Teban54 wrote:aspen wrote:Ubuntwo wrote:144kt was recorded shortly after the eye cleared out and 134kt was a few hours after weakening began.
KZC analysis for various MSLP:
Between the two flights avg. gale radius expanded from 65 nautical miles to 73, so 70 nm is an approximation for peak.
Translational speed can be averaged to 7 kt.
Latitude of peak is estimated at 14N.
Radius of outermost closed isobar I am pinning at 1011 mb based on model analyses.
Yeah you’re right, 144kt was on Saturday night with 130 kt FL winds. SFMR was definitely inflated a bit, but it does seem that Sam was 130-135 kt at that point.
Sam’s CDO started showing the impact of the starting EWRC by 20z-21z Sunday afternoon, and the 929mb drop was at ~22:35z when eye temps had cooled down to the negatives. Assuming that Sam leveled off 3-5mb deeper than when recon found it, that would support a 140 kt Cat 5 according to your KCZ analysis. Maybe it got deeper, but just to be safe I think a filling-in of 3mb between 18z and 22z is reasonable.
At this point I think the key to whether Sam gets upgraded to a Cat 5 will be whether NHC extrapolates its peak pressure to below 929 mb. If they do, the minimum pressure would be more likely to be accompanied by Cat 5 winds. If the pressure remains at 929, one can still argue Sam might have been a Cat 5 given the KZC and that Dvorak was consistently too low, but an upgrade becomes much less likely.
As I mentioned somewhere in the Sam thread, pressure extrapolation was done for Patricia, but not for Eta. The Eta TCR did mention the possibility of deepening after recon left, but they only lowered the pressure by 1 mb from operational estimates.
They should've dropped Eta's pressure by up to 5mb in the TCR (recon found a 5 mb/hr deepening rate an hour or so before the EWRC began to really take over), but this isn't an easy extrapolation to make, because we don't know exactly how much longer Eta was intensifying for and how its deepening rate slowed. It started off at 5mb/hr but definitely slowed as the EWRC neared, but how quickly did that happen? We just don't know. By contrast, Patricia and Sam have two recon fixes in which their peaks fell between, allowing for limits to be put on their peaks based on recon data and structural evolution on satellite.
Recon fixed Sam at 929mb for its first pass on Sunday night, then 932mb, and finally 943mb, all about an hour apart from each other. The filling rate doubled over the course of the flight, so extrapolating that gives a pressure of 926-927mb about an hour before recon arrived. Perhaps it could've been 1-2mb lower than that at Sam's peak. However, based on its steady satellite presentation from 10z-18z and the MPI of the region (around 925mb), it can then be inferred that Sam levelled off in the 925-927mb range for most of the day before starting an exponential weakening trend at 19-20z. A blend of the two KCZ estimates for 925mb and 927mb is either 140 kt or 145 kt, but as I said before, 140 kt is the safe bet.
Also, back to Jose comparisons: Sam had a much longer lasting and more consistent W-ring than Jose ever did. On CIRA's storm archive, I can only find a single frame of a complete W ring for Jose around the time of its 135kt/938mb peak; all other frames have a slightly broken W-ring, like Douglas '20.
Sam, on the other hand, had a true W ring with no B pixels for several hours, up until about 16:30z. For about 2-2.5 hours afterwards, before the rapid collapse of the eye, Sam had a mostly complete ring, although it wasn't good enough to qualify as T#7.0.
The better and more consistent satellite presentation supports Sam being the stronger storm, not just by pressure but also likely by winds. Also, I double-checked Jose's TCR, and it is quite apparent that it was kept at 135kt due to concerns about SFMR. Recon found max FL winds of 135kt and max SFMR of 142kt at ~00:30z 9/9/17, when Jose had significantly degraded from the time of the image further up. I could definitely see it peaking a few mbar deeper and maybe even as a 140kt Cat 5, although it probably would've been briefer than Sam's peak.