EPAC: OTIS - Aftermath - Discussion

[NotoSans]

Just put down my thought on a Twitter (or X) thread. A comparison with several WPAC cases (Noru'22 being the example used) highlighted possible similarities between these RI misses.

Two key areas to look at: (a) shear diagnosis and mechanism of intensification under moderate / suboptimal shear; (b) improved poleward outflow due to upper-level trough (even though there isn't direct trough interaction).

It may also be important to spot the moment when a storm transitions from a shear pattern to a CDO pattern. It may just come down to one round of downshear convective bursts, but a deeper look is needed here.

These are just my amateur thoughts. Looking forward to others sharing their insights!

 https://twitter.com/squirtleinhk/status/1717095245089812513

[Hurricane2022]

From Acapulco
 https://twitter.com/newsandufology/status/1717100333602681098



 https://twitter.com/Rob_louzada/status/1717097464069505313



 https://twitter.com/AttentiveCEE/status/1717084934462906495



 https://twitter.com/agustincr3/status/1717099767527002343

[Hurricane2022]

From Acapulco, II
 https://twitter.com/zepedavic/status/1717074522136813674



 https://twitter.com/xNewsMonitor/status/1717110553787670635



 https://twitter.com/Pedrola51624238/status/1717095006874353945

[Hurricane2022]

 https://twitter.com/zeb199818/status/1717096003881558022



 https://twitter.com/zeb199818/status/1717064646526713997



 https://twitter.com/zeb199818/status/1717063202566185367



 https://twitter.com/zeb199818/status/1717054692038172878

[doomhaMwx]

Obs from an AWS in Roqueta Island (107m elevation). At 06:45Z, the station recorded an MSLP of 957.4 mb in the eyewall with sustained winds of 70.6 kt, gusting to 116 kt. The station continuously reported gusts above 100kt from 06:30Z to 07:30Z, with a maximum of 117.2 kt!

[aspen]

I don’t believe what I’m seeing. A 145 kt landfall over a major city when just 24 hours earlier, every forecast and model was calling for a TS or maybe a weak hurricane at the most. Almost no time for proper warnings. Hopefully Otis’ near-record RI was communicated effectively to people in Acapulco, or at least as effectively as it could’ve been when a Cat 5 literally forms out of thin air right before landfall.

[ThunderForce]

The level of destruction seen in all of these images is heartbreaking.

[Hypercane_Kyle]

No doubt in my mind this was the biggest fail for the models I've ever seen. A Cat 5 into a major city with no warning.

[mrbagyo]

It's strange to see this thread with only 12 pages for such a historic storm
We're all caught off guard.

[kevin]

I haven't been tracking storms for a few days and then I open Storm2k to this... No words, by far the biggest model bust I've ever seen. And pretty much the worst-case scenario imaginable. Not only is it an unprecedented cat 5 landfall over a major city in Mexico, but also a cat 5 landfall that wasn't expected at all with practically 0 preparation time. I fear that we might be looking at a major catastrophe unfolding.

[cycloneye]

BULLETIN
Hurricane Otis Intermediate Advisory Number 13A
NWS National Hurricane Center Miami FL EP182023
700 AM CDT Wed Oct 25 2023

...STRONG WINDS CONTINUING TO SPREAD INLAND OVER SOUTHERN MEXICO...
...HEAVY RAINFALL AND FLASH FLOODING OCCURRING OVER PORTIONS OF
SOUTHERN MEXICO...


SUMMARY OF 700 AM CDT...1200 UTC...INFORMATION
----------------------------------------------
LOCATION...17.7N 100.3W
ABOUT 60 MI...100 KM NNW OF ACAPULCO MEXICO
MAXIMUM SUSTAINED WINDS...110 MPH...175 KM/H
PRESENT MOVEMENT...NNW OR 345 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...965 MB...28.50 INCHES

[Category5Kaiju]

It's strange to see this thread with only 12 pages for such a historic storm
We're all caught off guard.

I think there are 2 reasons for this. One, because it was so unexpected (heck, even the legendary Josh Morgerman missed this storm). Two, because it was an EPAC storm (generally speaking, Atlantic storms get more attention, and I can bet you that this website would have likely crashed multiple times if this was an Atlantic storm we were talking about, especially if it hit a major US city).

[kevin]

An estimate of peak intensity using the Knaff-Zehr-Courtney wind-pressure relationship.

Inputs
Vmax = 145 kt
Translation speed = 9.2 kt
R34 = 61 nm
Latitude = 16.8N
Background pressure = 1008 mb

KZC has a different equation below 18N and above 18N with slightly different results. Even though Otis was still below 18N, NHC often uses the >18N version for very intense systems close to the boundary. For example the >18 N equation is how the 872 mb value for Patricia was verified. Since 16.8N is kind of an edge case I'll show a range of both equations (the <18N equation results in a slightly more intense system).

Output
Peak intensity = 917 - 920 mb

So Otis was most likely a little deeper than NHC indicated in its discussion, but that will be something for post-season analysis and could also benefit from surface observations near Acapulco. If NHC underestimated the winds the pressure could've been even lower. Here are estimates of the minimum pressure of Otis depending on the maximum wind speed. An upgrade to 150 kt in post-season could thus cause an even lower pressure estimate.

140 kt = 922 - 925 mb
145 kt = 917 - 920 mb
150 kt = 911 - 915 mb
155 kt = 905 - 910 mb

Link to the latest version of the KZC relationship that NHC uses to my knowledge: https://rammb.cira.colostate.edu/resources/docs/Courtney&Knaff_2009.pdf

[Zonacane]

This was even crazier than Wilma or Patricia.

[Kingarabian]

Very strange not seeing kingarabian commenting here

I honestly wrote this system off early yesterday.

I'm reading all the posts right now. This is actually crazy that this happened and that I missed it in real time.

Prayers out to those in its way. Very potentially tragic situation.

[cycloneye]

 https://twitter.com/ExtremeStorms/status/1717172107191161196

[Kingarabian]

A massive bust by the models that has led to direct consequences. That will be scrutinized.

[shah83]

One place to keep an eye on is the area to the east of Acapulco. It's basically a low area with the sea in the front and a lagoon in the back, and doesn't seem to have high construction standards.

[kevin]

Both internet and other communication services are almost completely lost after Otis. But slowly some videos and images are coming through and the damage looks total. I hope the damage somehow turns out to be 'less than expected' as we get more images now that the sun rises, but I'm afraid this is like Mexico's equivalent of Katrina.

[Kingarabian]

Just looking at photos posted during its peak, you can see that its outflow and resulting overall look did not suggest an optimal environment for a cat.5. But it did it anyway.