ATL: ISAAC - Post-Tropical - Discussion

[Gustywind]

An area of low pressure centered about 500 miles west of the Cabo
Verde Islands is gradually becoming better defined, although the
associated shower and thunderstorm activity has not yet increased
much in organization. Environmental conditions are conducive for
further development, and a tropical depression is expected to form
within the next day or two while the system moves slowly westward
across the tropical Atlantic Ocean.
* Formation chance through 48 hours...high...80 percent.
* Formation chance through 5 days...high...90 percent.

They adjusted their official track south, with it heading almost due west for the next 5 days. Damn.

really... ho ho that's not the best 5 days projections we want to see Luis, Msbee and Gustywind. That's a pretty straight west race?

[Gustywind]

They fixed the Best Track to have the latitude at 13.5N at 00z.It has been in that same latitude since 12z.

AL, 92, 2018090612, , BEST, 0, 135N, 312W, 25, 1008, LO
AL, 92, 2018090618, , BEST, 0, 135N, 325W, 25, 1008, LO
AL, 92, 2018090700, , BEST, 0, 135N, 334W, 25, 1008, LO

Exactly. Great analysis Luis.

[Gustywind]

Tropical Weather Discussion...Updated
NWS National Hurricane Center Miami FL
850 PM EDT Thu Sep 6 2018

...SPECIAL FEATURES...

A broad and elongated area of low pressure is centered several hundred miles west-southwest of the Cabo Verde Islands is denoted
by a tropical wave with its axis along 32W/33W and extending from 04N to 20N. A 1008 mb low is on the wave axis near 14N32W.
This system is moving westward at 10 to 15 kt. The associated shower and thunderstorm activity has not yet increased in organization.
Latest satellite imagery shows scattered moderate isolated strong convection within 210 nm of the low in the NE quadrant, and
within of the low in the W quadrant. Scattered moderate convection is within 30 nm of 15N33W. Environmental conditions are conducive
for development, and a tropical depression is expected to form within the next day or two while the system moves slowly westward
or west-northwestward across the tropical Atlantic. The chance of this system becoming a tropical cyclone during the next 48 hours
remains high.

[MississippiWx]

They fixed the Best Track to have the latitude at 13.5N at 00z.It has been in that same latitude since 12z.

AL, 92, 2018090612, , BEST, 0, 135N, 312W, 25, 1008, LO
AL, 92, 2018090618, , BEST, 0, 135N, 325W, 25, 1008, LO
AL, 92, 2018090700, , BEST, 0, 135N, 334W, 25, 1008, LO

Exactly. Great analysis Luis.

That’s about as due west as you can get.

[Steve]

Euro/GFS don't do much with 92L... NHC seems pretty confident a TD will form...

I wonder how the MJO is going to play into it in the long run. Seems like the timing could be late in regards to the move from 8. NCEP swings it across to 2. But JMA brings it to 3 and the EC back to the circle. So while the Atlantic is juiced at the moment, maybe it won’t be later. I don’t know. Seems like 10-11 days we will be in not a as favorable of a Phase on this side. It will be close.

[1900hurricane]

I guess I should pay attention to this one too.

[TheStormExpert]

Wouldn't be surprised if 92L falls apart before the Caribbean at this point. Don't understand why the NHC still has 48hr. development chances at 80%.

[djones65]

What data or observations do you have to support such a bold statement?
I personally see an increasingly organizing low level circulation.... with a gradual increase in convection west of the center...
I am very confident this will be classified tomorrow based on the improvement of the low level circulation... it is not as elongated as previously and now more circular.

I am just curious...

[TheStormExpert]

What data or observations do you have to support such a bold statement?
I personally see an increasingly organizing low level circulation.... with a gradual increase in convection west of the center...
I am very confident this will be classified tomorrow based on the improvement of the low level circulation... it is not as elongated as previously and now more circular.

I am just curious...

This , and the fact that model support is dwindling.

 https://twitter.com/MJVentrice/status/1037864258845978626

[NDG]

[Bocadude85]

What data or observations do you have to support such a bold statement?
I personally see an increasingly organizing low level circulation.... with a gradual increase in convection west of the center...
I am very confident this will be classified tomorrow based on the improvement of the low level circulation... it is not as elongated as previously and now more circular.

I am just curious...

This , and the fact that model support is dwindling.

 https://twitter.com/MJVentrice/status/1037864258845978626

Correct me if I am wrong but didn’t the 12Z Euro and 18z GFS develop 92L into a hurricane?

[CyclonicFury]

I don't think 92L is going to fall apart. It still has strong model support (both GFS and Euro develop it into a strong TS/C1 hurricane). The circulation is gradually becoming better defined. SHIPS shows a very favorable environment for the next five days. It should have favorable conditions until around 50-55W. After that, it's uncertain.

[Hammy]

What data or observations do you have to support such a bold statement?
I personally see an increasingly organizing low level circulation.... with a gradual increase in convection west of the center...
I am very confident this will be classified tomorrow based on the improvement of the low level circulation... it is not as elongated as previously and now more circular.

I am just curious...

This , and the fact that model support is dwindling.

[tweet]https://twitter.com/MJVentrice/status/1037864258845978626

How is model support dwindling? This was always forecast (with the exception of a few runs) to be the weaker system between 92L and 93L, and all the major models develop it within 48 hours.

[djones65]

A tweet from Michael Ventrice about a "modeled" simulation of a future outcome is your reasoning for discounting what the real-time situation is?
Okay. I am glad that you offered some evidence of your reasons for thinking the experts at the NHC are wrong.
In my opinion, the circulation has become better organized, and overnight we will see a corresponding increase in deep convective organization.

[KAlexPR]

What data or observations do you have to support such a bold statement?
I personally see an increasingly organizing low level circulation.... with a gradual increase in convection west of the center...
I am very confident this will be classified tomorrow based on the improvement of the low level circulation... it is not as elongated as previously and now more circular.

I am just curious...

This , and the fact that model support is dwindling.

Reactionary, much? It's best to wait for consistency before jumping to bold conclusions. It has an 80% chance because conditions are favorable and there has been consistent support for development for more than a couple of days. Additionally, satellite imagery shows an organizing system with hints of an LLC trying to spin up. As for model support, both the GFS and the Euro still show a minimal hurricane in the medium range.

[NDG]

What data or observations do you have to support such a bold statement?
I personally see an increasingly organizing low level circulation.... with a gradual increase in convection west of the center...
I am very confident this will be classified tomorrow based on the improvement of the low level circulation... it is not as elongated as previously and now more circular.

I am just curious...

This , and the fact that model support is dwindling.

https://twitter.com/MJVentrice/status/1 ... 8845978626]

I don't see any dwindling model support, the two most trusted models still show this becoming a strong TS if not a hurricane as it enters the Caribbean.

Edit: BTW, the model MJVentrice showed has Florence tracking over Bermuda, no reliable model is showing that solution any more so what makes him trust it that 92L will fizzle out.

[cycloneye]

And..... look how convection is increasing.

[SoupBone]

As an aside, last night's GFS did have 92L fizzle out after passing through the Caribbean, only to regenerate at the tip of the Yucatan and head toward Florida.

[galaxy401]

90%/90%.

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 AM EDT Fri Sep 7 2018

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

Shower and thunderstorm activity associated with an area of low
pressure centered about 500 miles west of the Cabo Verde Islands has
become a little more concentrated over the past couple of hours, but
recent satellite data show that this system is still fairly broad
and elongated. Environmental conditions appear conducive for
development, and a tropical depression is expected to form within
the next day or so while the system moves slowly westward across the
tropical Atlantic Ocean.
* Formation chance through 48 hours...high...90 percent.
* Formation chance through 5 days...high...90 percent.

Which invest will be Helene, which will be Isaac? Place your bets!

[lando]

Euro with 92l a significant cane in the N CARIB at 977 low res 216 hours