ATL: IDALIA - Post-Tropical - Discussion

[CrazyC83]

The story is not finished and there is more to be told, but as of now, here is my analysis for the best track of Idalia (NOT official).

AL102023, IDALIA, xx

20230826, 1200, , LO, 20.8N, 86.1W, 25, 1005,
20230826, 1800, , TD, 21.0N, 86.2W, 25, 1005,
20230827, 0000, , TD, 21.2N, 86.4W, 30, 1003,
20230827, 0600, , TS, 20.6N, 86.6W, 35, 1001,
20230827, 1200, , TS, 20.1N, 86.2W, 40, 998,
20230827, 1800, , TS, 20.0N, 85.7W, 45, 994,
20230828, 0000, , TS, 19.8N, 85.4W, 50, 991,
20230828, 0600, , TS, 19.9N, 85.2W, 55, 989,
20230828, 1200, , TS, 20.6N, 85.2W, 55, 988,
20230828, 1800, , TS, 21.2N, 85.1W, 55, 986,
20230829, 0000, , TS, 21.8N, 85.0W, 60, 983,
20230829, 0030, L, TS, 21.9N, 84.9W, 60, 982,
20230829, 0600, , TS, 22.6N, 84.9W, 60, 980,
20230829, 1200, , HU, 23.8N, 84.8W, 65, 977,
20230829, 1800, , HU, 25.3N, 84.8W, 75, 974,
20230830, 0000, , HU, 26.9N, 84.7W, 90, 963,
20230830, 0000, , HU, 26.9N, 84.7W, 90, 963,
20230830, 0600, , HU, 28.3N, 84.5W, 105, 944,
20230830, 0800, I, HU, 28.9N, 84.3W, 110, 940,
20230830, 1135, L, HU, 29.9N, 83.6W, 100, 950,
20230830, 1200, , HU, 30.0N, 83.6W, 90, 953,
20230830, 1800, , TS, 31.5N, 82.9W, 60, 981,
20230831, 0000, , TS, 32.7N, 80.9W, 50, 985,
20230831, 0600, , TS, 33.5N, 79.0W, 45, 990,
20230831, 1200, , TS, 33.8N, 76.9W, 50, 991,
20230831, 1800, , EX, 33.6N, 74.8W, 55, 993,

Some key notes:

* Genesis is unchanged. The erratic movement in the Yucatan Channel is smoothed out some. There is determined to be no landfall in Cozumel (the current BT shows it) as the track is adjusted slightly east at that point on the bend.

* In the early life, the intensities are smoothed out as well to cover periods with no Recon.

* A landfall is added on the extreme western tip of Cuba. At the time, Recon was circumnavigating due to airspace restrictions. Winds are analyzed at 60 kt at that time. Due to a long period without Recon and later findings, hurricane status is delayed 6 hours.

* The rapid intensification in the eastern Gulf is actually made more rapid due to some points having lower intensities. That said...

* The peak intensity is analyzed to have been 110 kt, and that was at a non-synoptic point, 0800Z. That was based on that Recon finding of 123 kt flight-level winds, while the 115 kt SFMR reading (the support for the NHC operational intensity) I believe was questionable due to shoaling issues and nearby islands. That may have been wave-contaminated. The minimum pressure, 940 mb, is analyzed at that same point.

* Recon and later surface data clearly show some filling before landfall. The last pass about 20 minutes before landfall found a pressure of 949 mb. There were numerous readings from just inland (near 1200Z) of around 953-954 mb. Based on continued filling before landfall and faster filling afterward, the landfall pressure is analyzed at 950 mb. Likewise, the wind data also suggests a decrease of about 10 kt before landfall. Hence, the landfall intensity is estimated at 100 kt, which likely occurred in largely uninhabited areas near Keaton Beach. (That's a decrease of 10 kt from operational).

* Adjustments are also made post-landfall to account for the lower landfall intensity.

[CrazyC83]

Going back through the data, it probably peaked at 110 kt at 0800Z, with a pressure of 940 mb. The SFMR was probably inflated by the shallow water in the area and the many islands, and the flight level winds (123 kt peak) support 111 kt at the surface.

As far as the landfall intensity (1130Z), I would set it at 100 kt, which likely was limited to almost uninhabited areas near the coastline. The pressure at the time I estimate was 950 mb. I'll write a full BT either later tonight or tomorrow.

I agree with this assessment wholeheartedly. Didn’t agree with the Cat 4 upgrade based on a single recon pass when the EWRC was imminent. Don’t think it was really a Cat 4. Been following hurricanes for 20 years, and NHC is usually much more reserved in upgrading these. Likely it was due to land proximity in this case.

That seems correct. I wrote my thoughts in more detail. The landfall intensity I also estimate was lower for the same reason.

[ElectricStorm]

Like others have stated I don't think this was a Cat 4, and I think this has a decent chance to be downgraded slightly in the TCR. Of course a 5kt difference doesn't really matter that much, there just so happens to be a category change there. It does seem odd they upgraded it based on recon pass that didn't even really support it (outside of a questionable SFMR) but maybe they saw something else that supported an upgrade that we don't have access to.

Doesn't change the fact that it was a destructive major though, but honestly could have been much worse.

The TCR will be interesting

[Gums]

Salute!

I found one of the pics of "catastrophic" surge. My other one is not on a URL and is more depressing, but will try to find a way.

In all honesty, another contributor and Steve have somewhat supported my opinion that this event was not "catastrophic". And I make the assertion due to my family's experience with Betsy, Camille, Katrina, Ike and Rita and my own with Opal and Erin and Alma (1966)....

So here is what many of us that have grown up along the coast view as "catastrophic", and I have not seen anything close except Mexico Beach a few year ago, and there are homes there that came thru Michael as if nothing happened, yet the old ones built in the 50's are rubble. So look at Holly Beach before and after...:



If image not coming thru, try direct link:

https://www.usgs.gov/media/images/and-a ... -louisiana

Hope I am not viewed as a cold-hearted curmuddgeon, but am just tired of the constant "unprecendented", "historical", "catastrophic", "highest in recorded history ( yeah, all 160 years of decent weather data)", and the beat goes on....

We are a resilient and innovative bunch here in the U.S., and if some wish to live in a high threat area that has earthquakes, tornados, hurricanes, wildfires and tsunamis, then they must be prepared first to survive, then to re-build.

Gums sends...

[Sciencerocks]

[weeniepatrol]

To be entirely fair, 160 years is a decent data sample. Plus we have enough data to make observations about decadal trends which apply to our current and future environment

[ConvergenceZone]

Hope everyone did okay through this horrible storm. Also glad that all other potential areas of interest/storms are heading out to sea. Great news!

[NC George]

All kinds of warnings. But, dead calm steady rain. Dry slot soon.

Wondering if we will escape.

Stay tuned for as the storm turns.

Fellow eastern NCer here. I work in Greenville, live in Washington and just had to drive down 264 between the two, torrential rain made me slow down to around 40. We were really dry here all summer though, so the ground seems to be absorbing all the water, the ditches on the side of the road weren't even half full. This evening in Greenville we had pretty light rain and no winds until around midnight, when the wind started a little and the rain picked up a bit.

[Hurricane Mike]

Idalia reminded me a lot of Hurricane Dennis in 2005. Very small core, weakening at landfall in the Florida panhandle. In fact, Dennis made landfall with 115 mph winds (lowered from 120 mph operationally) and a pressure of 946 mb.

I think Idalia may have been more in the 115-120 mph range at landfall, rather than the operational assessment of 125 mph. The pressure also rose to around 949 mb, similar to Dennis, and the surge was nasty and similar, but Dennis hit a more populated area of the Florida panhandle than Idalia struck.

[Hurricane2022]

If Idalia manages to return to the Gulf of Mexico, is there any chance of it returning to hurricane status?

[Landy]

If Idalia manages to return to the Gulf of Mexico . . .

That ship has long since sailed.

[caneman]

Salute!

I found one of the pics of "catastrophic" surge. My other one is not on a URL and is more depressing, but will try to find a way.

In all honesty, another contributor and Steve have somewhat supported my opinion that this event was not "catastrophic". And I make the assertion due to my family's experience with Betsy, Camille, Katrina, Ike and Rita and my own with Opal and Erin and Alma (1966)....

So here is what many of us that have grown up along the coast view as "catastrophic", and I have not seen anything close except Mexico Beach a few year ago, and there are homes there that came thru Michael as if nothing happened, yet the old ones built in the 50's are rubble. So look at Holly Beach before and after...:

https://www.usgs.gov/media/images/and-after-pictures-hurricane-rita-and-holly-beach-louisiana

If image not coming thru, try direct link:

https://www.usgs.gov/media/images/and-a ... -louisiana

Hope I am not viewed as a cold-hearted curmuddgeon, but am just tired of the constant "unprecendented", "historical", "catastrophic", "highest in recorded history ( yeah, all 160 years of decent weather data)", and the beat goes on....

We are a resilient and innovative bunch here in the U.S., and if some wish to live in a high threat area that has earthquakes, tornados, hurricanes, wildfires and tsunamis, then they must be prepared first to survive, then to re-build.

Gums sends...

While not catastrophic, it certainly was one of the worse surge events in this area in a long time. Simply look up the photos from local news sources. We had the luck of a more unpopulated area being hit and being struck at low tide (king hide tide would have added another 3 feet). You are entitled to your opinion and I am entitled to my facts. I've lived here sine 1976 and it's the worse surge we've had since the No Name Storm of 1993.

[cycloneye]

Moving fast away from the coast.

[Iceresistance]

Moving fast away from the coast.

https://i.imgur.com/NCOuZhG.gif

This does not even look like a Tropical Cyclone!

It's very close to a front per WPC.


https://s11.gifyu.com/images/SgCDu.gif

[wxman57]

Yes, Idalia looks like a frontal low this morning. Recon is finding some strong wind behind it that look more like cool air flowing offshore behind a front. No convection anywhere near its center. I've been monitoring sustained wind and gusts the past 2 days. I could not find any hurricane force sustained wind inland over Florida. That's what TWC was saying in the past hour. Basically, winds inland were TS strength. I could not find any sustained 40 mph wind across SC or NC. Possibly very near the coast at a coastal buoy. There were wind gusts to hurricane strength that almost reached the Georgia border. As the eyewall started a replacement cycle, all stronger winds lifted above the surface. These strong winds aloft would occasionally dip down to the surface, producing 80-90 mph gusts in areas with sub-39 mph sustained wind. We saw something like that with Rita in 2005 and Lily in 2002.

Next question involves Idalia's track once it passes Bermuda this weekend. ICON stalls it near Bermuda next Thursday and weakens it to a remnant low. GFS takes it northward and merges it with a front well south of Nova Scotia next Thursday. Euro has it stalled not far east of Cape Cod late next week as a strong TS or H (don't like that scenario for personal reasons). I choose the slow northward movement well out to sea next week. That agrees with most guidance.

[ElectricStorm]

New advisory calls for it to become ET soon (looks like it's just about there already) before becoming a TC again in a few days. Haven't really seen too many storms do that

[Ubuntwo]

Salute!

I found one of the pics of "catastrophic" surge. My other one is not on a URL and is more depressing, but will try to find a way.

In all honesty, another contributor and Steve have somewhat supported my opinion that this event was not "catastrophic". And I make the assertion due to my family's experience with Betsy, Camille, Katrina, Ike and Rita and my own with Opal and Erin and Alma (1966)....

So here is what many of us that have grown up along the coast view as "catastrophic", and I have not seen anything close except Mexico Beach a few year ago, and there are homes there that came thru Michael as if nothing happened, yet the old ones built in the 50's are rubble. So look at Holly Beach before and after...:

https://www.usgs.gov/media/images/and-after-pictures-hurricane-rita-and-holly-beach-louisiana

If image not coming thru, try direct link:

https://www.usgs.gov/media/images/and-a ... -louisiana

Hope I am not viewed as a cold-hearted curmuddgeon, but am just tired of the constant "unprecendented", "historical", "catastrophic", "highest in recorded history ( yeah, all 160 years of decent weather data)", and the beat goes on....

We are a resilient and innovative bunch here in the U.S., and if some wish to live in a high threat area that has earthquakes, tornados, hurricanes, wildfires and tsunamis, then they must be prepared first to survive, then to re-build.

Gums sends...

Fortunately this was not a ‘catastrophic’ surge event. I believe that term was being thrown around prior to landfall due to the potential, not fully realized due to factors discussed earlier…

As far as previous catastrophic events (Rita, Ike, etc). Construction as you touch on is a major factor in comparing these storms. Holly beach and Bolivar had purely wood construction leading to the ‘wiped clean’ appearance. Ft Myers Beach and Mexico Beach both have a solid proportion of modern up to code buildings… which may outwardly appear to withstand the surge but are completely gutted on the inside. Rita’s surge peaked at 10ft and I suspect high water mark analysis will find similar heights with Idalia. For a modern example of what you call a catastrophic event look no further than Rutherford beach in Laura.

Agreed as far as ‘unprecedented’ storms. I understand the term’s value for risk communication (ie this will be the worst storm in memory for locals), but I fear its overuse has the potential to breed complacency.

[underthwx]

Like others have stated I don't think this was a Cat 4, and I think this has a decent chance to be downgraded slightly in the TCR. Of course a 5kt difference doesn't really matter that much, there just so happens to be a category change there. It does seem odd they upgraded it based on recon pass that didn't even really support it (outside of a questionable SFMR) but maybe they saw something else that supported an upgrade that we don't have access to.

Doesn't change the fact that it was a destructive major though, but honestly could have been much worse.

The TCR will be interesting

If I understand this correctly, there were no winds of Hurricane intensity recorded anywhere inland?

[tallywx]

These strong winds aloft would occasionally dip down to the surface, producing 80-90 mph gusts in areas with sub-39 mph sustained wind.

Sustained wind in the eyewall around Perry, FL was far above sub-39mph. I’d peg it as cat 1 sustained. I believe the Perry, FL ASOS had a sustained 62mph in the back eyewall

[cheezyWXguy]

Salute!

I found one of the pics of "catastrophic" surge. My other one is not on a URL and is more depressing, but will try to find a way.

In all honesty, another contributor and Steve have somewhat supported my opinion that this event was not "catastrophic". And I make the assertion due to my family's experience with Betsy, Camille, Katrina, Ike and Rita and my own with Opal and Erin and Alma (1966)....

So here is what many of us that have grown up along the coast view as "catastrophic", and I have not seen anything close except Mexico Beach a few year ago, and there are homes there that came thru Michael as if nothing happened, yet the old ones built in the 50's are rubble. So look at Holly Beach before and after...:

https://www.usgs.gov/media/images/and-after-pictures-hurricane-rita-and-holly-beach-louisiana

If image not coming thru, try direct link:

https://www.usgs.gov/media/images/and-a ... -louisiana

Hope I am not viewed as a cold-hearted curmuddgeon, but am just tired of the constant "unprecendented", "historical", "catastrophic", "highest in recorded history ( yeah, all 160 years of decent weather data)", and the beat goes on....

We are a resilient and innovative bunch here in the U.S., and if some wish to live in a high threat area that has earthquakes, tornados, hurricanes, wildfires and tsunamis, then they must be prepared first to survive, then to re-build.

Gums sends...

Fortunately this was not a ‘catastrophic’ surge event. I believe that term was being thrown around prior to landfall due to the potential, not fully realized due to factors discussed earlier…

As far as previous catastrophic events (Rita, Ike, etc). Construction as you touch on is a major factor in comparing these storms. Holly beach and Bolivar had purely wood construction leading to the ‘wiped clean’ appearance. Ft Myers Beach and Mexico Beach both have a solid proportion of modern up to code buildings… which may outwardly appear to withstand the surge but are completely gutted on the inside. Rita’s surge peaked at 10ft and I suspect high water mark analysis will find similar heights with Idalia. For a modern example of what you call a catastrophic event look no further than Rutherford beach in Laura.

Agreed as far as ‘unprecedented’ storms. I understand the term’s value for risk communication (ie this will be the worst storm in memory for locals), but I fear its overuse has the potential to breed complacency.

This is a good take imo. And technically, had Idalia made landfall at peak strength (assuming peak actually was 115kt) it would have been “unprecedented” since no cat4 has made landfall in that area in our records.

In a lot of cases articles are largely written in advance so outlets can try to be the first to report on an event. Since it weakened last minute, I suspect most of the outlets either didn’t know or didn’t care to update with that level of nuance. I’m not a fan of that practice, but it’s pretty common to see.