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Atlantic Tropical Action 2012 - Part I


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The wave that the models are developing is in the MDR, behind the sacrificial wave. Seems to be forming an area of low pressure due to the eastern leg of the inverted "V" signature from the first wave. NHC has this down to 1009 mbs already, and 850 mb vort looks semi-decent for being in the MDR. I could see how the NHC recognizes this within 48 hours.

850mb vort:

18z GFS is the strongest run yet, but has some wicked winds in the Caribbean while it's passing through. Not too confident in this one becoming anything significant for two strong reasons. First off, the environment isn't great to begin with and wont be getting better as this progresses into the Caribbean. Second, the GFS has a track over a majority of the Greater Antilles.

Midget storm in the SE Caribbean.

0z GFS still developing the area in the MDR, this should be invested soon. Also tries to get something going off the East Coast with the front.

I don't think the key is what this storm does in the Caribbean... thats far too far down the road to get into specifics. The key is the next 72 hours as the storm will have to traverse to the south of a pretty large and unseasonably deep upper tropospheric trough. You can see on the standaridized anomalies this upper level low is 2-3 standard deviations below normal, and it will take a system moving very far to the south to escape the westerly shear this impulse will produce. If this system survives that impact (the GFS says it will, the ECMWF says it will not) then the system will the be in a much better upper level pattern in the East Caribbean, with two upper level lows helping to ventilate the system. Thus, its the short term, not the long term environment, that are key for this systems prospects.

awuf4n.gif

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*dusts off the tropical stuff* Stewart comes through for the night owls

and this is now 99L

A TROPICAL WAVE ACCOMPANIED BY A SURFACE LOW PRESSURE SYSTEM IS

LOCATED ABOUT 750 MILES SOUTHWEST OF THE CAPE VERDE ISLANDS. THIS

DISTURBANCE IS SHOWING SIGNS OF ORGANIZATION...AND ENVIRONMENTAL

CONDITIONS ARE CONDUCIVE FOR SOME GRADUAL DEVELOPMENT TO OCCUR OVER

THE NEXT FEW DAYS. THIS SYSTEM HAS A LOW CHANCE...20 PERCENT...OF

BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES

WESTWARD AT ABOUT 15 MPH.

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The GFSE are more suggestive of development further W in the Western Caribbean near the Yucatan where conditions would tend to be more favorable in the longer range. Other than increased moisture, I tend to think Florida is safe with this one. In fact several members suggest the NW Gulf may be the area to watch for any future development. We will see.

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The GFSE are more suggestive of development further W in the Western Caribbean near the Yucatan where conditions would tend to be more favorable in the longer range. Other than increased moisture, I tend to think Florida is safe with this one. In fact several members suggest the NW Gulf may be the area to watch for any future development. We will see.

FWIW, Canadian at 240 hours still has it moving a tad bit West of true North. Yes, this falls into weenie-ish "a boy can dream" territory, but w/ the forum being heavily I-95 megalopolis weighted, this could be the best thing that ever happened to American.

Early fears are about Shredderola, but 8 days out, it can miss in several different ways... I will say, I barely missed Allen, just moving from New York, and I was training in Orlando during Alicia and didn't know it happened, and was protecting y'all from the Iranians during Gilbert. But I have an instinctive dislike of boarding windows, and losing AC in August, But I wouldn't have to board windows for a TX/MX border storm, so I am always silver lining positive.

post-138-0-08882200-1343646417_thumb.gif

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The GFSE are more suggestive of development further W in the Western Caribbean near the Yucatan where conditions would tend to be more favorable in the longer range. Other than increased moisture, I tend to think Florida is safe with this one. In fact several members suggest the NW Gulf may be the area to watch for any future development. We will see.

Put me in the W Caribbean camp, if it develops at all.

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The 06Z HWRF which has be performing better this season since some major upgrades to that Hurricane model suggest a weak system nearing the Islands in 126 hours at a lower latitude than the GFDL which does tend to favor what the ensembles are sniffing.

post-32-0-96026100-1343655807_thumb.png

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With a 270/4 heading, we have a good deal of time to follow this one. I think as the system begins to transition out of the monsoon trof, the models will get a better handle on strength/track. Looking forward to what some of the experts on this board have to say.

(Large red line is the consensus of all the 12z models)

12z99l.png

12z consensus guidance with the new LLC position is a little stronger with a moderate-strong tropical storm passing through the islands. SHIPS (using the BAMM track which is the purple line near PR) has some dry air affecting the cyclone by the end of the period. Shear doesn't seem bad FWIW.

* ATLANTIC SHIPS INTENSITY FORECAST	 *
			 * GOES AVAILABLE,	 OHC AVAILABLE	 *
			 *	 INVEST AL992012 07/30/12 12 UTC *
TIME (HR)		 0	 6 12 18 24 36 48 60 72 84 96 108 120
V (KT) NO LAND 20 20 21 23 26 33 43 53 63 68 73 76 75
V (KT) LAND	 20 20 21 23 26 33 43 53 63 68 73 76 75
V (KT) LGE mod 20 20 21 22 23 25 28 33 40 47 54 59 62
Storm Type	 TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP
SHEAR (KT)		 1	 6	 5	 4	 4	 8	 9	 2	 3	 4	 1	 9	 8
SHEAR ADJ (KT)	 9	 7 10 10	 8	 8	 8 15 11 11 10	 7	 3
SHEAR DIR	 358 323 340 337	 3 13 31 82 83 153 164 205 221
SST (C)		 28.3 28.3 28.2 28.0 27.9 27.9 28.1 28.2 28.2 28.3 28.2 28.1 28.1
POT. INT. (KT) 140 141 140 137 136 136 138 139 139 141 140 139 139
ADJ. POT. INT. 139 143 142 139 137 136 139 139 139 141 141 140 140
200 MB T (C) -53.3 -53.4 -53.6 -53.9 -53.6 -53.4 -54.0 -53.4 -53.3 -52.9 -53.1 -52.6 -52.9
TH_E DEV (C)	 6	 6	 7	 6	 6	 6	 6	 6	 6	 7	 8	 9	 9
700-500 MB RH	 62 63 61 63 66 66 68 65 63 63 59 57 52
GFS VTEX (KT)	 8	 8	 9 10 10 10 12 14 16 17 18 18 16
850 MB ENV VOR 48 42 35 33 32 30 28 36 33 35 32 38 31
200 MB DIV	 -3	 9 25 34 20 64 39 63 27 37 26 34 32
700-850 TADV	 -5 -8 -10 -9 -7 -13 -10 -7 -4 -2	 0	 0	 4
LAND (KM)	 1382 1362 1351 1342 1321 1196 1020 898 798 704 670 695 515
LAT (DEG N)	 8.7 8.9 9.0 9.1 9.2 9.5 9.8 10.1 10.5 10.8 11.4 12.3 13.3
LONG(DEG W)	 35.5 36.5 37.5 38.6 39.7 41.8 44.0 45.9 47.9 49.9 52.0 54.4 57.0
STM SPEED (KT)	 7 10 10 11 11 10 10	 9 10 10 11 13 14
HEAT CONTENT	 9	 9	 9 10 15 25 27 34 32 40 52 48 63

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Steve, On July 25th the MJO was in phase 5. Phases 6 and 7 are usually unfavorable for development especially for the western Carribean (sp?) and Gulf of Mexico. Phases 1 and 2 are usually the good phases and they are still probably a couple of weeks away....at least to this non tropical guy.

MJO wave should be at low amplitude (CoD) for most of the next 2 weeks...models have some resurgence of the wave in favorable phases 1 & 2 by the end of the period, that's past Aug 5th.

The Caribbean has been inhospitable so far this season (as most seasons are in July), with the GoM and tropical Atlantic being a little more benevolent shear wise, though there has been plenty of dry air and loose lapse rates (diminished vertical instability), thanks to SAL and mid/low level heat ridges. Overall shear hasn't been that much of an issue, but the lack of a moist environment and an unfavorable MJO (hence unfavorable/sinking 200 hpa velocity potential anomalies) has precluded any development for July.

Here's a tool from Frank and Roundy that looks at 5 convectively coupled atmospheric waves and intraseasonal oscillations (mixed Rossby-gravity, easterly, equatorial Rossby, MJO and Kelvin + ENSO) in concert (not just the MJO) as a predictor of development potential:

waves%20forecast.gif

Here's a link to the corresponding paper for the experimental tool:

The Role of Tropical Waves in Tropical Cyclogenesis

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Just commenting on any landfall potential. It seems like the pattern through a good bit of early-mid AUG (and possibly beyond) would be unfavorable for a landfall to the CONUS anywhere. Of course, unfavorable doesn't mean impossible. I don't know how the East Coast (including FL) could see anything formidable other than some POS that forms off the SE coast possibly with a weakness in the jet stream (nothing Irene-like of course).

I suppose the eastern GOM / western FL could see something worth talking about with good trough timing in the upper Midwest and something coming along out of the western Caribbean that moves northward. Anyone north and east of there would just see remnants (SE coast etc.) of whatever came up.

Take my thoughts with a grain. This was just a few initial thoughts after quickly looking over medium range data.

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Here's a tool from Frank and Roundy that looks at 5 convectively coupled atmospheric waves and intraseasonal oscillations (mixed Rossby-gravity, easterly, equatorial Rossby, MJO and Kelvin + ENSO) in concert (not just the MJO) as a predictor of development potential:

Here's a link to the corresponding paper for the experimental tool:

The Role of Tropical Waves in Tropical Cyclogenesis

Paul's tool does a good job identifying periods of TCs over the Warm Pool regions but this tool does not perform well over the Atlantic. Therefore, you have to take this forecast over the Atlantic as a grain of salt becuase you'll get burned if you depend on it for that particular region.

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A "sleeper" would certainly favor the W Carib and GOM...that is, the more it simmers before any decent development (TS+), the higher the possibilities to get further west. The CMC overdevelops it in the short term, IMO, which is no shocker given it's history...the GFS starts a more poleward trajectory, as a rather flat trough in the eastern third weakens the subtropical ridging a bit and crashes the disturbance into Hispaniola. The Euro is a complete "sleeper", maintaining status quo for most of it's trek from it's current position to Nicaragua.

Ensembles from the GFS and Euro show mostly zonal ridging over the SE, which wouldn't be enough to prevent recurvature for a strong system, but could keep a weaker one in a WNW track trough the caribbean. Being early August at the time, there's little chance for a sharp trough (a la Charley) to recurve it towards W FL, so if it develops in the W Caribbean I lean toward N GoM to W GoM. OTOH, if it's an earlier developer, and misses Hispaniola, chances are for a near miss for the E Coast, as I don't see the sharp trough that you want to see in the MW...although there's some ridging over the N Atl.

Finally, we are still on an unfavorable period in the planetary waves aspect, the MJO is still at least a week away from becoming a little more favorable, and things will start farther west, so this also favors a sleeper, rather than a boomer.

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What's going on off the East Coast? The GFS develops this area but does not give it much time to organize as a warm-core system.

Low embedded in a cold front...conditions are ok for it to occlude and transition to warm core, but it will be moving toward cooler SSTs rather fast for it to complete the transition and detach from the front.

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Low embedded in a cold front...conditions are ok for it to occlude and transition to warm core, but it will be moving toward cooler SSTs rather fast for it to complete the transition and detach from the front.

The appearence is deceiving because it looks very symmetrical, I wouldn't be surprised if something 'hurricane chris' esque occured eventually with this frontal disturbance. Also considering the warm sea-surface temperatures this year favors development, not as significant as other factors though. If it's pushing at 30 kts like the GFS says then no; a subtropical system at best.

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The appearence is deceiving because it looks very symmetrical, I wouldn't be surprised if something 'hurricane chris' esque occured eventually with this frontal disturbance. Also considering the warm sea-surface temperatures this year favors development, not as significant as other factors though. If it's pushing at 30 kts like the GFS says then no; a subtropical system at best.

There's already an upper level ridge near atop of the low, so it could transition rather fast...so if it becomes a named system I'd favor a tropical over a subtropical one...it just needs to detach from the front...being over the Gulf stream doesn't hurt either

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There's already an upper level ridge near atop of the low, so it could transition rather fast...so if it becomes a named system I'd favor a tropical over a subtropical one...it just needs to detach from the front...being over the Gulf stream doesn't hurt either

As long as they wait 36 more hours to name it...

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Paul's tool does a good job identifying periods of TCs over the Warm Pool regions but this tool does not perform well over the Atlantic. Therefore, you have to take this forecast over the Atlantic as a grain of salt becuase you'll get burned if you depend on it for that particular region.

I thought that might draw someone from Albany out. Thanks for the insight on the limitation. He was smart to slap "Experimental" on the output, no one in their right mind should depend on experimental output for anything other than research.

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The sacrificial wave currently in the E Carib, isn't only sacrificing by removing some dry air from the path of the C Atlantic wave, but also by pushing the TUTT, which has been plaguing the Carib with shear, to the north. Now, as Phil mentions, we'll have to deal with the C Atlantic trough, which will try to extend back to the SW, but if it can pinch off an ULL and move in tandem and keep a healthy distance from the disturbance, it can benefit it with a strong poleward venting exhaust.

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