ATL: GERT - Remnants - Discussion

[Subtrop]

AL, 99, 2023081700, , BEST, 0, 111N, 363W, 20, 1009, DB, 34, NEQ, 0, 0, 0, 0, 1011, 150, 75, 0, 0, L, 0, , 0, 0, INVEST, S, 0, , 0, 0, 0, 0, genesis-num, 018,

https://ftp.nhc.noaa.gov/atcf/btk/bal992023.dat

[ElectricStorm]

This one probably has a pretty good chance of developing despite the last couple GFS runs backing off. Should be a recurve but too early to know if it's a Bermuda threat.

[ElectricStorm]

1. Central Tropical Atlantic (AL99):
Disorganized showers and thunderstorms continue in association with
an elongated trough of low pressure centered about 875 miles
west-southwest of the Cabo Verde Islands. Environmental conditions
appear conducive for gradual development of this system, and a
tropical depression could form during the next several days while
it moves west-northwestward at 10 to 15 mph across the central
tropical Atlantic.
* Formation chance through 48 hours...medium...40 percent.
* Formation chance through 7 days...medium...60 percent

[LarryWx]

0Z UKMET: yet again a TS in the Leewards, but this run then has it go NNW and later NNE track that aims well to the E of Bermuda:

NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 84 HOURS
FORECAST POSITION AT T+ 84 : 16.9N 58.9W

LEAD CENTRAL MAXIMUM WIND
VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)
-------------- ---- -------- ------------- -------------
1200UTC 20.08.2023 84 16.9N 58.9W 1006 28
0000UTC 21.08.2023 96 17.6N 60.3W 1005 34
1200UTC 21.08.2023 108 19.2N 60.9W 1005 42
0000UTC 22.08.2023 120 20.2N 61.4W 1003 39
1200UTC 22.08.2023 132 22.0N 61.8W 1003 44
0000UTC 23.08.2023 144 23.8N 62.3W 1004 35
1200UTC 23.08.2023 156 25.6N 61.8W 1005 31
0000UTC 24.08.2023 168 26.9N 60.9W 1004 27

[USTropics]

Here is a general outline of the systems currently in the Atlantic to clear up any confusion and a blend of the 5-day 00z GFS/ECMWF tracks:

[abajan]

Excerpt from 8 AM Tropical Weather Update:

Disorganized showers and thunderstorms continue in association with
an elongated trough of low pressure centered over 900 miles
west-southwest of the Cabo Verde Islands. Environmental conditions
appear conducive for gradual development of this system, and a
tropical depression could form during the next several days while
it moves west-northwestward at 10 to 15 mph across the central
tropical Atlantic.
* Formation chance through 48 hours...medium...40 percent.
* Formation chance through 7 days...medium...60 percent.

[cycloneye]

AL, 99, 2023081712, , BEST, 0, 115N, 384W, 20, 1009, DB

[Sciencerocks]

[johngaltfla]

The local forecasts do seem to be latching on to a storm solution off the East Coast of FL if their wind/rain predictions are accurate for next week.

[Blown Away]

IMO NHC going to shift 99L's cone more W or tag a new Invest to the disturbance to the W of 99L. Clearly this afternoon the models are backing off 99L in favor of the disturbance to the W.

[Sciencerocks]

[ElectricStorm]

With the area to the west becoming favored by the models, this probably won't end up doing much

What a difference a day makes for the models, yesterday it looked like this had a decent chance

[cycloneye]

AL, 99, 2023081800, , BEST, 0, 125N, 408W, 25, 1009, DB

[BobHarlem]

Convection increasing again on 99Ltonight. But the whole Atlantic here.. jeesh.

[Teban54]

With 99L's current convective activity (much better than 98L despite having lower formation chances), I wonder if it's trying to defy model expectations and if we'll see three TCs in the MDR. Not very likely, but still.

[Teban54]

7-day chances down to 40%.

2. Central Tropical Atlantic (AL99):
An elongated trough of low pressure located more than 1000 miles
west-southwest of the Cabo Verde Islands is producing some
disorganized showers and thunderstorms. Environmental conditions are
only marginally conducive for further development of this system,
but a tropical depression could still form during the next couple of
days while it moves west-northwestward at 10 to 15 mph across the
central tropical Atlantic. Thereafter, upper-level winds are
forecast to become unfavorable for any further development.
* Formation chance through 48 hours...medium...40 percent.
* Formation chance through 7 days...medium...40 percent.

[USTropics]

The ECMWF 00z closes this off briefly in the next 24 hours:


The issue begins when 99L begins lifting north at 48 hours, where there is strong westerly flow aloft (purple). Meanwhile, we still have easterly trades (red) at the low-levels, and this creates a sheared environment:


If you look at the 48 hour 00z ECMWF sounding, you can see this shear evident as we build levels in the atmosphere. In combination with a relatively dry background environment (~50-60% RH values):


The caveat to this is at 72 hours, while the system is clearly sheared, the short-term corrections in a more consolidated system creates a moisture surge north of the Puerto Rico/Greater Antilles that provides a more suitable environment for the area SW of 99L currently:


past 5 runs of the ECMWF for 5-day (120 hour) trend:

[jlauderdal]

The ECMWF 00z closes this off briefly in the next 24 hours:
https://i.imgur.com/L3ydhIP.png

The issue begins when 99L begins lifting north at 48 hours, where there is strong westerly flow aloft (purple). Meanwhile, we still have easterly trades (red) at the low-levels, and this creates a sheared environment:
https://i.imgur.com/ouFzM7a.png

If you look at the 48 hour 00z ECMWF sounding, you can see this shear evident as we build levels in the atmosphere. In combination with a relatively dry background environment (~50-60% RH values):
https://i.imgur.com/avjr26r.png

The caveat to this is at 72 hours, while the system is clearly sheared, the short-term corrections in a more consolidated system creates a moisture surge north of the Puerto Rico/Greater Antilles that provides a more suitable environment for the area SW of 99L currently:
https://i.imgur.com/HSPKv9y.png

past 5 runs of the ECMWF for 5-day (120 hour) trend:
https://i.imgur.com/G6pkCph.gif

Excellent analysis as always. These weak systems will clear out over the next week or so and then the basin can really get going, its marginally favorable right now, best shot seems to be the gulf system but not until it gets west of 85

[TomballEd]

I know it faces issues, but of the lemons, oranges and cherries it looks best, to me, of all of them. Hard to tell from satellite, but it may not be that far from closing a circulation.

[cycloneye]

AL, 99, 2023081812, , BEST, 0, 133N, 440W, 25, 1009, DB