ATL: HELENE - Post-Tropical

[tolakram]

Just coming into range of these loops.

http://wwwghcc.msfc.nasa.gov/cgi-bin/ge ... umframes=5

[KWT]

The deep convection which was over the center is now decently to the south of the circulation, which is evident both in Vis and the microwave images.

Looks like it did get a burst of shear last night that forced the convection well south. Still the system is starting to wrap around again so that may just be a quick burst that went along with the WSW motion overnight.

It does need some deeper convection and the SAL may cause it troubles in that respect but I should think formation is probable still in the next 24-36hrs. After that and its going to need an awful lot of luck getting through 50-65W given the increase in the LL winds and also the increase of the shear caused by the TUTT to its north with 20-30kts of shear. It'd be best if the system kept diving WSW towards 12N to avoid that shear.

[Blown Away]

Aug 8th 00z dynamic model guidance.


Aug 9th 06z dynamic model guidance.

[Gustywind]

09/1045 UTC 13.7N 41.5W T1.0/1.0 92L
09/0545 UTC 14.4N 39.3W T1.0/1.0 92L

[Gustywind]

Curiously NHC has it at 15 N 39W and SSD at much souther and more west.

[cycloneye]

12z Best Track

AL, 92, 2012080912, , BEST, 0, 137N, 417W, 25, 1010, LO

ftp://ftp.nhc.noaa.gov/atcf/tcweb/inves ... 012.invest

[wxman57]

13.7N looks ok, but I'd put it at 40.5W presently. Struggling with dry air and low-level shear due to the fast movement. Also moving south of west as ridge builds to its north. No development today. Will most likely be a struggling TD/weak TS when it reaches the islands of the eastern Caribbean Saturday night/Sunday morning. Mostly a rain event.

[KWT]

Curiously NHC has it at 15 N 39W and SSD at much souther and more west.

Best track further SW, though as Wxman57 said I don't think its as far west as they think right now.

[cycloneye]

12z Models

Code: Select all

WHXX01 KWBC 091252
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS NATIONAL HURRICANE CENTER MIAMI FL
1252 UTC THU AUG 9 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) 20120809 1200 UTC
 
        ...00 HRS...   ...12 HRS...   ...24 HRS. ..   ...36 HRS...
        120809  1200   120810  0000   120810  1200   120811  0000
 
         LAT    LON     LAT    LON     LAT    LON     LAT    LON
BAMS    13.7N  41.7W   14.0N  45.4W   14.2N  49.6W   14.7N  53.9W
BAMD    13.7N  41.7W   13.9N  44.4W   14.0N  47.1W   14.3N  49.6W
BAMM    13.7N  41.7W   14.2N  44.6W   14.5N  47.8W   15.0N  50.8W
LBAR    13.7N  41.7W   13.7N  44.7W   13.7N  48.0W   13.9N  51.3W
SHIP        25KTS          29KTS          35KTS          42KTS
DSHP        25KTS          29KTS          35KTS          42KTS
 
        ...48 HRS...   ...72 HRS...   ...96 HRS. ..   ..120 HRS...
        120811  1200   120812  1200   120813  1200   120814  1200
 
         LAT    LON     LAT    LON     LAT    LON     LAT    LON
BAMS    15.2N  58.4W   15.9N  67.5W   16.7N  77.0W   17.1N  85.5W
BAMD    14.8N  51.7W   16.1N  55.0W   17.6N  57.6W   18.7N  60.1W
BAMM    15.5N  53.8W   16.8N  58.8W   18.0N  62.8W   19.2N  66.1W
LBAR    14.4N  54.5W   16.0N  59.4W   18.2N  61.7W   20.9N  62.5W
SHIP        48KTS          55KTS          60KTS          62KTS
DSHP        48KTS          55KTS          60KTS          62KTS
 
         ...INITIAL CONDITIONS...
LATCUR =  13.7N LONCUR =  41.7W DIRCUR = 265DEG SPDCUR =  15KT
LATM12 =  14.1N LONM12 =  38.5W DIRM12 = 266DEG SPDM12 =  15KT
LATM24 =  13.9N LONM24 =  35.4W
WNDCUR =   25KT RMAXWD =   50NM WNDM12 =   25KT
CENPRS = 1010MB OUTPRS = 1013MB OUTRAD =  150NM SDEPTH =   S
RD34NE =    0NM RD34SE =    0NM RD34SW =    0NM RD34NW =   0NM


[Blinhart]

So it looks like this will be a long tracking TC once he forms. Will it take a Dean/Felix path or a Katrina/Andrew path?

[Blown Away]

Aug 9th 12z dynamic model guidance.

[NDG]

Image below agrees with the 12z Best Track position, IMO.

[gatorcane]

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

I'm not quite sure the reason why they issued a special TWO last night to bump it from 50% to 70% when they could have waited two hours until the 2AM TWO. My thinking continues to be more like 40% on this system as was my thinking yesterday. Reason is because of SAL and dry air plus it's lacking support from the dynamic models. SAT images are not that impressive this morning either as convection continues to degenerate due to SAL intrusion, however, there is a chance it could reach depression status because it has a nice structure and the SSTs it is heading towards are warm with light shear expected for the next few days (hence my 40% prediction).

[KWT]

Actually yes I can see the LLC further west now, looks like the lower level flow is already starting to make this system suffer.

Looks like its weakening a little at the moment with convection struggling a touch.

[SFLcane]

Into CA it appears...

[Blown Away]

HPC has 92L just south of Haiti in 7 days, notice the trough digging over the SE CONUS.

[Gustywind]

Given some posters... as the SAL and dry could pose some troubles for 92L (even if NHC TWD do not mention it ?!, or maybe i miss it lol), can someone put a chart please ? We could have a better idea on 92L chances to acquire possible cyclonic characteristics during the next couple of days...

[tolakram]

SAL



That map is available from: http://tropic.ssec.wisc.edu/

[drezee]

http://www.ndbc.noaa.gov/station_page.php?station=41041

This buoy should be directly in the path of 92L...

[Aric Dunn]

Looks like it has been moving slightly just south of west over the last few hours. Convection starting to rebuild and the some more pronounced banding. we should see a td by tonight.