
MIA: BUT IF  
THE RIDGE BUILDS STRONG ENOUGH AND THE TROUGH IS NOT QUITE AS DEEP  
AS CURRENTLY BEING FORECAST THEN A WESTWARD SHIFT IS NOT OUT OF  
THE REALM OF POSSIBILITY.
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