ATL: MICHAEL - Post-Tropical - Discussion

[PandaCitrus]

Hi RailDawg, thank you for sharing your insights. It sounds like you went through a lot and I'm glad you got home safe and sound. There was chaser video from a Panama City garage on youtube. Was this what your experience looked like?

https://www.youtube.com/watch?v=C6zGEMMMjws&t=128s

[Rail Dawg]

Hi RailDawg, thank you for sharing your insights. It sounds like you went through a lot and I'm glad you got home safe and sound. There was chaser video from a Panama City garage on youtube. Was this what your experience looked like?

https://www.youtube.com/watch?v=C6zGEMMMjws&t=128s

Hey thanks for this!

I was right there and can in fact see Big Truck lol.

I don’t do pictures or videos but count on others.

This is really appreciated.

[TheStormExpert]

Death toll now up to 31 in 4 states.

[crm6360]

I hope the reanalysis provides greater insight into Michael's nearly unprecedented intensification right up through landfall. When I look at Camille, Michael and Charley -- all intensifying major hurricanes approaching the eastern or northern gulf coast -- a couple things jump out:

- They were all relatively small cyclones. An argument is made that a smaller circulation is less prone to entrainment of continental air on approach.
- They all had not peaked in intensity in the days or hours preceding landfall.
- They all were moving at a decent clip which mitigated the relatively shallow depths of OHC near the coast.

Things that were unique to Michael:

- Complete eyewall formation was stunted until the last day or so before landfall, and yet the storm continued to slowly intensify throughout.
- Favorable trough interaction on the last day seemed to play a big role in helping to storm organize. Seem to recall something similar with Charley as well.
- Re: the last point, not sure if that trough was also responsible for moistening the entire column in Michael's vicinity near the coast. There was plenty of dry air over the Western Gulf during Michael's trek, and maybe this was responsible for the delayed eyewall development.

Needless to say, reanalysis should be fascinating.

[Hammy]

Just wanted to post this while it's still available--the eerie data vacancy after Michael went through, where instruments either lost power or were blown apart.

[SconnieCane]

Mexico Beach destruction on Google Street View. Really brings it home more so than flyovers and photographs.

https://www.google.com/maps/@29.9415672 ... 000!8i5500

[tolakram]

[youtube]https://youtu.be/7W9LRCZMZfQ[/youtube]

[Ubuntwo]

Article on F-22s at Tyndall

Interesting excerpt:

As Hurricane Michael passed overhead, Tyndall’s own weather monitoring facilities registered wind gusts up to nearly 130 miles per hour. Holmes said that, based on other data, the actual peak speed was closer to 172 miles per hour.

[SconnieCane]

Damage video from Panama City some may not have seen yet. Pretty dramatic.

[youtube]https://youtu.be/wwukvznNPD0[/youtube]

[SconnieCane]

Another sobering damage video. This one has gotten more exposure, although I hadn't seen it before.

[youtube]https://youtu.be/gdCLnjEHPos[/youtube]

[ColdMiser123]

Going off of some of the recent discussion in the Gordon thread, some radial velocities at 3500 feet AGL were documented at >200 mph for Hurricane Michael. Using a conversion
factor of 0.8 for those heights, that is within Category 5 range at the surface. This is likely something that is being looked at for the final Michael TCR.

 https://twitter.com/meteoKB/status/1050070379832565760

[CrazyC83]

Going off of some of the recent discussion in the Gordon thread, some radial velocities at 3500 feet AGL were documented at >200 mph for Hurricane Michael. Using a conversion
factor of 0.8 for those heights, that is within Category 5 range at the surface. This is likely something that is being looked at for the final Michael TCR.

https://twitter.com/meteoKB/status/1050070379832565760

That is correct: 176 kt at that height supports 141 kt at the surface. I know for 1,500 feet the factor is 0.75 and for 5,000 feet it is 0.80 based on Recon relationships. Given the fact that Michael was rapidly intensifying, the stronger estimate is probably more likely.

Flight level winds and pressure relationships also support cat 5, while SFMR does too but it wasn't reliable due to shoaling.

[cycloneye]

Here is the precipitation graphic.

[WAcyclone]

Going off of some of the recent discussion in the Gordon thread, some radial velocities at 3500 feet AGL were documented at >200 mph for Hurricane Michael. Using a conversion
factor of 0.8 for those heights, that is within Category 5 range at the surface. This is likely something that is being looked at for the final Michael TCR.

https://twitter.com/meteoKB/status/1050070379832565760

That is correct: 176 kt at that height supports 141 kt at the surface. I know for 1,500 feet the factor is 0.75 and for 5,000 feet it is 0.80 based on Recon relationships. Given the fact that Michael was rapidly intensifying, the stronger estimate is probably more likely.

Flight level winds and pressure relationships also support cat 5, while SFMR does too but it wasn't reliable due to shoaling.

Do you know for sure the SFMR was flagged due to shoaling? The location of that 138 kt measurement, 29.783N 85.667W, seems to be quite far away from the coast (25 km/15 mi) and in waters around 27 m (88 ft) deep. I wonder if the high rain rate (41 mm/hr) or the comparatively low flight level winds (123 kt) triggered the flagging algorithm. It will be interesting to see how the NHC interprets this reading...

[CrazyC83]

Going off of some of the recent discussion in the Gordon thread, some radial velocities at 3500 feet AGL were documented at >200 mph for Hurricane Michael. Using a conversion
factor of 0.8 for those heights, that is within Category 5 range at the surface. This is likely something that is being looked at for the final Michael TCR.

https://twitter.com/meteoKB/status/1050070379832565760

That is correct: 176 kt at that height supports 141 kt at the surface. I know for 1,500 feet the factor is 0.75 and for 5,000 feet it is 0.80 based on Recon relationships. Given the fact that Michael was rapidly intensifying, the stronger estimate is probably more likely.

Flight level winds and pressure relationships also support cat 5, while SFMR does too but it wasn't reliable due to shoaling.

Do you know for sure the SFMR was flagged due to shoaling? The location of that 138 kt measurement, 29.783N 85.667W, seems to be quite far away from the coast (25 km/15 mi) and in waters around 27 m (88 ft) deep. I wonder if the high rain rate (41 mm/hr) or the comparatively low flight level winds (123 kt) triggered the flagging algorithm. It will be interesting to see how the NHC interprets this reading...

I know in the last advisory it was mentioned that it may have been incorrectly calibrated, but I am sure they are investigating. The highest flight level winds were 152 kt, which converts to 137 kt at the surface.

[ncforecaster89]

As I've shared on the AMWX forum, the 152 kt 700 MB FL wind measured by Recon is arguably the greatest single data point favoring a category-five reclassification. The accuracy of the 138 kt SFMR, notwithstanding.

As "Crazy C83" already noted, that FL wind corresponds to 136.8 knots at the surface. The NHC rounds that value to the nearest 5 kt interval; in this case, 135 kt... which matches the operational intensity.

Being the fact that it's highly unlikely that Recon was able to actually measure the absolute peak wind located anywhere in the eyewall, it stands to reason that there was a 700 MB FL wind of at least 153 kt (corresponding to 138 kt at the surface) equating to category-five intensity.

Although the totality of the available data supports a possible post-storm upgrade (very strongly so, IMHO), it will ultimately come down to the subjective determination of the NHC. As former NHC forecaster, Todd Kimberlain, shared during our correspondence on Twitter, the NHC is very reluctant to go against their operational intensity estimate. In this case, I'd respectfully argue that's exactly what they should do; reclassifying Michael as a landfalling 140 kt category-five hurricane.

[ncforecaster89]

Thought it might be beneficial to review the last Recon VDM for both Maria (2017) and Michael (2018), prior to their respective landfalls in Puerto Rico and the Florida Panhandle. Especially, given they were each designated as 135 kt high-end category-four hurricanes when they came ashore, operationally.

 Hurricane Maria (9/20/2017):

000
URNT12 KNHC 200831
VORTEX DATA MESSAGE AL152017
A. 20/08:04:10Z
B. 17 deg 51 min N
065 deg 28 min W
C. 700 mb 2365 m
D. 116 kt
E. 212 deg 11 nm
F. 330 deg 108 kt
G. 221 deg 14 nm
H. 917 mb
I. 10 C / 3055 m
J. 18 C / 3041 m
K. NA / NA
L. CLOSED
M. CO10-28
N. 12345 / 7
O. 0.02 / 1 nm
P. AF302 0715A MARIA OB 27
MAX OUTBOUND AND MAX FL WIND 146 KT 032 / 16 NM 08:11:00Z
CNTR DROPSONDE SFC WIND 165 / 5 KT
;

https://www.nhc.noaa.gov/archive/recon/2017/REPNT2/

 Hurricane Michael (10/10/2018):

000
URNT12 KNHC 101752
VORTEX DATA MESSAGE AL142018
A. 10/17:09:50Z
B. 29.97 deg N 085.64 deg W
C. 700 mb 2402 m
D. EXTRAP 922 mb
E. NA
F. CLOSED
G. C18
H. 138 kt
I. 186 deg 12 nm 17:06:00Z
J. 287 deg 129 kt
K. 187 deg 9 nm 17:07:00Z
L. 133 kt
M. 117 deg 15 nm 17:23:30Z
N. 224 deg 152 kt
O. 117 deg 12 nm 17:22:30Z
P. 14 C / 2962 m
Q. 19 C / 3048 m
R. 10 C / NA
S. 12345 / 7
T. 0.02 / 1 nm
U. AF301 1514A MICHAEL OB 22
MAX FL WIND 152 KT 117 / 12 NM 17:22:30Z
SLP EXTRAP FROM 700 MB

https://www.nhc.noaa.gov/archive/recon/2018/REPNT2/

The Comparison:

1) Hurricane Maria made landfall at 1015z; two hours after the last Recon obs, above. It had begun an eyewall replacement cycle shortly after the 0310z VDM provided by Recon, seven hours earlier, when the eye measured 10 nm and contained a minimum central pressure of 910 mb. During that interval, the eye had expanded to 28 nm and the pressure rose to 917 mb. The pressure is presumed (by the NHC) to have continued to fill to an estimated 920 mb by the time it crossed the Puerto Rican shoreline.

The highest flight-level wind (FLW) of 157 kt was observed at 2221z on the 19th (roughly 12 hours preceding landfall). By the time of the last pre-landfall mission, max FLWs were down to 146 kt. Since Maria was continuing to weaken during the subsequent two hours, it’s highly likely max winds had decreased, as well.

2) Hurricane Michael made landfall at 1730z; less than thirty minutes after the last Recon obs, above. In contrast to Maria, hurricane Michael was rapidly intensifying all the way up to and through landfall. At 0904z, only 8.5 hours prior to blasting ashore, the eye measured 20 nm with a minimum central pressure of 937 mb. By the time of the aforementioned last VDM, the eye had contracted to less than 18 nm and the pressure had fallen to 919 mb. As can be seen by examining the radar imagery, the eye had shrunken even further, and it’s presumed that the central pressure deepened a little more, as well, during the period between the last VDM and the center crossing the coastline.

The highest FLW of 152 kt was measured just prior to the center pushing onshore. At 0900z, 8.5 hours earlier, the maximum FLWs were measured at 130 kt. As noted above, Michael was still undergoing a period of rapid intensification, and it’s most probable that there were even stronger winds that Recon didn’t sample.

 NHC Post Storm Report (TCR):

The NHC chose to retain their operational landfalling intensity estimate of 135 kt for hurricane Maria in Puerto Rico. In it, the authors stated that they based their conclusions on the extrapolation of the weakening trend noted by Recon, following the ERC.

https://www.nhc.noaa.gov/data/tcr/AL152017_Maria.pdf

If the NHC felt justified in retaining the 135 kt operational intensity estimate for Maria, based primarily on the Recon data, it provides even greater emphasis that hurricane Michael had achieved 140 kt category-five strength at landfall.

Comparatively, Michael had higher observed flight-level winds and a lower barometric pressure. Maria was weakening significantly, while Michael was rapidly intensifying.

I won’t go through and reiterate all the other data points that strongly support Michael’s upgrade, but simply wanted to provide this quick examination of the Recon data between the two storms. 

[CrazyC83]

Revisiting what I believe the best track should be. I wrote up my thoughts operationally, but with some new data, I've made some changes. This is COMPLETELY unofficial, but here is what I would have:

AL142018, MICHAEL, 43,
20181006, 1200, , LO, 17.5N, 86.2W, 25, 1009,
20181006, 1800, , LO, 17.8N, 86.6W, 25, 1008,
20181007, 0000, , TD, 18.1N, 86.9W, 30, 1007,
20181007, 0600, , TD, 18.4N, 86.8W, 30, 1007,
20181007, 1200, , TS, 18.7N, 86.5W, 40, 1004,
20181007, 1800, , TS, 19.0N, 85.9W, 45, 1001,
20181008, 0000, , TS, 19.7N, 85.5W, 50, 996,
20181008, 0600, , TS, 20.2N, 85.3W, 60, 986,
20181008, 1200, , HU, 20.9N, 85.1W, 70, 982,
20181008, 1800, , HU, 21.7N, 85.0W, 80, 978,
20181008, 1900, L, HU, 21.9N, 84.9W, 85, 977, Landfall - western tip of Cuba
20181009, 0000, , HU, 22.7N, 85.2W, 85, 973,
20181009, 0600, , HU, 23.6N, 85.7W, 85, 971,
20181009, 1200, , HU, 24.6N, 86.1W, 95, 967,
20181009, 1800, , HU, 25.6N, 86.3W, 105, 958,
20181010, 0000, , HU, 26.6N, 86.5W, 110, 951,
20181010, 0600, , HU, 27.8N, 86.6W, 120, 944,
20181010, 1200, , HU, 29.0N, 86.3W, 130, 934,
20181010, 1500, T, HU, 29.6N, 86.0W, 135, 924,
20181010, 1730, L, HU, 30.0N, 85.5W, 140, 916, Landfall - west of Mexico Beach, FL and peak intensity
20181010, 1800, , HU, 30.2N, 85.4W, 130, 920,
20181011, 0000, , HU, 31.5N, 84.4W, 70, 960,
20181011, 0600, , TS, 32.9N, 83.1W, 50, 979,
20181011, 1200, , TS, 34.4N, 81.6W, 45, 984,
20181011, 1800, , TS, 35.8N, 79.8W, 45, 985,
20181012, 0000, , EX, 36.6N, 77.7W, 55, 984,
20181012, 0600, , EX, 37.3N, 75.5W, 60, 981,
20181012, 1200, , EX, 38.7N, 72.1W, 65, 979,
20181012, 1800, , EX, 39.8N, 67.0W, 65, 977,
20181013, 0000, , EX, 41.2N, 63.4W, 70, 976,
20181013, 0600, , EX, 43.9N, 57.6W, 70, 974,
20181013, 1200, , EX, 45.6N, 49.0W, 65, 972,
20181013, 1800, , EX, 48.0N, 41.1W, 60, 973,
20181014, 0000, , EX, 48.8N, 34.5W, 55, 975,
20181014, 0600, , EX, 48.9N, 26.8W, 50, 979,
20181014, 1200, , EX, 48.3N, 21.0W, 50, 981,
20181014, 1800, , EX, 47.3N, 17.3W, 45, 985,
20181015, 0000, , EX, 45.6N, 14.0W, 40, 990,
20181015, 0600, , EX, 42.8N, 12.2W, 40, 995,
20181015, 1200, , EX, 41.0N, 11.5W, 35, 1002,
20181015, 1800, , EX, 40.3N, 11.0W, 30, 1006, dissipated shortly afterward

[ncforecaster89]

Here’s something I’ve yet to hear anyone talk about: Hurricane Michael technically made two separate landfalls on the Florida Panhandle.

The center of the eye crossed the coastline (just S of hwy 98) near 30.0168 N & 85.5346 W, around 1730 UTC. After subsequently crossing over East Bay, Michael made a second landfall near 30.0916 N & 85.4902 W, just SSW of Sandy Creek Air Park around 1745 UTC. These are the best approximations I could make by closely analyzing the radar images and loops, available online.

It’ll be interesting to see how the NHC handles these two distinct landfalls. This situation is very similar to hurricanes Charley in 2004, Arthur in 2014, and Harvey in 2017...that each crossed over bays or sounds before making a second landfall. In each one of those cases, the NHC chose to list both landfalls in their respective Best Tracks.

Then again, the NHC may elect to just simply note the initial landfall. That was the case with hurricane Ike of 2008, which made an initial landfall on the Northern end of Galveston Island. Shortly thereafter, the center reemerged over water and passed through Galveston Bay, before making a second landfall near Baytown, TX. The HURDAT2 Best Track only lists the landfall on Galveston Island.

[1900hurricane]

Two more factors I haven't seen discussed that I see could be in favor of a category 5 landfall upgrade for Michael is KZC output and straight eye-CDO differential.

Beginning with Knaff & Zehr '07 and continuing with Courtney & Knaff '09, the Knaff, Zehr, & Courtney Wind/Pressure Relationship (KZC) was developed as a flexible W/P relationship to be useful in most situations. This is achieved by using storm size (usually via the average radius of 34 kt winds (r34)), storm speed, latitude, and environmental pressure as inputs instead of just maximum winds or pressure. Knapp et al also developed a way to use the radius of the outermost closed isobar (ROCI) instead of r34 to estimate storm size, which I have slightly tweaked for better performance at higher intensities. With Python programs that I have written, I can implement KZC directly from best track data from the NHC. Using both the r34 method and ROCI method (respectively), here is what I get running KZC for Michael.

Date & Time Lat/Lon Vmax(kt) Speed Mean Analyzed OCI
exp(opr) (kt) R34 Pressure
------------------------------------------------------------------------
10/04/2018 18Z: 14.5N 83.2W 26 ( 20), 5, 0, 1007, 1009
10/05/2018 0Z: 14.9N 83.5W 26 ( 20), 5, 0, 1007, 1009
10/05/2018 6Z: 15.3N 83.8W 26 ( 20), 5, 0, 1007, 1009
10/05/2018 12Z: 15.7N 84.0W 26 ( 20), 4, 0, 1008, 1010
10/05/2018 18Z: 16.2N 84.5W 27 ( 25), 7, 0, 1007, 1009
10/06/2018 0Z: 16.8N 85.1W 27 ( 25), 8, 0, 1007, 1009
10/06/2018 6Z: 17.3N 85.8W 28 ( 25), 8, 0, 1007, 1009
10/06/2018 12Z: 17.5N 86.2W 26 ( 25), 4, 0, 1007, 1009
10/06/2018 18Z: 17.8N 86.6W 28 ( 25), 5, 0, 1006, 1009
10/07/2018 0Z: 18.1N 86.9W 35 ( 25), 4, 0, 1004, 1009
10/07/2018 6Z: 18.4N 86.9W 35 ( 30), 3, 0, 1004, 1010
10/07/2018 12Z: 18.7N 86.7W 35 ( 35), 4, 75, 1004, 1010
10/07/2018 18Z: 19.0N 86.0W 44 ( 45), 7, 75, 999, 1009
10/08/2018 0Z: 19.7N 85.4W 46 ( 50), 9, 112, 997, 1009
10/08/2018 6Z: 20.2N 85.4W 64 ( 60), 5, 115, 983, 1008
10/08/2018 12Z: 20.9N 85.1W 65 ( 65), 8, 112, 982, 1007
10/08/2018 18Z: 21.7N 85.1W 72 ( 70), 8, 110, 978, 1008
10/09/2018 0Z: 22.7N 85.2W 83 ( 75), 10, 122, 970, 1008
10/09/2018 6Z: 23.6N 85.7W 76 ( 80), 10, 128, 973, 1007
10/09/2018 12Z: 24.6N 86.1W 81 ( 90), 11, 122, 968, 1005
10/09/2018 18Z: 25.6N 86.3W 91 (105), 10, 125, 960, 1006
10/10/2018 0Z: 26.6N 86.5W 105 (110), 10, 125, 949, 1006
10/10/2018 6Z: 27.8N 86.6W 109 (115), 12, 128, 945, 1006
10/10/2018 12Z: 29.0N 86.3W 122 (125), 12, 122, 934, 1006
10/10/2018 18Z: 30.2N 85.4W 141 (135), 14, 102, 919, 1008
10/11/2018 0Z: 31.5N 84.5W 99 ( 80), 15, 75, 955, 1008
10/11/2018 6Z: 32.8N 83.2W 66 ( 50), 17, 60, 979, 1008
10/11/2018 12Z: 34.1N 81.7W 54 ( 45), 18, 60, 987, 1008
10/11/2018 18Z: 35.6N 80.0W 40 ( 45), 20, 50, 991, 1004
10/12/2018 0Z: 36.5N 77.7W 41 ( 45), 21, 90, 988, 1002
10/12/2018 6Z: 37.3N 75.0W 49 ( 55), 23, 118, 983, 1002
10/12/2018 12Z: 39.0N 70.0W 52 ( 55), 43, 118, 984, 1002
------------------------------------------------------------------------

Date & Time Lat/Lon Vmax(kt) Speed Mean Analyzed OCI
exp(opr) (kt) ROCI Pressure
------------------------------------------------------------------------------
10/ 4/2018 18Z: 14.5N 83.2W 27 ( 20), 5, 100, 1007, 1009
10/ 5/2018 0Z: 14.9N 83.5W 27 ( 20), 5, 100, 1007, 1009
10/ 5/2018 6Z: 15.3N 83.8W 27 ( 20), 5, 100, 1007, 1009
10/ 5/2018 12Z: 15.7N 84.0W 27 ( 20), 4, 100, 1008, 1010
10/ 5/2018 18Z: 16.2N 84.5W 28 ( 25), 7, 100, 1007, 1009
10/ 6/2018 0Z: 16.8N 85.1W 29 ( 25), 8, 100, 1007, 1009
10/ 6/2018 6Z: 17.3N 85.8W 29 ( 25), 8, 110, 1007, 1009
10/ 6/2018 12Z: 17.5N 86.2W 27 ( 25), 4, 110, 1007, 1009
10/ 6/2018 18Z: 17.8N 86.6W 29 ( 25), 5, 110, 1006, 1009
10/ 7/2018 0Z: 18.1N 86.9W 36 ( 25), 4, 110, 1004, 1009
10/ 7/2018 6Z: 18.4N 86.9W 31 ( 30), 3, 240, 1004, 1010
10/ 7/2018 12Z: 18.7N 86.7W 30 ( 35), 4, 270, 1004, 1010
10/ 7/2018 18Z: 19.0N 86.0W 38 ( 45), 7, 270, 999, 1009
10/ 8/2018 0Z: 19.7N 85.4W 42 ( 50), 9, 270, 997, 1009
10/ 8/2018 6Z: 20.2N 85.4W 60 ( 60), 5, 270, 983, 1008
10/ 8/2018 12Z: 20.9N 85.1W 63 ( 65), 8, 210, 982, 1007
10/ 8/2018 18Z: 21.7N 85.1W 69 ( 70), 8, 240, 978, 1008
10/ 9/2018 0Z: 22.7N 85.2W 80 ( 75), 10, 240, 970, 1008
10/ 9/2018 6Z: 23.6N 85.7W 74 ( 80), 10, 240, 973, 1007
10/ 9/2018 12Z: 24.6N 86.1W 79 ( 90), 11, 200, 968, 1005
10/ 9/2018 18Z: 25.6N 86.3W 90 (105), 10, 210, 960, 1006
10/10/2018 0Z: 26.6N 86.5W 103 (110), 10, 210, 949, 1006
10/10/2018 6Z: 27.8N 86.6W 108 (115), 12, 210, 945, 1006
10/10/2018 12Z: 29.0N 86.3W 121 (125), 12, 210, 934, 1006
10/10/2018 18Z: 30.2N 85.4W 139 (135), 14, 210, 919, 1008
10/11/2018 0Z: 31.5N 84.5W 97 ( 80), 15, 210, 955, 1008
10/11/2018 6Z: 32.8N 83.2W 64 ( 50), 17, 220, 979, 1008
10/11/2018 12Z: 34.1N 81.7W 50 ( 45), 18, 220, 987, 1008
10/11/2018 18Z: 35.6N 80.0W 39 ( 45), 20, 180, 991, 1004
10/12/2018 0Z: 36.5N 77.7W 40 ( 45), 21, 160, 988, 1002
10/12/2018 6Z: 37.3N 75.0W 48 ( 55), 23, 180, 983, 1002
10/12/2018 12Z: 39.0N 70.0W 50 ( 55), 43, 180, 984, 1002
------------------------------------------------------------------------------

Both methods estimate winds of about 140 kt given the 919 mb pressure and other parameters. It should be noted that KZC estimates should not take precedence over direct measurements, but may be worth a look in borderline situations such as this one, especially given some of the inadvertent undersampling that occurs as the system circulation begins moving over land near landfall.

Additionally, It's worth noting the differential between the eye and CDO just prior to landfall. With an eye temp of 19.73ºC and and average CDO temp of -72.68ºC, the difference across the two is 92.41ºC, which I've found is usually enough for a category 5 in most cases. In fact, as it currently stands, Michael is the only occurrence of a system having an eye/CDO differential of >90ºC in the entire western hemisphere and not been a category 5.



Again, this isn't something that should take precedence over direct observations, but may be worth a look to help nudge a decision one way or another.

If Michael does get upgraded to a category 5, it will be the first time in recorded history that the NAtl, EPac, CPac, and WPac have all had a SSHWS Category 5 in once season (or one month even)!