ATL: MARCO - Remnants - Discussion

[storm_in_a_teacup]

Could take off very soon.
Picking up a moisture feed from the south and tracking into the anticyclone.

https://i.imgur.com/9lKxMuJ.png

https://i.imgur.com/z1k13uF.png

(Again, excuse my ignorance but...)
Is this anticyclone associated with the storm’s outflow or is it an independent feature? I thought anticyclones were high pressure areas so how does the storm go into it?

[GCANE]

Could take off very soon.
Picking up a moisture feed from the south and tracking into the anticyclone.

https://i.imgur.com/9lKxMuJ.png

https://i.imgur.com/z1k13uF.png

(Again, excuse my ignorance but...)
Is this anticyclone associated with the storm’s outflow or is it an independent feature? I thought anticyclones were high pressure areas so how does the storm go into it?

Anticyclones are upper-level features showing winds circulating in a clockwise pattern.
There are two types I am aware off.
1) Convective anticyclone comes from the updraft of strong convection. Coriolis forces twist the air parcels clockwise as they rise in the troposphere. When they hit the top of the troposphere, they spread out horizontally.
2) A synoptic-scale anticyclone is derived from large air currents in the upper troposphere. One of the common ones is the Anticyclone Rossby Wave Break as I described earlier.

High pressure at the surface is actually air sinking from the upper troposphere.

[Javlin]

It's a feature in the upper atmosphere conducive to cyclone development.From wiki

Anticyclones aloft can form within warm core lows such as tropical cyclones, due to descending cool air from the backside of upper troughs such as polar highs, or from large scale sinking such as the subtropical ridge. The evolution of an anticyclone depends upon variables such as its size, intensity, and extent of moist convection, as well as the Coriolis force.[2]

[GCANE]

Could take off very soon.
Picking up a moisture feed from the south and tracking into the anticyclone.

https://i.imgur.com/9lKxMuJ.png

https://i.imgur.com/z1k13uF.png

(Again, excuse my ignorance but...)
Is this anticyclone associated with the storm’s outflow or is it an independent feature? I thought anticyclones were high pressure areas so how does the storm go into it?

Anticyclones are upper-level features showing winds circulating in a clockwise pattern.
There are two types I am aware off.
1) Convective anticyclone comes from the updraft of strong convection. Coriolis forces twist the air parcels clockwise as they rise in the troposphere. When they hit the top of the troposphere, they spread out horizontally.
2) A synoptic-scale anticyclone is derived from large air currents in the upper troposphere. One of the common ones is the Anticyclone Rossby Wave Break as I described earlier.

High pressure at the surface is actually air sinking from the upper troposphere.

Forgot to mention the effect of an anticyclone on the vort column of a TC.

An anticyclone actually raises the height of the top of the troposphere, aka the tropopause.
When a vort column tracks into an anticyclone, the vort column expands vertically and becomes more vertically align (stacked).
The vort columns essentially stretches vertically, which due to conservation of angular momentum must make the vort column spin faster.
Its the analogy of the spinning skater pulling his arms in.

[MississippiWx]

This one is looking a little more interesting in visible imagery this afternoon. I think it’s only going to get better organized as it slows down in the Western Caribbean.

[cycloneye]

Showers and thunderstorms have become more concentrated today in
association with a tropical wave currently located over the central
Caribbean Sea. Some gradual development of this system is possible
over next day or so while it moves westward at about 15 to 20 mph
across the central Caribbean Sea. After that time, the wave is
forecast to move more slowly west-northwestward, and a tropical
depression is likely to form later this week when the system
reaches the northwestern Caribbean Sea.
* Formation chance through 48 hours...medium...60 percent.
* Formation chance through 5 days...high...80 percent.

[MississippiWx]

Showers and thunderstorms have become more concentrated today in
association with a tropical wave currently located over the central
Caribbean Sea. Some gradual development of this system is possible
over next day or so while it moves westward at about 15 to 20 mph
across the central Caribbean Sea. After that time, the wave is
forecast to move more slowly west-northwestward, and a tropical
depression is likely to form later this week when the system
reaches the northwestern Caribbean Sea.
* Formation chance through 48 hours...medium...60 percent.
* Formation chance through 5 days...high...80 percent.

And right on cue.

I know all the focus from the board is on 98L because it could impact FL, but this one has my interest. It has a very healthy signature in the lower levels.

[chaser1]

Getting hungry here. Anyone care to join me for a hefty bowl of Kellogs ARC Cloud Cereal?

[gfsperpendicular]

If 98L had been closer to the Lesser Antilles could potentially have had two PTCs at once, which I don't think has happened before

I'm not sure why the excitement around the "PTC" designation. All they are is a wave that's not a tropical cyclone yet, but is close enough to land and has a good enough chance to become a TC before affecting that land that NHC wants to initiate advisories before it technically becomes a tropical depression, so watches/warnings can be issued.

There are no particular requirements for strength or organization for PTC advisories to be initiated, other than NHC thinks it has a good enough chance to become a tropical cyclone and bring tropical storm/hurricane conditions to land within 36 hours.

Personally, I enjoy reading the NHC's forecast discussions and I would really like to see a concrete intensity and track forecast from the NHC. I also like the concept of the PTC since with a weaker TC the winds aren't the hazard anyways.

[GCANE]

IR satellite analysis is putting the approximate 850mb CoC at 13.9N 72.6W.
Vis sat showing a lot of inflow into that area.

[GCANE]

Looks like west winds are very close to the surface.
Swirl is also gaining some convection.

[Aric Dunn]

Looks like west winds are very close to the surface.
Swirl is also gaining some convection.

https://i.imgur.com/aHcn8xZ.png

Yeppers.
more and more developing low level cloud line flowing into the SW side. this convection is getting it done..

just needs to continue into the evening and overnight.

[GCANE]

There goes the shear.
Ice imagery indicates a large area of UL cirrus outflow quickly developing on the east of the CoC.

[Steve]

People are really sleeping on this system right now, incredibly high THC content lies ahead of it, shear in the vicinity of the system is very low, and to my amateur eye it sure looks to be getting its act together

Jamaica is not too too far away mon.

[GCANE]

[GCANE]

BTW, 925mb vort quickly developing in the GoM.
Genevieve debris firing up more spotty convection.
Could alter the setup in the GoM if the convection continues for a couple days.
The ever-present pool of high-CAPE air SE of Houston is a permanent fixture.

[cycloneye]

97L INVEST 200819 1800 14.1N 73.4W ATL 30 1008

[GCANE]

And there goes a good chunk of the dry air.
Countdown continues at T minus 6, 5 ....

[Astromanía]

Watching this closely, It's going to affect Mexico, isn't?

[Cpv17]

And there goes a good chunk of the dry air.
Countdown continues at T minus 6, 5 ....

https://i.imgur.com/7eOLlzA.png

Is it possible that a new center could form further north under that flare up?