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Tropical Depression Don


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Things are certainly starting to look interesting again... The 200mb flow looks rather favorable as on the most recent 00z GFS, and if those easterly winds aloft verify, most of the "dry" air in the Gulf of Mexico won't really be advected into the circulation and it should maintain its moist canopy over the vorticity currently.

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Things are certainly starting to look interesting again... The 200mb flow looks rather favorable as on the most recent 00z GFS, and if those easterly winds aloft verify, most of the "dry" air in the Gulf of Mexico won't really be advected into the circulation and it should maintain its moist canopy over the vorticity currently.

I still think this thing has little chance of amounting to much. Just curious.... What do you feel is the max intensity this thing could get to? It just does not seem like it will have enough time to get it's act together first , then intensify into anything substantial. As I said before I can see some mild organization but in the end I think this runs out of time.

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I still think this thing has little chance of amounting to much. Just curious.... What do you feel is the max intensity this thing could get to? It just does not seem like it will have enough time to get it's act together first , then intensify into anything substantial. As I said before I can see some mild organization but in the end I think this runs out of time.

Well at this point it has plenty of time to get its act together... around 72-96 hours if you want to believe the GFS expected forward motion. While this disturbance may have not looked that impressive over the past 24 hours, its becoming more evident that the forecast conditions over the next 24-48 hours are becoming increasingly more favorable. That map I showed above shows evidence of poleward and equatorward outflow developing on a global model, which is usually a sign of a developing tropical cyclone when coupled with significant vorticity. At this current time, the gfs is showing a pretty small vorticity signature, which means we likely won't be seeing a large sprawling mess we saw with Arlene earlier in the season. Overall, I don't want to place any forecast on intensity until something actually develops, but I'm certainly not ruling out a significant system, because if this thing can get going in the next 24 hours (which is possible given the improving IR presentation tonight), the conditions are ripe for intensification imo.

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1. SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A TROPICAL WAVE OVER THE

NORTHWESTERN CARIBBEAN SEA HAVE INCREASED SLIGHTLY DURING THE PAST

SEVERAL HOURS. DEVELOPMENT...IF ANY...OF THIS SYSTEM IS EXPECTED

TO BE SLOW TO OCCUR AS IT MOVES TO THE WEST-NORTHWEST AT 10 TO 15

MPH. THIS SYSTEM HAS A LOW CHANCE...10 PERCENT...OF BECOMING A

TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

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Here are some of my morning thoughts... I'm growing more optimistic for development, despite the latest ECWMF coming in looking pretty bearish.

http://philstropicalweatherblog.wordpress.com/2011/07/26/invest-90l-hanging-on-still-has-the-potential-to-become-a-tropical-cyclone-in-the-gulf-of-mexico/

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Probably the best the invest has looked since it was a 30% tangerine back over the eastern Caribbean.

I still remain modestly optimistic about development chances for this system over the Gulf. I was personally not expecting any sort of tropicalcyclonegenesis until Wednesday at the earlist. Right now I still feel comfortable with that. While convection is the most intense and consolidated since at least two days ago and possibly the best it has looked since this system was named an invest, right now there is no convincing evidence of a surface circulation (although the mid level rotation has definitely become better defined), so I have a feeling this will take at least 24 hours to get the well defined surface circulation needed for the invest to be declared a depression.

The invest does look to be splitting the strongest shear however, and looks to be in a marginal to good environment for development with some modest dry air to worry about from here on out:

post-525-0-62890600-1311663169.gif

The TUTT over the southwestern Gulf will have to continue retrograding for significant development to occur, however.

post-525-0-46922600-1311663378.jpg

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A very weak circulation appears to be forming according to meso-analysis.

Might see "orange" later today...

dtk, if you're around, how useful is the NAM RUC initialization here at diagnosing the surface wind vectors? My gut says probably not much, but I honestly don't know.

EDIT: I don't think it matters much either way, but it's the RUC not the NAM

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dtk, if you're around, how useful is the NAM initialization here at diagnosing the surface wind vectors? My gut says probably not much, but I honestly don't know.

It's actually the RUC, so it's pretty high-grade stuff. It actually matches up with the surface-obs quite nicely. If anything, it maybe a tad loose on the circulation in the NW quad.

By the way, I would never use the NAM on here. That's just beggin' for a weenie stamp on my forehead.

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It's actually the RUC, so it's pretty high-grade stuff. It actually matches up with the surface-obs quite nicely. If anything, it maybe a tad loose on the circulation in the NW quad.

Right, but it's still an interpolated grid point model. There's obviously no observations of a closed circulation. So exactly is causing that initialization? It could be a bogussed vortex for all I know.

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Right, but it's still an interpolated grid point model. There's obviously no observations of a closed circulation. So exactly is causing that initialization? It could be a bogussed vortex for all I know.

Could be.

Personally, I'd wait for at least 7-10 updates showing the vortex before I started to really consider it.

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(BTW, I know who posts my images on others boards, so don't do it!devilsmiley.gif )

Might see "orange" later today...

Ahem. That happens to me all the time. I will agree with a tangerine possibility this evening or tomorrow. The RUC may not be the best example by the way. We are still in the deep tropics…;)

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Well at this point it has plenty of time to get its act together... around 72-96 hours if you want to believe the GFS expected forward motion. While this disturbance may have not looked that impressive over the past 24 hours, its becoming more evident that the forecast conditions over the next 24-48 hours are becoming increasingly more favorable. That map I showed above shows evidence of poleward and equatorward outflow developing on a global model, which is usually a sign of a developing tropical cyclone when coupled with significant vorticity. At this current time, the gfs is showing a pretty small vorticity signature, which means we likely won't be seeing a large sprawling mess we saw with Arlene earlier in the season. Overall, I don't want to place any forecast on intensity until something actually develops, but I'm certainly not ruling out a significant system, because if this thing can get going in the next 24 hours (which is possible given the improving IR presentation tonight), the conditions are ripe for intensification imo.

I respect your analysis very much Phil, you are a gem to have in our Southeast forums. You have much more meteorological knowledge than I do. But, I really disagree with you. I'm not denying that conditions are favorable. As I said before I don't doubt it has time to get it's act together ie. Organized TC Depression. What I do doubt is that it has time to do that and intensify into anything substantial. I would LOVE to see a TC in the GoM but the clock is seriously ticking.

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Hurricane Hunters may fly tommorrow.

WEATHER RECONNAISSANCE FLIGHTS

CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.

1030 AM EDT TUE 26 JULY 2011

SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)

VALID 27/1100Z TO 28/1100Z JULY 2011

TCPOD NUMBER.....11-056

I. ATLANTIC REQUIREMENTS

1. SUSPECT AREA (NEAR TIP OF YUCATAN)

FLIGHT ONE -- TEAL 70

A. 27/1800Z

B. AFXXX 01DDA INVEST

C. 27/1530Z

D. 22.0N 87.0W

E. 27/1730Z TO 27/2130Z

F. SFC TO 10,000 FT

2. OUTLOOK FOR SUCCEEDING DAY: BEGIN 6-HRLY FIXES

AT 28/1200Z NEAR 23.0N 91.5W IF SYSTEM DEVELOPS.

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The current GFS run is certainly interesting. http://moe.met.fsu.e...&hour=Animation

I'm surprised how fast this is organizing.

If this thing develops into a TC, it will be a lot different than Arlene was wrt to moisture shield. With Arlene, there was a favorable planetary wave, with very high PWs and a huge moisture envelope and broad upper level support. This time, we are in the subsident phases of the MJO, with limited PWs and narrow upper air support... which could bring us a micro cyclone...if it develops.

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If this thing develops into a TC, it will be a lot different than Arlene was wrt to moisture shield. With Arlene, there was a favorable planetary wave, with very high PWs and a huge moisture envelope and broad upper level support. This time, we are in the subsident phases of the MJO, with limited PWs and narrow upper air support... which could bring us a micro cyclone...if it develops.

That's a good point. It already has that micro look to it. The fact that it's confined and not sprawling may lead to faster development.

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That's a good point. It already has that micro look to it. The fact that it's confined and not sprawling may lead to faster development.

Exactly. As well as global models having a difficult time to get a good grip of it. Not impying that it will burst into a powerful microcane, but saying that even some explosive development is not out of the realm of possibility. The good thing is that the TUTT spun off it's tail end in the BoC, which will be slowly retrograding, leaving a better upper level environment in the GOM.

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