2020 Atlantic Post-Season Changes

[kevin]

The changes I predict regarding peak intensity (so not regarding earlier storm genesis or earlier intensification). Mostly just small tweaks with 2 category changes. Possibly 3 if they also decide to upgrade Sally to a major, but tbh I think it's unlikely.

Gonzalo: 55 -> 60 kts
Laura: 130 -> 135 kts
Nana: 65 -> 60 kts
Paulette: 90 -> 95 kts
Sally: 90 -> 95/100 kts (possibly cat 3 peak)
Gamma: 60 -> 70 kts (cat 1 peak)
Alpha: 45 -> 50 kts
Delta: 125 -> 120 kts
Zeta: 95 -> 100 kts (cat 3 peak)

[CrazyC83]

One thing I would do, which hasn't been mentioned much, is change Marco's status at landfall from tropical storm to remnant low. At that time, all the convection was FAR from the center, basically over land in Alabama with the center in southern Louisiana. Its 65 kt peak (and 35 kt at landfall, albeit not as a TC) both appear reasonable.

[CyclonicFury]

Marco: 65 → 60 kt
Nana: 65 → 55 kt
Sally: 90 → 95 kt
Teddy: 120 → 115 kt
Gamma: 60 → 75 kt
Delta: 125 → 115 kt
Epsilon: 100 → 105 kt

No other changes to the remaining systems

Out of curiosity, why do you think Marco was not a hurricane, when SFMR data supported 65-70 kt? Also, what is your justification for 75 kt for Gamma?

[Ubuntwo]

In terms of peak intensity, I could realistically see:
Dolly from 40kt -> 45kt
Laura from 130kt -> 135kt (perhaps not at landfall)
Nana from 65kt -> 60kt
Paulette from 90kt -> 95kt
Sally from 90kt -> 95kt
Delta from 125kt -> 120kt
Epsilon from 100kt -> 105kt

Big category changes for Sally, Zeta, and Gamma seem unlikely to me, even if there was some supporting data.

I also could see Isaias' intensity while passing east of Florida as a TS reduced, as with Sally between peaks and Teddy on approach to Canada.

[al78]

I'm not convinced NHC will downgrade Nana, even though its upgrade was very borderline to begin with. I don't ever recall NHC downgrading a hurricane to a tropical storm.

I'm not aware of any storm ever getting a post-season downgrade, but if any deserve it that would be Nana.

I definitely agree that Nana would be worthy of a downgrade. It’s pressure of 994mb doesn’t support hurricane intensity, nor did it look like one.

What was the reasoning for classifying it as a hurricane in real time?

[Ubuntwo]

I'm not aware of any storm ever getting a post-season downgrade, but if any deserve it that would be Nana.

I definitely agree that Nana would be worthy of a downgrade. It’s pressure of 994mb doesn’t support hurricane intensity, nor did it look like one.

What was the reasoning for classifying it as a hurricane in real time?

Looking at historical recon, 72kt FL winds and 62kt SFMR, each on a separate pass. Objectively this would support a hurricane, but further passes in the same quad found much lower winds, and the high FL were paired with very low SFMR readings (in the 40s) and vice versa.

[Shell Mound]

Marco: 65 → 60 kt
Nana: 65 → 55 kt
Sally: 90 → 95 kt
Teddy: 120 → 115 kt
Gamma: 60 → 75 kt
Delta: 125 → 115 kt
Epsilon: 100 → 105 kt

No other changes to the remaining systems

Out of curiosity, why do you think Marco was not a hurricane, when SFMR data supported 65-70 kt? Also, what is your justification for 75 kt for Gamma?

Satellite estimates for Marco mostly did not support hurricane intensity, and neither did flight-level winds, so the SFMR data seemed rather isolated when taken contextually. The lowest MSLP was only 991 mb, which did not really support a hurricane moving NNW in the subtropics (the Gulf of Mexico qualifies as part of the subtropics). As for Gamma, that storm was rapidly deepening prior to and during landfall, satellite presentation arguably supported hurricane status, the MSLP of 980 mb relative to outermost closed isobar (environmental pressure) supported winds of ~75 knots, the eye continued to clear out even shortly after landfall, and reconnaissance failed to properly sample the strongest quadrant(s), nor were there any land-based stations or buoys that experienced the peak winds in the RMW.

[MarioProtVI]

I definitely agree that Nana would be worthy of a downgrade. It’s pressure of 994mb doesn’t support hurricane intensity, nor did it look like one.

What was the reasoning for classifying it as a hurricane in real time?

Looking at historical recon, 72kt FL winds and 62kt SFMR, each on a separate pass. Objectively this would support a hurricane, but further passes in the same quad found much lower winds, and the high FL were paired with very low SFMR readings (in the 40s) and vice versa.

There is a thing called shoaling which can mess with SFMR and give lower values.

[Ubuntwo]

What was the reasoning for classifying it as a hurricane in real time?

Looking at historical recon, 72kt FL winds and 62kt SFMR, each on a separate pass. Objectively this would support a hurricane, but further passes in the same quad found much lower winds, and the high FL were paired with very low SFMR readings (in the 40s) and vice versa.

There is a thing called shoaling which can mess with SFMR and give lower values.

This was in quite deep water off the shelf, hundreds of meters deep. Also, all literature I can find says shoaling artifically inflates SFMR values, not the opposite. If you have a reputable study saying otherwise please post it because I've been looking.

[Ryxn]

Eta anyone?

[aspen]

Eta anyone?

Peak of 916 (+/-4) mbar and 140 kt at 5-6z, to account for the deepening and dropsonde winds observed by recon before it left and the other one broke.

[Kazmit]

I don't think I've ever been so confident in a cat 5 post-season upgrade. If Michael got upgraded, Eta certainly will too, and I think Eta was stronger.

[kevin]

Tbh looking at that full pink ring I think it might've been even stronger than 140 kts at its peak, but I guess we just have to accept that we'll never know for sure. However, 140 kts should be an easy call imo, I also feel a lot more confident about this one than about Michael in 2018.

Gonzalo: 55 -> 60 kts
Laura: 130 -> 135 kts
Nana: 65 -> 60 kts
Paulette: 90 -> 95 kts
Sally: 90 -> 95/100 kts (possibly cat 3 peak)
Gamma: 60 -> 70 kts (cat 1 peak)
Alpha: 45 -> 50 kts
Delta: 125 -> 120 kts
Zeta: 95 -> 100 kts (cat 3 peak)
Eta: 130 -> 140 kts (cat 5 peak)

[Ryxn]

Tbh looking at that full pink ring I think it might've been even stronger than 140 kts at its peak, but I guess we just have to accept that we'll never know for sure. However, 140 kts should be an easy call imo, I also feel a lot more confident about this one than about Michael in 2018.

Gonzalo: 55 -> 60 kts
Laura: 130 -> 135 kts
Nana: 65 -> 60 kts
Paulette: 90 -> 95 kts
Sally: 90 -> 95/100 kts (possibly cat 3 peak)
Gamma: 60 -> 70 kts (cat 1 peak)
Alpha: 45 -> 50 kts
Delta: 125 -> 120 kts
Zeta: 95 -> 100 kts (cat 3 peak)
Eta: 130 -> 140 kts (cat 5 peak)

These changes would push 2020's numbers to 28 tropical storms, 13 hurricanes and 7 major hurricanes. I could see 2 more possible Category 1 hurricanes and 1 other tropical storm in November with another one in December for a season total of:

Tropical Depressions: 33 (record high)
Tropical Storms: 32 (record high)
Hurricanes: 15 (record high, tied with 2005)
Major Hurricanes: 7 (record high, tied with 2005)

EDIT: Didn't realize you downgraded Nana. In that case, the hurricane total would be 14, which is just shy of the record.

But say December sees a rare Category 1 storm like Epsilon in 2005 but instead forming December 1 or later.

[ElectricStorm]

Tbh looking at that full pink ring I think it might've been even stronger than 140 kts at its peak, but I guess we just have to accept that we'll never know for sure. However, 140 kts should be an easy call imo, I also feel a lot more confident about this one than about Michael in 2018.

Gonzalo: 55 -> 60 kts
Laura: 130 -> 135 kts
Nana: 65 -> 60 kts
Paulette: 90 -> 95 kts
Sally: 90 -> 95/100 kts (possibly cat 3 peak)
Gamma: 60 -> 70 kts (cat 1 peak)
Alpha: 45 -> 50 kts
Delta: 125 -> 120 kts
Zeta: 95 -> 100 kts (cat 3 peak)
Eta: 130 -> 140 kts (cat 5 peak)

While I do think Eta was certainly a 140kt Cat 5, I completely understand the NHC not upgrading it operationally since no recon data ever supported it. But for me, a post season upgrade is a must

[ElectricStorm]

One thing is for sure though... Eta's TCR is going to be an interesting one considering it might redevelop

[Hypercane_Kyle]

I honestly didn't see much compelling evidence to support an upgrade to Eta to a Cat 5. Zeta is the only system that deserves an upgrade.

[aspen]

I honestly didn't see much compelling evidence to support an upgrade to Eta to a Cat 5. Zeta is the only system that deserves an upgrade.

There is some, but it’s mainly assumptions and extrapolations based on what was observed by the final recon plane that actually made it to Eta. If that 4 mb/hr deepening rate continued for 3 hours, leading up to when the EWRC finally began to degrade the pinhole, then Eta could’ve bottomed out as low as 910 mbar. The only direct observations supporting an intensity greater than 130 kt are a single 135 kt SFMR reading and a 155 kt dropsonde, both in the southern half of the storm. Since the northern half and likely the NW quadrant are usually stronger, it can be inferred that perhaps there were sustained Cat 5 winds in the unsampled quadrant.

At the very least, Eta’s pressure should be lowered by a couple of mbar.

[ElectricStorm]

I honestly didn't see much compelling evidence to support an upgrade to Eta to a Cat 5. Zeta is the only system that deserves an upgrade.

There is some, but it’s mainly assumptions and extrapolations based on what was observed by the final recon plane that actually made it to Eta. If that 4 mb/hr deepening rate continued for 3 hours, leading up to when the EWRC finally began to degrade the pinhole, then Eta could’ve bottomed out as low as 910 mbar. The only direct observations supporting an intensity greater than 130 kt are a single 135 kt SFMR reading and a 155 kt dropsonde, both in the southern half of the storm. Since the northern half and likely the NW quadrant are usually stronger, it can be inferred that perhaps there were sustained Cat 5 winds in the unsampled quadrant.

At the very least, Eta’s pressure should be lowered by a couple of mbar.

In terms of data that recon sampled, nothing supported Cat 5. However, I think it's safe to assume that it was a Cat 5 briefly after recon left, assuming the pressure kept dropping. And final Ts on ADT kept rising too

[EquusStorm]

When recon leaves a rapidly deepening 130kt storm with pressure tanking and there are no measurements for hours, it's easily assumed 140kt would follow very shortly thereafter. That said, for absolutely no apparent reason they didn't use that logic on Jose in 2017 so I kinda doubt Eta gets its objectively deserved upgrade just based on that precedent. Filing it away 1s 140-150kt personally; just don't have recon data when it mattered most.