ATL: FLORENCE - Post-Tropical - Discussion

[BobHarlem]

I wonder if we will get some live storm surge video this time around. It’s so hard to really stream live surge because it’s so dangerous. If we could see it live I think people would take it more seriously.

That's what Mark at hurricanetrack.com does with the remote cameras.

[cheezyWXguy]

IR looks remarkably close to what the models indicated it would a few days ago.

It actually really does. I had my doubts, and posted about it the other night, but that simulated IR feature has won me over.

It seems that PV anomaly mentioned earlier, and the SW shear has been keeping Florence in check. I don't recall seeing anything the in the models that explicitly showed this feature, but in retrospect, it makes sense to me now as to why these models depicted the storm undergoing at most modest strengthening, despite supposedly very low shear and very warm water temps.

[jlauderdal]

There is no shortage of surge footage, send any doubters over to youtube that will be all the evidence they need

I wonder if we will get some live storm surge video this time around. It’s so hard to really stream live surge because it’s so dangerous. If we could see it live I think people would take it more seriously.

[CrazyC83]

Do you all realize that recon is showing 80 miles of cat2 flight level winds!!! That is a huge wow from the EWRC...not good for storm surge

Recon has been in hurricane force flight level winds for 40 mins+

Unbelievable. And yet another EWRC is about to start; storm surge risk could be terrible.

In Hampton Roads, they are not very prepared to evacuate for storm surge. I hope it doesn't come to that.

I'd expand the order to Zone B tomorrow morning if I were them.

[Sciencerocks]

Can dry air ingestion initiate an ERC?

Yes,

Within my years of watching these I can clearly say without a doubt that dry air causes a unlimited number of these.

Ike 2008
Rita 2005
Frances 2004

For a few examples.

I don't know of any science that describes exactly what causes an ERC.

https://en.wikipedia.org/wiki/Eyewall_replacement_cycle

Do you know of any?

Water vapor not only affects TC intensity. Prior modeling studies have demonstrated impacts from environmental water vapor on TC structure. These impacts can also affect intensity change. Specifically, enhanced water vapor content within the TC enhances the rainbands, which can lead to an eyewall replacement cycle, causing a temporary weakening, followed by re-intensification. This thesis evaluates observational and high resolution MM5 model output from Hurricanes Katrina and Rita from the Hurricane Rainband and Intensity Experiment (RAINEX) to evaluate the effects of varying water vapor distributions on TC structure.

While the two hurricanes were of similar intensity, they had different water vapor distributions and structures. Rita
underwent an eyewall replacement cycle while under RAINEX surveillance while Katrina did not. Rita was also located within a dry environment and had a strong horizontal moisture gradient, while Katrina was in a moist environment and had a weak
moisture gradient.

Results suggest that a strong horizontal water vapor gradient, with a moist TC and dry outer environment may confine the hurricanes into a pattern that causes them to have high circularity, promoting the formation of a secondary eyewall. The dry outer environment had strong atmospheric stability and was less favorable for deep convection far from the center in the Rita case. The moist environment in the Katrina case was more unstable. This may have allowed for the rainbands to be farther from the center in a less circular pattern than Rita. The results presented in this thesis suggest that
this pattern is less favorable for an eyewall replacement cycle.

https://scholarlyrepository.miami.edu/c ... =oa_theses

Frances and ike are two other cases I believe want through this.

[drezee]

Recon drop shows 140kts+ winds above surface and 116kts surface

[CrazyC83]

Recon drop shows 140kts+ winds above surface and 116kts surface

Interesting, that goes against both the flight level winds and the SFMR.

[drezee]

Recon drop shows 140kts+ winds above surface and 116kts surface

Interesting, that goes against both the flight level winds and the SFMR.

From drop:
966mb 85° (from the E) 116 knots (133 mph)
962mb 105° (from the ESE) 92 knots (106 mph)
961mb 100° (from the E) 92 knots (106 mph)
957mb 95° (from the E) 106 knots (122 mph)
955mb 95° (from the E) 121 knots (139 mph)
953mb 90° (from the E) 125 knots (144 mph)
948mb 90° (from the E) 124 knots (143 mph)
941mb 100° (from the E) 131 knots (151 mph)
933mb 100° (from the E) 122 knots (140 mph)
927mb 110° (from the ESE) 141 knots (162 mph)
922mb 110° (from the ESE) 129 knots (148 mph)
919mb 110° (from the ESE) 127 knots (146 mph)
914mb 115° (from the ESE) 130 knots (150 mph)
909mb 115° (from the ESE) 128 knots (147 mph)
903mb 120° (from the ESE) 132 knots (152 mph)
898mb 120° (from the ESE) 129 knots (148 mph)
891mb 120° (from the ESE) 135 knots (155 mph)
874mb 120° (from the ESE) 130 knots (150 mph)
850mb 125° (from the SE) 133 knots (153 mph)
697mb 140° (from the SE) 126 knots (145 mph)

[jlf7]

ith these closeups sometimes we lose sight at how big these storms can get. The eye is bigger than a city

 https://twitter.com/HeatherZWeather/status/1039667155493679111

[supercane4867]

If an EWRC starts tonight it will likely complete before the storm nearing land unless there's shear to disrupt the process

[Aric Dunn]

Just a little perspective.

[Ian2401]

Just for future refrence, where do you guys find the microwave imagery of the inner structure of the system?? it's one of my favorite tools that I see on wxtwitter, but don't know the source for it.

[dukeblue219]

Recon drop shows 140kts+ winds above surface and 116kts surface

Interesting, that goes against both the flight level winds and the SFMR.

I feel like this happens a lot with Atlantic Cat4/5's that undergo an EWRC or some kind of major land interaction. They recover from the event and look potent, but successive recon flights struggle to find surface winds that are expected. Meanwhile dropsonde after dropsonde finds insane winds 20-100mb above the surface.

I'm also not convinced by the 116kt number quoted. Technically it was 2mb above splash, and it was an outlier from the previous trends for that drop. Might've just been a transient gust.

[tolakram]

Water vapor not only affects TC intensity. Prior modeling studies have demonstrated impacts from environmental water vapor on TC structure. These impacts can also affect intensity change. Specifically, enhanced water vapor content within the TC enhances the rainbands, which can lead to an eyewall replacement cycle, causing a temporary weakening, followed by re-intensification. This thesis evaluates observational and high resolution MM5 model output from Hurricanes Katrina and Rita from the Hurricane Rainband and Intensity Experiment (RAINEX) to evaluate the effects of varying water vapor distributions on TC structure.

While the two hurricanes were of similar intensity, they had different water vapor distributions and structures. Rita
underwent an eyewall replacement cycle while under RAINEX surveillance while Katrina did not. Rita was also located within a dry environment and had a strong horizontal moisture gradient, while Katrina was in a moist environment and had a weak
moisture gradient.

Results suggest that a strong horizontal water vapor gradient, with a moist TC and dry outer environment may confine the hurricanes into a pattern that causes them to have high circularity, promoting the formation of a secondary eyewall. The dry outer environment had strong atmospheric stability and was less favorable for deep convection far from the center in the Rita case. The moist environment in the Katrina case was more unstable. This may have allowed for the rainbands to be farther from the center in a less circular pattern than Rita. The results presented in this thesis suggest that
this pattern is less favorable for an eyewall replacement cycle.

https://scholarlyrepository.miami.edu/c ... =oa_theses

Frances and ike are two other cases I believe want through this.

That's Derek's paper. Interesting. Thanks.

[cjrciadt]

Wow like riding a rail to its target!

[Hammy]

Recon drop shows 140kts+ winds above surface and 116kts surface

Interesting, that goes against both the flight level winds and the SFMR.

I feel like this happens a lot with Atlantic Cat4/5's that undergo an EWRC or some kind of major land interaction. They recover from the event and look potent, but successive recon flights struggle to find surface winds that are expected. Meanwhile dropsonde after dropsonde finds insane winds 20-100mb above the surface.

I'm also not convinced by the 116kt number quoted. Technically it was 2mb above splash, and it was an outlier from the previous trends for that drop. Might've just been a transient gust.

I thought the sondes only measured gusts though.

[dukeblue219]

I thought the sondes only measured gusts though.

Essentially yes, and apologies if I wasn't clear about that.

[bp92]

A cousin of mine is currently working at Chapel Hill, NC. She comes from Colombia, so she has no clue of what she should expect from a hurricane, let alone something like Florence.

What should I tell her to expect, regarding evacuations and potential threats she will face? I presume mostly rain, since Chapel Hill is inland and Flo would likely be weak by the time it gets to her location (especially if it stalls before landfall), but I have no clue if she's at risk of flash flooding or something else.

[sponger]

Water vapor not only affects TC intensity. Prior modeling studies have demonstrated impacts from environmental water vapor on TC structure. These impacts can also affect intensity change. Specifically, enhanced water vapor content within the TC enhances the rainbands, which can lead to an eyewall replacement cycle, causing a temporary weakening, followed by re-intensification. This thesis evaluates observational and high resolution MM5 model output from Hurricanes Katrina and Rita from the Hurricane Rainband and Intensity Experiment (RAINEX) to evaluate the effects of varying water vapor distributions on TC structure.

While the two hurricanes were of similar intensity, they had different water vapor distributions and structures. Rita
underwent an eyewall replacement cycle while under RAINEX surveillance while Katrina did not. Rita was also located within a dry environment and had a strong horizontal moisture gradient, while Katrina was in a moist environment and had a weak
moisture gradient.

Results suggest that a strong horizontal water vapor gradient, with a moist TC and dry outer environment may confine the hurricanes into a pattern that causes them to have high circularity, promoting the formation of a secondary eyewall. The dry outer environment had strong atmospheric stability and was less favorable for deep convection far from the center in the Rita case. The moist environment in the Katrina case was more unstable. This may have allowed for the rainbands to be farther from the center in a less circular pattern than Rita. The results presented in this thesis suggest that
this pattern is less favorable for an eyewall replacement cycle.

https://scholarlyrepository.miami.edu/c ... =oa_theses

Frances and ike are two other cases I believe want through this.

That's Derek's paper. Interesting. Thanks.

Derek Ortt! Miss him around here. His call on Jeanne looping well before models was epic. The modeling has come such a long way in so short a time.

[StormPyrate]

A cousin of mine is currently working at Chapel Hill, NC. She comes from Colombia, so she has no clue of what she should expect from a hurricane, let alone something like Florence.

What should I tell her to expect, regarding evacuations and potential threats she will face? I presume mostly rain, since Chapel Hill is inland and Flo would likely be weak by the time it gets to her location (especially if it stalls before landfall), but I have no clue if she's at risk of flash flooding or something else.

contact the local officials or listen to local news. inland flooding can be damning, not familiar if that area is prone to flooding, but inland has little to do with wind and more to do with flooding
wind wise not as big a deal