ATL: OSCAR - Remnants - Discussion

[TallyTracker]

Another tool that may be implemented would be if the NHC can get old-fashioned damage surveys from the Cuban government at the landfall location. The tree and building damage could give at least some insight into what type of winds occurred at landfall.

[GCANE]

Quite a bit of moisture is streaming in from the west and will impact the trough in a few hours.
Could be significantly eroded by the time it would have an effect on Oscar

https://weather.cod.edu/satrad/?parms=r ... orbar=data

[Sanibel]

Bumping N out of stall now IMO...

[Sciencerocks]

[TomballEd]

The low level center is exposed and not very organized, NHC can downgrade this to post-tropical at any time although the discussion suggests they'll carry it as a TD until it merges with or becomes the frontal low.

[cycloneye]

Bye.

120 PM EDT Tue Oct 22 2024

...OSCAR IS NO LONGER A TROPICAL CYCLONE..

[Iceresistance]

Bye.

120 PM EDT Tue Oct 22 2024

...OSCAR IS NO LONGER A TROPICAL CYCLONE..

Very unusual for a TCU to kill off a TC

[CrazyC83]

Based on the post-Recon intensification, with slight lean to the SAR pass, I estimate the landfall intensity was 85 kt. The SAR does seem to have a high bias but the satellite estimates were starting to get close to T5.0.

[CrazyC83]

As far as Oscar's BT, here is how I would analyze it. A lot of changes from operational.

AL162024, OSCAR, 14,
20241018, 1800, , LO, 19.5N, 65.7W, 30, 1009,
20241019, 0000, , TS, 20.1N, 67.1W, 35, 1007,
20241019, 0600, , TS, 20.8N, 68.4W, 45, 1002,
20241019, 1200, , TS, 21.2N, 69.8W, 55, 998,
20241019, 1800, , HU, 21.4N, 70.6W, 70, 989,
20241020, 0000, , HU, 21.5N, 71.7W, 75, 987,
20241020, 0600, , HU, 21.2N, 72.7W, 75, 986,
20241020, 1200, , HU, 20.8N, 73.6W, 75, 985,
20241020, 1800, , HU, 20.6N, 74.1W, 80, 982,
20241020, 2145, L, HU, 20.4N, 74.4W, 85, 978,
20241021, 0000, , HU, 20.3N, 74.5W, 65, 987,
20241021, 0600, , TS, 20.1N, 74.9W, 45, 996,
20241021, 1200, , TS, 20.2N, 75.4W, 40, 1000,
20241021, 1800, , TS, 20.3N, 75.7W, 35, 1003,
(Opened into a trough at 00Z October 22)

* The time of genesis is up for debate and difficult to determine.
** The lack of ASCAT passes on October 18 (last Friday) were frustrating, as was the lack of any Recon.
** The first obvious signs of a surface circulation were the microwave imagery at 1200Z (showing a formative eyewall) and a HY-2C pass with 35 kt barbs (and low resolution) before 0900Z. However, the small size and satellite signature suggests it had been doing well for a while. That does suggest that it was already at least 45-50 kt by the time of that pass, and 55 kt by the time of that microwave image. (Operationally, it was still an Invest then!)
** Dvorak was consistently around T1.5 in that time period, however, we saw that be seriously off when Recon arrived.
** Hence, with uncertainty, genesis is placed at 0000Z October 19 (as a tropical storm), but that could be conservative. A closed low likely formed around 1800Z October 18, but there isn't enough to prove it was a TC yet.
* Recon shocked us around 1800Z October 19 when it found a hurricane. It was likely already a hurricane by the first pass around 1645Z, and the last pass around 1915Z supported 75 kt with a pressure of 987 mb. That supports the trends earlier as well. Satellite imagery was virtually unchanged afterward.
* The next aircraft arrived around 1200Z October 20 and found little change in the intensity, along with a slightly lower pressure (lowest was 984 mb - 986/19 at 1400Z). Additionally, the satellite signature was starting to improve at that time, which suggests that Oscar intensified before landfall.
* Landfall took place at approximately 2145Z October 20. Dvorak numbers had risen and was T4.5 to T5.0 on some estimates. Unfortunately, no Recon or good surface data was available. There was a solid eyewall on microwave imagery. The SAR supported 95-100 kt but is likely inflated. Based on all the data, the best landfall intensity estimate is a possibly conservative 85 kt. The pressure at the time is estimated at 978 mb based on the same trends.
* Post-landfall weakening I think was more rapid than operational, and decay moved up significantly. Recon yesterday struggled to find a center, and that may not have really been one. I estimate it degenerated into a trough at 0000Z October 22, 18 hours earlier than operational.

[sasha_B]

As far as Oscar's BT, here is how I would analyze it. A lot of changes from operational.

* The time of genesis is up for debate and difficult to determine.
** The lack of ASCAT passes on October 18 (last Friday) were frustrating, as was the lack of any Recon.
** The first obvious signs of a surface circulation were the microwave imagery at 1200Z (showing a formative eyewall) and a HY-2C pass with 35 kt barbs (and low resolution) before 0900Z. However, the small size and satellite signature suggests it had been doing well for a while. That does suggest that it was already at least 45-50 kt by the time of that pass, and 55 kt by the time of that microwave image. (Operationally, it was still an Invest then!)
** Dvorak was consistently around T1.5 in that time period, however, we saw that be seriously off when Recon arrived.
** Hence, with uncertainty, genesis is placed at 0000Z October 19 (as a tropical storm), but that could be conservative. A closed low likely formed around 1800Z October 18, but there isn't enough to prove it was a TC yet.
* Recon shocked us around 1800Z October 19 when it found a hurricane. It was likely already a hurricane by the first pass around 1645Z, and the last pass around 1915Z supported 75 kt with a pressure of 987 mb. That supports the trends earlier as well. Satellite imagery was virtually unchanged afterward.
* The next aircraft arrived around 1200Z October 20 and found little change in the intensity, along with a slightly lower pressure (lowest was 984 mb - 986/19 at 1400Z). Additionally, the satellite signature was starting to improve at that time, which suggests that Oscar intensified before landfall.
* Landfall took place at approximately 2145Z October 20. Dvorak numbers had risen and was T4.5 to T5.0 on some estimates. Unfortunately, no Recon or good surface data was available. There was a solid eyewall on microwave imagery. The SAR supported 95-100 kt but is likely inflated. Based on all the data, the best landfall intensity estimate is a possibly conservative 85 kt. The pressure at the time is estimated at 978 mb based on the same trends.
* Post-landfall weakening I think was more rapid than operational, and decay moved up significantly. Recon yesterday struggled to find a center, and that may not have really been one. I estimate it degenerated into a trough at 0000Z October 22, 18 hours earlier than operational.

This is a great and thorough explanation, and I'm convinced that 85kt is a solid, conservative estimate of Oscar's peak/landfall intensity. If you don't mind my asking, though, didn't SAR estimates accurately reflect Oscar's 70kt intensity (as corroborated by recon, and prior to the final round of intensification) earlier that day? And if so, did the factors that would inflate SAR intensity estimates become more significant closer to landfall? I'm not familiar with the technology, and I've seen a number of differing perspectives on the reliability of the SAR data in this case over the past couple of days.

[CrazyC83]

As far as Oscar's BT, here is how I would analyze it. A lot of changes from operational.

* The time of genesis is up for debate and difficult to determine.
** The lack of ASCAT passes on October 18 (last Friday) were frustrating, as was the lack of any Recon.
** The first obvious signs of a surface circulation were the microwave imagery at 1200Z (showing a formative eyewall) and a HY-2C pass with 35 kt barbs (and low resolution) before 0900Z. However, the small size and satellite signature suggests it had been doing well for a while. That does suggest that it was already at least 45-50 kt by the time of that pass, and 55 kt by the time of that microwave image. (Operationally, it was still an Invest then!)
** Dvorak was consistently around T1.5 in that time period, however, we saw that be seriously off when Recon arrived.
** Hence, with uncertainty, genesis is placed at 0000Z October 19 (as a tropical storm), but that could be conservative. A closed low likely formed around 1800Z October 18, but there isn't enough to prove it was a TC yet.
* Recon shocked us around 1800Z October 19 when it found a hurricane. It was likely already a hurricane by the first pass around 1645Z, and the last pass around 1915Z supported 75 kt with a pressure of 987 mb. That supports the trends earlier as well. Satellite imagery was virtually unchanged afterward.
* The next aircraft arrived around 1200Z October 20 and found little change in the intensity, along with a slightly lower pressure (lowest was 984 mb - 986/19 at 1400Z). Additionally, the satellite signature was starting to improve at that time, which suggests that Oscar intensified before landfall.
* Landfall took place at approximately 2145Z October 20. Dvorak numbers had risen and was T4.5 to T5.0 on some estimates. Unfortunately, no Recon or good surface data was available. There was a solid eyewall on microwave imagery. The SAR supported 95-100 kt but is likely inflated. Based on all the data, the best landfall intensity estimate is a possibly conservative 85 kt. The pressure at the time is estimated at 978 mb based on the same trends.
* Post-landfall weakening I think was more rapid than operational, and decay moved up significantly. Recon yesterday struggled to find a center, and that may not have really been one. I estimate it degenerated into a trough at 0000Z October 22, 18 hours earlier than operational.

This is a great and thorough explanation, and I'm convinced that 85kt is a solid, conservative estimate of Oscar's peak/landfall intensity. If you don't mind my asking, though, didn't SAR estimates accurately reflect Oscar's 70kt intensity (as corroborated by recon, and prior to the final round of intensification) earlier that day? And if so, did the factors that would inflate SAR intensity estimates become more significant closer to landfall? I'm not familiar with the technology, and I've seen a number of differing perspectives on the reliability of the SAR data in this case over the past couple of days.

I can't remember the SAR from the peak but it's possible. That said, it hasn't been proven in complete accuracy when tested against Recon in several other storms, but I do give it a bit of weight. Kind of like the SFMR which over-estimates in many high-end storms (like with Milton, the SFMR was showing as high as 175 kt which was much too high).

[HurricaneBelle]

 https://x.com/tropicalupdate/status/1849166731995910503

[WeatherBoy2000]

 https://x.com/FerragamoWx/status/1849170836076245340