ATL: ISAIAS - Post-Tropical - Discussion

[gatorcane]

Not looking too great because of the SAL as expected. Development looks to be slow and gradual. The very favorable conditions might have to wait until after is passes the islands. The GFS may be much too aggressive in deepening this, siding more with the Euro here.

[cycloneye]

Is moving fast and that will delay development at it approaches the Lesser Antilles. Hopefully it stays as it is now and bring needed rains to Puerto Rico and the U.S Virgin Islands that are going thru a severe drought.

[CourierPR]

Not looking too great because of the SAL as expected. Development looks to be slow and gradual. The very favorable conditions might have to wait until after is passes the islands. The GFS may be much too aggressive in deepening this, siding more with the Euro here.

I will side with the NHC at 60% and 90%.

[gatorcane]

Not looking too great because of the SAL as expected. Development looks to be slow and gradual. The very favorable conditions might have to wait until after is passes the islands. The GFS may be much too aggressive in deepening this, siding more with the Euro here.

I will side with the NHC at 60% and 90%.

I am not saying it won’t develop in the next 5 days but significant development (if any) may have to wait a bit longer

[cycloneye]

 https://twitter.com/AndyHazelton/status/1287358567188762624

[cycloneye]

12z Best Track:

AL, 92, 2020072612, , BEST, 0, 113N, 360W, 20, 1010, DB, 34, NEQ, 0, 0, 0, 0, 1012, 120, 50, 0, 0, L, 0, , 0, 0, INVEST, M, 0, , 0, 0, 0, 0, genesis-num, 021,

[Shell Mound]

Not looking too great because of the SAL as expected. Development looks to be slow and gradual. The very favorable conditions might have to wait until after is passes the islands. The GFS may be much too aggressive in deepening this, siding more with the Euro here.

I will side with the NHC at 60% and 90%.

I am not saying it won’t develop in the next 5 days but significant development (if any) may have to wait a bit longer

Aside from the SAL surge to the north and west, conditions are actually quite conducive now. Vertical wind shear is relatively low, outflow is well established, and low-level vorticity, however broad, is vigorous and evident on visible satellite imagery. Additionally, 92L is in close proximity to the ITCZ, so ample PWATs exist nearby. One can already see convection attempting to develop near the vorticity maximum during the diurnal minimum. Once a low-level centre becomes established, I would not be surprised to see steady, even rapid, intensification within the next five days, especially once 92L approaches the Lesser Antilles.

Not exactly sure as to why people are leaning toward the “bearish” side in regard to 92L’s short-term development...

[Frank2]

https://www.star.nesdis.noaa.gov/GOES/s ... &length=24

Nice view of 92L and the accompanying dust and dry air.

It seems strong waves exiting the mainland cause some SAL outbreaks, or at least strengthen them - the chicken or the egg question...

[drezee]

 https://twitter.com/andretrotter/status/1287378495316930560

[toad strangler]

 https://twitter.com/IreneSans/status/1287271727517638656

[MetroMike]

https://twitter.com/IreneSans/status/1287271727517638656?s=20

I will go with I-zay-us keep it simple to say.

[NDG]

Not looking too great because of the SAL as expected. Development looks to be slow and gradual. The very favorable conditions might have to wait until after is passes the islands. The GFS may be much too aggressive in deepening this, siding more with the Euro here.

The GFS so far has a bad track record in the last few days in its medium range forecast, horrible is the word.

[eastcoastFL]

Can anyone tell me where the circulation is on this one? I feel like I see two different circulations but I’m sure that’s not correct...

[USTropics]

Unfortunately lead time for genesis hasn't been great from the operational global models this season. The GFS forecast at 72 hours has been, let's say, lacking.

72 hour forecast for Gonzalo on the 19th:


What actually happened 3 days later:


I'd give it a pass on Gonzalo given the system's size/background state, but Hanna was even worse:

72 hour forecast for Hanna on the 23rd:


What actually happened 3 days later:


Ensembles and biases/trends become even more important with the low lead time by the globals this season (and this is seen in other basins as well, not just an Atlantic issue).

[toad strangler]

92L is one potent looking wave.

[toad strangler]

Unfortunately lead time for genesis hasn't been great from the operational global models this season. The GFS forecast at 72 hours has been, let's say, lacking.

72 hour forecast for Gonzalo on the 19th:

What actually happened 3 days later:

I'd give it a pass on Gonzalo given the system's size/background state, but Hanna was even worse:

72 hour forecast for Hanna on the 23rd:

What actually happened 3 days later:

Ensembles and biases/trends become even more important with the low lead time by the globals this season (and this is seen in other basins as well, not just an Atlantic issue).

ooof that's a huge swing and miss on Hanna. #nogood

[TheStormExpert]

Emily 2011 anyone?

 https://twitter.com/derekortt/status/1287276547343351809

[jlauderdal]

Emily 2011 anyone?

 https://twitter.com/derekortt/status/1287276547343351809

How could i forget how poorly the models handled emily 2011

Sent from my SM-G973U using Tapatalk

[USTropics]

This is not just a GFS issue either, the ECMWF 72 hour operational forecast has also been suspect (in multiple basins now):

00z forecast on July 19 for Gonzalo:


What actually happened 3 days later:


00z forecast on July 23 for Hanna:


What actually happened:

[aspen]

Since the GFS and Euro have been so bad with the development of Gonzalo and Hanna, and those issues definitely won’t magically correct themselves for 92L just days afterwards, it’s probably likely that the actual future of 92L will be very different. Two broad possibilities seem the most plausible:

1.) the complete opposite of Gonzalo and Hanna happens — 92L fails to develop despite strong model support and either rams into the Greater Antilles or becomes Gonzalo 2.0, gulping SAL and limping its way to its deathbed.

2.) 92L exceeds expectations and becomes a stronger system than any of the models were anticipating, either on the same track they’re now showing or on a Caribbean Cruiser track.

I wouldn’t rule out a Gonzalo Sequel from 92L, mainly because it’s still late July and not late August (regardless of what 2020 thinks), but as I mentioned yesterday, I find a complete bust hard to believe when systems have been developing out of the blue. If models are showing something strong for once, then there’s a good chance they’re at least somewhat right.