ATL: LEE - Post-Tropical - Discussion

[Iceresistance]

Could not get on the FNMOC site for the microwave passes, but I found this on CIMSS


https://s11.gifyu.com/images/S428K.png

[GeneralChow]

I Dont get how this shear surprised people… Yesterday the 20kt shear zone was present NW of the system.

Not everybody knows how to read a Satellite, or know how to find and utilize shear and vorticity maps. It's not like they have a simple-to-use index and explanation of maps and links at their fingertips. Most of the casuals are waiting for others to post images and analyses. Most people are routinely exposed to the hype on Twitter, Youtube, and the Forum, because it's easier to digest. It's simple. And Simplicity is king when it comes to people coming home after a hard 9-5.
https://tropic.ssec.wisc.edu/real-time/ ... oom=&time=

And it isn't exactly 20knot shear that's causing Lee to rapidly struggle. It's the the direction SW shear, because it forces rising warm and cold downburst on the surface level to underlap the naturally cold west and warm east side of the storm. So the cold dry wind shear is located on the cool side of the cyclone, and warm, moist air at the surface is displaced towards the east side. Therefore, you get an assymetric distribution of temperatures.
https://www.aoml.noaa.gov/impact-of-win ... intensity/

Also, many people think a pinhole eye is always a sign of intensification. Many times a storm will contract when dry air pushes toward the inner core. We see this with landfalling hurricanes that are feeling the effects of dry air over land, or from a mid-level low in the Gulf that's directing dry SW shear from Mexico into the storm.

[Iceresistance]

Is Lee tapping into the Amazonian Tropical Moisture?


https://s11.gifyu.com/images/S42F5.gif

[cheezyWXguy]

Visible and IR seem to suggest the pinhole eye is on the nw edge of a larger eye, similar to the one we saw yesterday. Weird because I didn’t really get that impression from the mw images posted above

[dukeblue219]

After AF306, when is the next recon mission?

A pair of missions take off at 430 and 530pm EDT, and should start making center fixes around 8ish, continuing until a little after midnight.

https://www.nhc.noaa.gov/text/MIAREPRPD_last.shtml?

[RevanTheJedi96]

The track for Lee still isn't too great but the conditions for it are not nearly as good as people thought. No one was even mentioning the sheer.

[Ntxw]

I Dont get how this shear surprised people… Yesterday the 20kt shear zone was present NW of the system.

Also, many people think a pinhole eye is always a sign of intensification. Many times a storm will contract when dry air pushes toward the inner core. We see this with landfalling hurricanes that are feeling the effects of dry air over land, or from a mid-level low in the Gulf that's directing dry SW shear from Mexico into the storm.

I think there are some misunderstandings between an intense (fully warm) pinhole eyes associated with extreme cyclones. It needs to be fully warm. Struggling changes (weakening and/or formation of eye features) start or go to small sizes but are relatively colder, is not the same.

[eastcoastFL]

The track for Lee still isn't too great but the conditions for it are not nearly as good as people thought. No one was even mentioning the sheer.

I beg to differ. It took off like a rocket exactly as expected.

[HurricaneEnzo]

Is Lee tapping into the Amazonian Tropical Moisture?

https://s11.gifyu.com/images/S42F5.gif
https://s11.gifyu.com/images/S42F5.gif

http://tropic.ssec.wisc.edu/real-time/m ... anim=html5

Doesn't really appear to be. Maybe a little bit. Still pulling some from the itcz.

[WalterWhite]

It appears as if Lee is going to underperform the models significantly. The HAFS models were consistently expecting Lee to break the 170-kt barrier, and even the NHC forecast had this peaking at 155 kt. For now, it appears as if Lee will peak at only 145 kt unless wind shear subsides.

[GeneralChow]

Visible and IR seem to suggest the pinhole eye is on the nw edge of a larger eye, similar to the one we saw yesterday. Weird because I didn’t really get that impression from the mw images posted above

The pinhole eye looks to have been covered-up by the Central Dense Overcast, and that's really evident in the last frame of Satellite. There is definitely an indentation within the cloud top covering the COC (formerly the Pinhole Eye), but it is no longer completely visible. I'm pretty sure sure the larger area of circulation surrounding it (aka the "larger eye") is a broader area of descending pressure between the precise COC with the lowest pressure and the stronger convection bands with elevated pressures, but I'm not very confident in my explanation. Basically, the Center of Circulation is broadening as Lee weakens from SW Shear.
https://www.tropicaltidbits.com/sat/sat ... t=vis_swir

[Teban54]

 https://twitter.com/MikeFischerWx/status/1700212117977072079

[Tekken_Guy]

It appears as if Lee is going to underperform the models significantly. The HAFS models were consistently expecting Lee to break the 170-kt barrier, and even the NHC forecast had this peaking at 155 kt. For now, it appears as if Lee will peak at only 145 kt unless wind shear subsides.

Isn’t the shear expected to go away in about a day?

[HurricaneEnzo]

It appears as if Lee is going to underperform the models significantly. The HAFS models were consistently expecting Lee to break the 170-kt barrier, and even the NHC forecast had this peaking at 155 kt. For now, it appears as if Lee will peak at only 145 kt unless wind shear subsides.

Isn’t the shear expected to go away in about a day?

It is but shear can be tricky. Most of the strength models didn't indicate Lee struggling with shear like it has the last day or so until after it was already happening. It is modeled to lessen but it's better to take a wait and see approach.

[ElectricStorm]

HAFS-B shows continued weakening for a few more hours (gets into the 950s) before bombing to a Cat 5 again by Sunday afternoon. HAFS-A also has a second Cat 5 peak.

Shear should subside over the next day or so, so even if we see continued weakening today, I fully expect another round of intensification over the weekend.

With strong cyclones like these, fluctuations in intensity like this are quite common so I wouldn't be surprised to see multiple Cat 4/5 peaks over the next several days.

[Kazmit]

It appears as if Lee is going to underperform the models significantly. The HAFS models were consistently expecting Lee to break the 170-kt barrier, and even the NHC forecast had this peaking at 155 kt. For now, it appears as if Lee will peak at only 145 kt unless wind shear subsides.

I feel like we've normalized 145kt too much to say "only 145kt". Regardless, Lee still has several days to fluctuate in intensity so I wouldn't be surprised if it has a secondary peak maybe exceeding its first.

[GeneralChow]

It appears as if Lee is going to underperform the models significantly. The HAFS models were consistently expecting Lee to break the 170-kt barrier, and even the NHC forecast had this peaking at 155 kt. For now, it appears as if Lee will peak at only 145 kt unless wind shear subsides.

There's no way I can count Lee as an under-performer given the rapid intensification from Tropical Storm to Hurricane over a 30 hour period in the Central Atlantic. The fact that it even had a chance to hit 170 kts was impressive enough for me to almost pull an all-nighter. Another 6-12 hours and who knows!?!?

[aspen]

It appears as if Lee is going to underperform the models significantly. The HAFS models were consistently expecting Lee to break the 170-kt barrier, and even the NHC forecast had this peaking at 155 kt. For now, it appears as if Lee will peak at only 145 kt unless wind shear subsides.

I feel like we've normalized 145kt too much to say "only 145kt". Regardless, Lee still has several days to fluctuate in intensity so I wouldn't be surprised if it has a secondary peak maybe exceeding its first.

145 kt sure seems low in comparison to all the Irma/Dorian redux expectations and those insane HAFS-A/B runs. The odds of this actually breaking 170 kt were pretty low.

[cheezyWXguy]

It appears as if Lee is going to underperform the models significantly. The HAFS models were consistently expecting Lee to break the 170-kt barrier, and even the NHC forecast had this peaking at 155 kt. For now, it appears as if Lee will peak at only 145 kt unless wind shear subsides.

Isn’t the shear expected to go away in about a day?

It is but shear can be tricky. Most of the strength models didn't indicate Lee struggling with shear like it has the last day or so until after it was already happening. It is modeled to lessen but it's better to take a wait and see approach.

Are we actually even sure that this shear came out of left field and wasn’t picked up by the models? I know looking at the hurricane models there was an initial peak followed by a drop off and then a secondary peak, and it kind of felt like everyone assumed it was due to structural changes or an ERC. But was that verified, or could it have been picking up the shear (albeit underdoing it)?

[gatorcane]

Lee might be a good case study for the NHC to consider 7-day forecasts especially when models are in excellent agreement on some kind of turn north. Every model we have has pretty consistently showing a turn north for days and now it is just beyond the NHC 5-day track. In these situations, with such a powerful hurricane, it would be nice to show that turn with a wider cone of uncertainty after day 5 than a 5-day track with no turn at all to help ease some fears.