EPAC: OTIS - Aftermath - Discussion

[CrazyC83]

There has been very limited data, but that one weather station on Isla Roqueta - an island off the western side of Acapulco - provides valuable clues.

It never experienced the eye, and given the small size of the core, it may not have even been in the RMW, at the most it was at the edge of it. As the wind was out of the north-northeast and then northeast at 0645Z and southeast at 0700Z before shifting to due south as the storm passed well inland, the eye went to the east of the location. The city was largely either just west of the eye, or right in the eye on the eastern shore of Acapulco Bay (but not dead center). That also explains why there wasn't much storm surge flooding in Acapulco based on limited imagery (the flooding was likely rainfall). That said, the airport area likely saw very significant storm surge and we know NOTHING from there now.

The true landfall point I estimate was at 16.78N 99.82W on the eastern end of Punta Diamante (closer to Playa Diamante) and then the center went over the central part of the city at about 0700Z. It is likely that the intensity decreased in the last hour or so before landfall, but it is hard to say how much at this point. If the Schloemer equation is used based on the Isla Roqueta station at 0645Z, it results in:

* Outermost closed isobar: 1009 mb
* Distance from eye at 0645Z: 5 nautical miles
* RMW: 5.5 nautical miles
* Pressure at 0645Z: 957 mb (it likely was lower around 0650Z but don't have data)

(PR - Po) / (Pn - Po) = e^(-RMW/R)

(957 - Po) / (1009 - Po) = e^(-5.5/5) = 0.3328

Doing the calculations, at 0645Z, the pressure was likely around 933 mb. That suggests that the landfall pressure was probably in the range of 930 mb since it certainly filled some in those 20 minutes.

[cycloneye]

Remnants Of Otis Discussion Number 15
NWS National Hurricane Center Miami FL EP182023
400 PM CDT Wed Oct 25 2023

High-resolution visible satellite imagery and synoptic observations
indicate that the surface circulation of Otis has dissipated
over the mountains of southern Mexico. Therefore, this is the last
advisory on this system.

The remnants of Otis will continue to produce locally heavy rains
and flooding through Thursday.


Key Messages:

1. Heavy rains from Otis will continue to impact areas of
southwestern and south-central Mexico through Thursday. This
rainfall will produce flash and urban flooding, along with mudslides
in areas of higher terrain.


FORECAST POSITIONS AND MAX WINDS

INIT 25/2100Z 19.1N 100.8W 30 KT 35 MPH...REMNANTS OF OTIS
12H 26/0600Z...DISSIPATED

$$
Forecaster Pasch

[CrazyC83]

This is not official, but here is how I would analyze the best track of Otis.

EP182023, OTIS, 20,
20231021, 1200, , LO, 9.7N, 97.1W, 25, 1010,
20231021, 1800, , TD, 9.6N, 97.0W, 25, 1010,
20231022, 0000, , TD, 9.5N, 96.8W, 30, 1009,
20231022, 0600, , TD, 9.5N, 96.5W, 30, 1008,
20231022, 1200, , TS, 9.8N, 96.7W, 35, 1007,
20231022, 1800, , TS, 10.1N, 96.9W, 40, 1005,
20231023, 0000, , TS, 10.6N, 97.1W, 40, 1005,
20231023, 0600, , TS, 11.2N, 97.3W, 40, 1005,
20231023, 1200, , TS, 11.7N, 97.5W, 45, 1004,
20231023, 1800, , TS, 12.5N, 97.7W, 45, 1003,
20231024, 0000, , TS, 13.3N, 98.0W, 50, 1002,
20231024, 0600, , TS, 13.8N, 98.5W, 60, 998,
20231024, 1200, , HU, 14.3N, 99.0W, 75, 989,
20231024, 1800, , HU, 14.9N, 99.3W, 100, 973,
20231025, 0000, , HU, 15.7N, 99.6W, 135, 937,
20231025, 0430, I, HU, 16.4N, 99.7W, 150, 922,
20231025, 0600, , HU, 16.7N, 99.7W, 140, 928,
20231025, 0625, L, HU, 16.8N, 99.8W, 135, 930,
20231025, 1200, , TS, 17.9N, 100.5W, 60, 988,
20231025, 1800, , DB, 18.7N, 100.9W, 30, 1002,

After going through all the data, here are my thoughts on Otis:

* Genesis is moved up about 18 hours out of respect of T2.0 ratings on Dvorak. That's usually a good indicator an LLC has formed. An ASCAT pass at 0318Z on October 22 helps support that too.

* Intensification was slow at first, but the first sign of takeoff was at about 0700Z when hints of an eyewall structure were forming. Dvorak started giving out T4.0 ratings at 1200Z, but the Recon flight at 1900Z confirmed much higher winds. Hence, the winds are upped at 06Z and 12Z. Make no mistake, it still intensified explosively - 100 kt in 28 hours!

* The Recon flight and pressure drop were hints that it was exploding between about 1500Z and 0300Z. Once the eye cleared by about 2300Z, it was clear Otis was extremely intense. How much? That's a rough guess. The peak intensity is estimated to be at approximately 0430Z, when the eye looked most prominent and some T7.5 ratings were coming in by raw data-T ratings. At that point, I estimate the intensity was 150 kt, with a pressure of 922 mb.

* Otis weakened fairly quickly in the last 2 hours before landfall based on satellite structure and the sole surface observation found. Using the Schloemer equation, the estimated pressure just after landfall was 933 mb or so. I have estimated the landfall pressure at 930 mb, +/- 4 mb or so. Admittedly, the wind estimate is FAR more uncertain, but assuming a fairly rapid rate of weakening, I estimated it to be 135 kt. That is a highly uncertain estimate.

* Post-landfall intensities are dropped dramatically for a more realistic weakening over mountains.

[Teban54]

This is not official, but here is how I would analyze the best track of Hilary.

[CrazyC83]

This is not official, but here is how I would analyze the best track of Hilary.

Copied it from there as a template. Forgot to make the change.

[Yellow Evan]

Would not use Schloemer with the rugged terrain of Mexico that can easily modify the pressure gradient. We've seen some weird P-W relationships with and without its use in this area of the world.

[CrazyC83]

Would not use Schloemer with the rugged terrain of Mexico that can easily modify the pressure gradient. We've seen some weird P-W relationships with and without its use in this area of the world.

True, but it's the only non-Dvorak estimate available and could always be changed.

[Yellow Evan]

Is it just my imagination, or did it look like the eye was "falling apart" a little before Otis crossed the coastline. Any chance he weakened below catastrophic levels before the worst reached Acapulco? I know there has been widespread damage, but the devastation from a weakening storm would be "better."

Yes but it probably didn't meaningfully lower the winds by that point.

[Astromanía]

That was a great analysis but I just want to say when hurricanes make landfall in the pacific coast of Mexico the pressure tend to go up quikly due to the high terrain near the coast but the winds are slower to respond to this, that's why we have weakening hurricanes making landfall with high pressures for the wind speed that is reported on land, in my opinion I don't think winds have weaken a lot at landfall with Otis, I guess they stayed at 145kt or they weakened to 140kt but not more, there was not an inibitor for Otis to weaken at landfall more than land interaction

[Xyls]

 https://twitter.com/WxNB_/status/1717268663663751597

[Iceresistance]

Catastrophic Damage in Acapulco...

 https://twitter.com/azucenau/status/1717284451456082422

[CrazyC83]

I think we are already starting to learn what at least played a part in the EPIC FAIL of the computer models. The only data we had was satellite and it was in a difficult position, with the jet stream not too close but not too far and wind shear appeared to be misdiagnosed. Additionally, there was only one Hurricane Hunter flight with no radar, and no coastal radar, and no upper-air weather stations in the area (plus very few surface stations).

Some models didn't even bring it to landfall - at any intensity.

[mmmmsnouts]

If those awful scenes are from the beachfront, with probably the best-constructed buildings in the area, I'm worried that the video we get back from deeper in the city is going to be truly horrific.

[Hurricane2022]

Here... we... go.
 https://twitter.com/WXFatalities/status/1717314104216678637

[zhukm29]

What an absolutely catastrophic outcome for the global models, during what was likely the worst possible scenario: with Otis making the strongest EPAC landfall at night, directly over a city of 1+ million people who were expecting a tropical storm hours earlier. Hopefully a ton of research goes into why this happened to ensure that this never happens again - this must be used as an opportunity for us to do better

[Sciencerocks]

It is time for mexico to build some radars, buy a couple of recon planes so they can better prepare their own population for storms lie this.

There's no reason why there shouldn't be a radar for cities of a million plus people. No reason why they don't have a recon to send into storms like this on short notice and would be far closer to the storms...

[Hurricane2022]

I have a bad feeling that the historic Hurricane Otis could leave meteorologists a little traumatized, but also more cautious from today onwards.
... Mark Sudduth explains here that, despite this epic and deadly failure of the forecast models with Otis' ERI, they showed an ingredient that, besides the low shear and the boiling waters (almost) no one noticed, was probably the biggest culprit for this misfortune to happen.
https://youtu.be/vVXaIvTLcHo?si=bdohE9-zN1kvt-2E

[Yellow Evan]

What was not captured by models is the alignment of the LLC and MLC’s within a few hours early on 10/24 once a low level core had developed (despite being exposed at the time) and convection overcame a caping inversion. This set the stage for the infamous RI.

On another note, Mexico needs to give permission for the USAF to station Recon planes much like Barbados.

Mexico also really needs to up the number of radiosonde launches and install Doppler radars throughout. Same goes for a lot of countries in the tropics tbf most of which aren’t quite as developed.

[canebeard]

What was not captured by models is the alignment of the LLC and MLC’s within a few hours early on 10/24 once a low level core had developed (despite being exposed at the time) and convection overcame a caping inversion. This set the stage for the infamous RI.

On another note, Mexico needs to give permission for the USAF to station Recon planes much like Barbados.

Mexico also really needs to up the number of radiosonde launches and install Doppler radars throughout. Same goes for a lot of countries in the tropics tbf most of which aren’t quite as developed.

Considering that about10% of homes in Mexico still do not have plumbing or running water, one might conclude that these modern meteorological "necessities" are not high on their yearly budget wish list.

I do recall when frequenting the NHC decades ago, the NOAA recon. folks would get budgeted in some Octobers to station in Acapulco for a couple of weeks. That would happen when the yearly apportioned expenses were not used up by the dearth of Atlantic basin missions in those years.

[kevin]

Still not that much footage from the damage after Otis, but what we do get looks like extreme damage. All the footage we get is from urbanized areas in Acapulco, I can't even imagine what smaller wooden villages near Acapulco look like, they're probably completely gone. Still not a clear view on the total damage and potential casualties, but I'm afraid the number might be high.