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Atlantic Tropical Action 2012 - Part I


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...Or most of the models depict a problematic environment upon entering the Caribbean, as has been highlighted by numerous posters here...

Yep, problem is strong low level easterlies, which, despite having easterly upper level anomalies, give a net westerly shear...The TUTT has been modeled as having less impact now as the current upper ridge in the Caribbean lifts north, limiting the TUTT's reach...but 99L is modeled too far south, very close to the SA continent, where low level easterlies are rather strong this time of the year...so, the best would be to gain a little bit of latitude before entering the Caribbean...preferently north of Barbados...low level flow is still strong, but a little less so, but no so far north to mess with the Leeward islands or get back inside arm's reach of the TUTT.

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Yep, problem is strong low level easterlies, which, despite having easterly upper level anomalies, give a net westerly shear...The TUTT has been modeled as having less impact now as the current upper ridge in the Caribbean lifts north, limiting the TUTT's reach...but 99L is modeled too far south, very close to the SA continent, where low level easterlies are rather strong this time of the year...so, the best would be to gain a little bit of latitude before entering the Caribbean...preferently north of Barbados...low level flow is still strong, but a little less so, but no so far north to mess with the Leeward islands or get back inside arm's reach of the TUTT.

PotD. Pretty much covers it.

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Early thoughts here...

99L looks to be experiencing some type of shear this morning as it looks a bit disheveled. Might have gained just enough latitude to feel the affects of the TUTT (but I'm tired and I'll leave that to the mets to decide). Also, the SHIPS has really backed off with shear in the Caribbean this morning for some reason. The track concensus looks to be just north of SA, which is pretty much guaranteed death. Not sure how that will happens, but it would be interesting to see. Somehow, this manages to pull off 78 knots by the end of the period.

00z HWRF briefly weakens 99L, but has it strengthening at the end of the run.

06z LGEM brings 99L up to 85 knots...

Last thin, notice how the SHIPS is being run off the OFPI track and not the BAMM tack. The NHC is getting close to tagging this.

TIME (HR)		 0	 6 12 18 24 36 48 60 72 84 96 108 120
V (KT) NO LAND 25 27 29 32 34 43 50 56 64 71 75 77 78
V (KT) LAND	 25 27 29 32 34 43 50 56 64 71 75 77 78
V (KT) LGE mod 25 26 27 29 31 35 40 47 55 66 78 85 85
Storm Type	 TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP
SHEAR (KT)		 9	 9 10	 8 10	 8 10	 7	 5	 4	 8	 6	 8
SHEAR ADJ (KT)	 4	 3	 4	 9	 4	 2 -1	 1	 0	 1	 0 -1 -3
SHEAR DIR	 355 348 360 326 325 313 289 340 13 10 282 339 268
SST (C)		 28.1 28.2 28.3 28.3 28.3 28.3 28.3 28.2 27.5 27.9 27.7 26.9 27.2
POT. INT. (KT) 140 141 143 143 143 143 143 142 132 137 134 123 126
ADJ. POT. INT. 144 147 149 149 149 149 150 147 135 140 134 119 121
200 MB T (C) -54.0 -53.9 -53.4 -53.5 -53.8 -53.4 -53.7 -53.3 -53.5 -53.2 -53.2 -53.2 -53.2
TH_E DEV (C)	 6	 6	 7	 7	 7	 8	 8 10	 8 10	 8 10	 7
700-500 MB RH	 66 66 66 66 67 61 64 62 64 70 68 69 74
GFS VTEX (KT)	 10 11 10 11 10 12 12 11 12 11 11	 9	 8
850 MB ENV VOR	 1	 4	 7 12 12 21 34 38 47 49 78 80 96
200 MB DIV	 21 25 15 24 22 31 66 19 18 23 32 51 24
700-850 TADV	 -13 -10 -13 -15 -12 -7 -6 -6 -1	 3	 3	 1	 2
LAND (KM)	 1013 913 832 754 694 628 487 163 177 224 104 78 238
LAT (DEG N)	 9.7 xx.x xx.x xx.x xx.x xx.x xx.x xx.x xx.x xx.x xx.x xx.x xx.x
LONG(DEG W)	 44.0 xxx.x xxx.x xxx.x xxx.x xxx.x xxx.x xxx.x xxx.x xxx.x xxx.x xxx.x xxx.x
STM SPEED (KT) 14 15 15 16 16 16 17 17 16 15 13 10	 9
HEAT CONTENT	 20 25 28 18 20 36 33 52 32 27 54 11 13

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The SHIPS is not of great use until the system forms, as others have noted.

The reason the SHIPS intensity forecast jumped upward from 0Z to 6Z is that NHC changed the track from the BAMM to its official track (close to the TVCN). The 6z official NHC track is significantly faster, enough to negate some of the effects of the strong low-level easterlies in the e. Caribbean, and also further south, enough to avoid some of the strong upper level westerlies further north in the Caribbean.

See ftp://ftp.nhc.noaa.gov/atcf/stext/12080100AL9912_ships.txt vs.

ftp://ftp.nhc.noaa.gov/atcf/stext/12080106AL9912_ships.txt

The FIM and 6z GFS both illustrate what could happen if 99L into the W. Caribbean and manages to slow down enough to take advantage of a more favorable 200 mb pattern. I wouldn't forecast that because there is much uncertainty in how fast 99L moves and on the upper level pattern 3+ days out, but it's something to watch carefully.

The GFS is sticking firmly to that deep-S track. (It looks like super-hawt Joan 1988. :sun:)

I know I'm not supposed to talk about it, but the SHIPS has gotten way more aggro all of a sudden-- now bringing it up to almost 80 kt.

post-19-0-30454100-1343807874_thumb.gif

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The 06Z GFS is suggesting 99L may make a run at Depression Status or even as Tropical Storm Ernesto into the Lesser Antilles. That model as suggests shear ahead of a possible Ernesto would remain rather stout until is slows down in the NW Caribbean and conditions could become a bit more favorable for development as it nears the Yucatan. We will see.

post-32-0-63482400-1343825494_thumb.gif

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Might have storm-specific model issues today.

OOF!

NOUS42 KWNO 011048

ADMNFD

SENIOR DUTY METEOROLOGIST NWS ADMINISTRATIVE MESSAGE

NWS NCEP CENTRAL OPERATIONS CAMP SPRINGS MD

1043Z WED AUG 01 2012

NCEP`S PRIMARY SUPER COMPUTER WENT DOWN...WE ARE CURRENTLY

SWITCHING TO THE BACKUP...THERE WILL BE DELAYS IN NCEP MODEL

PRODUCTION BECAUSE OF THIS...MORE DETAILS WILL BE PROVIDED AS

THEY ARE AVAILABLE.

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Seeing that always pretty feathery cirrus outflow on the East side, when it can get that on the West side, I think its business.

Fine line, IMHO and amateur opinion, between shear that distorts and ruins a system, and strong winds just North of the system that aid in outflow.

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PotD. Pretty much covers it.

The 0z Euro and 0z/06z GFS demonstrates some of the points outlined. 0z GFS is too far south, and it opens back into a TW. 0z Euro is too far north and crashes with Hispaniola and is kept very weak because is under the influence of the TUTT. Finally, 06z treks over Barbados, a bit north of the 0z run, and fares a lot better, keeping a distinct circulation until it reaches the W Caribbean, where it restrengthens before visiting Chetumal.

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