ATL: LORENZO - Post-Tropical - Discussion

[Ken711]

Just WOW. A Category 5 at 45W is absolutely nuts.

Yes, very impressive.

[northjaxpro]

There is sufficient data for maintaining Lorenzo's Cat 5 status with the wind and T 7.0 . Recon was in there this time around to support Cat 5 data and presentation.

I would be rather surprised for NHC to pull an abrupt about face about this now.

Lorenzo will remain in the record book as a groundbreaking one at that being the farthest Easternmost Cat 5 tropical cyclone ever in the North Atlantic basin.

but the NHC forecasters are all on twitter this morning talking about Lorenzo reaching Category 5 last night.

Yeah, they are on there talking on Twitter because they know damn well that Lorenzo attained Cat 5 status. Lorenzo stays a Cat 5!

[AnnularCane]

There is sufficient data for maintaining Lorenzo's Cat 5 status with the wind and T 7.0 . Recon was in there this time around to support Cat 5 data and presentation.

I would be rather surprised for NHC to pull an abrupt about face about this now.

Lorenzo will remain in the record book as a groundbreaking one at that being the farthest Easternmost Cat 5 tropical cyclone ever in the North Atlantic basin.

They're not going to. Best Track will be updated correctly to reflect the intensity I'm sure, but the NHC forecasters are all on twitter this morning talking about Lorenzo reaching Category 5 last night.

Yeah, seems like that would be like taking away a horse's Kentucky Derby title or something...oh, never mind.

[Buck]

Wow, just landed in Istanbul from an overnight flight and getting caught up. Lorenzo... you did it. Just incredible!

[Cleveland Kent Evans]

Legitimately an out of place supertyphoon. Seems to have been nothing even remotely comparable in the satellite era; I don't know what we would even call this besides an Atlantic typhoon. Might also join the record books as one of the few 5s to avoid retirement unless it hits the Azores extremely hard. In which case Luigi is the only appropriate replacement to match Mario on the EPac list.

If it does happen it could actually happen... both names are Italian origin (I'm Italian myself, sharing the same name with this storm) and don't they have to match the same language?

Lorenzo is on the list because of its status as a Spanish name, not an Italian one. (There are many names which are traditionally the same in both Spanish and Italian.)

And in the Atlantic replacement names do NOT have to "match the same language", as shown by Margot replacing Maria, Isaias replacing Ike, etc.

[Ptarmigan]

I am not surprised that Lorenzo is a Category 5 hurricane.

Me either. I stated earlier in the week on this thread that he had a good shot at achieiving history out in the Far Eastern Tropical Atlantic basin.

He has indeed!! An increfible ttopical cyclone! I still maintain he msy have reached Cat 5 intensity back on Thursday night. So, he has had 2 rapid intensification cycles in the past 48 hours!
Simply amazing!

If I remember correctly, it was also you who mentioned in the first pages of the Dorian thread that you felt as though the precursor for Dorian (99L) would grow into a potentially formidable tropical cyclone.

I am not surprised if Lorenzo was a Category 5 hurricane on Thursday. We shall see.

Frankly, I was no surprised that Dorian became a Category 5 hurricane.

As October approaches, I would not be surprised if we see another Category 5 hurricane. Many Category 5 hurricanes have formed in October. Most of the most intense hurricanes in their respective basins have formed in October.

[1900hurricane]

It's worth noting that microwave intensity estimates were running well below 140 kt. Given the DT of 7.0, I might shrug them off if they were in the 130-135 kt range due to margin of error, but the highest estimate was only 120 kt from a remarkably clean ATMS pass. Despite how much I want to see the category 5 retained, dropping to 135 kt is probably the right move.

[TheAustinMan]

It's worth noting that microwave intensity estimates were running well below 140 kt. Given the DT of 7.0, I might shrug them off if they were in the 130-135 kt range due to margin of error, but the highest estimate was only 120 kt from a remarkably clean ATMS pass. Despite how much I want to see the category 5 retained, dropping to 135 kt is probably the right move.

It's worth noting though that at 1231 UTC, AMSU estimated a central pressure of 927mbar as Lorenzo was weakening from the overnight peak intensity. This was pretty close to the estimated minimum pressure of 925mbar from the NHC. This seems a little high given the Category 5 intensity and Lorenzo's size, but using the UW-CIMSS ADT environmental parameters and AMSU estimated pressure, KZC already gets me to 135 kt in the weakening phase, so there may be enough peripheral evidence alongside the Dvorak analyses to support maintaining Lorenzo at Category 5 intensity in post.

I'm not sure on the specifics of microwave wind estimates, but at least for AMSU I think that the algorithm was designed with pressure in mind first (pressures are strongly correlated with warm core temperature anomalies), so I would lend more weight to microwave pressure estimates rather than microwave wind estimates. I'm not too familiar with the ATMS/SSMIS algorithms (I would guess that they use a similar methodology to AMSU), but at least from what I've seen AMSU does a pretty spectacular job estimating pressures for high end storms.

[TropicalAnalystwx13]

It is extremely unlikely the change in Best Track is an indication of a Category 5 downgrade. The much more likely answer is that the Cat 5 point will be a special point between 0z and 6z. Remember that SAB was only T5.5 at 0z but T7.0 at 01:30z.

[Emmett_Brown]

Lorenzo is huge and powerful ACE machine. 275 mi radius of TS winds; he is no doubt a huge wave producer. It will be fascinating to see how long he can hold on to tropical characteristics as he moves NE, and how he might affect the UK, assuming he tracks that far E.

[1900hurricane]

It's worth noting that microwave intensity estimates were running well below 140 kt. Given the DT of 7.0, I might shrug them off if they were in the 130-135 kt range due to margin of error, but the highest estimate was only 120 kt from a remarkably clean ATMS pass. Despite how much I want to see the category 5 retained, dropping to 135 kt is probably the right move.

It's worth noting though that at 1231 UTC, AMSU estimated a central pressure of 927mbar as Lorenzo was weakening from the overnight peak intensity. This was pretty close to the estimated minimum pressure of 925mbar from the NHC. This seems a little high given the Category 5 intensity and Lorenzo's size, but using the UW-CIMSS ADT environmental parameters and AMSU estimated pressure, KZC already gets me to 135 kt in the weakening phase, so there may be enough peripheral evidence alongside the Dvorak analyses to support maintaining Lorenzo at Category 5 intensity in post.

I'm not sure on the specifics of microwave wind estimates, but at least for AMSU I think that the algorithm was designed with pressure in mind first (pressures are strongly correlated with warm core temperature anomalies), so I would lend more weight to microwave pressure estimates rather than microwave wind estimates. I'm not too familiar with the ATMS/SSMIS algorithms (I would guess that they use a similar methodology to AMSU), but at least from what I've seen AMSU does a pretty spectacular job estimating pressures for high end storms.

That is certainly good to note, thanks. I certainly would have preferred if there was an AMSU estimate to supplement the ATMS estimate around that time (I wonder why an estimate wasn't made on the 0003Z MetOp-B pass). As far as microwave intensity estimate go, AMSU estimates have been around the longest and are probably the most refined. However, ATMS estimates have shown good performance relative to recon verified intensities with the intense systems of 2017 and 2018 in regards to both pressure and wind. I've noted that resolution sometimes plays an issue with small systems (like peak Dorian), but Lorenzo can't exactly be classified as small, so I wouldn't think that would be an issue here. It's honestly a headscratcher to see the ATMS estimated intensity so low, especially since I don't see anything wrong with the data. I wouldn't have an issue probably if the 140 kt peak was retained, but I think the ATMS estimate has to be given some weight, which would argue for the drop to 135 kt that has occurred in best track.

Somewhat unrelated, but I personally think Barbara had a stronger case for 140 kt than Lorenzo due to higher microwave estimates and a much warmer eye.

[EquusStorm]

It's definitely the most ragged eye I've seen in a modern category five and if they hadn't already announced it and made a big deal of it, 135kt definitely seems feasible; but I would certainly hope they will leave it as it is just for bizarro statistical purposes. Am still pretty floored they decided to pull the trigger on it to start with (I don't disagree but that's pretty bold from the NHC) and really makes me wonder just how violent Isabel was.

Given its massive size already, I'd wager it becomes one of the largest wind fields on Atlantic record once it starts opening up into a post tropical system.

[Hypercane_Kyle]

Interesting tidbit: Since the beginning of the satellite era (60s onward) there have only been 5 seasons that have featured >=2 category 5 hurricanes and almost all of them were in the last 15 years: 1961, 2005, 2007, 2017, and 2019.

[BYG Jacob]

Interesting tidbit: Since the beginning of the satellite era (60s onward) there have only been 5 seasons that have featured >=2 category 5 hurricanes and almost all of them were in the last 15 years: 1961, 2005, 2007, 2017, and 2019.

No trend there at all.

[Highteeld]

Huge outer eyewall

[1900hurricane]

Pressure gradient is blown way up. First pass only supports about 80 kt. Pressure above 950 mb. ATMS may have been on to something.

[Hypercane_Kyle]

Pressure gradient is blown way up. First pass only supports about 80 kt. Pressure above 950 mb. ATMS may have been on to something.

I don't think so, rather I think Lorenzo has rapidly weakened over the past few hours due to a combination of a significant EWRC, dry air, and shear. The satellite presentation isn't even half as impressive as it was overnight.

[Highteeld]

For me, the fact that recon did not pass through Lorenzo at either of its two peaks makes it impossible for me to conclude if ADT was running hot or not, especially regarding the NHC upgrade.

[Highteeld]

For me, the fact that recon did not pass through Lorenzo at either of its two peaks makes it impossible for me to conclude if ADT was running hot or not, especially regarding the NHC upgrade.

On a second note, the outer eyewall is pretty stout. Having that many 100 kt flight level obs in the NE quadrant at such a broad radius is very impressive. Tighten that up and you could probably get ~ 150 kt flight level. There is a considerable amount of angular momentum in that outer eyewall.

[1900hurricane]

There's some higher flight level winds now way out in the outer eyewall of about 100 kt.