ATL: HELENE - Post-Tropical

[cycloneye]

18z Models

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WHXX01 KWBC 081848
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS NATIONAL HURRICANE CENTER MIAMI FL
1848 UTC WED AUG 8 2012
 
DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.
 
ATLANTIC OBJECTIVE AIDS FOR
 
DISTURBANCE INVEST (AL922012) 20120808 1800 UTC
 
        ...00 HRS...   ...12 HRS...   ...24 HRS. ..   ...36 HRS...
        120808  1800   120809  0600   120809  1800   120810  0600
 
         LAT    LON     LAT    LON     LAT    LON     LAT    LON
BAMS    14.2N  36.2W   14.7N  39.2W   15.0N  42.3W   15.1N  45.7W
BAMD    14.2N  36.2W   14.6N  38.4W   14.8N  40.6W   14.8N  42.6W
BAMM    14.2N  36.2W   14.8N  38.6W   15.2N  41.1W   15.3N  43.5W
LBAR    14.2N  36.2W   14.6N  38.7W   14.8N  41.6W   14.8N  44.6W
SHIP        25KTS          29KTS          33KTS          39KTS
DSHP        25KTS          29KTS          33KTS          39KTS
 
        ...48 HRS...   ...72 HRS...   ...96 HRS. ..   ..120 HRS...
        120810  1800   120811  1800   120812  1800   120813  1800
 
         LAT    LON     LAT    LON     LAT    LON     LAT    LON
BAMS    15.4N  49.4W   16.5N  56.7W   17.9N  63.3W   19.8N  69.0W
BAMD    14.8N  44.6W   15.3N  48.0W   16.0N  51.2W   16.7N  55.0W
BAMM    15.6N  46.0W   16.3N  50.5W   17.4N  54.2W   18.9N  57.8W
LBAR    14.9N  47.7W   15.8N  53.1W   18.2N  56.0W   22.1N  58.0W
SHIP        44KTS          46KTS          44KTS          42KTS
DSHP        44KTS          46KTS          44KTS          42KTS
 
         ...INITIAL CONDITIONS...
LATCUR =  14.2N LONCUR =  36.2W DIRCUR = 290DEG SPDCUR =  14KT
LATM12 =  13.3N LONM12 =  33.8W DIRM12 = 287DEG SPDM12 =  14KT
LATM24 =  11.8N LONM24 =  31.3W
WNDCUR =   25KT RMAXWD =   60NM WNDM12 =   25KT
CENPRS = 1010MB OUTPRS = 1013MB OUTRAD =  150NM SDEPTH =   S
RD34NE =    0NM RD34SE =    0NM RD34SW =    0NM RD34NW =   0NM


[KWT]

92L is pretty much totally gone by 180hrs, long open wave and about to run into 30-40kts of shear, though the tendency is for it to reduce by that time as well.

It does develop, but if the ECM shows anything more than a TD/marginal TS I'd be surprised!

[KWT]

Still looks a few days away at least. You can really see those LL clouds racing west.

Its trying to get going but conditions really aren't the best for this system at the moment with regards to that LL winds. I suspect we may see development in the end because it is rotating nicely but its going to face a struggle to keep itself going.

ps, I'd personally go with 60% next time.

[AEWspotter]

50-55W will be the sweet spot where 92L develops. Its representation has improved drastically throughout the day despite the fast movement.

[Aric Dunn]

50-55W will be the sweet spot where 92L develops. Its representation has improved drastically throughout the day despite the fast movement.

It has improved today quite a bit. So following the trend we would likely see TD late tomorrow into friday. I think 55 is a little to far down the line, conditions there should be conducive for strengthening as well if it develops earlier.

[SFLcane]

50-55W will be the sweet spot where 92L develops. Its representation has improved drastically throughout the day despite the fast movement.

Care to speculate any possible threats for southeast? Great having you on the boards.

[KWT]

50-55W will be the sweet spot where 92L develops. Its representation has improved drastically throughout the day despite the fast movement.

Interestingly thats exactly where the ECM smashes this system into increasing shear, the ECM shows 40-50kts very near-by that area right down to about 12N. It is backing off to the west but that'd be a close run thing. It might well convectivly flare-up in that zone and who knows, if its not too far north that may just help the system.

[ConvergenceZone]

50-55W will be the sweet spot where 92L develops. Its representation has improved drastically throughout the day despite the fast movement.

Interestingly thats exactly where the ECM smashes this system into increasing shear, the ECM shows 40-50kts very near-by that area right down to about 12N. It is backing off to the west but that'd be a close run thing. It might well convectivly flare-up in that zone and who knows, if its not too far north that may just help the system.

I know that many people(including mets) on here have mentioned that the models
aren't that great at forecasting shear in the future, and on the opposite extreme,
I've seen the models forecasting no shear, and all the sudden shear develops and rips
apart a system...So I never pay much attention to shear forecasts down the road.

Welcome back KWT, missed seeing all your posts around here

[HurricaneMaster_PR]

Should be interesting to watch it later tonight as the Diurnal Maximum plays its part..

[Ivanhater]

Marked improvement today..the Globals looked to have missed this one as well

http://www.grib2.com/LATEST_ETropics_VIS.jpg

[cycloneye]

Good signature.

[KWT]

Rotation is a clear sign that this one probably will develop despite the SAL which is just to the north. As I said before, I'd go with 60% now, enough for a cherry.

[AEWspotter]

Maybe this system is far enough removed from the dust that dry air entrainment won't be an inhibitor of its development. I only say as far west as 55W because that's where 36km WRF runs have developed this system for the past 2 days. I agree that it could go sooner. As for talk about a threat to the SE U.S., it is way too early to tell. However, the subtropical high has been extending pretty far to the west and is causing systems to propagate W or WNW. If we look at the GFS ensemble members, the consensus is to take this system into the Caribbean like our old friend Ernesto. Given the skill of the GFS forecasting Ernesto, maybe that's not a bad scenario to stick with for now. 2 things to note about this GFS Ensemble members: 1) There are members that think the system will gain latitude (so recurving is at least a possibility) and 2) Much better agreement that 92L will at least stick around for a while (all but 2 members maintain the system for 4+ days).

[KWT]

A track closer to the Islands IMO is likely (and probably headlong into the TUTT's shear zone) as it is already a good 2-3 degrees north of where Ernesto was at this point.

The idea of a track clsoe to Ernesto probably isn't a bad call right now though, unless it does pull a shocker and strengthens alot.

ps, looking at the ensembles, most DO have a system at 60W, but rapidly destroy it after that, only 1-2 runs show anything of any note bar an open wave beyond that point.)

[ConvergenceZone]

Well, Ernesto struggled in horrible conditions and shear in the carib and STILL became a hurrcane later on......

[KWT]

Yep, the big difference with Ernesto though is it managed to slip under the TUTT and its shear by being far enough south. I'm not sure this will be the case with 92L as its already further north than Ernesto was when it entered the Caribbean.

Most models do at least show something developing from this and so I think the NHC will become more bullish about development soon due to this and the increasingly good presentation over today.

[wxman57]

It's already nearly 5 deg north of where Ernesto's incipient disturbance passed. (9.7N vs. 14.1N). That's quite far north for so far east. Models do indicate a fairly strong ridge to its north, though. Cannot rule out an east Caribbean threat, though conditions aloft don't appear to be extremely favorable for it to become a strong TS or H before reaching the Caribbean.

[SFLcane]

It's already nearly 5 deg north of where Ernesto's incipient disturbance passed. (9.7N vs. 14.1N). That's quite far north for so far east. Models do indicate a fairly strong ridge to its north, though. Cannot rule out an east Caribbean threat, though conditions aloft don't appear to be extremely favorable for it to become a strong TS or H before reaching the Caribbean.

Interesting take there on 92L wxman. I believe this system will track just north of the islands in time.

[ConvergenceZone]

It's already nearly 5 deg north of where Ernesto's incipient disturbance passed. (9.7N vs. 14.1N). That's quite far north for so far east. Models do indicate a fairly strong ridge to its north, though. Cannot rule out an east Caribbean threat, though conditions aloft don't appear to be extremely favorable for it to become a strong TS or H before reaching the Caribbean.

I don't consider this too good news though, because if we want a recurve, we would want it
to ramp up quickly......

[AEWspotter]

Is the TUTT forecast to go anywhere in the next 3-5 days? I see that the GFS has the current TUTT dissipate in about 2 days, just as a new TUTT digs down from about 30N. Is there a chance this first TUTT moves out before it imposes doom upon 92L?

http://mag.ncep.noaa.gov/NCOMAGWEB/appc ... mageSize=M