ATL: IDALIA - Post-Tropical - Discussion

[Woofde]

I'll be honest I'm very surprised in a positive manner regarding what's transpired today. I was fully expecting a strong cat 2 by this point, right now the pretty has been dropping pretty slowly and the winds still appear to only support a category 1.

I hope this continues and it struggles to get to category 2, I was fully anticipating a 4, now I have serious doubts that transpires.

Let's hope for continued good news

Isn’t it a category two right now with 91kt.

NHC just pinned it as one yes.

[ElectricStorm]

I'll be honest I'm very surprised in a positive manner regarding what's transpired today. I was fully expecting a strong cat 2 by this point, right now the pretty has been dropping pretty slowly and the winds still appear to only support a category 1.

I hope this continues and it struggles to get to category 2, I was fully anticipating a 4, now I have serious doubts that transpires.

Let's hope for continued good news

Isn’t it a category two right now with 91kt.

That's flight level wind.
EDIT: Well I guess they went ahead and upgraded it, maybe they're assuming NE quad is stronger, which it should be

[xironman]

The eye is just about to clear out for sunset

[Extratropical94]

65kt surface (982 mb) wind on SE eyewall dropsonde. 98 knots at 955 mb, that's 700 feet above the surface

[InfernoFlameCat]

The eyewall has become better organized in the last few frames on radar. Let’s see if it can maintain that trend.

[Highteeld]

Hot towers firing on the NW quadrant. The dry air issue looks legit to me too like others have said. It slowed down the storm a bit over the last few hours, but the outflow is still very good right now. I think the structure improvement will preclude the RI phase in terms of wind. RI is still happening IMO.

[bjackrian]

The difference in NW vs SE wind speeds and wind radii is remarkable. Would not want to be on the east side of Idalia.

[tolakram]

[cheezyWXguy]

Hurricane intensification does not occur at a consistent rate. It can lag expectations or exceed them, often one following the other. I can remember this with Ian, Ida, and Laura specifically and I’m pretty sure I’ve seen this discussion transpire on pretty much every major hurricane I’ve tracked on here. Cat4 is still easily on the table. So if you’re in the path of this storm prepare for the impacts that the nhc has specified for your area. If not, it’s ok to take a step back from the microtrends and watch the show.

Now that we have recon, let’s take a look at how the windfield evolves. To see this go boom, it requires the windfield to symmetrize. If future passes show improvement in that windfield, we will know the cap is coming off. Given its environment, I hope it’s running out of time when that occurs, because there isn’t much else to slow it down.

[ScottNAtlanta]

Eye is starting to warm

[tolakram]

000
WTNT45 KNHC 292056
TCDAT5

Hurricane Idalia Discussion Number 13
NWS National Hurricane Center Miami FL AL102023
500 PM EDT Tue Aug 29 2023

The first stages of an eye have been taking shape in visible
satellite imagery. The hurricane has a relatively small Central
Dense Overcast and a prominent band of deep convection extending
over the eastern semicircle, reaching across the Florida peninsula
southward across western Cuba. An Air Force Reserve Hurricane
Hunter aircraft just measured a peak 700-mb flight-level wind of 91
kt with the pressure falling to 972 mb. The initial intensity is
therefore set at 85 kt.

Idalia is moving faster toward the north, or 360/14 kt, between a
mid-level trough over the northwestern Gulf of Mexico and a
subtropical ridge over the Greater Antilles. Idalia is expected to
continue moving northward and turn north-northeastward as it
approaches the Big Bend region of Florida during the next 12-24
hours. There is very little spread among the track guidance, and
the NHC official forecast has been placed very close to the HCCA
and TVCX consensus aids during the first 24 hours. This has
resulted in a westward shift of about 20-25 n mi compared to the
previous forecast, although it should be stressed that additional
shifts to the track will be possible until the center reaches land.

After landfall, Idalia is expected to turn toward the northeast and
then east, moving near or along the coast of Georgia and the
Carolinas in 36-48 hours. Uncertainty in the track forecast is
still quite large after 48 hours, with many of the global models
turning Idalia southward, while some of the regional hurricane
models still show the storm moving out to sea. As a result, the
official track forecast continues to show slow motion on days 4 and
5.

The 12-hour intensity forecast shows a 100-kt major hurricane. It
is imperative to realize that Idalia is expected to continue
strengthening beyond that time, possibly close to the 110 kt shown
in the previous forecast, before the center reaches land.
Weakening is expected after landfall, but due to the system's
expected fast motion, it is possible that Idalia could maintain
hurricane intensity as it moves across southern Georgia and
approaches the coasts of Georgia and South Carolina. After
Idalia's center moves offshore over the western Atlantic, strong
shear is likely to limit re-intensification, and the official
forecast essentially flatlines the intensity on days 2-5.


KEY MESSAGES:

1. Catastrophic impacts from storm surge inundation of 10 to 15 feet
above ground level and destructive waves are expected somewhere
between Aucilla River and Yankeetown, Florida. Life-threatening
storm surge inundation is likely elsewhere along portions of the
Florida Gulf Coast where a Storm Surge Warning is in effect.
Residents in these areas should follow any advice given by local
officials.

2. There is the potential for destructive life-threatening winds
where the core of Idalia moves onshore in the Big Bend region of
Florida, with hurricane conditions expected elsewhere in portions of
the Hurricane Warning area along the Florida Gulf Coast. Strong
winds will also spread inland across portions of northern Florida
and southern Georgia near the track of the center of Idalia where
Hurricane Warnings are in effect. Residents in these areas should be
prepared for long-duration power outages. Damaging hurricane-force
winds are possible in portions of eastern Georgia and southeastern
South Carolina where Hurricane Watches are in effect.

3. Areas of flash, urban, and moderate river flooding, with locally
considerable impacts, are expected across the Florida Big Bend,
central Georgia and South Carolina, through eastern North Carolina
later tonight into Thursday.



FORECAST POSITIONS AND MAX WINDS

INIT 29/2100Z 26.1N 84.8W 85 KT 100 MPH
12H 30/0600Z 28.3N 84.5W 100 KT 115 MPH
24H 30/1800Z 31.0N 82.9W 75 KT 85 MPH...INLAND
36H 31/0600Z 32.9N 80.2W 50 KT 60 MPH...INLAND
48H 31/1800Z 33.9N 77.1W 45 KT 50 MPH...OVER WATER
60H 01/0600Z 33.8N 74.2W 45 KT 50 MPH
72H 01/1800Z 33.3N 71.8W 45 KT 50 MPH
96H 02/1800Z 32.3N 69.6W 45 KT 50 MPH
120H 03/1800Z 31.7N 69.0W 45 KT 50 MPH

$$
Forecaster Berg

[tolakram]

[Chris90]

I remember something similar happening with Ida a couple years ago. She hovered around the upper 960s to 970s for awhile and intensification was slower than people expected, and people started to think that she wouldn't live up to expectations. She then bombed overnight.

I do think Idalia needs to improve her CDO if she's going to intensify at a faster rate. She's still quite bandy and she will need to beef up her CDO before more appreciable pressure falls can occur in my opinion. My personal guess is that she will peak around 110kts/949mb. Not a professional, very amateur, so don't take that guess too seriously. Look to the NHC if you are in the path of this storm.

[xironman]

https://i.imgur.com/r3Hz0AI.png

The mesos are awesome. One analogy I remember is pig pong balls in a pan.

[USTropics]

Dual hot towers rotating around the eyewall now, that should close off the NW side again:

[HurricaneBelle]

And along the lines of my previous post (and a few others just like it), the header on the advisory thread which says "ATL: IDALIA - Advisories= 5 PM=100 mph / New peak down to 100kt" should be corrected.

[Hypercane_Kyle]

Definitely starting to look fierce. Still has plenty of time to become a major hurricane.

[ScottNAtlanta]

Definitely starting to look fierce. Still has plenty of time to become a major hurricane.

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

The Hurricane Gods are pleased with you now after your earlier transgression

[xironman]

Good thing it is not going ashore now. Those super cells look pretty imposing.

[Steve]

We got a little bonus rain since the outermost NW band is set up over us. It’s really the point where the two air masses come together. I figured we’d be dry since it’s only rained twice the last couple of months. But one can clearly see by the orientation of the bands that’s what they are.

https://www.weather.gov/lix/