Amped Posted August 10, 2012 Share Posted August 10, 2012 That's a small core LMAO. It will be lucky to make it through the next few days let alone strengthen. If it somehow makes it to the west Caribbean it has a chance. Link to comment Share on other sites More sharing options...
MississippiWx Posted August 10, 2012 Share Posted August 10, 2012 SE periphery of a ridge is the most unfavorable side for a developing tropical cyclone due to the subsidence it brings. A strong ridge is present to the NW of TD7 and is suppressing TD7's ability to enhance its convective field. You can see how the moisture/cloud envelope is oriented SW to NE. This is due to the ridge's influence. This is not favorable for a focused area of surface convergence and that is a huge reason why TD7 continues to struggle with convection. Once TD7 is more oriented on the southern side of the ridge, it should organize better if it has time to do so before encountering higher shear. Link to comment Share on other sites More sharing options...
phil882 Posted August 10, 2012 Share Posted August 10, 2012 This system is incredibly tiny, but does have some banding features. Last nights TRMM pass even had a low-level eye lol. The NHC mentions that the shear should remain low for the next 12-24 hours. The time is now for it to obtain some better convective organization. Otherwise at its current size, I don't think it can survive the hostile conditions ahead. Link to comment Share on other sites More sharing options...
Ed Lizard Posted August 10, 2012 Share Posted August 10, 2012 SHIPS has 7L strengthening even with 26 knots of SW shear forecast in 2 days. I wonder about that. I'm am always upbeat on these things, and the possibility steering would become favorable in a week to come into the Gulf was interesting, but based on facts on the ground, and reliable global models, this is lucky to ever get named, and I doubt it is even a well developed wave by day 5, and there will be nothing to get steered into the Gulf. A small area of 700 mb RH above 70% in the Gulf, with no apparent shift in winds may be 7L in 8 days on 0Z and 6Z GFS. My amateur opinion. It is small and weak. I guess the only chance it has is to really take advantage of the short window between dry surroundings and increasing shear, and that looks to be a very short window. Amateur opinion, NHC 5 day forecast position is wrong in that this doesn't exist as more than a weak wave in 5 days. Link to comment Share on other sites More sharing options...
Ed Lizard Posted August 10, 2012 Share Posted August 10, 2012 Staring hard at visible loops, and am not 100% sure Tropical Depression 7 has West winds South of the center. Link to comment Share on other sites More sharing options...
carley5 Posted August 10, 2012 Share Posted August 10, 2012 as fast as its moving it probably doesnt. i dont see any west winds either. Link to comment Share on other sites More sharing options...
Ed Lizard Posted August 10, 2012 Share Posted August 10, 2012 NHC keeping it for six more hours, at least. But not hoisting watches. I suspect Berg et al think the globals are correct, but want to be sure, and hence taking a middle position. Link to comment Share on other sites More sharing options...
phil882 Posted August 10, 2012 Share Posted August 10, 2012 NHC keeping it for six more hours, at least. But not hoisting watches. I suspect Berg et al think the globals are correct, but want to be sure, and hence taking a middle position. There is a surface circulation that is partially embedded in the convection... in fact it continues to look very similar to Ernesto at this time frame. Ernesto: TD #7 Link to comment Share on other sites More sharing options...
Ed Lizard Posted August 10, 2012 Share Posted August 10, 2012 There is a surface circulation that is partially embedded in the convection... in fact it continues to look very similar to Ernesto at this time frame. Ernesto: TD #7 If there are Earth relative West winds, they are well obscured by that small area of convection. And the presentation is degrading on the MIMIC TPW loop. It may still technically be a TD, hard to know for sure off of satellite imagery, but even if it is a depression now, the future looks grim, from what I can tell. Do you think the current NHC forecast has a reasonable chance of verifying intensity wise (within reasonable limits, +/- 10 knots)? Honest question, you are on of the red tags I follow rather closely on tropical matters. Link to comment Share on other sites More sharing options...
phil882 Posted August 10, 2012 Share Posted August 10, 2012 If there are Earth relative West winds, they are well obscured by that small area of convection. And the presentation is degrading on the MIMIC TPW loop. It may still technically be a TD, hard to know for sure off of satellite imagery, but even if it is a depression now, the future looks grim, from what I can tell. Do you think the current NHC forecast has a reasonable chance of verifying intensity wise (within reasonable limits, +/- 10 knots)? Honest question, you are on of the red tags I follow rather closely on tropical matters. Microwave imagery still shows pretty conclusive proof of a circulation, with a hint of some banding features. I think there is still plenty of time (12-24 hours) for this system to become a tropical storm. Yes I agree its got a difficult road ahead of it, but the models have continued to poorly capture the CCKW that is moving across the Caribbean Sea / South America at this time. It is worth repeating that both the ECMWF and GFS were forecasting Ernesto to dissipate in the Caribbean last week at this time, but the CCKW was able to slow down the low-level flow enough to allow Ernesto to survive, while giving it a convective kick to boot. Link to comment Share on other sites More sharing options...
MississippiWx Posted August 10, 2012 Share Posted August 10, 2012 Ouch, getting a little personal in here now. Nothing wrong with debate, but let's try to keep the discussion civil and professional. Btw MississippiWx welcome to the forum for I don't think anyone welcomed you in this thread. Thanks for the welcome! Link to comment Share on other sites More sharing options...
am19psu Posted August 10, 2012 Share Posted August 10, 2012 New thread split off here: Link to comment Share on other sites More sharing options...
Ed Lizard Posted August 10, 2012 Share Posted August 10, 2012 Not discussing model strengths, other than to say I'm leaning toward the globals and trying to account for resolution limitations. I think TD & probably opens into a wave, and will become weak. In a week or 8 days, an enhanced area of rain will be in the BoC associated with what I believe are the remnants of TD 7. Assuming the GFS is slightly underdoing the strength of the remnant feature, there is a chance something could come Northwest or even Northward in the Gulf beyond 8 days. I am hoping talk of CCKW interaction and keeping TD #7 alive will happen, that could shift the potential target (if there is a potential target) to better chase locations in Florida as compared to the Central or Western Gulf. Just my opinion, and as always, it is free, and worth it. Link to comment Share on other sites More sharing options...
Ed Lizard Posted August 10, 2012 Share Posted August 10, 2012 Back on TD #7, and my weak understanding of Kelvin Waves, will this enhance convection (ands then lessen forecast Westerly shear after it passes) enough to allow it to maintain as a closed cyclone through the Eastern and Central Caribbean? Link to comment Share on other sites More sharing options...
phil882 Posted August 10, 2012 Share Posted August 10, 2012 Back on TD #7, and my weak understanding of Kelvin Waves, will this enhance convection (ands then lessen forecast Westerly shear after it passes) enough to allow it to maintain as a closed cyclone through the Eastern and Central Caribbean? Here is what we know. 1. There is a strong CCKW that is currently across the Caribbean Sea and is moving eastward towards TD#7. This particular map shows the upper level (200 hPa velocity potential) component of the kelvin wave. Since kelvin waves are tilted, the low-level component is at some longitude ahead of this portion, probably approaching our disturbance. 2. There is a deepening TUTT that is amplifying due to the amplifying upper level ridge over Bermuda. This will cause the belt of upper level westerly flow to sag southward towards TD#7. What happens next is the question. Its a matter of which feature is synoptically stronger. CCKW are associated with both deep and stratiform convection. Convection typically produces cyclonic vorticity in the low-mid levels, and anticyclonic vorticity in the upper levels. In borderline cases such as this, CCKW can modulate the environment to negate the effects of TUTT features that are on the outer periphery of TCs. So its a matter of how strong the TUTT will be vs. how large of an impact the CCKW will make. The TUTT should be well captured by the models, but the CCKW typically isn't. Thus, based on this presumption, it is plausible to expect the TUTT to perhaps be weaker than forecasted by the models as its modulated by the CCKW. Will it be enough to let TD#7 survive... thats still up in the air. Link to comment Share on other sites More sharing options...
Derecho! Posted August 10, 2012 Share Posted August 10, 2012 12Z NOGAPS is weenie-rific for TD7, btw. I actually remember when people would seriously discuss NOGAPS in tropical threads...I am old. Link to comment Share on other sites More sharing options...
Mike.Ventrice Posted August 10, 2012 Share Posted August 10, 2012 Here is what we know. 1. There is a strong CCKW that is currently across the Caribbean Sea and is moving eastward towards TD#7. This particular map shows the upper level (200 hPa velocity potential) component of the kelvin wave. Since kelvin waves are tilted, the low-level component is at some longitude ahead of this portion, probably approaching our disturbance. 2. There is a deepening TUTT that is amplifying due to the amplifying upper level ridge over Bermuda. This will cause the belt of upper level westerly flow to sag southward towards TD#7. What happens next is the question. Its a matter of which feature is synoptically stronger. CCKW are associated with both deep and stratiform convection. Convection typically produces cyclonic vorticity in the low-mid levels, and anticyclonic vorticity in the upper levels. In borderline cases such as this, CCKW can modulate the environment to negate the effects of TUTT features that are on the outer periphery of TCs. So its a matter of how strong the TUTT will be vs. how large of an impact the CCKW will make. The TUTT should be well captured by the models, but the CCKW typically isn't. Thus, based on this presumption, it is plausible to expect the TUTT to perhaps be weaker than forecasted by the models as its modulated by the CCKW. Will it be enough to let TD#7 survive... thats still up in the air. Could the TUTT be part of the dynamical structure of the CCKW? More specifically, when there is upper-level westerly flow at the equator in association to the upper-level westerly wind phase of the Kelvin wave, might extra-tropical troughs be encouraged to propagate equatorward into the tropics due to the creation of a westerly wind duct in the tropics? It becomes extremely hard to separate the two features. Link to comment Share on other sites More sharing options...
CUmet Posted August 10, 2012 Share Posted August 10, 2012 I wouldn't be surprised if this was a minimal TS already given how quickly it's moving and how vigorous the low level circulation appears on visible imagery. Link to comment Share on other sites More sharing options...
Ed Lizard Posted August 10, 2012 Share Posted August 10, 2012 12Z NOGAPS is weenie-rific for TD7, btw. I actually remember when people would seriously discuss NOGAPS in tropical threads...I am old. I could be wrong, but I think the last major upgrade to NOGAPS was 1998, and the last physics package adjustment was 2003. I mentioned that, NRL is all about the TC-COAMPS, but I hate the web site. Link to comment Share on other sites More sharing options...
hm8 Posted August 10, 2012 Share Posted August 10, 2012 I mentioned that, NRL is all about the TC-COAMPS, but I hate the web site. FWIW, here's what it says for TD7... EDIT: I actually kinda like the site for this model...it has some nice verification products Did pretty well with Ernesto Link to comment Share on other sites More sharing options...
Ed Lizard Posted August 10, 2012 Share Posted August 10, 2012 FWIW, here's what it says for TD7... Anybody know what it is initialized/bounded from? I have a theory... Link to comment Share on other sites More sharing options...
hm8 Posted August 10, 2012 Share Posted August 10, 2012 Anybody know what it is initialized/bounded from? I have a theory... you'd be correct... "COAMPS® system is currently designed to use fields from the Navy Operational Global Atmospheric Prediction System (NOGAPS) for first guess fields and lateral boundary conditions. Quality controlled observational data for the atmosphere and the ocean are used by the COAMPS® 3-dimensional multi-variate optimum interpolation (MVOI) atmospheric and ocean analyses, respectively." " http://www.nrlmry.navy.mil/coamps-web/web/init Link to comment Share on other sites More sharing options...
Ed Lizard Posted August 10, 2012 Share Posted August 10, 2012 New advisory forecasts dissipation. But a scattering of watches... WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY... THE GOVERNMENT OF FRANCE HAS ISSUED A TROPICAL STORM WATCH FOR GUADELOUPE AND MARTINIQUE. THE GOVERNMENT OF BARBADOS HAS ISSUED A TROPICAL STORM WATCH FOR BARBADOS...ST. VINCENT AND THE GRENADINES...AND DOMINICA. THE GOVERNMENT OF ST. LUCIA HAS ISSUED A TROPICAL STORM WATCH FOR ST. LUCIA. Link to comment Share on other sites More sharing options...
Analog96 Posted August 10, 2012 Share Posted August 10, 2012 New advisory forecasts dissipation. But a scattering of watches... WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY... THE GOVERNMENT OF FRANCE HAS ISSUED A TROPICAL STORM WATCH FOR GUADELOUPE AND MARTINIQUE. THE GOVERNMENT OF BARBADOS HAS ISSUED A TROPICAL STORM WATCH FOR BARBADOS...ST. VINCENT AND THE GRENADINES...AND DOMINICA. THE GOVERNMENT OF ST. LUCIA HAS ISSUED A TROPICAL STORM WATCH FOR ST. LUCIA. Because they think it could pulse up to TS before dissipation. Link to comment Share on other sites More sharing options...
Ed Lizard Posted August 10, 2012 Share Posted August 10, 2012 Because they think it could pulse up to TS before dissipation. Official forecast is through the islands at 35 knots... Link to comment Share on other sites More sharing options...
Amped Posted August 10, 2012 Share Posted August 10, 2012 I never thought NHC needs to issue warnings for a 40mph TS. Wind Advisory, Flood Watch, Gale Warning seems to cover it. TS Warning just confuses people. Link to comment Share on other sites More sharing options...
Wannabehippie Posted August 10, 2012 Share Posted August 10, 2012 I could be wrong, but I think the last major upgrade to NOGAPS was 1998, and the last physics package adjustment was 2003. I mentioned that, NRL is all about the TC-COAMPS, but I hate the web site. How come NOGAPS doesn't get any upgrade/adjustments? Link to comment Share on other sites More sharing options...
Analog96 Posted August 10, 2012 Share Posted August 10, 2012 How come NOGAPS doesn't get any upgrade/adjustments? Because the Navy doesn't want to spend money on upgrading it. Link to comment Share on other sites More sharing options...
MississippiWx Posted August 10, 2012 Share Posted August 10, 2012 Funny that the NHC mentioned that TD7 was becoming elongated in their discussion. I mentioned last night (pg.2) that it was becoming elongated SW to NE due to being on the SE periphery of the Bermuda Ridge and the fast easterly flow giving it a squeeze play. This evening, TD7 is more oriented to the south of the ridge and thus the shape is actually more symmetrical than it has been for the past 24 hours. It is also oriented in a way where subsidence on the SE periphery of the ridge is no longer a factor and the result is more convection (increased SSTs is part of cause as well). Still not seeing much in the way of a sheared system. Seems that every time the CIMSS page updates, the shear backs away. The small anticyclonic flow in the upper levels that TD7 has is barely shielding it for now...probably won't be much luck with that when it encounters a more stout area of shear near the islands (according to models). You can see here in the TPW loop how TD7 is becoming a little more symmetrical and the TPW has increased some recently. Link to comment Share on other sites More sharing options...
Wannabehippie Posted August 10, 2012 Share Posted August 10, 2012 Because the Navy doesn't want to spend money on upgrading it. So why bother even keeping it around? Link to comment Share on other sites More sharing options...
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