ATL: ERNESTO - Post-Tropical - Discussion

[skyline385]

Still intensifying and looking some of the best it ever did.

[ElectricStorm]

I know looks aren't everything but I'm thinking it's stronger now than it ever was previously. Might be closer to 90kts or even higher now but I doubt NHC will go that high

[ElectricStorm]

05L ERNESTO 240819 0600 39.3N 61.1W ATL 75 972

[WaveBreaking]

This is ridiculous.

[aspen]

05L ERNESTO 240819 0600 39.3N 61.1W ATL 75 972

I don’t get why the NHC is going so low with Ernesto. Seems to be an issue with hurricanes at this latitude, because I remember Don ‘23 looked stronger than the NHC’s official estimates. Maybe manual and automatic Dvorak fixes, along with other satellite estimates, struggle with storms like this in the mid-latitudes?

[WaveBreaking]

A hurricane with a pinhole eye at 40N was not on my 2024 bingo card.

[cheezyWXguy]

A hurricane with a pinhole eye at 40N was not on my 2024 bingo card.

https://i.imgur.com/2oSQZvq.jpeg

I think it’s more that the eye is being partially shrouded by convective bursts, but either way I’m struggling to understand why the intensity is being held so low

[kevin]

Wow, Dvorak CI up to 5.2, supports an intensity of 952 mb / 95 kt. One of the most impressive systems I've ever seen at high latitudes and definitely stronger than 75 kt. Wouldn't be surprised if this is/was a minimal MH, crazy stuff.

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 9.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 19 AUG 2024 Time : 121020 UTC
Lat : 40:41:23 N Lon : 59:34:11 W


CI# /Pressure/ Vmax
5.2 / 951.6mb/ 94.8kt


Final T# Adj T# Raw T#
5.1 4.7 4.7

Center Temp : -44.7C Cloud Region Temp : -55.6C

Scene Type : EMBEDDED CENTER CLOUD REGION

[Ubuntwo]

I believe a recon flight would find low-end major hurricane force winds given the thick CDO and deep convection relative to latitude, as well as the boost from forward motion. Similar to Zeta in that regard - which probably would have also been pegged around high end 1/low end 2 without recon.

[cycloneye]

 https://x.com/AndyHazelton/status/1825499083747844445

[tolakram]

Given the opportunity Ernesto has gone quite 2005 ish with strengthening where it should not. I'm not sure how accurate the intensity estimates actually are but seems low, and more subjective than anything else. Reanalysis should be interesting.

[emeraldislenc]

What is the ACE for Ernesto? Just curious?

[REDHurricane]

This might be a dumb question but I'll ask it anyway: why isn't it possible to determine wind speeds of a tropical cyclone just by analyzing satellite footage alone? We know the time interval between satellite frames and we know the amount of distance covered by any individual part of the storm, so I would think that there would be an accurate method of measuring the wind speed at the higher levels of the atmosphere and then extrapolating that to surface winds without needing the Dvorak and other satellite estimates. Is it that the satellite resolution isn't high enough to accurately measure wind speeds in the lower levels of the atmosphere? But even then would the initializations of hurricane-specific models like HAFS, HWRF, etc. not be better estimates of wind speed than the other methods? Like here, the 00z HAFS-A initialization of Ernesto seems to be reasonably accurate to me:







So I guess my real question is, and I'm not sure if anyone will even be able to answer, why does the NHC favor certain methods of approximating wind speeds (Dvorak, etc.) over others like HAFS-A/B, HWRF, or even just directly measuring wind speeds by measuring each frame of satellite imagery?

[Buck]

What is the ACE for Ernesto? Just curious?

Currently at 12.1.

[Nuno]

I will be disappointed if this isn't properly reanalyzed.

[Ubuntwo]

This might be a dumb question but I'll ask it anyway: why isn't it possible to determine wind speeds of a tropical cyclone just by analyzing satellite footage alone? We know the time interval between satellite frames and we know the amount of distance covered by any individual part of the storm, so I would think that there would be an accurate method of measuring the wind speed at the higher levels of the atmosphere and then extrapolating that to surface winds without needing the Dvorak and other satellite estimates. Is it that the satellite resolution isn't high enough to accurately measure wind speeds in the lower levels of the atmosphere? But even then would the initializations of hurricane-specific models like HAFS, HWRF, etc. not be better estimates of wind speed than the other methods? Like here, the 00z HAFS-A initialization of Ernesto seems to be reasonably accurate to me:

https://i.ibb.co/dr89pC6/hafsa-sat-IR-05-L-5.png

https://i.ibb.co/QptXk1v/1a16b16e-8dd7-4ffb-969b-82ead5aad5fb.jpg

https://i.ibb.co/PcJtK4b/hafsa-mslp-wind-05-L-5.png

So I guess my real question is, and I'm not sure if anyone will even be able to answer, why does the NHC favor certain methods of approximating wind speeds (Dvorak, etc.) over others like HAFS-A/B, HWRF, or even just directly measuring wind speeds by measuring each frame of satellite imagery?

Because there is an established process for the Dvorak technique, and research supporting its efficacy. I agree there is probably value in model sat analysis too and research should be done. For what it’s worth, ADT currently pegs this at 95kt.

[kevin]

Raw T# now up to 5.4, 100 kt...

[FrontRunner]

Wow, only up to 80 kts. They must really not believe those satellite estimates. I thought for sure they'd at least go up to 85-90 kts.

[aspen]

Since Ernesto is about to cross over the Gulf Stream into cooler waters, this was likely the last advisory where the NHC could’ve operationally assessed it as the Cat 2 (or maybe low-end major) it likely is right now. Not sure why they think it’s “slowly strengthening” when it’s vastly improved over the last 24 hours and looks far healthier than when recon found a marginal Cat 2, with a strong eyewall and rotating deep convection.

[Teban54]

Ernesto continues to slowly gain strength. Satellite images
indicate that the eye of the hurricane has become a little better
defined, but the storm still has a convective asymmetry with the
strongest thunderstorms on the north side. The latest Dvorak
estimates from TAFB and SAB were 4.5/77 kt and the objective
satellite guidance is a little higher. Based on the data and the
improved structure, the initial wind speed is increased to 80 kt.
A very recent ASCAT pass indicated that Ernesto remains a large
tropical cyclone. The strongest winds and largest radius of
hurricane and tropical-storm-force winds are located in the
southeastern quadrant.

I wouldn't call 95-100 kt estimates "a little higher", lol