ATL: ISAIAS - Post-Tropical - Discussion

[chaser1]

It's still a nothing-burger. That may change tomorrow or early Thursday. Westward-ho! Shift those models again.

[Hammy]

Why are they consistently avoiding the area that the LLC would most likely be?

[STRiZZY]

Why are they consistently avoiding the area that the LLC would most likely be?

I guess they know something we don't.

[tropicwatch]

SUMMARY OF 200 AM AST...0600 UTC...INFORMATION
----------------------------------------------
LOCATION...14.9N 60.3W
ABOUT 50 MI...80 KM ENE OF MARTINIQUE
ABOUT 450 MI...725 KM ESE OF SAN JUAN PUERTO RICO
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...WNW OR 295 DEGREES AT 25 MPH...41 KM/H
MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES

[CM2]

Why are they consistently avoiding the area that the LLC would most likely be?

I know, I don't think anybody actually knows where the storm is located. For all we know it might of actually buggered off into the Caribbean already.

[STRiZZY]

SUMMARY OF 200 AM AST...0600 UTC...INFORMATION
----------------------------------------------
LOCATION...14.9N 60.3W
ABOUT 50 MI...80 KM ENE OF MARTINIQUE
ABOUT 450 MI...725 KM ESE OF SAN JUAN PUERTO RICO
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...WNW OR 295 DEGREES AT 25 MPH...41 KM/H
MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES

DISCUSSION:
"Environmental conditions are expected to be conducive for
additional development, and a tropical storm is forecast to form
later today."

[SFLcane]

Winds up to 45 mph at 2am.

[Shell Mound]

Based on current satellite trends, I think there is a decent chance that this will “close off” and be christened Isaias by 11:00 a.m. EDT (15:00 UTC).

[hurrtracker79]

 https://twitter.com/hurrtrackerapp/status/1288362604440756224

[AdamFirst]

5 AM disco

000
WTNT44 KNHC 290846
TCDAT4

Potential Tropical Cyclone Nine Discussion Number 4
NWS National Hurricane Center Miami FL AL092020
500 AM AST Wed Jul 29 2020

Satellite and surface data indicate that the system remains a
trough of low pressure, elongated from SSW to NNE, with almost all
of the strong winds far north of the center position. The most
significant curvature in the low-level wind field and on radar are
near Dominica now, which has good continuity from the previous
advisory, so this feature will continue to be used as the center.
A combination of unflagged SFMR winds from an Air Force plane and
earlier scatterometer winds support 40 kt as the initial wind speed.

The initial motion estimate is about the same as before or 295/20
kt. The ridge to the north of the disturbance is forecast to remain
strong for the next 36 h, which keeps the system moving speedily in
a general west-northwestward direction just south of the Leeward
Islands today, and near or over the Greater Antilles on Thursday.
The ridge is forecast to weaken after that time, which should cause
the cyclone to slow down, and potentially gain more latitude over
the southwestern Atlantic. The model guidance is generally showing
a narrow ridge persisting for a bit longer, however, causing a
small south and west shift in the new NHC forecast at long range.
However, it should be emphasized that this forecast track is highly
uncertain until a true center forms.

Satellite images indicate that a large burst of convection is
occuring near the poorly defined center, which will likely lead to
the system becoming a tropical storm later today. Further
intensification is possible before landfall in the Dominican
Republic on Thursday, assuming the structure continues to improve,
and the wind speed forecast is adjusted slightly higher in the near
term. The cyclone will probably take some time to recover after
moving over the very high mountains of Hispaniola, and some of the
guidance after that time shows an increase in southwesterly shear
over the Straits of Florida that could limit the potential of the
cyclone. Simply put, there are a lot of hurdles in the system's
way, so it is best to stay on the conservative side at the moment
and continue to stress the large uncertainty after it leaves the
Caribbean. Little change was made to the forecast intensity,
although the guidance has come down at longer range for many of the
models.

Interests in Hispaniola, the Bahamas, Cuba, and Florida should
continue to monitor forecasts as changes to both the track and
intensity are likely.

[GCANE]

I don't see anything moving west to east on radars.
Looks like any type of friction / convergence interaction with the islands didn't produce a surface low.
Circulation is above the top of the boundary layer.

This is a big ass wave packing a lot of moisture which will move thru the Carib.
Any low that may develop at the tip of the wave will either be shredded by the islands or by the UL Jet from the Rossby Wave that will move thru the Midwest.
Any major development action will likely happen in the west Carib / GOM.
Here, GFS is forecasting the development of a Anticyclonic Rossby Wave Break to be over or near the Yucatan Channel on Sunday.

Stay tuned.

[Blown Away]

Still looks like a trough, but convection popping around the NHC 5am point area... @15.7/61.0.

5am disco noting intense storms well N of their 15.3N 5am position, now maybe the center relocates a little N once land interaction starts. It looked like consolidation would happen a bit farther S a few hours ago. No clear anything!

[NDG]

Not surprising that the recon did not find a closed circulation, ASCAT clearly showed it last night that it was still not closed.

[SFLcane]

Convection looks a bit more concentrated this morning. If trend continues we "may" see an upgrade later this morning.

[Vdogg]

Zoomed out satellite IR presentation starting to look pretty classic, and there is a noticeable North component to the central convection. It's still possible that a large portion of the storm misses the shredder, none the worse for wear.

[Nimbus]

IR signature doesn't look closed but the models have all shifted west either south Florida or gulf tracks.
No idea why the models didn't see that SW lobe becoming dominant, but they can shift the track west again if the system spins up late and passes south of Hispaniola.
Might still be Thursday or later before we can talk about a CONUS landfall intelligently.

[Vdogg]

Convection looks a bit more concentrated this morning. If trend continues we "may" see an upgrade later this morning.

https://i.imgur.com/Zd9XEdz.gif

It's also slowed down a little (not much, only by 2 mph). That slow down is probably helping it organize a little bit.

[Vdogg]

IR signature doesn't look closed but the models have all shifted west either south Florida or gulf tracks.
No idea why the models didn't see that SW lobe becoming dominant, but they can shift the track west again if the system spins up late and passes south of Hispaniola.
Might still be Thursday or later before we can talk about a CONUS landfall intelligently.

Not sure I'm buying a gulf solution just yet, especially considering that it has finally taken on a more northerly turn.

[msbee]

Good morning
The wind is very high this morning in St Maarten.
Definitely tropical storm force gusts.
No rain. Cloudy skies.
Government has ordered all businesses closed by 11:00 AM. Everyone off roads by noon.
After Irma, no one is taking any chances.
Thankfully this is no Irma.

[Shell Mound]

This probably has some of the strongest outflow and mid-level rotation I have ever seen in association with a system that doesn’t yet have a closed LLC.

If it were only more vertically stacked/aligned, I’d liken its overall appearance to that of a well-formed hurricane, lopsidedness (tilt) notwithstanding.

 https://twitter.com/MJVentrice/status/1288427718107967488