ATL: IDALIA - Post-Tropical - Discussion

[tolakram]

 https://twitter.com/AndyHazelton/status/1696836362803007873

[Teban54]

At most the current recon data supports 110 kt. But no way the NHC is going to operationally lower the intensity of a major this close to land. Perhaps there was data earlier to support 115 kt.

Also, props to the Euro for sniffing this one out ahead of the GFS. One of the few Euro Ws in recent years.

The pass that came in just before advisory time did support 115 kt, as noted in the discussion:

Idalia continues to undergo rapid intensification. Maximum
flight-level winds were 123 kt, with believable SFMR values of 115
kt. Satellite images show a small eye surrounded by very cold
clouds tops, especially in the western quadrant. The initial wind
speed is set to 115 kt, making Idalia an extremely dangerous
category 4 hurricane.

That was also just before the EWRC started, and subsequent passes through the same E eyewall reported lower winds.

[dukeblue219]

Those poor folks in southeast Georgia and SC are waking up to a hurricane warning this morning

Most likely, impacts in South Carolina won't be any different than they expected yesterday - windy and wet. A tornado is still a threat but it won't linger long enough for catastrophic flooding and the winds (regardless of what the advisories say aloft) won't be anything like coastal Florida that far inland...

[La Sirena]

Those poor folks in southeast Georgia and SC are waking up to a hurricane warning this morning

Most likely, impacts in South Carolina won't be any different than they expected yesterday - windy and wet. A tornado is still a threat but it won't linger long enough for catastrophic flooding and the winds (regardless of what the advisories say aloft) won't be anything like coastal Florida that far inland...

Having lived on Tybee I’d say it’s still a decent threat with water and wind. There’s always a chance of tornados being an issue in GA during a summer thunderstorm. Wouldn’t downplay any of this for GA/SC.

[Blown Away]

Fish Creek landfall point? No real coastal communities but Fish Creek?

[rickcorvin]

At most the current recon data supports 110 kt. But no way the NHC is going to operationally lower the intensity of a major this close to land. Perhaps there was data earlier to support 115 kt.

Also, props to the Euro for sniffing this one out ahead of the GFS. One of the few Euro Ws in recent years.

The pass that came in just before advisory time did support 115 kt, as noted in the discussion:

Idalia continues to undergo rapid intensification. Maximum
flight-level winds were 123 kt, with believable SFMR values of 115
kt. Satellite images show a small eye surrounded by very cold
clouds tops, especially in the western quadrant. The initial wind
speed is set to 115 kt, making Idalia an extremely dangerous
category 4 hurricane.

That was also just before the EWRC started, and subsequent passes through the same E eyewall reported lower winds.

NHC 7:00 et update lowered max winds to 125 mph and noted EWRC.

[tolakram]

[TallyTracker]

Extreme Wind Warning
FLC029-123-301315-
/O.NEW.KTAE.EW.W.0001.230830T1009Z-230830T1315Z/

BULLETIN - EAS ACTIVATION REQUESTED
Extreme Wind Warning
National Weather Service Tallahassee FL
609 AM EDT Wed Aug 30 2023

The National Weather Service in Tallahassee has issued a

* Extreme Wind Warning for...
Western Dixie County in Big Bend Florida...
Southern Taylor County in Big Bend Florida...

* Until 915 AM EDT.

* At 608 AM EDT, National Weather Service Doppler radar indicated
extreme winds, associated with the eyewall of Hurricane Idalia,
were moving onshore 34 miles southwest of Steinhatchee, moving
northeast at 20 mph. THIS IS AN EXTREMELY DANGEROUS AND LIFE-
THREATENING SITUATION!

* Locations impacted include...
Steinhatchee, Horseshoe Point, Horseshoe Beach, Tennille, Fish
Creek, Jug Island, Howell Place, Clara, Carbur, Jena, Adams Beach,
Dekle Beach, Jonesboro, Jack Lee Island, Keaton Beach, Bird Island,
Salem, Blue Springs, Athena, and Cedar Island.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TAKE COVER NOW! Treat these imminent extreme winds as if a tornado
was approaching and move immediately to the safe room in your
shelter. Take action now to protect your life!

The safest place to be during a major landfalling hurricane is in a
reinforced interior room away from windows. Get under a table or
other piece of sturdy furniture. Use mattresses, blankets or pillows
to cover your head and body. Remain in place through the passage of
these life-threatening conditions.

&&

A Tornado Watch remains in effect until 300 PM EDT for Big Bend
Florida.

LAT...LON 2941 8331 2950 8340 2966 8348 2974 8360
2991 8373 3001 8396 3009 8383 2999 8343
2995 8337 2982 8335 2982 8330 2940 8316
TIME...MOT...LOC 1008Z 226DEG 17KT 2941 8388

$$

42-DVD

[SecondBreakfast]

Good morning everyone. Going to be an interesting morning of going from staring at satellite/radar to staring at my confocal. Reed Timmer on the YouTube feed says the surge is really coming in on Cedar Key. He has bad service so it’s a live feed from other chasers.

[TallyTracker]

The leftovers of the inner eyewall are coming onshore at Keaton Beach/Fish Creek. Perry looks like it’s gonna get walloped shortly too.

Tallahassee looks like it will largely be spared due to that right hook. I am thankful for that though not wishing this on anyone.

[wx98]

I sorta question the upgrade to Cat 4, given the somewhat marginal recon data. We’ve seen as similar data in years past to support Cat 5 vs Cat 4 and they never pull the trigger. Seems the forecasters have a much lower threshold to upgrade to a 4 vs upgrading to a 5.

[Joe Snow]

Looks like its going to make land fall by Dekle Beach, Live Oak point just south of there

[Teban54]

I sorta question the upgrade to Cat 4, given the somewhat marginal recon data. We’ve seen as similar data in years past to support Cat 5 vs Cat 4 and they never pull the trigger. Seems the forecasters have a much lower threshold to upgrade to a 4 vs upgrading to a 5.

I imagine NHC will use techniques like radar reflexivity during post-season analysis to decide if they'll downgrade it to Cat 3 peak. Such downgrades have happened before, most notably with Iota (Cat 5 to Cat 4, which is a more substantial difference than Cat 4 to Cat 3).

[ouragans]

Fish Creek landfall point? No real coastal communities but Fish Creek?

Just said around Keaton Beach as per my personal estimation, which is a non-populated area, hopefully

[NDG]

Highest winds so far in gusts in 81 mph in Horseshoe Beach.
Officially in Perry only 48 mph but that's about to change.

[kevin]

I sorta question the upgrade to Cat 4, given the somewhat marginal recon data. We’ve seen as similar data in years past to support Cat 5 vs Cat 4 and they never pull the trigger. Seems the forecasters have a much lower threshold to upgrade to a 4 vs upgrading to a 5.

The highest found FL winds were 123 kt at 07:46Z. The same pass also found the highest SFMR value of 116 kt. 123 kt FL adjusted for the surface is roughly 111 kt. So a blend of SFMR and FL gives 113/114 kt. This pass also indicated an RMW of ~10 nm between the eye and the highest wind measurements which results in an almost negligible underestimate/undersampling correction of roughly 1%. Based on this you'd get 114/115 kt -> 115 kt seems like a reasonable estimate for that time. Especially considering the previous very solid support for 110 kt and the continuous decrease in pressure. I do agree that afterwards the intensity quickly fell as the EWRC started. During the second 115 kt advisory I estimate Idalia probably already weakened to 105 kt.

[InfernoFlameCat]

The eyewall looks better than earlier. Seems as though it’s trying to intensify again last minute.

[NDG]

Pretty good storm surge in Cedar Key, places further north have to be worst.

https://www.youtube.com/watch?v=26FTVrcCtBw

[dukeblue219]

The eyewall looks better than earlier. Seems as though it’s trying to intensify again last minute.

The Tampa radar is at extreme range but it makes the E side of the eyewall look a lot better than what we've been seeing out of Tallahassee radar. Maybe just be the elevation of course.

[tolakram]

Very close to landfall