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Post Tropical Cyclone Debby


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One week in the same spot :D ... until coarser resolution brought to you by day 8 brings in some sense and moves it ashore around Mobile...whatever is left of it.

Looks like it kicks a piece of it out across florida early then hangs back a chunk that festers for a week?

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This invest will be interesting to watch play out over the next several days…

I’m not necessarily an expert, but in my opinion I don’t think development is imminent. As Phil pointed out, the low and mid level centers are currently not aligned as can be seen clearly on the vorticity plots, as the 500mb vorticity center is displaced to the south-southeast of the surface low pressure and associated low level (850mb) vorticity:

post-525-0-92479100-1340341920_thumb.gif

As a result, an earlier burst of convection associated with 96L was focused to the east of the surface low pressure. In addition, although upper level winds over the invest are currently marginally favorable for organization, there is a 20-30kt upper level westerly flow across much of the Gulf of Mexico. For the time being, there is an upper level anti-cyclone over the Yucatan Peninsula, but it is not making much northward progress, as is shown by shear not decreasing over the past 24 hours over the Gulf.

post-525-0-71679600-1340342020_thumb.gif

The 0z GFS and 12z Euro both show an upper level low developing over the northwestern GOM during the next 48-72 hours before slowly weakening, accounting for a 20-40 knot flow over a good portion of the northern and western Gulf through the next 4-5 days.

0z GFS:

post-525-0-79556200-1340342057_thumb.gif

12z Euro:

post-525-0-27659500-1340342103_thumb.png

Although it appears upper level winds will not be extremely unfavorable, the combination of a currently broad low level circulation which is not aligned well with the associated mid level circulation will itself result in a somewhat slow organization process over the next couple days. Potential moderate westerly to southwesterly shear will only slow this process. Essentially, I believe tropical cyclone genesis will probably not occur within the next 24 hours but will likely occur at some point within the next 48-72 hours, so at some point Saturday night into Sunday would be my guess.

post-525-0-55301500-1340342188_thumb.gif

In the short term, there is a weakness in the low level ridging to the north of the invest, so it will likely slowly drift towards the north-northeast. Assuming the system remains weak, it should not be picked up by this weakness and rushed out to sea.

As an unseasonably deep trough/upper low builds over the eastern lake/northeastern US, the northwest flow aloft should cause the system to slow down/stall out in about 72 hours as shown by the Euro over the northern Gulf:

post-525-0-23044600-1340342259_thumb.gif

As the trough eventually pulls out towards the latter half of next week ridging should build north of the invest, pushing the system westward towards TX/MX.

This solution is generally well supported by recent operational and ensemble guidance, however if the invest moves too far to the north or east before it stalls, ridging may not build north of it and it may stall for a longer period of time.

Assuming the system slowly develops over the next 2-3 days upper level winds are shown to relax over the GOM as upper level ridging expands, which may support an eventual tightening and organization of any system as we head into next week. However, a very dry northwest flow will impinge on the system in that same time frame, so while I believe this stands a decent chance at being classified as a tropical cyclone this weekend, it will be difficult for this become more than a low to moderate end tropical storm before a potential landfall in the western Gulf in about a week.

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Euro solution would be glass 3/8ths full for much wanted rain on the lawn. AccuWx PPV verbatim is heaviest rain South of I-10 but can't keep my natural born optimism down, and it appears rainfield "tightens up", if Dolly could rain in SETX from way down by BRO, I can't help but see the silver lining.

Euro vernatim 10 day rains are 3 inches plus entire Rio Grande/Rio Bravo del Norte from BRO to almost ELP with 5"+ South Texas towards SAT. I know, touch weenie to be getting 10 day rainfall totals from a model when the situation is fluid. Part of the silver lining optimism, I guess.

South Florida Water Management District model tracks graphic is the proverbial squashed spider, so obviously rainfall totals from Euro are as much entertainment as actual likelihood.

More immediately, should I be appreciating -80ºC cloud tops or concerned they are all East of latest analyzed surface low?

post-138-0-54702300-1340365562_thumb.jpg

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96L remains unorganized. The surface low N of the Yucatan and the 500mb vort which is displaced to the E over the Yucatan Channel will need to become vertically stacked before any real development.

post-32-0-14162400-1340366847_thumb.png

post-32-0-91704600-1340366857_thumb.png

post-32-0-33072400-1340367175_thumb.jpg

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Rather moist is kind of an understatement! 4-5 standard deviations moist! I see 2.6"+ PWAT values right now.

Yeah, flooding is going to be a big concern for the areas that eventually see the greatest impact from this storm.

We saw earlier this month what all that moisture in the atmosphere could do down around the Gulf.

http://ido.wunderground.com/blog/JeffMasters/comment.html?entrynum=2117

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I am actually under glass half full optimistic on a recon flight today. Just slightly under glass half full. 7/16ths full. Be less than that except maybe deep convection develops new surface low farther East.

Yeah, it really isn't looking too hot right now.

The northern Yucatan surface low is really poorly organized and a new center is trying to form jet east of Cozumel.

There really isn't much to fly into.

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The USA hasn't had a June hurricane landfall since 1986-- so it's climatologically very unusual.

June landfalls in the USA since 1950:

1986 - Bonnie - TX

1972 - Agnes - FL (NW)

1966 - Alma - FL (NW)

1957 - Audrey - LA/TX

As you can see, all of them were on the Gulf Coast, and none of them were majors.

Re: Audrey... Yes, it's officially a Cat 4, but it hasn't been reanalyzed yet. Contemporary analysis done by reputable researchers (like Brian Jarvinen) suggests it was much, much weaker-- maybe even a strong Cat 1. Let's see what the Best Track Committee says. My guess is they compromise and settle on Cat 2 (like 85 or 90 kt).

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WEATHER RECONNAISSANCE FLIGHTS

CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.

1015 AM EDT FRI JUN 22 2012

SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)

VALID 23/1100Z TO 24/1100Z JUN 2012

TCPOD NUMBER.....12-035

I. ATLANTIC REQUIREMENTS

1. SUSPECT AREA (GULF OF MEXICO)

FLIGHT ONE -- TEAL 70 --

A. 23/1800Z

B. AFXXX 01AAA INVEST

C. 23/1615Z

D. 25.5N 888.5W

E. 23/1715Z TO 23/2130Z

F. SFC TO 10,000 FT

FLIGHT TWO -- TEAL 71 --

A. 24/1200,1800Z

B. AFXXX 0204A CYCLONE

C. 24/1015Z

D. 27.1N 88.5W

E. 24/1100Z TO 24/1800Z

F. SFC TO 10,000 FT

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

3. REMARK: LOW LEVEL INVEST FOR 22/1800Z CANCELED

BY NHC AT 22/1230Z.

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HPC: Euro solution but low confidence.

Same. About 1/3 of the Euro ensemble members still take it on the northeastern route.

Sometimes these early season threads are like pre season football. The starters come in for a couple plays, show why they are starters then the 5 th deep walk ons appear and show why they are walk ons. Nice to see some starters ops. should be an interesting weekend thread, hopefully you two get more playing time as the regular season begins.. LOL

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HH hunter flight cancelled. No surprise since there is nothing out there to look at right now. It will probably start to look better around this time tomorrow and really get going on Sunday. Sunday 21z is my guess for the upgrade to TD (unless they upgrade the slopgyre disturbance beforehand).

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Sometimes these early season threads are like pre season football. The starters come in for a couple plays, show why they are starters then the 5 th deep walk ons appear and show why they are walk ons. Nice to see some starters ops. should be an interesting weekend thread, hopefully you two get more playing time as the regular season begins.. LOL

Thanks, Ginx. I actually won't be around much. I'm headed on vacation out of the country through next weekend.

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Not surprised at all by the recon cancellation either. The current low level "centre" I believe is not going to survive... it's just too weak and disjointed from the main area of convection and the MLC. Look for the LLC to reform under/near the MLC and the convection... when that happens, boom.

Because the convection fluctuated a bit last night showing that it still isn't stable, and because of the LLC/MLC situation, I'm adjusting my original classification prediction from ~5 AM tomorrow to perhaps 11 PM tomorrow. Afternoon recon tomorrow should be cutting it close on when the system will be organised enough to be TD 4.

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Not surprised at all by the recon cancellation either. The current low level "centre" I believe is not going to survive... it's just too weak and disjointed from the main area of convection and the MLC. Look for the LLC to reform under/near the MLC and the convection... when that happens, boom.

I agree with your series of events, I just think the time frame will be longer. At least in the WPAC when dealing with monsoon depression-type disturbances, it takes a lot of latent heat release to reorganize the mass field and get the main LLC to tighten underneath the deepest convection. Granted, there is no convection over the current LLC right now, which may help, but I'm skeptical that this will be a process that takes <36 hours.

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