ATL: TROPICAL DEPRESSION TWO - DISCUSSION

[IvanSurvivor]

vorticity remains strong



wind shear isn't bad

On this image posted earlier by Hurakan...does that show a steering pattern headed to the Northern Gulf Coast? Still learning how to read all these maps, etc. Thanks.

[KWT]

I am beginning to become concerned that yet another heavy rainfall event may play out across TX and LA. We certainly have been in a pattern to bring disturbances toward the Western Gulf this early season.

Yep I think thats quite a good point, unless this does strengthen more than planned the flooding risks to E.Tx and LA will probably be the main story with this system, esp in light of 95L also enhancing convection when it comes onshore.

[dolebot_Broward_NW]

What I don't understand is if the overhead is good why the convection is so discomblobulated?

Now I'm no meteorologist, but I'm fairly sure that one does not produce the other in this case.

Good conditions aloft do not create convection if I'm not mistaken, but can aid in its continuation.

Convection is built by a number of items, here in the SE at the coast it is often seabreeze convergence at the surface, often in the open ocean it is high SST and weaker convergence. In the great plains it can only be strong convergence, West of the Rockies and along the western Appalachians it is often orographic. There must be some external mechanism to generate the lift.

It can be aided by good conditions aloft. But by there being "good" (which is actually BAD meteorologically speaking) conditions aloft only provides a path for convection which is the most natural and easiest path. There are other paths for convection to escape, such as when there exist a strong cap, it escapes by advection.

In order for convection to occur there must be several ingredients present:

1. Enough convective energy available (CAPE) and plenty of moisture.
2. Unstable environment aloft (a vertical path for the convective energy)
3. Surface convergence providing the forcing mechanism OR significant surface heating creating buoyancy.

Sometimes you can take away one of the 3 above if the other 2 are strong. This is the case with FL afternoon t-storms - often we have a cap, or a level of inherently stable upper atmosphere. Significant heating overcomes the cap and generates an unstable atmosphere, or the seabreeze comes in and generates forcing which breaks the cap, or substitutes for not quite enough CAPE.

In order for a Thunderstorm (organized continuous convection) to occur you must add vertical shear, which generally forces the updraft away from the downdraft, this allowing the storm's heat engine to develop.

In order for a cyclone to occur you must add vorticity to the above and the requirement of being over water with its nearly inexhaustible supply of moisture. Generally speaking this best done with an anticyclone aloft. Sometimes this develops all by itself, sometimes things just stack up.

[BigA]

I'm lost as to where the center of the action is (which likely implies a lack of organization). The map has 96L in the Yucatan channel, but most of the action is to the south of there, and the vorticity shows the action only a little to the north of Honduras (though I have reason to think this map may be 12 to 24 hours old).

[KFDM Meteorologist]

Center may be trying to form near the Channel.

[Weatherfreak000]

Haha, Invest 93L naysaying all over again.


I feel like for as long as I can remember watching invests unless the invest was truly prodigious (Like we believed Invest 92L almost was) then you can rest assured knowing it's going to fall apart and make everyone believe it's dead, just to come back to life again at 12.


Welcome to the tropics. (btw I think this is looking good, appears to have shrunken and is trying to consolidate further North making the BoC solution least likely. Going through the channel is going to be a huge advantage for this invest. Still very much alive and looking healthy as new convection is firing)

[KWT]

I'm lost as to where the center of the action is (which likely implies a lack of organization). The map has 96L in the Yucatan channel, but most of the action is to the south of there, and the vorticity shows the action only a little to the north of Honduras (though I have reason to think this map may be 12 to 24 hours old).

Well there is some low level turning occuring in the Yucatan still, looks to me like there is some decent mid level turning occuring with the convection as well. Convection is firing but is clearly still being sheared.

Probably will have enough time to become a weak system IMO but beyond that is probably a big ask given conditions don't appear to be that condusive aloft really.

[ConvergenceZone]

Wow, amazing that yesterday there were 4 or maybe 3 really good areas that looked like they would develop, now I look at the satellite this morning, and every single one of those areas seems to have diminished in convection and potential. Hmmmm, perhaps we will get lucky and get our break afterall...

[HouTXmetro]

Center may be trying to form near the Channel.

KDFM are you basing that off your professional opinion, satellite imagery or surface obs?

[TwisterFanatic]

Convection is really starting to fire near the Yucatan channel..

[KFDM Meteorologist]

All of the above. Several Vorticies battling it out to see who becomes dominant. We'll see what happens.

[Weatherfreak000]

One thing is for sure, this invest is far from dead.

Invest 95L may be dead, but something is being seen off the Florida East Coast by the models soon. The wave in the caribbean has a few days before it makes it to the favorable zone.


I am completely confident between the two we should have the B storm. I find it alot more probable we may even get to the C storm. I believe we just reached the point where Dennis is going to form so alot of ground to catch up on as far as 2005 numbers.


Being a NOLA resident, it's ominous seeing tracks like Alex and this low may have. The real test is going to be when it makes it to the GOM. If it can intensify there, it'll be over warmer waters at deeper levels. Alex definitely woke me up to the reality the GOM may be dangerous this season.

[KWT]

If you look at the high resolution Sat.imagery you really can see the turning with the convection to the east of the Yucatan right now so I think at least we do have some sort of MLC trying to develop.

[wxman57]

Here's a recent surface plot with satellite overlay. No evidence of any rotation in the observations. Any turning in the clouds is above the surface. My impression is that it is very poorly organized and not likely to develop. A 20% shot, maybe. And that would be high for a typical July disturbance. But before any development was to occur, convection would have to increase significantly and concentrate in one area for a day or so. Considering it's now maybe 60 hours from reaching Louisiana, there isn't much time for it to consolidate and develop.

[cycloneye]

TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT MON JUL 5 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SHOWERS AND THUNDERSTORMS REMAIN DISORGANIZED IN ASSOCIATION WITH A
SMALL AREA OF LOW PRESSURE LOCATED ABOUT 50 MILES SOUTH OF MORGAN
CITY LOUISIANA. ENVIRONMENTAL CONDITIONS ARE NOT FAVORABLE FOR
DEVELOPMENT...AND THERE IS A LOW CHANCE...NEAR 0 PERCENT...OF THIS
SYSTEM BECOMING A TROPICAL CYCLONE BEFORE IT MOVES INLAND BY
LATE TONIGHT.

A BROAD AREA OF LOW PRESSURE OVER THE NORTHWESTERN CARIBBEAN SEA AND
THE SOUTHEASTERN GULF OF MEXICO IS PRODUCING WIDESPREAD CLOUDINESS
AND DISORGANIZED THUNDERSTORMS. UPPER-LEVEL WINDS ARE FORECAST TO
BECOME MORE CONDUCIVE FOR DEVELOPMENT...AND A TROPICAL DEPRESSION
COULD FORM OVER THE NEXT COUPLE OF DAYS AS THIS SYSTEM MOVES
NORTHWESTWARD AT ABOUT 15 MPH. THERE IS A MEDIUM CHANCE...30
PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS. REGARDLESS OF DEVELOPMENT...LOCALLY HEAVY RAINFALL
AND GUSTY WINDS ARE POSSIBLE OVER THE YUCATAN PENINSULA AND WESTERN
CUBA OVER THE NEXT DAY OR SO.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BLAKE/KIMBERLAIN

[vbhoutex]

A look at current visibles confirms what Wxman57 has already shown us. I see no hint of a LLC or for that matter of a broad low level turning(obviously NHC has info I don't). Definite blow up of strong convection SE of Cozumel. Could that provide the energy to push something to the surface or is something hiding underneath this blow up? What I am seeing in NW Carib, GOM is becoming concerning to me as most of the models are bringing anything that could develop out of all of the different areas either W or NW and if that means TX, we don't need any more rain for a while after Alex and his remnants. Unfortunately anything coming out of the Caribbean that doesn't move E of LA would be bringing more oil onshore and continues to substantially disrupt the work of containing the oil disaster.

[ConvergenceZone]

It looks like wxman57 was right. Percentages for development are coming down.

[Dean4Storms]

I do see Lower Level turning just off the very tip of the NE part of the Yucatan Peninsula. Giving that the buoy in the Yucatan pass recorded its lowest pressure at 9:30pm last night that puts the low about in that vicinity IMO.

[MGC]

Belching out a huge outflow boundry right now....don't think it is getting better organized ATT.....MGC

[cycloneye]

18z Best Track

AL, 96, 2010070518, , BEST, 0, 217N, 868W, 30, 1009, DB

ftp://ftp.tpc.ncep.noaa.gov/atcf/tcweb/ ... 010.invest