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Ex-Helene remnant trof


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THE CIRCULATION ASSOCIATED WITH A SMALL LOW PRESSURE SYSTEM LOCATED

ABOUT 950 MILES WEST OF THE SOUTHERN CAPE VERDE ISLANDS HAS

CONTINUED TO BECOME BETTER DEFINED OVER THE PAST SEVERAL HOURS.

THUNDERSTORM ACTIVITY IS ORGANIZING AROUND THE SURFACE CENTER...AND

UPPER-LEVEL WINDS ARE EXPECTED TO BE CONDUCIVE FOR THE DEVELOPMENT

OF A TROPICAL DEPRESSION OVER THE NEXT COUPLE OF DAYS. THIS SYSTEM

HAS A HIGH CHANCE...70 PERCENT...OF BECOMING A TROPICAL CYCLONE

DURING THE NEXT 48 HOURS AS IT MOVES WESTWARD AT ABOUT 15 MPH.

Looks like a "surprise" system is in the works tonight. This system has become much better organized over the past 24 hours with banding features and a small area of thunderstorms concentrated over the surface low. Dry air is currently to the NW, but the system has developed an envelope of moist air (for now) to shield it enough for gradual organization to occur.

The future of this system is bleak, but uncertain. Recon is scheduled for Saturday afternoon...if necessary

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THE CIRCULATION ASSOCIATED WITH A SMALL LOW PRESSURE SYSTEM LOCATED

ABOUT 950 MILES WEST OF THE SOUTHERN CAPE VERDE ISLANDS HAS

CONTINUED TO BECOME BETTER DEFINED OVER THE PAST SEVERAL HOURS.

THUNDERSTORM ACTIVITY IS ORGANIZING AROUND THE SURFACE CENTER...AND

UPPER-LEVEL WINDS ARE EXPECTED TO BE CONDUCIVE FOR THE DEVELOPMENT

OF A TROPICAL DEPRESSION OVER THE NEXT COUPLE OF DAYS. THIS SYSTEM

HAS A HIGH CHANCE...70 PERCENT...OF BECOMING A TROPICAL CYCLONE

DURING THE NEXT 48 HOURS AS IT MOVES WESTWARD AT ABOUT 15 MPH.

Looks like a "surprise" depression is in the works tonight. This system has become much better organized over the past 24 hours with banding features and a small area of thunderstorms concentrated over the surface low. Dry air is currently to the NW, but the system has developed an envelope of moist air (for now) to shield it enough for gradual organization to occur.

The future of this system is bleak, but uncertain. Recon is scheduled for Saturday afternoon...if necessary

NHC not going to issue an emergence update. Yeah I think it might be a TS now if it was in the Gomex but it's 6 days from land, if it makes it that far.

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One can see hints of forecast GFS shear in difference in speed and direction between shallow and deep/medium beta advection models.

As I stated on the Atlantic tropics thread, if the GFS is right, this would be near Central America/the YP in 8 days, and would have weakened greatly in the Caribbean, if anything is left, low level (700 and 850 mb) steering would take a weak system Northwest, almost Northward in the BoC.

Canadian developing Dominican Republic blob (it did have a couple of 18Z GFS ensemble members supporting it, but still) corrupts that 12Z run somewhat, Euro is further North and weak. GFS would, through the resolution reduction, pose a greater potential threat to the US Gulf Coast.

Attachment- Euro strongly suggests fish. GFS is very weak, entering BoC, but suggestions it would head NW

post-138-0-43469300-1344484312_thumb.gif

post-138-0-65586300-1344484447_thumb.gif

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Pretty fast improvement, I'm impressed with how quick the outflow and spiral bands outside the storm formed.

If it has a small core it's a TS already but the Tutt will probably be it's fate in 72hrs.

Notice the S of due west motion. The GFS has been steller with Debby, Ernesto, and now looks to be the superior model thus for invest 92L. I'm really taken aback on how well the GFS has been preforming in the ATL basin this season thus far.

So this is going to sound like a repeat performance, because it is. There are two players on the table that can decide the system's fate. We have once again the tropical upper tropospheric trough (TUTT) that will be digging in across the Central Atlantic over the next couple of days that will weaken the upper level easterly flow across 92L beyond 48 hours. Also, we have another, equally impressive convectively coupled kelvin wave (CCKW) which will be moving over the system nearly at the same place that Ernesto was located when it was impacted by the last CCKW. So once again, its a battle beween the upper level westerlies produced by the TUTT vs. the upper level easterlies produced in the wake of a CCKW. If you guys will recall, Ernesto didn't dissipate like the ECMWF was adamantly suggesting. The GFS while more bullish, was also too weak with the eventual vorticity signature associated with Ernesto.

The Players:

TUTT:

2llzygx.png

CCKW:

e9g3mx.png

There is also one things that needs to be taken note that hasn't been mentioned before. The GFS, despite being more accurate, was still way too slow with Ernesto. I have a dprog/dt map of the GFS on the Dynamic Tropopause with mean layer low level vorticity (925-850 hPa) overlayed in black contours. Models typically have a hard time with under-forecasting the intensity of mid-level ridges. This was most certainly the case with Ernesto in the last 10 or so runs (from 96 hours to Analysis), as the model shifts from 10N and 40W to 12N and 50W. Thats a pretty significant change from a day 4 forecast. If we see the same thing occur with 92L (which is certainly possible given the fast forward motion currently) it may be able to slide under the deepening TUTT and find itself under more favorable conditions in the Caribbean. Lets see if history repeats itself.

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So the 12z OFPI (the actual track is the DSHP) was run this morning and showed a somewhat more favorable track/future for 92L. There has been a noticable shift WSW over the past few hours. (as Phil and others have noted) GFS seems to be taking the lead again.

Nothing impressive by any means, but the only thing we have to watch right now (other than Ernesto)

12zatcfearlyinvest2best.gif

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LLC starting to get away from the convection now, looks like low level flow is too quick once again. Motion looks about 270 again at the moment, system has to slow down otherwise it's never going to get going.

Even if it does get going, its going to get real painful to watch by 60W...

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LLC starting to get away from the convection now, looks like low level flow is too quick once again. Motion looks about 270 again at the moment, system has to slow down otherwise it's never going to get going.

Even if it does get going, its going to get real painful to watch by 60W...

Yeah, it's still under Phil and Mikes unfavorable CCKW. I'll give it some more time regardless.

rgb-animated.gif

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Really not sure this was a great move, but okay. We'll see if the renumber holds until 11am.

AL, 07, 2012080912, , BEST, 0, 137N, 417W, 25, 1010, LO, 34, NEQ, 0, 0, 0, 0, 1013, 150, 50, 0, 0, L, 0, , 0, 0, SEVEN,

Disturbance Seven on the 12Z BAM/SHIPs guidance. Just because it may not last long is no reason not to upgrade it. It does appear to have closed off a low if one stares at vis loops with lat-long lines turned on.

New HWRF and GFDL guidance, like the globals, not enthusiastic at the point. Shallow BAM depiction of a racing cyclone doesn't bode well for shear compared to medium and deep BAM models, but SHIPS is just below hurricane strength as medium and deep are approaching the Antilles.

Globals/dynamic did way, way better than statistical tropical models, so I sort of doubt a storm just below hurricane strength approaching the Lesser Antilles.

This one interests me more than AEW, if it can survive the short to medium term hostile conditions, it could be a Gulf threat. Surviving would be the key word.

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Initial SHIPS run has TD 7 steadily strengthening and on the brink of a hurricane at 62 knots 5 days from now. I'm not that bullish long term.

Etnesto seemed to suggest global dynamic models, while not having sufficient resolution to predict actual intensity with accuracy, are superior to the statistical guidance designed for TCs, and until some storms bucks that trend, if global models say weak (and even dynamic tropical models unenthusiastic) weak is indeed the way to go.

GFS suggests a named storm for the Antilles that opens again in the Caribbean, and might be entering the BoC with a path NW in 8 days. As above, if there is anything left to follow shallow steering Northwest. Seems as reasonable as anything else now. TPC discussion will be interesting.

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Thanks! Is that an assumption or have they actually issued something saying the lack of convection held them back?

While it has not been officialy stated yet, they might issue a STWO to state that if convection increases, then this will be classified.

It's pretty anemic looking, so that is more than likely the reason.

20120809.1430.msg2.x.vis1km.92LINVEST.25kts-1010mb-137N-417W.100pc.jpg

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WEATHER RECONNAISSANCE FLIGHTS

CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.

1100 AM EDT FRI 09 AUGUST 2012

SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)

VALID 10/1100Z TO 11/1100Z AUGUST 2012

TCPOD NUMBER.....12-083

I. ATLANTIC REQUIREMENTS

1. SUSPECT AREA EAST OF ISLANDS

FLIGHT ONE - TEAL 70 --

A. 11/1200Z

B. AFXXX 01BBA INVEST

C. 11/0915Z

D. 13.8N 56.0W

E. 11/1130Z TO 11/1800Z

F. SFC TO 10,000FT

2. OUTLOOK FOR SUCCEEDING DAY: BEGIN 6 HOURLY FIXES AT

12/0000Z NEAR 14.0N AND 60W IF SYSTEM IS A THREAT.

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