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Tropical Depression Don


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8 AM

A tropical wave located about 425 miles east of the Windward Islandsis producing scattered showers and a few thunderstorms. Slowdevelopment of this system is possible during the next couple ofdays as it moves westward to west-northwestward at 15 to 20 mph. There is a low chance...20 percent...of this system becoming atropical cyclone during the next 48 hours. Regardless ofdevelopment...brief periods of locally heavy rainfall and gustywinds could spread across portions of the Lesser Antilles thisafternoon and tonight.

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With the path the storm is progged to take I can't see how it's possible it gets to strong TS/Cat1 Strength. A small deviation north or south would be a good thing for the storm but the current tracks take it over land nearly the entire time till it reaches the GOM.

This is looking a lot less interesting at the moment. But it is also important to note that currently it remains to be seen where any potentital low level center may end up forming if it does develop. Without a consolidated center this thing could easily jump north or south of that progged track.

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This is looking a lot less interesting at the moment. But it is also important to note that currently it remains to be seen where any potentital low level center may end up forming if it does develop. Without a consolidated center this thing could easily jump north or south of that progged track.

Those models also kind of blow. I still wouldn't be surprised to see some major land interaction, though.

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I'm at condition winer for this, shear/convergence issues, not to mention Hispaniola, just not seeing it.

20 to 30 knot low level flow in the Caribbean implies not only shear, but poor surface convergence.

I don't think it does anythinng any time/place before about 75º or 80ºW, if ever.

wg8dlm1.GIF

GFS analyzed 850 mb winds 0Z...

gfs_85v_000l.gif

Unofficial Ed alert condition- wiener:

6.jpg

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I'm at condition winer for this, shear/convergence issues, not to mention Hispaniola, just not seeing it.

20 to 30 knot low level flow in the Caribbean implies not only shear, but poor surface convergence.

I don't think it does anythinng any time/place before about 75º or 80ºW, if ever.

GFS analyzed 850 mb winds 0Z...

Unofficial Ed alert condition- wiener:

This happens often during hurricane season, it seems... though I thought it had decreased in occurrence. I really don't understand why some people post these products showing current shear, etc. and assume it is going to stay like that for the next 6 days while the system being discussed travels across the area.

Keep in mind that the NHC has noted in their TWO that conditions are forecast to become more conducive for development over the next few days.

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This happens often during hurricane season, it seems... though I thought it had decreased in occurrence. I really don't understand why some people post these products showing current shear, etc. and assume it is going to stay like that for the next 6 days while the system being discussed travels across the area.

Keep in mind that the NHC has noted in their TWO that conditions are forecast to become more conducive for development over the next few days.

Not so much shear as howling Easterlies in the Caribbean. I didn't post a shear map. One can infer they'll be shear when 850 mb flow looks to be 20 knots or higher.

Edit to add- at 66 hours, GFS forecast shear isn't too bad in the Eastern Caribbean with almost 20 knot Easterlies at 250 mb. But I'd still think surface convergence would tend to be poor with strong low level Easterlies. But the PSU is a pro, and I am just an interested hobbyist. I shall listen and learn for a while.

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I actually disagree strongly with the idea that conditions will become more conducive in a couple days. The GFS and ECMWF both have shear increasing significantly in a couple days due to the strengthening of the low-level flow between the subtropical ridge and the lower pressures in the SW Caribbean, and the persistence of an east-west trough feature with a westerly-component of the upper-level winds associated with it. This combined with land-interaction issues with Hispaniola, and the utter lack of model support anywhere, means that this is very unlikely to amount to anything.

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I actually disagree strongly with the idea that conditions will become more conducive in a couple days. The GFS and ECMWF both have shear increasing significantly in a couple days due to the strengthening of the low-level flow between the subtropical ridge and the lower pressures in the SW Caribbean, and the persistence of an east-west trough feature with a westerly-component of the upper-level winds associated with it. This combined with land-interaction issues with Hispaniola, and the utter lack of model support anywhere, means that this is very unlikely to amount to anything.

I can't say that or people would call me 'rainstorm'. But I suspect, in my amateur opinion, that you are right.

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IMHO, the only chance this has in the next 4 or 5 days is to close off a circulation quickly, then barely survive a hostile Eastern Caribbean, then come out in the Western Caribbean into the Gulf. Ala Claudette in 2003.

And I would not mind a Cat 1 landfalling in Texas at all.

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I actually disagree strongly with the idea that conditions will become more conducive in a couple days. The GFS and ECMWF both have shear increasing significantly in a couple days due to the strengthening of the low-level flow between the subtropical ridge and the lower pressures in the SW Caribbean, and the persistence of an east-west trough feature with a westerly-component of the upper-level winds associated with it. This combined with land-interaction issues with Hispaniola, and the utter lack of model support anywhere, means that this is very unlikely to amount to anything.

Every other tropical system this year formed without significant model support. Also, Whatever NCEP did to the GFS two years ago really changed the way it predicts tropical cyclones. You don't see the 384hr supercanes anymore, lol.

:rolleyes:

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I think the models are underestimating the low level vorticity in their initialization, especially the GFS... the same happened with Bret...

Look at the 12zGFS valid at 15z today:

aP0dE.gif

Look at UWisc analysis:

LoIvH.gif

Also, I don't think shear profile will be that good, but I don't think it's gonna be destructive...let's say marginally conducive...but the further north it goes, the stronger the shear, probably

At about this time tomorrow, our probable LLC will be in the NE part of the Eastern Caribbean:

vNKiS.png

But I doubt it can dodge La Hispaniola, and that will be it's doom.

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:unsure:

Not untill it actually formed an LLC. I remember seeing some weak H5 on euro before Bret formed but it backed off. We knew something would come from a stalled out coastal front though.

GFS has been and continues to be completely oblivious. And nothing, that I am aware of predicted Cindy.

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12z Euro is back to being a bit stronger, hits FL while the trough barely misses to the north, and then a ridge is rebuilding, which should probably direct whatever is there to the West/WNW.

Edit: And there you have it, upper TX coast.

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Intensity models like

WHXX01 KWBC 221824

CHGHUR

TROPICAL CYCLONE GUIDANCE MESSAGE

NWS NATIONAL HURRICANE CENTER MIAMI FL

1824 UTC FRI JUL 22 2011

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 (AL902011) 20110722 1800 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...

110722 1800 110723 0600 110723 1800 110724 0600

LAT LON LAT LON LAT LON LAT LON

BAMS 14.1N 56.2W 14.9N 59.4W 15.9N 62.8W 17.1N 66.4W

BAMD 14.1N 56.2W 15.0N 59.3W 15.8N 62.1W 16.6N 64.7W

BAMM 14.1N 56.2W 14.7N 59.5W 15.5N 62.9W 16.3N 66.2W

LBAR 14.1N 56.2W 14.5N 59.4W 15.2N 62.9W 15.7N 66.3W

SHIP 20KTS 23KTS 28KTS 35KTS

DSHP 20KTS 23KTS 28KTS 35KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...

110724 1800 110725 1800 110726 1800 110727 1800

LAT LON LAT LON LAT LON LAT LON

BAMS 18.4N 70.0W 20.3N 76.6W 21.6N 81.4W 23.2N 85.1W

BAMD 17.4N 67.2W 18.8N 71.4W 20.3N 74.7W 21.6N 77.8W

BAMM 17.4N 69.4W 18.9N 74.9W 19.9N 79.3W 21.3N 83.4W

LBAR 16.4N 69.4W 18.1N 73.9W 20.5N 76.4W 22.8N 78.4W

SHIP 43KTS 55KTS 65KTS 69KTS

DSHP 43KTS 51KTS 60KTS 65KTS

...INITIAL CONDITIONS...

LATCUR = 14.1N LONCUR = 56.2W DIRCUR = 280DEG SPDCUR = 16KT

LATM12 = 13.5N LONM12 = 53.1W DIRM12 = 281DEG SPDM12 = 16KT

LATM24 = 12.8N LONM24 = 49.8W

WNDCUR = 20KT RMAXWD = 40NM WNDM12 = 20KT

CENPRS = 1012MB OUTPRS = 1015MB OUTRAD = 175NM SDEPTH = S

RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM

$$

NNNN

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12z Euro is back to being a bit stronger, hits FL while the trough barely misses to the north, and then a ridge is rebuilding, which should probably direct whatever is there to the West/WNW.

Yep... looks a borderline tropical cyclone at 96 hours. I'll be posting my thoughts in a bit in my blog. Upper level winds don't looks amazing, but are still mainly light easterly for the next 48-72 hours according to the GFS. It be likely be more of a matter of how strong the low level flow is, since there is a pretty significant low to mid level ridge over the Tropical Atlantic right now.

29z26g0.gif

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