ATL: ISAIAS - Post-Tropical - Discussion

[GCANE]

Here's another look at the ASCAT from last night showing the closed circulation nicely. I think it has been doing a cyclonic loop just like models were showing yesterday. Gaining latitude during the night after this shot.

https://i.imgur.com/uMuR6Oy.png

Interesting, something I wouldn't have thought of.
Must have been a very quick relocation of the center.
Buoy 42059 at 15.25N 67.48W reported a south wind at 11.7 knots one hour ago.

[CM2]

You can see the eye trying to form on Radar!

[GCANE]

Two towers firing off from the convergence of the LL winds as they hit the SW side of PR.

[NDG]

Here's another look at the ASCAT from last night showing the closed circulation nicely. I think it has been doing a cyclonic loop just like models were showing yesterday. Gaining latitude during the night after this shot.

https://i.imgur.com/uMuR6Oy.png

Interesting, something I wouldn't have thought of.
Must have been a very quick relocation of the center.
Buoy 42059 at 15.25N 67.48W reported a south wind at 11.7 knots one hour ago.

Per the latest fix by the NHC it is NNW from this buoy so it makes sense winds now shifting to the south as the winds flow into the deep convection NE of the LLC.

[NDG]

You can see the eye trying to form on Radar!
https://imgur.com/FKpbzM3

IMO, that's a mid level feature and the LLC will eventually follow it.

[NDG]

The NHC puts the LLC to the SW of the deep convection, I agree.

[Vdogg]

this may gave more time get stronger if more south and nhc have it 8pm

Would be weaker due to land interaction.

Looks like it's about to thread the needle. And it's intensifying.

[northjaxpro]

Good morning everyone. Got in a little sleep and a very interesting day is greeting us with Isaias.

[CM2]

The NHC puts the LLC to the SW of the deep convection, I agree.

https://i.imgur.com/WKl0u2n.jpg

I'm not sure, the LLC might actually already be in the convection. I remembered following a low level feature which did turn out to be the LLC for Nine to become named. I think once the convection kind of kicked off around it, all sorts of things kind of fell into line. You can see on radar the storm trying to wrap an eye around already. This storm is rapidly intensifying in my unprofessional opinion.

[NDG]

Exactly my thoughts and what models have been persistent on, from the latest NHC Forecast Discussion.

Model forecasts are showing a complex evolution of the tropical
cyclone during the next day or two. There is good agreement that
Isaias will move across Hispaniola later today, and its low-level
center will likely become disorganized over the high terrain.
However, the strong burst of convection currently near Puerto Rico
is associated with a mid-level circulation, which should pass
along the north coast of Hispaniola later today. Most of the model
guidance suggest that this feature will cause the re-development of
a surface center over the northern part of the broader system while
the mid-level circulation moves close to the southeastern Bahamas.

[GCANE]

The towers are heating up the mid-level which is what is showing up on radar.
IR sat has the center to the SW which for the past couple days has been an estimate of the 850 to 700 mb vort.
I think the two will cyclonically spin around each other for the next few hours.

Tons of UL divergence over this.
A movement to the NW will track into greater shear but keep the convection firing since its on a gradient creating uplift.
Hard to tell if this makes it thru the Mona Passage or tangles with DR.

[Vdogg]

NHC Marked Isaias at 15.8N this evening.

This morning, they forecast it to be at 16.9N now.
Last night, they forecast it to be at 17.4N now.

East shifts for a system that's continuing to run South of forecast doesn't entirely sit right with me. Tomorrow, we should finally have answers. Should the NHC deem TS Watches necessary for parts of SFL, logically they would be issued at 11am or 5pm (at the latest).

It's moving NW. The east shifts were correct.

[GCANE]

Good morning everyone. Got in a little sleep and a very interesting day is greeting us with Isaias.

Good morning Northjaxpro.
I just finished my second cup of coffee.
Very complex to figure out what Isaias will do next.

[Hammy]

The NHC puts the LLC to the SW of the deep convection, I agree.

https://i.imgur.com/WKl0u2n.jpg

Looks like it's out-running the upper high. Starting to run into the PV streamer that was mentioned a few days ago?

[northjaxpro]

Yeah, it looks like a new center may reform somewhere off the North coast of Hispaniola later today as it moves west -northwest.

[CM2]

Exactly my thoughts and what models have been persistent on, from the latest NHC Forecast Discussion.

I generally have to disagree. The storm has been obviously taking a much mor NNE path and is now starting to curb over. I believe the center is right next to PR though even if the LLC is off to the SW (The pink line), the trend of the storm's movement still would indicate that it is mostly going to be avoiding DR (and especially the mountians.) If the storm is doing what I believe it's doing, then it has MAJOR ramifications on the intensification forecast.

Again, this is my unprofessional opinion so take it for what you will

[USTropics]

You can see the eye trying to form on Radar!
https://imgur.com/FKpbzM3

IMO, that's a mid level feature and the LLC will eventually follow it.

Yea what I've witnessed on radar tonight are multiple mesovortices (circled in white are a few of these meso features throughout the night) rotating around a broad low-level circulation. Highlighted in red is the mid-level circulation, which is where we should watch for some type of concentration of low-pressures (low-level vorticity has been slightly displaced to the west of this tonight).




Fellow FSU grad student Mark Nissenbaum (https://twitter.com/markniss_?lang=en) has some amazing radar loops that update locations based on threats http://moe.met.fsu.edu/~mnissenbaum/radar.html.

[GCANE]

The NHC puts the LLC to the SW of the deep convection, I agree.

https://i.imgur.com/WKl0u2n.jpg

Looks like it's out-running the upper high. Starting to run into the PV streamer that was mentioned a few days ago?

I think the PV Streamer is more over east Cuba.
UL winds show good divergence over the Mona Passage but then a strong jet further west just offshore of north Hispaniola.

[CM2]

Meanwhile pressure is dropping in PR.

[NDG]

Nice TS force winds by buoy just off the southern coast of Puerto Rico, just in case wxman57 says he can't find any TS force winds near it



https://www.ndbc.noaa.gov/station_page. ... tion=42085