ATL: FOUR - Potential Tropical Cyclone - Discussion

[SouthDadeFish]

Looks like a wave axis. Satellite can be quite deceiving.

Yup. Vorticity looks to still be focused in mid-levels for now. I would imagine if convection persists, we will see a closed surface vortex form before landfall.

[cycloneye]

NHC will initiate advisories on Potential Tropical Cyclone Four, located over the southwestern Gulf of Mexico, at 400 PM CDT (2100 UTC).

[NDG]

Looks like a wave axis. Satellite can be quite deceiving.

Yup. Vorticity looks to still be focused in mid-levels for now. I would imagine if convection persists, we will see a closed surface vortex form before landfall.

I am sure it will develop an LLC as soon as it makes landfall tomorrow as it has been the case this season so far

[skyline385]

Looks like a wave axis. Satellite can be quite deceiving.

Yup. Vorticity looks to still be focused in mid-levels for now. I would imagine if convection persists, we will see a closed surface vortex form before landfall.

I am sure it will develop an LLC as soon as it makes landfall tomorrow as it has been the case this season so far

Will probably also develop an eye once inand


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[wxman57]

Yup. Vorticity looks to still be focused in mid-levels for now. I would imagine if convection persists, we will see a closed surface vortex form before landfall.

I am sure it will develop an LLC as soon as it makes landfall tomorrow as it has been the case this season so far

Will probably also develop an eye once inand

Peaking in intensity over northern Chihuahua, MX? Maybe. Still waiting for the NHC's graphics. Their lat/lon points look right on TVCN, which is what I followed. Landfall near 25N.

[WiscoWx02]

Yup. Vorticity looks to still be focused in mid-levels for now. I would imagine if convection persists, we will see a closed surface vortex form before landfall.

I am sure it will develop an LLC as soon as it makes landfall tomorrow as it has been the case this season so far

Will probably also develop an eye once inand


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It’s a PTC now…that’s a double strike against it in my opinion PTC’s always take forever to develop i.e. PTC01L and PTC02L this year alone and the PTC’s last year…plus this area is nowhere near closed at the surface based on recon…all easterly wind. Not even a notch in the flow to be found.

[SoupBone]

I am sure it will develop an LLC as soon as it makes landfall tomorrow as it has been the case this season so far

Will probably also develop an eye once inand


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It’s a PTC now…that’s a double strike against it in my opinion PTC’s always take forever to develop i.e. PTC01L and PTC02L this year alone and the PTC’s last year…plus this area is nowhere near closed at the surface based on recon…all easterly wind. Not even a notch in the flow to be found.

This thread got really quiet when recon readings started coming in. I definitely learned a lot today.

[wxman57]

Still no track graphics on the NHC website, or am I missing something?

P.S. Links to graphics are starting to appear now.

[USTropics]

Still no track graphics on the NHC website, or am I missing something?

Looks like a server issue, other products are missing as well (like the GIS shapefiles they use to produce the graphics).

[Hammy]

NHC notes there is actually zero model support for development so I wonder if they jumped the gun a bit on the 70% chance. Still good to have watches/warnings up either way.

[aspen]

The NW to SE pass finally showed a change in wind directions around 20.5-21.5N and 94.5-95.0W, so it looks like an LLC is developing.

[weeniepatrol]

NHC notes there is actually zero model support for development so I wonder if they jumped the gun a bit on the 70% chance. Still good to have watches/warnings up either way.

I see 80% now

[REDHurricane]

Look at that outflow -- certainly looks like a TS or something that will very soon become a TS. 80% likely means the NHC is nearly ready to classify it as Danielle but will wait until tonight's update to do so, right? Given that this system is going to make landfall in 24-32 hours, I'd figure they would be less hesitant to call it a TS than if it were out in the open sea, but we'll just have to wait and see.

[Audrey2Katrina]

I'll admit it looks nice from satellite view; but it had better vorticity yesterday than what I'm seeing today. NO other global model, that I know of yet, seems to be developing this system, though I by no means checked them all, One thing I can say after looking at a lot of sat. data on ground wind speeds, there is no way I believe this system has "one minute sustained" winds of 35 mph. But I can almost guarantee you that by this time tomorrow.... we'll see a "Danielle" posted up there. I think this system is headed for landfall in extreme NE Mexico just a little south of Texas, then a veer to a more northerly (than straight NW) course once inland.

A2K

[Hammy]

NHC notes there is actually zero model support for development so I wonder if they jumped the gun a bit on the 70% chance. Still good to have watches/warnings up either way.

I see 80% now

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

It almost feels like they raised it in response to my claim

If we're getting a LLC forming it looks about in here based on the wind direction from the last pass.

[Steve]

The NW to SE pass finally showed a change in wind directions around 20.5-21.5N and 94.5-95.0W, so it looks like an LLC is developing.

Thanks for that recon update. QPF shows big relief coming next week for some drought stricken areas of east and northeast Texas with the boundary and tropical moisture coming together. Here’s the 7 day totals and the current US Drought map showing large scale reversals.

https://www.wpc.ncep.noaa.gov/qpf/p168i.gif?1660946402

https://droughtmonitor.unl.edu/CurrentM ... nitor.aspx

It’s just a cool little system out in the Gulf mid August. Best I can tell MJO is about to Phase 1 or will be tonight (then Phase 2 for a week or so). And when you look at the temperature and precipitation patterns for JAS (posted ASO the other day), you can see the correlation with the much cooler and rainier SEUS and Texas. So 99l or whatever it becomes and then its remnants are part of what you’d expect to see. You never know what’s going to contribute the cooling and moisture, but it’s often the tropics this time of year. If you looked at the QPF map, see how that correlates with the expectation. You may have to click JAS since I’m on mobile.

Temperature -Jul/Aug/Sep MJO Phase 2
https://www.cpc.ncep.noaa.gov/products/ ... _image.png

Precipitation-Jul/Aug/Sep MJO Phase 2
https://www.cpc.ncep.noaa.gov/products/ ... _image.png

What you should also note on the precipitation pattern is Phase 1 Jul/Aug/Sep. Check out S Texas and the N Mexican Gulf Coast. That’s where rain should be in Phase 1 which incidentally we probably will be at least for the next day or so before 2.

[ElectricStorm]

Ah I see we have PTC 4 now. I think the NHC forecast looks pretty good to me, should see Danielle tomorrow I would think.

[DorkyMcDorkface]

 https://twitter.com/tropicaltidbits/status/1560763125724434433

[jasons2k]

This came from Jeff Lindner at 4:27PM. My apologies for the delay - it's been a busy day...

NHC has begun advisories on Potential Tropical Cyclone #4

Tropical Storm Warnings are issued for the western Gulf coast from Boca de Catan, MX to Port Mansfield, TX including the southern Laguna Madre.

Discussion:

USAF plane investigating 99L this afternoon was unable to close off a defined low level circulation and instead found mainly southeast winds with very weak winds on the southwest edge of the large mass of deep convection. IR Satellite Loop for Invest 99L | Tropical Tidbits It is possible that a low level center may form near the southwest edge of the thunderstorms where the plane found weak winds, or a new low level circulation to develop further to the northeast closer to the deep thunderstorms and the mid level circulation. The plane did find an area of 25-30kt winds well to the northeast of the weak wind field near the active thunderstorms.

Track:

The system is generally moving toward the NW at around 15mph on the southwestern edge of a mid level high pressure ridge over the eastern Gulf of Mexico and this motion is expected to continue through the next 24-36 hours bringing the center ashore near the northeast coast of Mexico just south of the Rio Grande River. While there is some uncertainty in exactly where a low level center will form there is fairly high confidence on a general NW track through 48 hours and the guidance cluster is showing little spread.

Intensity:

The system is in favorable conditions for development with light vertical wind shear, warm sea surface temperatures and good upper level outflow to the north, south, and east. Additionally, developing tropical systems in this part of the Gulf of Mexico tend to have some help in developing due to the shape of the coastline which can help tighten a developing low level circulation. 99L is expected to make landfall as a 45mph tropical storm in 24 hours, although most guidance keeps the system in the 35-40mph range and the system will only have about 24 hours over the water. Tropical storm conditions may extend as far north as deep southern Texas depending on exactly where the center eventually forms.

It is likely 99L will become absorbed into the incoming low pressure and frontal system over Texas early next week and this may help to enhance already high forecasted rainfall amounts.

[Sciencerocks]