ATL: ISAIAS - Post-Tropical - Discussion

[eastcoastFL]

Nhc isn’t buying into it dying as many here seem to think

From Disco:

Little change in strength is expected through
Sunday, and Isaias is forecast to remain a hurricane during this
time. Slow weakening is expected to begin by late Monday

[Dean4Storms]

It’s getting stretched west to east with the shear and on a weakening trend, that is also why the LLC is now moving more WNW out from under the MLC and upper level cyclone. The storm is not stacked and dry air is going to impede it more. Not telling anyone to lower their guard along the Coasts but you can clearly see what is taking shape on visible and WV imagery. This is good news and hopefully it weakens to nothing more than weak TS unable to inflict much erosion and damage along the coasts.
This is my opinion only and please go by your local officials and official weather forecasts.

As of 11am NHC still forecasting an 80mph cat 1 approaching SFL

If it’s able to occasionally jog back under the MLC I could see that, but not looking good right now.

[Dean4Storms]

Nhc isn’t buying into it dying as many here seem to think

From Disco:

Little change in strength is expected through
Sunday, and Isaias is forecast to remain a hurricane during this
time. Slow weakening is expected to begin by late Monday

Nobody is talking about it killing over, but weakening is a possibility with its current state.

[HurricaneFrances04]

Stewart wrote this advisory lol

However, the still
impressive vertical structure of the cyclone should allow for some
re-strengthening after the center moves back over the warm Gulf
Stream by this evening. The current SHIPS analyzed westerly
vertical wind shear of 25 kt could be too high due to the model
incorporating some of the storm's outflow. The models forecast the
shear to weaken somewhat over the next 36 h while Isaias is moving
over the Gulf Stream, and the 06Z UKMET shows Isaias moving
underneath a 200-mb anticyclone, which would normally favor some
strengthening. Given all of these factors, the official forecast
maintains a steady intensity through Monday night.

[AutoPenalti]

Stewart wrote this advisory lol

However, the still
impressive vertical structure of the cyclone should allow for some
re-strengthening after the center moves back over the warm Gulf
Stream by this evening. The current SHIPS analyzed westerly
vertical wind shear of 25 kt could be too high due to the model
incorporating some of the storm's outflow. The models forecast the
shear to weaken somewhat over the next 36 h while Isaias is moving
over the Gulf Stream, and the 06Z UKMET shows Isaias moving
underneath a 200-mb anticyclone, which would normally favor some
strengthening. Given all of these factors, the official forecast
maintains a steady intensity through Monday night.

Gotta love Stacy

[artist]

Stewart wrote this advisory lol

However, the still
impressive vertical structure of the cyclone should allow for some
re-strengthening after the center moves back over the warm Gulf
Stream by this evening. The current SHIPS analyzed westerly
vertical wind shear of 25 kt could be too high due to the model
incorporating some of the storm's outflow. The models forecast the
shear to weaken somewhat over the next 36 h while Isaias is moving
over the Gulf Stream, and the 06Z UKMET shows Isaias moving
underneath a 200-mb anticyclone, which would normally favor some
strengthening. Given all of these factors, the official forecast
maintains a steady intensity through Monday night.

Gotta love Stacy

He does get it right alot of the time...

Revisit his discussion of Hanna 24 hours before she became a hurricane-
Hanna's convective cloud shield remains very asymmetrical with the
bulk of the convection confined to the southern semicircle despite
the otherwise symmetrical and expanding upper-level outflow pattern.
More recently, some deep convection has developed near the center
and the aforementioned possible mid-level eye feature. Hanna is
forecast to remain in relatively low vertical wind shear regime and
over SSTs of 30C or more, a combination that typically favors
significant intensification. However, nearby dry mid-level air noted
in 1200Z soundings from Corpus Christi and Brownsville has been
eroding and preventing convection from developing in the northwest
quadrant and near the center, which has inhibited strengthening over
the past couple of days despite the low shear conditions. The latest
global model guidance shows the dry air mixing out in about 24 h
just prior to landfall, which should allow for at least gradual
strengthening until landfall occurs in about 30 h or so. However, if
an eyewall forms during the next 12 h, then it is possible that
Hanna could be near 60 kt when it makes landfall. The new NHC
intensity forecast is similar to the previous advisory, and is a
blend of the IVCN and HCCA consensus intensity forecasts.

[LCfromFL]

5500 CAPE to the NE of FL, 5000 to the west.
Clear skies over the state. No CIN.
Ominous.

GCANE - can you explain in layman’s terms for us amateurs, please?

CAPE is a measure of unstable air.
5000+ is extreme.
That will fill in over FL later today.
Skies are clear this morning which rapidly heats the land.
The rising heat mixed with the very unstable air will set off large thunderstorms later today.
The moist remains of the thunderstorms will flow into Isaias adding fuel and likely give it a nudge west.

Great explanation, GCANE.

[gatorcane]

Looks like we may get a completely exposed LLC soon. Center crossing northern Andros island. West side of island has some breaks in the clouds. This is a hurricane?

[AutoPenalti]

Looks like we may get a completely exposed LLC soon. Center crossing northern Andros island. West side of island has some breaks in the clouds. This is a hurricane?

Welp, according to Stewart it is, may just be temporary weakening.

[DestinHurricane]

Going to have to go NNW soon to make NHC track.

[HurricaneEnzo]

Current state of Isaias is it looks like garbage. Its convective mass isn't even moving as the LLC pulls away. Not saying it won't eventually recover but I have to believe there will be at least some short term weakening. Maybe back to TS strength

https://www.tropicaltidbits.com/sat/sat ... product=ir

Sent from my SM-N975U using Tapatalk

[DestinHurricane]

Is that a new eyewall forming back east on radar?

[Kat5]

Should start a NNW movement in a few. The 06z GFS within 12 hours makes sense.

[Hurricaneman]

Perhaps they need a lesson in Geography, central is not northern
Perhaps trying to make their forecast track look better

...ISAIAS MAKING LANDFALL ON NORTHERN ANDROS ISLAND

https://i.imgur.com/9nxscaj.png

Oops, nobody’s perfect

[DestinHurricane]

Should start a NNW movement in a few. The 06z GFS within 12 hours makes sense.

06Z Gfs moves it off Andros too far north.

[cp79]

Time to put this thing on life support. It looks bad but that’s great news for Fla and parts north.

[Steve]

This thing looks dreadfully sick on IR this morning. The deepest convection near the center is confined between Andros and Eleuthera. Cloud tops have been warming, with storms collapsing and pushing outflow to the west. That could, incidentally, actually help to moisten the environment heading toward Florida. I don’t think it’ll be down for too long.

None of this should be a surprise to anyone who looks at the IR simulations. Nor will it be a surprise later when it blows back up.

HRRR 10:00am


HRRR 10:00pm


NAM 10:00am

[Steve]

Time to put this thing on life support. It looks bad but that’s great news for Fla and parts north.

It may or may not hit Florida. But this post won't age well even today.

[Blown Away]

https://www.tropicaltidbits.com/sat/sat ... roduct=vis
Is that the circulation center moving NW about to exit Andros on the NW side. Zoom in.

[NDG]

Nassau is now in the warm moist section of the Hurricane.
Now that's what temps & dewpoints are supposed to be during a hurricane.

Conditions at: MYNN observed 01 August 2020 15:00 UTC
Temperature: 26.0°C (79°F)
Dewpoint: 25.0°C (77°F) [RH = 94%]
Pressure (altimeter): 29.78 inches Hg (1008.5 mb)
Winds: from the ESE (110 degrees) at 36 MPH (31 knots; 16.1 m/s)
gusting to 49 MPH (43 knots; 22.4 m/s)
Visibility: 6 miles (9 km)
Ceiling: 2000 feet AGL
Clouds: scattered clouds at 1600 feet AGL
broken clouds at 2000 feet AGL
overcast cloud deck at 8000 feet AGL
Present Weather: -RA (light rain)
MYNN 011500Z 11031G43KT 9000 -RA SCT016CB BKN020 OVC080 26/25 A2978