ATL: ISAIAS - Post-Tropical - Discussion

[SecondBreakfast]

Looks like our friend here, whether he’s tropical or no will be rolling over us as low tide moves into full moon high tide up here on Long Island. Yuck.

[wxman57]

I'm seeing signs of rapid organization. Wind shear dropping and squalls are rotating west of center. Could still make hurricane strength by tonight.

Oh bummer, I was hoping you'd say it was going to fall apart

Most definitely it will fall apart, by the time it reaches Maine on Wednesday morning.

[Vdogg]

Surprised they went with 70, but NHC is sticking to their guns and they're still calling for a hurricane.

[southportwxfan]

I'm seeing signs of rapid organization. Wind shear dropping and squalls are rotating west of center. Could still make hurricane strength by tonight.

Oh bummer, I was hoping you'd say it was going to fall apart

Most definitely it will fall apart, by the time it reaches Maine on Wednesday morning.

LOL- I was kind of hoping that it would be a bit sooner. I don't know whether to root for it to go more east- which will hit me in Southport, or more west- which will get me in Raleigh. Right now I believe I'm in a no win situation

[weathaguyry]

Looks like our friend here, whether he’s tropical or no will be rolling over us as low tide moves into full moon high tide up here on Long Island. Yuck.

Yup, it doesn’t take a lot to cause flooding here, so this will be more than enough, especially with the full moon. I’m in Southern Nassau on the bay in Island Park. High tide is at 9pm for us on tomorrow, so it’ll depend on how well the strongest winds time up with the high tide.

[wxman57]

Interesting that the NHC used the descriptive term "disheveled", as that's exactly the term I used in our last advisory, before I changed it to "ragged". They see the same thing I do, shear decreasing, squalls increasing all around the center. It doesn't take long for a TS to become a H given a favorable environment. At least it won't have a large area of hurricane-force wind.

[Ken711]

11:00 AM Advisory

The decrease in the shear should result in less tilt to the cyclone, allowing Isaias to strengthen and regain hurricane status just before making landfall, and most of the intensity guidance shows a 60-65 kt system at that time.

[Ntxwx]

Surprised they went with 70, but NHC is sticking to their guns and they're still calling for a hurricane.

Who isn’t calling for a Hurricane?

[wxman57]

Surprised they went with 70, but NHC is sticking to their guns and they're still calling for a hurricane.

Who isn’t calling for a Hurricane?

Note that it will be impossible to differentiate between a 70 mph TS and a 75 mph hurricane. The only difference is that "hurricane" sounds scarier. Yes, this could become a hurricane, but it will only have hurricane-force wind over a tiny area NE of the center. Winds may be 20-25 mph less west of the center, and 35 mph less southwest of the center. It may not even have TS wind SW of the center at landfall.

[Nuno]

Isaias definitely caused a lot of fatigue. What an exhausting storm to track... Good luck to our Carolinian friends.

[HurricaneEnzo]

Western edge of the storm is flat and ragged. Still being blasted with shear.

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

[galaxy401]

I swear Isaias hates nightfall. Every time I wake up, I find that the some has become a lot less organized compared to the previous evening.

[HurricaneEnzo]

You can still see the taller cloud tops getting blown off to the east on visible.

https://tropicaltidbits.com/sat/satloop ... roduct=vis

[USTropics]

It's not unusual for systems to undergo these pulsing events, and it's actually a pretty common trait in the MDR. It's most likely a combination of the formative stages/less than ideal localized background state (i.e. system begins to convectively organize, vorticity improves, and then mid-level dry air intrusion halts the process). This will continue for Isaias lifespan, but there are increasing reasons to believe this will obtain hurricane status. The past few days, the mid-level flow has displaced the system (see GFS analysis, wind flow boxed in green):


This of course has displaced the mid/upper level circulation from the lower-level ciruclation for the past 48 or so hours, as seen in 500mb flow below (circled in green is the low-level circulation):


This is essentially because we have this southwesterly flow, but the system was still moving NNW or N (causing shear). As the system begins to move more towards the NNE and NE later today, this flow will become aligned with the storm's direction (and shear will decrease some):


As this approaches the coastline, gradient forcing (see image below) will really accelerate the wind flow in the NE quadrant. Frictional tightening of the circulation will also allow for the low-level circulation to become vertically aligned (coupled with a decrease in shear):


This is what is forecast by the latest GFS run as well:

[Vdogg]

Western edge of the storm is flat and ragged. Still being blasted with shear.

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

I wouldn't say blasted. Shear is definitely present, but less than it was even a few hours ago (and no where near yesterday). Convection is deepening closer to the LLC.

[Craters]

I swear Isaias hates nightfall. Every time I wake up, I find that the some has become a lot less organized compared to the previous evening.

As with All Things Tropical, Wxman57 has addressed this very phenomenon:
http://www.storm2k.org/phpbb2/viewtopic.php?f=59&t=121049&p=2825708#p2825708

[HurricaneEnzo]

Western edge of the storm is flat and ragged. Still being blasted with shear.

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

I wouldn't say blasted. Shear is definitely present, but less than it was even a few hours ago (and no where near yesterday). Convection is deepening closer to the LLC.

Yeah I doubt it sustains though. Pulses up just to fade away again. The typical battle a sheared system faces.

[HurricaneEnzo]

Recon isn't even finding any evidence of a sub-1000mb pressure right now. Looks like something went down though doesn't appear to be updating.

[tolakram]

saved loop

[NXStumpy_Robothing]

Recon isn't even finding any evidence of a sub-1000mb pressure right now.

Recon is also having issues with transmitting data, but it seems like there's enough evidence to justify the 998mb central pressure that the NHC said at 11 am.

It does seem to be taking its time to intensify, which is good news for the Carolinas.