Some thoughts about post-season changes this year:
1) Nana
I think there is a case to be made that this never reached hurricane intensity, since the hurricane force SFMRs were disjointed from the FL wind that supported hurricane intensity, however there was a deep burst of convection just before landfall and given the small circulation it could have easily spun up some more.
2) Laura
I like the NHC operational intensity of 130 kt for Laura. If there was an option to assign 133 kt as an intensity, that's probably what I would have gone with. Peak FL wind of 148 kt supported 133 kt at the surface, alongside 133 kt unflagged SFMR. While there was a 137 kt SFMR, this was flagged, so it may be worth checking again.
3) Gamma
I think this probably reached minimum hurricane intensity, as there was a significant pressure drop at landfall compared to what recon had observed a few hours earlier, but post-season analysis should give more conclusive answers on this.
4) Sally
This is where I think there could be a more significant discrepancy compared to the operational intensity, depending on how accurate the shallow water SFMR data is ruled in the TCR. Peak FL wind of 110 kt supports 99 kt at the surface, Category 3. There is some uncertainty mentioned in the NHC discussion as to whether these winds actually made it to the surface, from the 4 am CDT 9/16 discussion:
The reconnaissance aircraft has recently measured peak 700-mb
flight-level winds of 110 kt, but those winds may not be making it
down to the surface based on earlier buoy wind reports underneath
the eyewall.
However, there is evidence that these winds were making it down to the surface, from a dropsonde earlier:
These are instantaneous winds, so the 112 kt at the surface is not evidence by itself that this was a Category 3. However, what is most important, is that this dropsonde is evidence that winds aloft were successfully mixing down to the surface. That is the only way you get these kinds of tremendous gusts to be observed close to the surface. The standard conversion for the lowest 150 meter wind average in dropsondes is around ~0.85, which would support 96 kt, right at the border between a 95 kt Category 2, and a 96 kt Category 3. A more detailed radar analysis might be useful like it was with Michael, as there was some radar data suggesting winds were higher than 90 kt as well. I think post-analysis will be a close call between a high-end Category 2 (95 kt) or a low-end Category 3 (96-99 kt).
5) Zeta
FL winds were around 119 kt, which typically would support 107 kt at the surface, however, as Crazy and I discussed, this conversion may be lower, due to the interaction with an upper level trough. In Hurricane Wilma's TCR, the NHC used a conversion of 0.8 from FL wind to surface wind, since they noted shear was analyzed at around 25 kt, which would artificially inflate FL wind, and should reduce this conversion to surface wind as a result.
Shear for Zeta in this same atmospheric layer on the GFS was forecast to be around 10-15 kt, so a higher conversion than 0.8, but a lower conversion than 0.9 might seem reasonable. This is likely something the NHC will be taking a look at in the TCR, as well as the accuracy of the shallow water SFMR measurements, like with Sally. A compromise estimate of 0.85 in this case still gives 101 kt at the surface. Like with Sally, there was radar evidence that this had stronger wind than was operationally analyzed, since 123 kt was analyzed on radar just above ~3000 meters, which is close to 700 mb. This 0.85 conversion supports 104 kt at the surface. Dropsonde data also showed that winds were mixing effectively close to the surface, which supports that mid-level wind was mixing down, at least in gusts.
Damage was also quite extensive with Zeta, and there were some unofficial gusts well into Category 4 range. A detailed analysis should give us a better idea as to how accurate these surface observations were. I think the NHC TCR will find that the balance of evidence suggests this was a 100 kt Category 3.
6) Eta
This is tough, since recon was gone during the likely peak, and recon showed pressure still dropping significantly before it left. It is likely that we didn't observe the true peak, and while it was likely higher than 130 kt, it's tough to say if it made it to Category 5.
7) Iota
This gave one of the most significant FL wind to SFMR discrepancies that I've personally seen during the final pass. The north eyewall had a peak SFMR of 94 kt, while FL wind peaked 143 kt. It is interesting that the NHC appears to have discounted these low SFMR values on the final pass, since there is no mention of them in the final discussion before landfall. Like with Zeta and Sally, this will be interesting to see if these low SFMR values are believable since they were observed in shallow water.
That took a while to write up! Currently have MATLAB code that takes a while to run in the background, so I figured it would be a good time to write some thoughts down.
