Tropical Wave over the Eastern Caribbean

[Teban54]

Despite the sustained convection, the issue is that low-level vorticity remains concentrated near 48W, while the hot towers have moved to near 54W.

Shown here is 850 mb, but 925 and 750 mb are similar.



Notice how there's still a visible low-level rotation near 48W, but not moving in tandem with the convection racing west.

[GCANE]

The low-level vorts are looking better today.
More concentrated and circular.
Trouble is convection is far to the west.
Need to see if convection fires over the vorts.

A 355K PV streamer is located to the east of the vorts.
Looks like it popped up in the last 12 hrs.
This may account for the convection displacement.

[chaser1]

Stitched MON evening METOP-B and METOP-C ASCAT passes. Looks like the broad, ill-defined center was near 9.5N 46W about 6 hours ago. Roughly 24 hours,ASCAT showed a broad center near 7.9N 40W, so it is gaining latitude, and likely enough to avoid running into SOAM. But we'll see what happens when it enters the accelerating easterlies of the eastern Caribbean "graveyard".

https://i.imgur.com/I2brB5n.png

I LOVE the stitched ASCAT by the way. Just a smart way of making good use out of what otherwise would have been discarded data . As for this wave though, it looks it won't even have to wonder about the East Caribbean Graveyard. The Central Atlantic Graveyard beat it to the test

[chaser1]

Despite the sustained convection, the issue is that low-level vorticity remains concentrated near 48W, while the hot towers have moved to near 54W.

Shown here is 850 mb, but 925 and 750 mb are similar.

https://i.imgur.com/2f8Y3iA.png

Notice how there's still a visible low-level rotation near 48W, but not moving in tandem with the convection racing west.

https://i.imgur.com/92yiktJ.gif

Yep, in fact you can even see arc clouds being spit out toward the east from what is left of that LLC. It's a head-scratcher.

[REDHurricane]

Still looking pretty decent tonight surprisingly enough. I know this system has very limited model support (though if you check the 18z Euro operational you can just barely see the vorticity signature show up), but I think a trackable tropical disturbance that has sustained convection near the center, a defined 850mb vort signature, and a low shear environment ahead of it during the middle of September is at least worthy of a 10/10 lemon... I get that the NHC is dealing with the funding issues right now, but they should remember that those lemons are free to give out!

[BobHarlem]

Very elongated axis and attached to the flow, this is a case where NHC is accurate with the current outlooks.

[REDHurricane]

Very elongated axis and attached to the flow, this is a case where NHC is accurate with the current outlooks.

I'm not saying that this even deserves an invest, but I think a 10/10 lemon would certainly be prudent for a visible tropical disturbance approaching the Windward Islands at the peak of climatological hurricane season, no? Sure, there's no model support for further development, but in the same way that the models were unanimously wrong about 91L developing, it's equally possible that the models could be unanimously wrong about a disturbance not developing over the upcoming weeks. Plus, like i said, it costs them nothing to put up a lemon simply as a heads up to the people in the islands that there is a very low (but not zero) chance that a tropical system could be coming their way over the next few days.

Either way it's not going to develop so this doesn't actually matter, but from a weather communication/public safety perspective (and given recent "surprise" hurricanes e.g. Otis) I don't see any reason for the NHC to not give disturbances like these a lemon on the TWO because that's essentially the entire point of having the NHC in the first place.

[AJC3]

Given the location of this area, and the fact that the MANATI images for ASCAT passes cut off at both 10N and 45W, I went a little nuts this morning and and stitched together 8 images from the two adjacent METOP-B/METOP-C passes (4 images from each) covering the area east of French Guiana.

For those who might be wondering how this can be done with Photoshop or Paint Shop Pro (which is what I use), you make a negative of each image, then use the Arithmetic function (Add Images) to add the RGB count values of each image to create a new image. Then make a negative of those the resultant images, take one of them and enlarge the canvas by 2X in both length and width in one direction (depending on which image you use), and copy/paste together (with some slight cropping). For these or any image with a white background, you have to make a negative of each image for this to work, since RGB count values for white are 255 and 0 for black. If you don't, then the blank (white) areas on the passes will cover up almost everything (wind barbs, LALO lines, scale labels), because when you add the RGB count values, most will be at 255 for each of those 3 primary colors.

Thanks for coming to my image preocessing Ted Talk. Shoot me an IM if you want to be walked through how to do this. It's not as menacing as it might sound, since if the area you want to look at falls completely within one 10x10 LALO box on MANATI, you'll only need to stich 2 images together instead of 8.

[REDHurricane]

Nice little burst of convection near the center this morning -- still elongated and without much juice so I'd assume it probably won't do much of anything before it crosses over the Windward Islands, but it could be a factor down the line if it manages to survive through the east/central Caribbean graveyard

[GCANE]

Still keeping an eye on this.
LL Vorts look a little better and some convection is moving more to the vorts.
Looks stationary as ICON forecasted.
MSLP is too high to entrain any Amazon moisture yet.
Very low shear and SAL.
No model support at this point.

[GCANE]

Convection picking up significantly at 11N 53W
Looks like it is driven by a 500mb vort.
Could easily get down to the surface if a long-duration hot tower fires.
Can also pick up Coriolis forcing at this latitude.
Watching more closely.

[Teban54]

[GCANE]

Looks like it may be slowly coming together.
Strong convection and low-level vort are very close to each other.'
TUTT to the north is helping to ventilate it.

[Nimbus]

Looks like it may be slowly coming together.
Strong convection and low-level vort are very close to each other.'
TUTT to the north is helping to ventilate it.

Won't the TUTT pull it north and OTS eventually or will it miss because its too weak?

[GCANE]

Looks like it may be slowly coming together.
Strong convection and low-level vort are very close to each other.'
TUTT to the north is helping to ventilate it.

Won't the TUTT pull it north and OTS eventually or will it miss because its too weak?

Likely the TUTT will cause it to make a more NW trajectory.
Once it gets on the SW side of the TUTT, development becomes much more likely.
Already seeing a hot tower zip across east to west.

[tropicwatch]

Might take some time. Currently it is surrounded by dry air.

Looks like it may be slowly coming together.
Strong convection and low-level vort are very close to each other.'
TUTT to the north is helping to ventilate it.

Won't the TUTT pull it north and OTS eventually or will it miss because its too weak?

Likely the TUTT will cause it to make a more NW trajectory.
Once it gets on the SW side of the TUTT, development becomes much more likely.
Already seeing a hot tower zip across east to west.

[ChrisH-UK]

Looks like it has moved north a bit and is now due east of Barbados and it looks to be in a healthy state.

GEOS-19 GeoProxy 2 Hour Loop

[GCANE]

Overshooting tops building higher altitude cirrus.
Starting to fire up.

[GCANE]

Looks like it's in a moderate shear gradient due in large part to the TUTT to the north.
Likely this is firing off the convection.
Convection is vigorous so could move the LL vort more under it.
If not, then could rain out.
We'll see in the next 24 hrs.

[TomballEd]

Made my own Zoomed in WeatherNerds floater. Not much low level but upper divergence looks awesome. The slight lower level vorticity is not well aligned with the ML/UL vorticity