ATL: IOTA - Remnants - Discussion

[Cunxi Huang]

232030 1350N 08255W 6978 02768 9575 +145 +111 093119 122 088 001 00
232100 1349N 08255W 6966 02742 9530 +143 +129 094106 118 088 003 00
232130 1347N 08256W 6960 02712 9480 +157 +124 095106 107 088 002 03
232200 1346N 08256W 6967 02655 9426 +163 +125 095109 109 085 000 00
232230 1344N 08256W 6965 02606 9366 +168 +123 097110 113 091 000 00
232300 1342N 08256W 6962 02537 9310 +152 +146 098112 119 093 002 00

North quad FL 122 kt SFMR 93 kt. wut.

[supercane4867]

Pressure has not risen much if any but winds are likely a lot lower now. Should be a CAT4 landfall.

[supercane4867]

Remember the northern eyewall is the weakest part as shown on microwave

[NDG]

The N quadrant is unusually weak — 120/125 kt FL, and only 90/95 kt SFMR. Recon also wasn’t able to get the lowest pressure, although it’s still in the high 910s.

Last recon the strongest winds were in the nw & sw eyewall.

[ColdMiser123]

This is my concern with SFMR measurements as those measurements get closer to the coast in shallow water, a peak SFMR value of 93 kt in the northern eyewall with pressure ~920 mb is unheard of for a Caribbean tropical system.

That is my concern for Hurricanes Sally and Zeta as well concerning potentially faulty SFMR measurements in shallow water.

[NDG]

First pass doesn’t support a Cat 5

[ElectricStorm]

Very likely back down to Cat 4 now and will be at landfall. Catastrophic nonetheless though

[NDG]

This is my concern with SFMR measurements as those measurements get closer to the coast in shallow water, a peak SFMR value of 93 kt in the northern eyewall with pressure ~920 mb is unheard of for a Caribbean tropical system.

That is my concern for Hurricanes Sally and Zeta as well concerning potentially faulty SFMR measurements in shallow water.

https://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/Caribbean_Sea_Gulf_of_Mexico_shaded_relief_bathymetry_land_map.png/310px-Caribbean_Sea_Gulf_of_Mexico_shaded_relief_bathymetry_land_map.png

But flight level winds are also down.

[Sanibel]

Is there an intensity max connected to latitude that far south?

Could be an SST damper...

[ColdMiser123]

This is my concern with SFMR measurements as those measurements get closer to the coast in shallow water, a peak SFMR value of 93 kt in the northern eyewall with pressure ~920 mb is unheard of for a Caribbean tropical system.

That is my concern for Hurricanes Sally and Zeta as well concerning potentially faulty SFMR measurements in shallow water.

https://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/Caribbean_Sea_Gulf_of_Mexico_shaded_relief_bathymetry_land_map.png/310px-Caribbean_Sea_Gulf_of_Mexico_shaded_relief_bathymetry_land_map.png

But flight level winds are also down.

Yeah, the combination of a cooler eye plus the coldest convection now downshear suggested this was no longer a Category 5.

We'll have to see what pressure the dropsonde splashed at since the extrapolated pressure to dropsonde pressure relationship varies with flights, but it doesn't seem like there has been any significant pressure rise yet based on extrapolated pressure values.

[aspen]

This is my concern with SFMR measurements as those measurements get closer to the coast in shallow water, a peak SFMR value of 93 kt in the northern eyewall with pressure ~920 mb is unheard of for a Caribbean tropical system.

That is my concern for Hurricanes Sally and Zeta as well concerning potentially faulty SFMR measurements in shallow water.

https://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/Caribbean_Sea_Gulf_of_Mexico_shaded_relief_bathymetry_land_map.png/310px-Caribbean_Sea_Gulf_of_Mexico_shaded_relief_bathymetry_land_map.png

But flight level winds are also down.

Yeah, the combination of a cooler eye plus the coldest convection now downshear suggested this was no longer a Category 5.

We'll have to see what pressure the dropsonde splashed at since the extrapolated pressure to dropsonde pressure relationship varies with flights, but it doesn't seem like there has been any significant pressure rise yet based on extrapolated pressure values.

The extrapolated pressure is very similar to the end of the last flight, and it’s possible it might’ve gone below 916 mbar; pressure readings cut out briefly a few times while the plane was in the eye.

[ColdMiser123]

Dropsonde splashed at 919 mb with a 17 kt surface wind, supports 917-918 mb. No pressure rise so far.

[cheezyWXguy]

Microwave seems to tell a different story, but IR looks to me like some kind of structural change is occurring that’s flattening the gradient. Ring of deepest convection appears removed from the immediate eyewall. Maybe upwelling?

[supercane4867]

Microwave seems to tell a different story, but IR looks to me like some kind of structural change is occurring that’s flattening the gradient. Ring of deepest convection appears removed from the immediate eyewall. Maybe upwelling?

Broadening wind field without any pressure rise. Shallow coastal water induced upwelling could explain this.

[wx98]

First pass doesn’t support a Cat 5

I was still thinking probably a 120 kt/140 mph Cat 4.

[ElectricStorm]

First pass doesn’t support a Cat 5

I was still thinking probably a 120 kt/140 mph Cat 4.

Nah it won't be that low. Not with a 919 mb pressure. More like 130-135kts

[ClarCari]

Kept at Cat. 5 for Int. Adv. for cautionary reasons.

I imagine they either expect it to continue strengthening to “regain” Cat. 5 data upon landfall, or an EWRC to weaken it before landfall. Whatever happens should be apparent by the Full Advisory and NHC intensity then should reflect that.

[wxman57]

May be starting an eyewall replacement cycle. Storms can lose a couple categories during such a replacement. Earlier microwave suggested a "moat" was forming outside the eyewall.

[wx98]

They’re keeping Cat 5, but I’d expect a postseason downgrade for 0z and maybe even 18z.

7:00 PM EST Mon Nov 16
Location: 13.6°N 83.0°W
Moving: W at 9 mph
Min pressure: 918 mb
Max sustained: 160 mph

I know it was definitely Cat 5 this morning at 12z.

[wx98]

First pass doesn’t support a Cat 5

I was still thinking probably a 120 kt/140 mph Cat 4.

Nah it won't be that low. Not with a 919 mb pressure

Katrina made landfall as a 125 mph Cat 3 at 920.